best bbc cast heads [Archive] - Team Camaro Tech

: best bbc cast heads


badbilly21
Nov 27th, 10, 11:17 PM
i know there are alot of bbc heads. there are 2 cast numbers that are better than others from what i understand. can anyone give me those numbers. i think 1 of them ends in 290. and think the other is 048? thanks in advance.

SFR600
Nov 28th, 10, 12:31 AM
i know there are alot of bbc heads. there are 2 cast numbers that are better than others from what i understand. can anyone give me those numbers. i think 1 of them ends in 290. and think the other is 048? thanks in advance. I am assuming that by better you mean better flowing. I have flowed plenty of factory big block chevy heads, so here it goes. 290 & 049 heads have oval ports. 290s are closed chamber, 049s open chamber. They both flow similar numbers until .400 lift when the 049 head will flow better at higher lifts because of less valve shrouding. This is especially true when 2.19 intake valves are installed. The exhaust is a different story. With either stock or 1.88 valves, they flow identical. There is a compression difference between the two however because of the chamber difference. The same on rectangle port heads. 840s closed, 990s open. They already have the 2.19 intake valve and the 990s flow better at high lift. The exhaust seems different than the oval ports I mentioned earlier. 840s seem to flow better throughout the lift range over the 990s. So which is better? Compression ratio, lift of cam being used, and intended RPM all play a part. If you post what you are building I can steer you in the right direction.

Fred Ficarra
Nov 28th, 10, 01:00 PM
Steve'll take care of you, but don't forget 074's.
http://epitomesrebuild.com/images/204.JPG

Now with Lunati solid roller and shaft rockers.
http://epitomesrebuild.com/images/398.JPG

CMQuickcoupe
Nov 28th, 10, 01:08 PM
dont forget the 781 castings they are near identical to the 049 with flow and the open chamber but these open chambered heads are hard to make compression with without the use of a big dome piston.

badbilly21
Nov 28th, 10, 11:49 PM
im building a 396/325 motor for the supercar race series. so im sure they are gonna check the numbers on the heads. i really appreciate your help. how are the 781's???

Eleanor's Nemesis
Nov 29th, 10, 04:29 AM
I don't think the 396 came with 781s or 049s......if you have to run correct casting number heads you will probably have to run the closed chamber ovals for a 325 hp application.

To add to this, I am building a 68 or 69 camaro to race in NHRA stock and super stock eliminator, using a 396/325 or 396/350 most likely. For those years, as per the NHRA tech bulletins that were supplied by the OEMs back then, the accepted cylinder heads for '68 and '69 were heads with casting numbers ending in 215, 063, 290, and I think one more but can't recall now.

I called Dave Layer of Heads Up cylinder heads and asked him about the flow rates on these heads and which ones were the best choice.....he told me they have done lots of 063s and that there was something a little funky with the 215s.

That conversation was in regards to a super stock application which allows porting and epoxying of the runners as long as factory CC is maintained. For a stock application, where the heads have to be untouched, I would recommend calling people like Steve Koppien in North Dakota, Parsons and Myers racing engines, Bub Whitaker of Burtonsville Performance and Machine in Maryland, Warren Racing Engines in Clinton NC, and perhaps a few others that have considerable experience (and national records) with these applications.

I hope this helps!

Z15CAM
Nov 29th, 10, 07:38 AM
For Iron Oval Port usng Open Chamber Pistons, I would lean toward the: 3993820, 71, oval, OPEN, 402, 113cc chamber, 255/114 ports also found on the 71-84, 454 Passenger and Trucks.

Less Dome equals Best Chamber Ignition, when reaching for your desired Static Compression.

396's and 427's were Closed Chamber (Not talking about the 366T or 427T Mills which were Open Chamber and mainly Peanut Ports) - It was the 70 454 that introduced Open Chamber to Passenger Cars and the 402 (+.030" 396) went Open Chamber in 71. About the only exceptions were the 265Hp 69 396 112cc Open Chamber 3933148 Casting and the 3975950, 68-70, oval, OPEN, 396, 402 Truck, 366T, 427T Castings.

The 820/113cc, 781/118cc & 049/122cc chambers all Port Flow approx the same and Noted as the Best Flowing Large Oval Ports. Chamber Displacement are know to vary - So you have to CC anyway.

That's my understanding for MKIV Closed Vs Open Chamber Oval Port Iron Castings.

SFR600
Nov 29th, 10, 05:25 PM
If you have to run oval/closed heads the 063 or 290 are nearly identical and flow decent. These have a slightly different quench pad area in the chamber vs. other closed chamber heads. They cc around 100. I don't recall ever flowing 215 castings, so I can't comment on them. I don't know the rules that you have to follow, but bigger valves and porting would really help if allowed. Even better is if you can run the open chamber heads, but like mentioned in other posts I've never heard of them being on 396 engines.

CMQuickcoupe
Nov 29th, 10, 05:50 PM
If you have to run oval/closed heads the 063 or 290 are nearly identical and flow decent. These have a slightly different quench pad area in the chamber vs. other closed chamber heads. They cc around 100. I don't recall ever flowing 215 castings, so I can't comment on them. I don't know the rules that you have to follow, but bigger valves and porting would really help if allowed. Even better is if you can run the open chamber heads, but like mentioned in other posts I've never heard of them being on 396 engines.

Have u ever flowed a set of the 702 big oval closed chambered heads?
these were on 66 427 vetts and 66 396 chevelles,Thanks for any info

SFR600
Nov 29th, 10, 06:20 PM
I flowed a pair of 702 heads for a friend of mine about a year ago. He did some bowl work to both ports, nothing extreme, just a clean up. I wish I could have done them stock, but he already did the work. I gave him the flow sheet, so I can't remember all the numbers. I believe they maxed out in the 270's intake and 170's exhaust. Not great numbers, but it is what it is. I remember I couldn't talk him into putting bigger valves in them, so these were 2.06/1.72 valves. Again, I can't say for sure what they flow totally stock. Maybe someone else has flowed some bone stock.

