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 in 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 identically. 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, the 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.

 

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.

I have a 69 camaro with 396/375 block with 990 heads. I'm not sure what can they have in this motor.
Can someone give me some advice on this combination and if there is anything I should change while I have this motor out. Also it's a 4 speed car with 3.73 rear. I was thinking of doing can and lifter swap but could use some advice on cam selection as well.

 

Steve'll take care of you, but don't forget 074's.

Now with Lunati solid roller and shaft rockers.

 

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.

 

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???

 

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!

 

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.

 

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.

 

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

 

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?

 

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.

 

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

 

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.

 

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.

 

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)

 

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

 

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.

 

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.

 

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.

 

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:

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** .

 

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:

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** .

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.

 

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.

 

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!

 

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.

 

It looks like the 702s are the answer for your piston combination.

 

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.

 

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?

 

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.

 

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?

 

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. I would like to stay around 8.75:1 so I can safely run 87 octane fuel.

 

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?

 

I guess I'll just have to CC mine myself to settle it.

 

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"! 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?