400 SBC COMPRESSION RATIO - Team Camaro Tech
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post #1 of 38 (permalink) Old Dec 7th, 02, 05:26 PM Thread Starter
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What's the best way to achieve a moderate compression ratio around 10:25:1 on a 400 SBC? Is it better to use flat top pistons and a larger combustion chamber (74cc) in the head, or to use heads with average-sized combustion chambers (64) and dished pistons?


------------------
DTL504
"COMING SOON SBC 406"
84 Z28 Camaro, 2 Seater Convertible, w/283 bored 80 over,flat top pistons, 2.02/1.60 Camel Hump Heads 64cc (3782461), Blueracer Camshaft: Duration 230/230 @.050 Lift 480/480 109 degrees, Edelbrock RPM Maniford, Holley 670 Avenger Carb, Hooker Ceramic Coated 1 5/8 Headers, Pro-Built 700R4 Street/Strip Trans. A.C.T. 3000 T.Q.,
3:73 Limited Slip., Kyb Shocks, Spon LCA and ADJ. Panhard Rod.
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post #2 of 38 (permalink) Old Dec 7th, 02, 05:28 PM
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If it was me I'd stick with a flat top piston and a larger cc chamber. That way if you decide to go with higher compression later it only means a head change.

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post #3 of 38 (permalink) Old Dec 7th, 02, 07:38 PM
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I'd go with the flat tops and the smaller chambers.
I know you want the lower compression ratio, so use the fact that you want a given ratio to your advantage.
Working the heads to unshroud the valves will be an advance to your engine's ability to produce power!
Having those 64cc chambers worked by a professional (a good one, not just anyone) will increase the cylinder head CC, dropping compression down to where abouts you want it, and the Worked chambers will produce more power then the big unworked chambers.
Something to think about.

Dont just aim at a compression ratio ethier, becuase you'll try and cut compression by running more piston to head clearance, get optimal piston to head clearance then work from there.
Destroying the "squish" between the piston and head will produce more chance of detonation, even with lower compression.

Squish is essential to producing turbulance in the air/fuel mixture.
Our Goal afterall is making power

David Vizard is big on mimizing comression ratios, but being focused on optimizing power. Building something in a particular way that may make less compression, but makes enough "extra" power to offset the compression loss, then its a better way to build the engine.

Having less surface area in the combustion chamber is how to keep the power in the cylinder, becuase the more of the flame front the touches the chamber and piston, the more power will be lost to heat transfer through the cylinder heads and piston tops, as well as the cylinder walls as the piston travels down (but you cant help that).
So my personal perspective on things is to build with a given compression ratio "in mind" but try to achieve it with the least surface area touching the flame, optimized "squish", and a well worked chamber.
This will minimize chance of detonation, and therefore allow you to use lower octane gas, which makes more power becuase it burns faster.
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post #4 of 38 (permalink) Old Dec 8th, 02, 04:06 AM Thread Starter
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Here is what i have been planning, let me know what you think about this. With the Pistons and heads I plan on using should have me in a good ball park.

Engine: 400 SBC bored .030 over.
ID# 330817 / 14y139664 / T0508CSU
(4.155 bore X 3.750 stroke)

Crank: Scant 9000 3.750, Internally Balance

Piston: Keith Black (KB125) .030, -7cc 10.25:1cr

Rods: SCAT rods 5.7

Block: Zero Deck: 00.0000

Cam: Grind: XE274H-10, Duration @.050: 230IN / 236 EX, Adv. Duration 274 IN-286 EX, Valve Lift: 487 IN 490 EX, LSA110*. Intake Centerline: 106*, RPM Range: 1800-6000 or Roller Setup

Heads: AFR 195 23 valve angle, 74cc, and drilled steam holes

Intake: Edelbrock RPM #7101

Carb: Holley Street Avenger 770 or 750 (3310)

Harmonic Balancer: ATI super damper

I want this to be streetable/weekend car that might see the track probably 2 a year for tuning. I will use the Tranny and converter in my signature...