CMQuickcoupe
Nov 29th, 10, 08:21 PM
I flowed a pair of 702 heads for a friend of mine about a year ago. He did some bowl work to both ports, nothing extreme, just a clean up. I wish I could have done them stock, but he already did the work. I gave him the flow sheet, so I can't remember all the numbers. I believe they maxed out in the 270's intake and 170's exhaust. Not great numbers, but it is what it is. I remember I couldn't talk him into putting bigger valves in them, so these were 2.06/1.72 valves. Again, I can't say for sure what they flow totally stock. Maybe someone else has flowed some bone stock.

how bout with bigger valves and maybe alittle unshrouding do you think they wud pick up in flow?

SFR600
Nov 29th, 10, 09:08 PM
As long as you do the bowl work to match the larger valves also. My experience with the 063 or 290's i mentioned earlier usually flow 290-300 in. 200-210 ex. @ .600 lift with the 2.19/1.88 valves and bowl work. There's more in them but the short-turn needs work. Not hard, just takes more time. Personally, I always put bigger valves in the passenger car heads. With such easy work it's just a shame to leave that airflow gain untapped in my opinion.

CMQuickcoupe
Nov 29th, 10, 09:52 PM
As long as you do the bowl work to match the larger valves also. My experience with the 063 or 290's i mentioned earlier usually flow 290-300 in. 200-210 ex. @ .600 lift with the 2.19/1.88 valves and bowl work. There's more in them but the short-turn needs work. Not hard, just takes more time. Personally, I always put bigger valves in the passenger car heads. With such easy work it's just a shame to leave that airflow gain untapped in my opinion.


yea ive got a guy here thats a good head porter and has told me he likes to do the short turn radius on the big block heads and i have a set of these heads i was thinkin of using on a 454 ive got to help with compression a bit but i want the flow for sure,Thanks for the info

badbilly21
Nov 29th, 10, 10:07 PM
what about a 496 dressed to look like a 396 in a 69 camaro, want the look of a 396/325 using the right cast manifold and quadrajet carb.

Z15CAM
Nov 29th, 10, 10:54 PM
I believe you got some very good answers.

Suggest you check this MorTec Site out for whatever you plan to do: http://web.archive.org/web/20080513040220/www.mortec.com/bbc.htm

Be aware the ONLY 396 Block which can be punched out to a 496 Bore is the 3855961, 396/427, 65-66, 2 or 4 bolt Casting which uses the Groove in the Rear Cam Journal, other words, you have to use either a 427 or 454 block.

All MKIV Mills look identical irregardless of displacement - Unless you get down and Cross reference the Castings and Date Codes you can dress them up to look like whatever you want and no one would know the difference ;o)

dred
Nov 29th, 10, 11:18 PM
I flowed a pair of 702 heads for a friend of mine about a year ago. He did some bowl work to both ports, nothing extreme, just a clean up. I wish I could have done them stock, but he already did the work. I gave him the flow sheet, so I can't remember all the numbers. I believe they maxed out in the 270's intake and 170's exhaust. Not great numbers, but it is what it is. I remember I couldn't talk him into putting bigger valves in them, so these were 2.06/1.72 valves. Again, I can't say for sure what they flow totally stock. Maybe someone else has flowed some bone stock.

Hi Steve, I just picked up a set of 702 heads to use on my 468 with flat top pistons. (looking to bump compression) They have 2.19 / 1.88 valves and a bowl blend done. Can you give me your opinion on how these heads will flow? Would they flow similiar to 063 or 290 with big valves?

kettbo
Nov 29th, 10, 11:22 PM
For Iron Oval Port usng Open Chamber Pistons, I would lean toward the: 3993820, 71, oval, OPEN, 402, 113cc chamber, 255/114 ports also found on the 71-84, 454 Passenger and Trucks.

Less Dome equals Best Chamber Ignition, when reaching for your desired Static Compression.

396's and 427's were Closed Chamber (Not talking about the 366T or 427T Mills which were Open Chamber and mainly Peanut Ports) - It was the 70 454 that introduced Open Chamber to Passenger Cars and the 402 (+.030" 396) went Open Chamber in 71. About the only exceptions were the 265Hp 69 396 112cc Open Chamber 3933148 Casting and the 3975950, 68-70, oval, OPEN, 396, 402 Truck, 366T, 427T Castings.

The 820/113cc, 781/118cc & 049/122cc chambers all Port Flow approx the same and Noted as the Best Flowing Large Oval Ports. Chamber Displacement are know to vary - So you have to CC anyway.

That's my understanding for MKIV Closed Vs Open Chamber Oval Port Iron Castings.

1970 454s were closed chamber.

A bit of exotica but the Aluminum heads for the ZL-1 Camaro and L-88 Vette later in the 1969 production were Open Chamber. Small wonder these are THE cars being run hard for the Stock-Appearing classes.

Get with your sanctioning body re what casting numbers are acceptable.
Functional replacement of a 427 with a 454 block is one thing, they share the same bore. They may frown on you with a larger bore 427 or 454 block for your "396" then again, they look the same from the outside. We can only speculate. Check with your sanctioning body. Thinking they may complain about a Bowtie or Sportsman block

If I was going to do this, I would fake a 396/375 L89 Aluminum head option.

Z15CAM
Nov 29th, 10, 11:30 PM
1970 454s were closed chamber.

Oh Yah, the 290 Oval with either the Large or Small HEX Plug where CLOSED Chamber on 70 454's but there where also OPEN Chambered 6272292 Casting used on the 70 402 and 454. I was attempting to point out when Large Oval Port OPEN Chamber came on the scene and more or less became the norm. with my Statement: It was the 70 454 that introduced Open Chamber to Passenger Cars

I know the 330864 and 865.....68-84 Castings where OPEN designated by Mortec for 396, 402, 366T, 427T, 454 Truck but I believe they are Peanut Port or not much better for Air Flow - I could be wrong.

If you not tied to a Sanctioning Body or Class, I would not worry about it and as George suggests build a 69 375Hp 396 L78 look alike with 496 cubes. Very Impressive and Nostalgic for the 69; on the other hand' make it look like a 265Hp 69 396 sleeper - LOL

Eleanor's Nemesis
Nov 30th, 10, 04:56 AM
what about a 496 dressed to look like a 396 in a 69 camaro, want the look of a 396/325 using the right cast manifold and quadrajet carb.

That will certainly take a different balancer but you probably already know that.

The cast iron manifold doesn't flow very well, you will have to do quite a bit of porting on it and even though the quadrajet will work it just won't be the best choice.

RSSSfanatic
Nov 30th, 10, 05:47 AM
what about a 496 dressed to look like a 396 in a 69 camaro, want the look of a 396/325 using the right cast manifold and quadrajet carb.You should talk to Cliff Ruggles about getting that Q-Jet set up properly to handle the CFM that engine will need. If you are not concerned with an original Camaro Q-jet, I understand that the castings used on some of the Pontiacs and Buicks from the mid-70's have a larger primary venturi with the ability to flow 850+ CFM. You are going to need this to take advantage of those cubes.

RSSSfanatic
Nov 30th, 10, 05:52 AM
That will certainly take a different balancer but you probably already know that.

The cast iron manifold doesn't flow very well, you will have to do quite a bit of porting on it and even though the quadrajet will work it just won't be the best choice.I think the 496 reciprocating assembly can be bought already internally balanced. With this setup, I would think it would be possible to run the neutrally balanced 396/427 balancer and flywheel.

badbilly21
Nov 30th, 10, 09:36 AM
we are looking at an internally balanced 496. i have a few sets of 781 heads, wondered if they were worth playing with. my engine builder races stock elim. and is great with q-jet carbs. i can run the 454 block, but want it to look like the 325 horse motor, just a bit more sleeper look. i have a 68 nova that will get a big motor for the supercar race series.

Z15CAM
Nov 30th, 10, 01:30 PM
I run 2.19/1.9 781 with Pocket porting and a Venturi Exhaust Seat. My 10.2:1 .030" 454 with a Donovan Cam Gear Drive SR will hit 7000rpm with a Holley 830 Annular Booster/Edelbrock Air Gap or RPM Intake / M21 and 3:31 Gears putting out approx 625 Hp .

I can't see why a 9.5 to 10:1 Static Compression 496 running HFT or HR with a 850 Holley/ Edelbrock rpm or say a Q-Jet/Edelbrock 2001 sitting on 781's should not rev 6200 rpm and put out 500+ Hp.

Look at the CC-XM278H-12 or the XM288H-12 HFT Cam for what I'm guessing you after.

About my only complaint is that the 781's, as are all OEM Cast Iron Heads, are Heavy and something like the Edelbrock Alu- 454-O Heads will be more responsive for handling.

zlek131
Nov 30th, 10, 04:11 PM
dont forget the 781 castings they are near identical to the 049 with flow and the open chamber but these open chambered heads are hard to make compression with without the use of a big dome piston.
I have the 781's on my 496 built by Mark Jones. He loves these heads and does about 30 hours of flow work on them. He says (no secret) that one of the main reason his motors make the HP/TQ (see sig) is due to these heads.

SFR600
Nov 30th, 10, 08:56 PM
If you can disguise what the motor is then go for it. Do rect. ports, open chamber, 990 castings. Just basic port work they go 340. Tons of airflow out of a factory head.

SFR600
Nov 30th, 10, 09:18 PM
[QUOTE=dred;1508715]Hi Steve, I just picked up a set of 702 heads to use on my 468 with flat top pistons. (looking to bump compression) They have 2.19 / 1.88 valves and a bowl blend done. Can you give me your opinion on how these heads will flow? Would they flow similiar to 063 or 290 with big valves?[/QUOTE That is pretty much why I have so many closed chamber heads to work on. Easy compression. Most 454 Chevys you find these days are flat top piston. To answer your question, check out what I posted last night. Those are typical numbers of what can be expected. (Old school closed chamber on flat top truck 454 is alway better over the 236 factory on a street ride) More compression + more CFM = more fun.

vortecpro
Dec 1st, 10, 06:00 AM
[QUOTE=dred;1508715]Hi Steve, I just picked up a set of 702 heads to use on my 468 with flat top pistons. (looking to bump compression) They have 2.19 / 1.88 valves and a bowl blend done. Can you give me your opinion on how these heads will flow? Would they flow similiar to 063 or 290 with big valves?[/QUOTE That is pretty much why I have so many closed chamber heads to work on. Easy compression. Most 454 Chevys you find these days are flat top piston. To answer your question, check out what I posted last night. Those are typical numbers of what can be expected. (Old school closed chamber on flat top truck 454 is alway better over the 236 factory on a street ride) More compression + more CFM = more fun.Whats will make more power, a ported 9.5 comp 454 peanut port, or a flattop 454 with a ported closed chamber head (702)?

vortecpro
Dec 1st, 10, 06:07 AM
For Iron Oval Port usng Open Chamber Pistons, I would lean toward the: 3993820, 71, oval, OPEN, 402, 113cc chamber, 255/114 ports also found on the 71-84, 454 Passenger and Trucks.

Less Dome equals Best Chamber Ignition, when reaching for your desired Static Compression.