------------------
DTL504
"COMING SOON SBC 406"
84 Z28 Camaro, 2 Seater Convertible, w/283 bored 80 over,flat top pistons, 2.02/1.60 Camel Hump Heads 64cc (3782461), Blueracer Camshaft: Duration 230/230 @.050 Lift 480/480 109 degrees, Edelbrock RPM Maniford, Holley 670 Avenger Carb, Hooker Ceramic Coated 1 5/8 Headers, Pro-Built 700R4 Street/Strip Trans. A.C.T. 3000 T.Q.,
3:73 Limited Slip., Kyb Shocks, Spon LCA and ADJ. Panhard Rod.

[This message has been edited by DTL504 (edited 12-08-2002).]
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post #5 of 38 (permalink) Old Dec 8th, 02, 04:57 AM
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That setup should work very well for you. I have a similar iron-head engine in my daily driver and it runs well on 91 octane gas. My cam is a little smaller and even with the higher DCR I get no detonation at all.

------------------
1967 Nova coupe daily driver
406, 10:1, 224 cam, Q-jet, 700R4, 3465# w/driver
11.75 @ 117 thru the mufflers
18 mpg on the road
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post #6 of 38 (permalink) Old Dec 8th, 02, 04:58 AM
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"that might see the track probably 2 a year for tuning."

Since this is the case i seriously doubt that you need an ATI super Damper, while they are a very nice damper, you dont need an AFI approved damper unless your running 10.99 or faster.

Save your money and buy a NEW GM damper, and put timing tape on it. YOu can even get some with the timing marks already in them.

I doubt that you'll have 00.0000 deck height, probably something in the area of
A few thousands of an inch, find out from your machinist what your REAL deck height will be, based on what he likes to bring the height down to.

WHat head gasket thickness will you be using?

Why do you feel that you need "AFR 195 23 valve angle, 74cc, and drilled steam holes", You can get More power by having a set of Sportsman II IRON heads worked by a professional, and well you read what i wrote about the combustion chamber CC.
There are two local to my area racers that are running high 10's on a good day and usually 11 teens with sportsman II heads (ported) on a 355ci SBC engine, that runs 10:1 compression, an RPM intake, a 700DP carb, and a Flat tappet Solid lifter cam!
In a 3100lb camaro.

So thats why i feel that Sportsman II iron heads that have been worked are the best thing for your application.
In the end it wont be inexpensive (I'd be looking in the area of $1500 total cost (thats with heads parts, porting and assembly) when finished, but the results will be Much better ET's then capable of AFR aluminum Out of the box "cnc" ported heads.

On the cam choice, i think that Hydro Roller cams are too expensive for the results they produce.
I personally will be using one, but the Cam and lifters were given to me by my brother as a gift, so cost was no object.
Personally unless you really NEED the hydro roller, and the fact that you dont need to adjust the valves on them except when setting them initially, I'd look into a Solid Flat tappet cam.
The valvetrain will be lighter and Valve float will not be a problem in the upper RPM range of your engine.

I Like the choice on the Intake and Carb (The 3310)! Good choices there.
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post #7 of 38 (permalink) Old Dec 8th, 02, 05:20 AM Thread Starter
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I plan on using Fel-Pro 1014 head gasket or something that will give me a good Quench between .040 - .045. All will not come into play until the machinist have completed the work on the block. Right now im brainstorming the setup and trying to find the right combination of parts that will respond well on the street. Ok I understand the I dont need that damper, however the Price of getting them Sportsman II heads rework will cost more than the AFR straight out the box, correct me if im wrong. I have heard this is the best heads that you can get for street performance. I'm just looking at something to tame all these Cobra Mustangs here in Georgia with the loud exhaust that everyone think is so fast...

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DTL504
"COMING SOON SBC 406"
84 Z28 Camaro, 2 Seater Convertible, w/283 bored 80 over,flat top pistons, 2.02/1.60 Camel Hump Heads 64cc (3782461), Blueracer Camshaft: Duration 230/230 @.050 Lift 480/480 109 degrees, Edelbrock RPM Maniford, Holley 670 Avenger Carb, Hooker Ceramic Coated 1 5/8 Headers, Pro-Built 700R4 Street/Strip Trans. A.C.T. 3000 T.Q.,
3:73 Limited Slip., Kyb Shocks, Spon LCA and ADJ. Panhard Rod.
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post #8 of 38 (permalink) Old Dec 8th, 02, 07:18 AM
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My motor is very similar to your planned combo. Same heads, .040" overbore, and a hydraulic roller CC cam - (HR282) same duration, a bit more lift. (I ran the XE274 in a previous iteration and it's an excellent choice)

My answer to your question is that it really doesn't matter which way you go - as long as you can get the right chamber in the heads you select and set up for good quench.