396's and 427's were Closed Chamber (Not talking about the 366T or 427T Mills which were Open Chamber and mainly Peanut Ports) - It was the 70 454 that introduced Open Chamber to Passenger Cars and the 402 (+.030" 396) went Open Chamber in 71. About the only exceptions were the 265Hp 69 396 112cc Open Chamber 3933148 Casting and the 3975950, 68-70, oval, OPEN, 396, 402 Truck, 366T, 427T Castings.

The 820/113cc, 781/118cc & 049/122cc chambers all Port Flow approx the same and Noted as the Best Flowing Large Oval Ports. Chamber Displacement are know to vary - So you have to CC anyway.

That's my understanding for MKIV Closed Vs Open Chamber Oval Port Iron Castings.I would lean toward the: 3993820 Why would you want to use a head that has an inferior combustion chamber? This head (820) is basically a 215, 063, 290 with the quench pad removed. Flow is important, but theres more things to consider when trying to make better than average power.

Z15CAM
Dec 1st, 10, 09:44 AM
Why would you want to use a head that has an inferior combustion chamber?

It's not that the Combustion Chamber is inferior it's that Flat Top Pistons Promote a Better Flame during combustion and less prone to detonation using higher DCR.

Flow is important, but theres more things to consider when trying to make better than average power.

I'll go there read the following ;o)

In my case I'm running Speed Pro (TRW) Forged Pistons with a 25.7 cc dome with a Forged Rotating assembly. The 118cc Open Chamber of the 781's with a .019" Head gasket gives me a 10.2:1 Static Compression and about an Ideal 8:1 DCR with the SR Cam Profile I've chosen to reach 7000rpm with 460 cubes.

Because the 496 has bigger cubes your more then likely to use a flat top piston with say the 820 or 781 castings to obtain your desired Static Compression to run a Cam that will get the most out of Pump Fuel without detonating. A DCR no greater then 8:1 seems to be the accepted ratio to run Pump Gas without detonation.

You should be able to spin a 496 Cast Rotating assembly safely to 6400 rpm and choose a Cam that makes wide band Torque through to approx 6200 rpm - That's why I suggested the CC-XM278H-12 with say a 10:1 Static Compression 496 to accomplish an 8:1 DCR and get the biggest BANG out of Pump Gas and for the Buck.

Download and play with P. Kelley's DCR Calculator found here: http://www.empirenet.com/pkelley2/DynamicCR.html

With a 496 to reach a 10:1 Static Compression with say the 113cc 820 heads you going to need a Piston with a 10cc dome, or approx a 15cc Dome with 781 casting, or choose say a 98cc Closed Chamber with a Flat top piston running a .019 Head Gasket or you 0-Deck and run a .038" Composite gasket in order to keep the QUENCH a in a respectable .034" to .044" Range. Quench is a Critical Knock/Detonation Factor for extracting the most power out of Pump Gas with our Old LT1 and MKIV Mills.

If you Opt for Alu-Heads you have to 0-Deck as they use Composite Gaskets which are generally .038" thick = an Ideal Quench.

You will probably will get away with a .025"(OEM Deck Height) plus a .038" Composite Gasket = a .063" Quench with a 9.5:1 Static Compression (NOT 10 to 11:1) providing you keep the DCR below 8:1 through Cam Selection running Pump Gas.

I'm Old School and have been building Engines for 45 years. Here's the Top End of my Pump Gas 7000rpm 625Hp 460ci SR, 10.2:1, 8.1:1 DCR, MKIV with 781 Heads running a Lunati 502A1/CC-533 Springs & Crower HIPPO Lifters:
http://farm4.static.flickr.com/3371/3234547525_43e983d24e.jpg
I NOT saying the 781 are the answer for your build and application but work for me; other then, I would prefer Alu-Heads to reduce the Weight for better Road Handling - My Z is a Road Warrior not a Drag Machine.
Doesn't mean, I can't do a 10 Sec 1/4 ;o)

What I'm trying to say is that: YES OEM Heads (Cast or Alu) are feasible for how you desire to Build and DIAL-IN an ENG - Believe me, GM progressed Specs better then either Ford & Mopar; YET, I have never been able to build one Better then the Other; so don't think a BBC Camaro Conquers All when a 1968 4 Cyl B21 Volvo will Wipe Your A** :o.

RSSSfanatic
Dec 1st, 10, 02:56 PM
Slightly off topic from the original thread, and I don't want to hijack, but I am building a 489/496 for a marine application and need to decide what heads to run. I currently have a set of 820's with some mild pocket porting and 2.19 intake valves installed. The original builder did not install 1.88 exhausts for some reason - not sure if that makes much difference. For a marine engine, you have to be careful not to run too much compression. A safe compression ratio with the crummy gas that is often available on the water is around 8.75:1. Remember, a marine engine is under load all the time, and the more restrictive wet exhaust negates bleeding off compression with longer duration cams. So I guess my question is, can I stay around 8.75:1 CR with the 114 cc chamber 820 heads in a 4.25 stroke engine? Can I do this with a flat top piston, or will I have to go dished (if even available for a 496)?

Thanks for any help I can get.

vortecpro
Dec 1st, 10, 03:46 PM
It's not that the Combustion Chamber is inferior it's that Flat Top Pistons Promote a Better Flame during combustion and less prone to detonation using higher DCR.



I'll go there read the following ;o)

In my case I'm running Speed Pro (TRW) Forged Pistons with a 25.7 cc dome with a Forged Rotating assembly. The 118cc Open Chamber of the 781's with a .019" Head gasket gives me a 10.2:1 Static Compression and about an Ideal 8:1 DCR with the SR Cam Profile I've chosen to reach 7000rpm with 460 cubes.

Because the 496 has bigger cubes your more then likely to use a flat top piston with say the 820 or 781 castings to obtain your desired Static Compression to run a Cam that will get the most out of Pump Fuel without detonating. A DCR no greater then 8:1 seems to be the accepted ratio to run Pump Gas without detonation.

You should be able to spin a 496 Cast Rotating assembly safely to 6400 rpm and choose a Cam that makes wide band Torque through to approx 6200 rpm - That's why I suggested the CC-XM278H-12 with say a 10:1 Static Compression 496 to accomplish an 8:1 DCR and get the biggest BANG out of Pump Gas and for the Buck.

Download and play with P. Kelley's DCR Calculator found here: http://www.empirenet.com/pkelley2/DynamicCR.html

With a 496 to reach a 10:1 Static Compression with say the 113cc 820 heads you going to need a Piston with a 10cc dome, or approx a 15cc Dome with 781 casting, or choose say a 98cc Closed Chamber with a Flat top piston running a .019 Head Gasket or you 0-Deck and run a .038" Composite gasket in order to keep the QUENCH a in a respectable .034" to .044" Range. Quench is a Critical Knock/Detonation Factor for extracting the most power out of Pump Gas with our Old LT1 and MKIV Mills.

If you Opt for Alu-Heads you have to 0-Deck as they use Composite Gaskets which are generally .038" thick = an Ideal Quench.

You will probably will get away with a .025"(OEM Deck Height) plus a .038" Composite Gasket = a .063" Quench with a 9.5:1 Static Compression (NOT 10 to 11:1) providing you keep the DCR below 8:1 through Cam Selection running Pump Gas.

I'm Old School and have been building Engines for 45 years. Here's the Top End of my Pump Gas 7000rpm 625Hp 460ci SR, 10.2:1, 8.1:1 DCR, MKIV with 781 Heads running a Lunati 502A1/CC-533 Springs & Crower HIPPO Lifters:
http://farm4.static.flickr.com/3371/3234547525_43e983d24e.jpg
I NOT saying the 781 are the answer for your build and application but work for me; other then, I would prefer Alu-Heads to reduce the Weight for better Road Handling - My Z is a Road Warrior not a Drag Machine.
Doesn't mean, I can't do a 10 Sec 1/4 ;o)

What I'm trying to say is that: YES OEM Heads (Cast or Alu) are feasible for how you desire to Build and DIAL-IN an ENG - Believe me, GM progressed Specs better then either Ford & Mopar; YET, I have never been able to build one Better then the Other; so don't think the GM Camaro BBC Conquers All when a 1968 4 Cyl B21 Volvo will Wipe Your A** :o.Ron, I allways like to argue with you, your old school and a car guy to boot, god bless you. I do feel the 820 chamber is inferior, please do me a favor, take your car to a drag strip, then please report on the MPH. I have no problem with your post, but I gotta tell you my heads hurting trying to follow it.

Z15CAM
Dec 1st, 10, 03:50 PM
Well Yah! We always say our heads HURT - Even if they get us to 7000rpm.

If you read my post I'm running 781's and don't believe the 820 flow any different. Actually for my Build I would prefer the 820's to enhance that Static to 11:1 then Promote the Cam.

What's it going to give me - Another 25Hp - I'll never use it on the HWY or Street - Which I can't do NOW - Sish!

dred
Dec 1st, 10, 05:39 PM
Whats will make more power, a ported 9.5 comp 454 peanut port, or a flattop 454 with a ported closed chamber head (702)?
Mark, what is the answer? I'm going with the 702 heads for budget purposes only. I dont want to change over the flat tops in my motor so my choices are 8:1 with stock 781 heads or 9.5 : 1 with a set of big valve 702 heads that I have. Eventually I'm getting one of your motors but thats a year or two away.

SFR600
Dec 1st, 10, 05:55 PM
[quote=SFR600;1509176]Whats will make more power, a ported 9.5 comp 454 peanut port, or a flattop 454 with a ported closed chamber head (702)?

Well, I've never dynod or ported peanut ports so I cant say for certain. I would probably have a whole lot more work making 600hp or 300cfm out of a set of peanuts over closed chamber ovals though.

Z15CAM
Dec 1st, 10, 08:02 PM
Well I did comment that Quench is about inconsequential with a 9.5:1 Static Compression with a DCR is below 8:1; but, you will never approach 7000rpm with Pump Gas.

Not saying a 9.5:1 496 Cast Rotating assembly will not put out 500+ Hp at 5800 rpm on pump gas ;o)

I agree with you "Use a the Smaller CC Bath-Tub Close Chamber Head with a Cast Rotating Assembly 496, Flat Top Pistons." It's Practical and Least Expensive.

vortecpro
Dec 1st, 10, 11:58 PM
Mark, what is the answer? I'm going with the 702 heads for budget purposes only. I dont want to change over the flat tops in my motor so my choices are 8:1 with stock 781 heads or 9.5 : 1 with a set of big valve 702 heads that I have. Eventually I'm getting one of your motors but thats a year or two away.It looks like the 702s are the answer for your piston combination.

vortecpro
Dec 2nd, 10, 12:02 AM
Well I did comment that Quench is about inconsequential with a 9.5:1 Static Compression with a DCR is below 8:1; but, you will never approach 7000rpm with Pump Gas.

Not saying a 9.5:1 496 Cast Rotating assembly will not put out 500+ Hp at 5800 rpm on pump gas ;o)

I agree with you "Use a the Smaller CC Bath-Tub Close Chamber Head with a Cast Rotating Assembly 496, Flat Top Pistons." It's Practical and Least Expensive.The quench matters with any compression. If you took a 9.5 comp 820 headed engine, then a 781 headed 9.5 comp engine everything else the same, which engine will be more efficent?

Z15CAM
Dec 2nd, 10, 09:01 AM
If you took a 9.5 comp 820 headed engine, then a 781 headed 9.5 comp engine everything else the same, which engine will be more efficent?