I had dished pistons in mine and wanted AFR heads (I had run RPM heads with a 64cc chamber previously). The only way to get to my goal of 10.3 to 1 CR with those heads was to mill them quite a bit. I decided to swap to flattops and 74cc AFR heads instead. Came out right at 10.3 to 1 using the same gasket you mentioned and quench came in at .040" to .042".

I had my block decked to zero - which means a thousandth or two in reality. Not all the pistons will end up at exactly the same place so they'll deck it to slightly clear the highest one.

I like the AFR's myself because they'e excellent heads, aluminum is a bit lighter than iron, and the aluminum helps with detonation. I suppose you could also argue that a slightly lower CR and iron heads make a lot of sense for many reasons but I like aluminum heads.

I'm running the Victor Jr intake and 1-3/4" headers but I think the RPM intake and 1-5/8" headers are a better choice for the street for this motor. They will pull the torque curve down and fatten it out very nicely where you'll use it the most.

I recommend ARP main studs and tapping the big water holes in the deck for pipe plugs with a 5/16" hole drilled in them. I put mine in prior to decking the block so they were cut flush. Pipe threads are slightly tapered so when you tap the holes you can use the tap to actually set the depth of the plug depending on how deep you run the tap. Install them with generous amounts of red Locktite and they'll help stabilize the deck and prevent cracks from the nearest head bolt hole.

------------------
Scott
'69 400SB, Richmond 5-speed
www.geocities.com/sdenning1
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post #9 of 38 (permalink) Old Dec 8th, 02, 08:23 AM
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Yes the sportsman II's would cost more, they'd also perform better.
No amount of argueing will convince me that CNC ported aluminum heads will come close to matching professionally ported Iron heads.

So your basically paying $1200 for a 35lb weight reduction.

"I have heard this is the best heads that you can get for street performance." who'd you hear that from?


If your just looking to tame Mustangs (i think they run 12.9 with a GOOD driver at the TRACK, so they wont come near that fast of excelleration on the STREET with a LOUSY driver).
You wont need a hydro roller to tame them, or an ATI damper, or 10.25:1 compression
What you will need is a well thought out, well functioning Combo where all the parts complement each other (i.e. No parts are TOO big).

Take a Good look at Onovakind67's Combo, that will burn any mustang on the street, look at that ET 11.75! with a 224 dur. Cam Iron heads and 3465lb car.
More proof that a well designed chamber has more to do with lowering chance of detonation then the chamber material.

Thats an advertizing Gimick...if you use aluminum heads you can use 1 full point more compression witout detonation...
That doesnt mean that you will make more power, they just realise that most people want to hear Big numbers, they want to be able to say i have 11:1 compression!
What they dont tell you is that to effectively use aluminum you need 3 points higher in compression, so when you want to build a 14:1+ compression Race engine then start looking at aluminum heads.


I have nothing against you, just wanting to help you build what you want, which is a fast streetable pump gas daily driven car with minimal expensense unless neccessary.
I'm being taught the ways of profession builders, by not only Ed Bigley, but a few Division 1 stock eliminator racers (that are winning), and i've posed many a question to those like Jim Hand, and David Reher, amongst others.

If this isnt what your looking for, and its just bothering you, then i wont reply and further.
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post #10 of 38 (permalink) Old Dec 8th, 02, 11:14 AM Thread Starter
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CamaroNOTcamero
I want to hear all comments and recommendation to help me build my engine. I'm not trying to run anyone off this subject. I want the knowledge and everyone experience that will help me build a very good engine. I just trying to make the right decision so that I dont waste any money. I would like to Invest about $3000-3500 on this engine, so thats why im being careful on my selection of parts. I want the buy the best parts for my money.
By all means Please continue to post reply's.
Tanks: David