In Theory the Engine with the Lessor Dome Height. The 781 would require a Piston with 5cc more volume and therefore have a Higher Dome then the Engine running the lower Dome Piston and 820 Heads. So I would so I would say the engine running the 820 heads would be more efficient.

protree68
Dec 2nd, 10, 11:05 AM
It's not that the Combustion Chamber is inferior it's that Flat Top Pistons Promote a Better Flame during combustion and less prone to detonation using higher DCR.



I'll go there read the following ;o)

In my case I'm running Speed Pro (TRW) Forged Pistons with a 25.7 cc dome with a Forged Rotating assembly. The 118cc Open Chamber of the 781's with a .019" Head gasket gives me a 10.2:1 Static Compression and about an Ideal 8:1 DCR with the SR Cam Profile I've chosen to reach 7000rpm with 460 cubes.

Because the 496 has bigger cubes your more then likely to use a flat top piston with say the 820 or 781 castings to obtain your desired Static Compression to run a Cam that will get the most out of Pump Fuel without detonating. A DCR no greater then 8:1 seems to be the accepted ratio to run Pump Gas without detonation.

You should be able to spin a 496 Cast Rotating assembly safely to 6400 rpm and choose a Cam that makes wide band Torque through to approx 6200 rpm - That's why I suggested the CC-XM278H-12 with say a 10:1 Static Compression 496 to accomplish an 8:1 DCR and get the biggest BANG out of Pump Gas and for the Buck.

Download and play with P. Kelley's DCR Calculator found here: http://www.empirenet.com/pkelley2/DynamicCR.html

With a 496 to reach a 10:1 Static Compression with say the 113cc 820 heads you going to need a Piston with a 10cc dome, or approx a 15cc Dome with 781 casting, or choose say a 98cc Closed Chamber with a Flat top piston running a .019 Head Gasket or you 0-Deck and run a .038" Composite gasket in order to keep the QUENCH a in a respectable .034" to .044" Range. Quench is a Critical Knock/Detonation Factor for extracting the most power out of Pump Gas with our Old LT1 and MKIV Mills.

If you Opt for Alu-Heads you have to 0-Deck as they use Composite Gaskets which are generally .038" thick = an Ideal Quench.

You will probably will get away with a .025"(OEM Deck Height) plus a .038" Composite Gasket = a .063" Quench with a 9.5:1 Static Compression (NOT 10 to 11:1) providing you keep the DCR below 8:1 through Cam Selection running Pump Gas.

I'm Old School and have been building Engines for 45 years. Here's the Top End of my Pump Gas 7000rpm 625Hp 460ci SR, 10.2:1, 8.1:1 DCR, MKIV with 781 Heads running a Lunati 502A1/CC-533 Springs & Crower HIPPO Lifters:
http://farm4.static.flickr.com/3371/3234547525_43e983d24e.jpg
I NOT saying the 781 are the answer for your build and application but work for me; other then, I would prefer Alu-Heads to reduce the Weight for better Road Handling - My Z is a Road Warrior not a Drag Machine.
Doesn't mean, I can't do a 10 Sec 1/4 ;o)

What I'm trying to say is that: YES OEM Heads (Cast or Alu) are feasible for how you desire to Build and DIAL-IN an ENG - Believe me, GM progressed Specs better then either Ford & Mopar; YET, I have never been able to build one Better then the Other; so don't think a BBC Camaro Conquers All when a 1968 4 Cyl B21 Volvo will Wipe Your A** :o.

wow ware did you find that old school unilite distributor i remember working at supershops in the 80's selling those.

chevguy65
Dec 2nd, 10, 11:29 AM
Hmmm...

http://i174.photobucket.com/albums/w111/chevguy65/12021011041.jpg

Here is a 781 and 820 in pristine state.


On a 9.5:1 c/r 454 which head will be more efficient with all other factors the same (equal) and why?

RSSSfanatic
Dec 2nd, 10, 12:19 PM
Hmmm...


Here is a 781 and 820 in pristine state.


On a 9.5:1 c/r 454 which head will be more efficient with all other factors the same (equal) and why?

I can't answer your question, but just by looking at the combustion chambers, you would expect the 820's to have a much larger chamber than the 781's, yet I believe the 820 is supposed to be 114 cc and the 781 is supposed to be 119 or 120 cc or thereabouts. Has anyone cc'd the 820's and/or the 781's to verify this? The guy who built my original boat engine selected the 820's because he thought they had a larger combustion chamber and would drop the compression down to a manageable 9.2:1. I am so confused right now I don't know what head to use on my next build. :confused: I would like to stay around 8.75:1 so I can safely run 87 octane fuel.

Z15CAM
Dec 2nd, 10, 12:29 PM
WOWA! No Wonder we're quibbling - I'm now thinking there is a discrepancy with the 3993820....71......oval...OPEN...402, 113cc chamber, 255/114 ports - The ones I've seen had the 3/4 Combustion Chamber similar to the 781's but with a 113cc Chamber.

That 820 you show must surely have a 124cc Chamber.

RSSSfanatic
Dec 2nd, 10, 01:04 PM
I guess I'll just have to CC mine myself to settle it. :cool:

chevguy65
Dec 2nd, 10, 01:47 PM
WOWA! No Wonder we're quibbling - I'm now thinking there is a discrepancy with the 3993820....71......oval...OPEN...402, 113cc chamber, 255/114 ports - The ones I've seen had the 3/4 Combustion Chamber similar to the 781's but with a 113cc Chamber.

That 820 you show must surely have a 124cc Chamber.

Hmmmm again,

this is the only chamber I have ever seen on the 820.

So again, which is more efficient and why?

chevguy65
Dec 2nd, 10, 01:51 PM
And rsssfanatic,
you are correct the combustion chamber is smaller on the 820.

The 820 is a dirty head!
Meaning the combustion chamber is inefficient=no quench.

RSSSfanatic
Dec 2nd, 10, 01:58 PM
And rsssfanatic,
you are correct the combustion chamber is smaller on the 820.

The 820 is a dirty head!
Meaning the combustion chamber is inefficient=no quench.
Dirty head? That sounds, uhhh, "dirty"! :D Does that translate into decreased power and poor flow, or is it more prone to detonation, or both? I seem to recall reading somewhere that the 820's combustion chamber was designed this way for emissions, but I could be wrong. By appearances, it sure looks like a larger chamber than the 781. Is the 781 simply much deeper?

Z15CAM
Dec 2nd, 10, 02:12 PM
Man, I agree that 820 Casting shown by Carl would be a Dirty Head with minimal Quench but I swear I saw an 820 Casting that looked like a LT1 Turbo-Flow Chamber similar to the 781 chamber- Can't back it up and can't prove it and most likely misidentified it and barking up the wrong tree - Unless someone has a Photo of an 820 that I'm referring too - After all GM did vary Combustion Chamber shape & volumes in a Production run - Reaching here ;o)

Look at Grumpy Jenkins : He rolled back the lip of the Chamber approaching the Quench around the the Exhaust Valve to promote Exhaust Flow enhancing the Venture effect at the expense of Quench Area with the SBC Turbo-Flow 291 and 292 Castings.

RSSSfanatic
Dec 2nd, 10, 03:28 PM
Look at Grumpy Jenkins : He rolled back the lip of the Chamber approaching the Quench around the the Exhaust Valve to promote Exhaust Flow enhancing the Venture effect at the expense of Quench Area with the SBC Turbo-Flow 291 and 292 Castings.So how did that work out? I'm just trying to figure out if these heads are worth running on my next engine, or if they are turds. I would hate to hamstring my engine for all the money and time I will be dumping into it. If these are not the right head to run, I will start looking for some 049's or 781's, or even a set of L92 Vortec's or the 990 square ports.

dred
Dec 2nd, 10, 03:45 PM
And rsssfanatic,
you are correct the combustion chamber is smaller on the 820.

The 820 is a dirty head!
Meaning the combustion chamber is inefficient=no quench.

Great info here guys. I'm just learning all this but I agree, no quench on the 820 head shown. Here is my 720 head with big valves and 94 cc chambers. I would assume i would have a good quench with these heads, but due to the shrouding of the closed chambers flow would be compromised?

http://img39.imageshack.us/img39/4341/20100520113830.jpg (http://img39.imageshack.us/i/20100520113830.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

chevguy65
Dec 2nd, 10, 04:22 PM
Since I am not an expert I will try to explain within my limited resources and may plagiarize those that know.


"The quench distance is the compressed thickness of the head gasket plus the deck height. In other words, if your piston height, (not dome height), is above the block deck, you would subtract that from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of the piston that would contact a similar flat area on the cylinder head if you had .000" quench height. In a running engine, the .035" quench decreases to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity through the combustion chamber. This movement tends to cool hot spots, average the chamber temperature, reduce detonation and increase power."


I hope I explained this correctly and so it can be understood. If not I will get my butt chewed and correct myself at that time.

SFR600
Dec 2nd, 10, 07:50 PM
This is starting to get crazy. The original poster just wanted to know the difference between 290/049 heads.

chevguy65
Dec 2nd, 10, 08:18 PM
This is starting to get crazy. The original poster just wanted to know the difference between 290/049 heads.

Well in my mind it is better to give correct information when something is posted rather than to just let folks believe misinformation.
I also do not think it was deliberate, just a mistake.;)

There is way to much misinformation out there already.

SFR600
Dec 2nd, 10, 08:40 PM
Well in my mind it is better to give correct information when something is posted rather than to just let folks believe misinformation.
I also do not think it was deliberate, just a mistake.;)

There is way to much misinformation out there already.

I understand. I am just wondering what badbilly21 is really putting together so I can give the best info. I have available to me. My posts aren't opinions, they're facts of what has worked for me.

vortecpro
Dec 2nd, 10, 08:50 PM
I understand. I am just wondering what badbilly21 is really putting together so I can give the best info. I have available to me. My posts aren't opinions, they're facts of what has worked for me.Can you post a flow sheet on one of your closed chamber heads?

SFR600
Dec 2nd, 10, 09:07 PM
Can you post a flow sheet on one of your closed chamber heads?

Very simple work here. 290 castings. 2.19/1.88 just bowl work. No valve guide boss or short turn work.

.100 73
.200 150
.300 198
.400 240
.500 272
.600 290


.100 68
.200 109
.300 134
.400 162
.500 182
.600 198

This is a sheet I had right in front of me. Have others but need to locate them. I know, should be more organized. Forgot to mention 3/8 stem valves + no backcut on either intake or exhaust.

vortecpro
Dec 2nd, 10, 09:17 PM
Very simple work here. 290 castings. 2.19/1.88 just bowl work. No valve guide boss or short turn work.

.100 73
.200 150
.300 198
.400 240
.500 272
.600 290


.100 68
.200 109
.300 134
.400 162
.500 182
.600 198

This is a sheet I had right in front of me. Have others but need to locate them. I know, should be more organizedIf you were to build a 467 that needed to make 510 HP with 9.1 comp, a 228 @ .050 cam, which GM head would you use? Your choices are 236, 290, 063, 049

SFR600
Dec 2nd, 10, 09:44 PM
If you were to build a 467 that needed to make 510 HP with 9.1 comp, a 228 @ .050 cam, which GM head would you use? Your choices are 236, 290, 063, 049

That comp. is pretty much flat top with 290/063, or .200 dome with 049. I wouldn't use the peanut 236 unless that is all you have available. Myself would use the dome and 049 or 781 or 292/241 castings. Put in the bigger valves and bowl work. 510hp. easy, probably more.

rightnwrong
Dec 2nd, 10, 11:53 PM
Wow! It is the best bbc cast heads I've ever seen. :)

kettbo
Dec 3rd, 10, 12:06 AM
DRED,

Darryl Berg, aka Doc, aka FRYNTYR did those heads. They went well into the 10s on a 489. They will deliver any amount of bacon you can reasonably handle. IIRC, Doc unshrouded the valves as much as possible then got to shaving to get the chamber volume back down.