------------------
DTL504
"COMING SOON SBC 406"
84 Z28 Camaro, 2 Seater Convertible, w/283 bored 80 over,flat top pistons, 2.02/1.60 Camel Hump Heads 64cc (3782461), Blueracer Camshaft: Duration 230/230 @.050 Lift 480/480 109 degrees, Edelbrock RPM Maniford, Holley 670 Avenger Carb, Hooker Ceramic Coated 1 5/8 Headers, Pro-Built 700R4 Street/Strip Trans. A.C.T. 3000 T.Q.,
3:73 Limited Slip., Kyb Shocks, Spon LCA and ADJ. Panhard Rod.
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post #11 of 38 (permalink) Old Dec 8th, 02, 12:15 PM
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Go with the AFR's . . . you will not be disappointed. The difference between aluminum and iron with all other things being equal is very small. The weight savings and detonation resistance of aluminum is nice. You'll probably be able to run midgrade gas with aluminum heads and a tight quench area.

I like your combo with the flat tops and 74cc heads - well thought out and needs ZERO changes IMO. I agree the ATI dampener might be overkill - they sure look nice though.
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post #12 of 38 (permalink) Old Dec 8th, 02, 03:42 PM
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I like the AFR's also. Out of the box they have a max flow of 262CFM on the intake port which equals a horsepower potential of 538HP. If you decide to get them hand ported they can flow up to 300CFM or a HP potential of 616HP. Good luck George
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post #13 of 38 (permalink) Old Dec 8th, 02, 03:53 PM
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Eric, why do you figure BIG flow numbers and aluminum heads are necessary for street performance?
You pass off the ability of iron heads to make more power like its nothing, but everyone is always searching for the newest and best ways to make more power.

DTL504,
What your basically saying is that you want to beat the new mustang's ET, which is a 12.9 or thereabouts.
400 small blocks are an excellent start for a performance engine.
They'll make some serious mid range power numbers if built correctly.
To save money you can use the 1-5/8" headers you have already, the RPM manifold you have already and the carb you have already.
You dont need to drop $1200+ dollars on fancy AFR heads ethier, especially when Pro Topline Iron heads flow better (if flow numbers are a big deal to you) and On top of that its out of a Smaller Port volume, which means higher velocity at low speeds, and also means more Mid Range power!
Or you can do as I suggested and buy Sportsman II's but have them ported by a professional who knows your goals and will help you achieve them, dont lie to the man about your performance goals and he can help you make some serious power in the RPM range that you need it.

You can also pick out a Hydraulic Flat or Solid Flat tappet, instead of the hydro roller which will save you some serious money.
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post #14 of 38 (permalink) Old Dec 8th, 02, 06:27 PM
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CNC, how much more power do you think iron heads make over equal sized, shaped and flowing aluminum heads? Everything else being equal.

The difference will not be earth shattering.

DTL504, the combo you listed will run on pump gas and hit 11's with a proper tune and slicks. When you consider the total cost of the entire engine, an extra $400 is not that much. Porting will probably cost more. If you want to save some money, run a stock ballancer and use TFS 23 degree heads.

If you want to hit 10's spend A LOT more money on axles, rollbar, ballancer, 5000+ rpm converter, 4.88 gears, Sportsman II heads and port work...

For me, part of the fun of hotrodding is building my own combinations or trying to improve on others combo's. Sometimes it works, sometimes not. I don't think I can get myself to copy someones combo exactly. If I can't beat everyone, oh well. That's why I bracket race.

Lonnie

------------------
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67 Camaro, daily driver 388 12.07 @112
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post #15 of 38 (permalink) Old Dec 8th, 02, 06:39 PM
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Just another thought... not about heads. With a 400 engine and the XE274 cam, you are going to have a great powerband! In fact, I think a slightly tighter converter might work better for you in this application. Something along the lines of a 2400rpm stall speed. You are going to be making a good amount of torque starting around 2000rpm. I have the XE274 in a 355 and it really starts pulling hard just a little before 2500rpm.

As for the heads, I am running Pro Topline aluminum heads nad have been very impressed with them. No dyno numbers or track time, but they cost about $150 less than the AFRs and make better intake flow numbers and just about the as good flow numbers on the exhaust side with a smaller runners to boot.
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