Great info here guys. I'm just learning all this but I agree, no quench on the 820 head shown. Here is my 720 head with big valves and 94 cc chambers. I would assume i would have a good quench with these heads, but due to the shrouding of the closed chambers flow would be compromised?

http://img39.imageshack.us/img39/4341/20100520113830.jpg (http://img39.imageshack.us/i/20100520113830.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

dred
Dec 3rd, 10, 12:35 AM
Darryl Berg, aka Doc, aka FRYNTYR did those heads. They went well into the 10s on a 489. They will deliver any amount of bacon you can reasonably handle. IIRC, Doc unshrouded the valves as much as possible then got to shaving to get the chamber volume back down.


Thanks for the info George. Sounds like they will work well for my application. Just trying to understand all the variables of the different heads discussed here, very good info from knowledgeable folk.

Z15CAM
Dec 3rd, 10, 02:27 AM
Well I certainly wasn't aware that the 820 Quench was virtually none existent. I learn something all the time here at TC and enjoy a good exchange of info - Great presentation Mark ;o)

Busted Knuckles
Dec 3rd, 10, 04:47 AM
George, I have a couple of pairs of 702's that look a lot like yours. VortecPro will probably correct me, but I'd think that if the chambers were unshrouded correctly, they should flow fairly close to open chamber heads.

The 820 has very little quench and the 702 actually has two quench pads - one behind/under the spark plug and one in the conventional spot.
Kinda like what Mopar is calling a "hemi" on their new stuff.

RSSSfanatic
Dec 3rd, 10, 05:33 AM
Hmmm, so based on what is being said about lack of quench on the 820's, I am drawing the conclusion that I should stay away from these for my marine engine. Perhaps they contributed to the detonation that busted a half inch chunk off the ringland on my forged SpeedPros. :eek:

vortecpro
Dec 3rd, 10, 06:45 AM
Hmmm, so based on what is being said about lack of quench on the 820's, I am drawing the conclusion that I should stay away from these for my marine engine. Perhaps they contributed to the detonation that busted a half inch chunk off the ringland on my forged SpeedPros. :eek:That head didnt cause that, thats a butted ring.

vortecpro
Dec 3rd, 10, 06:46 AM
Well I certainly wasn't aware that the 820 Quench was virtually none existent. I learn something all the time here at TC and enjoy a good exchange of info - Great presentation Mark ;o)Thanks but Carl actually presented it.

vortecpro
Dec 3rd, 10, 07:00 AM
George, I have a couple of pairs of 702's that look a lot like yours. VortecPro will probably correct me, but I'd think that if the chambers were unshrouded correctly, they should flow fairly close to open chamber heads.

The 820 has very little quench and the 702 actually has two quench pads - one behind/under the spark plug and one in the conventional spot.
Kinda like what Mopar is calling a "hemi" on their new stuff.You know I couldnt say one way or the other how those closed chamber heads can be made to work, its my opinion that the big oval is on the big side for a street 454, mathmatically, and performance wise. I have built a flattop 454 with a closed chamber head, 230 @ .50 hyd cam, all I can say is my 9.1 peanut port 467 raped it in every way even with a smaller cam.

RSSSfanatic
Dec 3rd, 10, 08:57 AM
That head didnt cause that, thats a butted ring.That's a great point! The #3 piston was busted exactly the same way. This was #2 on the opposite bank. It had not occurred to me, but it is becoming more and more apparent that the guy who built this engine did not know what he was doing in regards to a marine engine. I do recall him checking with Speed Pro to make sure there was sufficient piston/cylinder clearance for a marine engine, and he did set that part of it up pretty loose. Damn thing always sounded like a diesel idling in there from all the piston slap. I guess it is not out of the question that he set the gap on the top compression ring too close for a marine engine. I will have to pull one of the rings to see what the end gap checks out to be.

RSSSfanatic
Dec 3rd, 10, 09:00 AM
You know I couldnt say one way or the other how those closed chamber heads can be made to work, its my opinion that the big oval is on the big side for a street 454, mathmatically, and performance wise. I have built a flattop 454 with a closed chamber head, 230 @ .50 hyd cam, all I can say is my 9.1 peanut port 467 raped it in every way even with a smaller cam.I have a complete, low hour 7.4L Gen VI 454 on my stand with the peanut port heads on it. Would you go in this direction for a marine engine rather than the large oval heads? The max RPM will probably be 5500-5800 RPM, although the conventional wisdom on most of the marine circles is to use the large oval heads. Hell, Merc has been using the rectangular port heads on all of their high performance products for years. Now my head is starting to hurt! :confused:

badbilly21
Dec 3rd, 10, 10:43 AM
tons of good info here!!!! too much is always better than not enough. i am building a 496, got a set of 781's, cast high rise intake, q-jet carb. looking for around 10 to 1 pump gas motor. it is a street car. want it to look like an ss clone. i appreciate all the help guys. i figure a good 496 should be around 500 hp. we will see. ill use the 781's til i find a better set for the right price.

Lonnie P
Dec 3rd, 10, 06:03 PM
What about 291 heads?
I have a ported set with 2.3" valves. Chambers were unshrouded around valves... not sure of the flow though.

http://www.lonniesperformance.com/68camaro/034.jpg