400 SBC COMPRESSION RATIO [Archive] - Team Camaro Tech

: 400 SBC COMPRESSION RATIO


DTL504
Dec 7th, 02, 06:26 PM
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?


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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.

40Coupe
Dec 7th, 02, 06:28 PM
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.

CamaroNOTcamero
Dec 7th, 02, 08:38 PM
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 http://www.camaros.net/forum/biggrin.gif

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.

DTL504
Dec 8th, 02, 05:06 AM
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 23º 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...

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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.

[This message has been edited by DTL504 (edited 12-08-2002).]

onovakind67
Dec 8th, 02, 05:57 AM
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.

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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

CamaroNOTcamero
Dec 8th, 02, 05:58 AM
"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 23º 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.

DTL504
Dec 8th, 02, 06:20 AM
CamaroNOTcamero
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.

RockyMtnRacer
Dec 8th, 02, 08:18 AM
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.

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Scott
'69 400SB, Richmond 5-speed
www.geocities.com/sdenning1 (http://www.geocities.com/sdenning1)

CamaroNOTcamero
Dec 8th, 02, 09:23 AM
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.

DTL504
Dec 8th, 02, 12:14 PM
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

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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.

Eric68
Dec 8th, 02, 01:15 PM
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.

run-a-way-69
Dec 8th, 02, 04:42 PM
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

CamaroNOTcamero
Dec 8th, 02, 04:53 PM
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.

Lonnie67
Dec 8th, 02, 07:27 PM
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, strip/street 410sb 11.63 @117.6
67 Camaro, daily driver 388 12.07 @112
website (http://www.geocities.com/lonnie67_1966/index1.html)
SHUT UP AND RACE!

boodlefoof
Dec 8th, 02, 07:39 PM
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.

CamaroNOTcamero
Dec 8th, 02, 08:21 PM
Lonnie, I was told By Ed Bigley that to make up for the change it head material (from Iron to aluminum) would REQUIRE 3 points more compression (from 9:1, to 12:1) that seems more then Earth shattering to me.
While i havent tested this myself, and doubt that i will get the chance to, i Do believe what Ed teaches me, as EVERYTHING has been correct so far, and i ask LOTS of questions http://www.camaros.net/forum/biggrin.gif
Why give up that kind of power over 35lbs in weight savings, i think you would agree with me that if you added 3 points more compression to your car, then added 35lbs to your car, overall it would still be going a hell off a lot quicker if it hooked up!
What isnt understood by many is that essentially the head manufacturers are there to MAKE A PROFIT, and since Aluminum is much easier to cast that helps them make more of a profit, especially since they can write off the down side of aluminum (less power) with saying that you can now use more compression that they will still be selling plenty of cylinder heads.

Why i dont doubt that your aluminum headed motor is very quick, since 12.07 is very quick no doubt about that!

If you really NEED aluminum the 1st heads i would be looking at would be the ones that Boodle has on his engine, Pro Topline, i'm quite impressed with the numbers they have and small runner volume that they get them out of, out of the box.

Eric68
Dec 9th, 02, 04:28 AM
<BLOCKQUOTE>quote:</font><HR>Originally posted by CamaroNOTcamero:
[B]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.

B]<HR></BLOCKQUOTE>

CNC - you need to switch to decaffinated coffee or something. Seriously. You have over 3200 posts here and God knows how many over at Team Chevelle and still have not completed your first engine build. Get away from the computer, get off the phone with Ed, get out in the garage, and do some wrenching buddy.


DLT 504,

I have only seen 1 test that compared iron to aluminum in a real apples to apples dyno test. It was done by HRM about a year ago with identical World castings. The ONLY difference was that the aluminum head was CNC machined which added (according to HRM) about 10 cfm flow. The aluminum heads made like 1 HP more than the iron and that was with the same compression ratio. They were THAT CLOSE. If you had compared as cast runners in both heads and bumped compression up a point on the aluminum head motor, they would have made identical numbers - and MAYBE the aluminum head engine would have come out on top.

The OEMs all use aluminum heads now days and they spend millions of R&D Dollars on studying this kind of stuff every year. I think they know something about the subject. Its not cheaper than cast iron either. Its lighter for better fuel economy, easier to machine (easier to repair for us) and YES they LOOK BETTER. There is nothing at all wrong with that.

The Sportsmans have a weak exhaust port out of the box, so by the time you pay to have that fixed you might as well have bought some good aluminum heads that didn't need any fixing. Then once they are ported (if you port the intake runners too) you have intake runners with ports that are a bit bigger than the 200 cc's you intended. If you want bigger runners and more flow just by the AFR 215's.

I'm not saying that iron castings are bad. They aren't. I've used the Sportsman II heads before on a couple 355 engines and they worked well. The Pro Toplines have better flow numbers than the Sportsmans and a much better exhaust port if you REALLY want an iron head. Then there are the Dart Iron Eagles - better flow numbers again than the Sportsmans.

Lonnie67
Dec 9th, 02, 06:32 AM
So if I build my 383 with iron heads and 6.5:1 compression, it will run the same? How about 8:1, I don't think so.

I do agree that iron heads make more power than an equal aluminum head, but the amount is being exaggerated.(sp?)

My buddy has a 383 very similar to mine, his compression is 9.4, mine is 9.5. He has SR Torqers with bowl porting, my Edelbrocks are out of the box. His race weight is 3850, he mph's at 99. When the outside temp is 110+, I can still run 87 octane, he has to run 91.

My race weight is 3350, I mph at 112.
Port design is more important than material.

I didn't buy my heads for the weight savings or because they are aluminum. I bought them for the quality of the ports compared to several out of the box iron heads I looked at, and cost. That was more than 4 years ago.

CNC, the more you try to force feed us your beliefs, the more resistance you are going to get. I wasn't aware that you don't have an engine, is that true?

Lonnie



------------------
67 Camaro, strip/street 410sb 11.63 @117.6
67 Camaro, daily driver 388 12.07 @112
website (http://www.geocities.com/lonnie67_1966/index1.html)
SHUT UP AND RACE!

Tracy Focht
Dec 9th, 02, 07:35 AM
Eric, here is a copy of that iron versus aluminum World heads shootout...

There was a “what-if” question addressed a few months ago in our Performance Q&A column that piqued our interest. The question was simple: If you had a set of iron and aluminum cylinder heads that were as identical as iron and alloy can be, which would make more power? Even the most ardent aluminum head supporter will admit that iron heads have the power advantage because aluminum transfers too much heat out of the chamber during combustion. So the real question is “How much horsepower?” Those are the kinds of questions we live for, so CHP decided to find out. The plan, because we’re such modest gearheads, was simple. Bolt a motor together, stuff a big cam in it, and then use the short-block to test iron versus aluminum to really nail down the difference. Then there’d be one less question in the world to ponder. Or so we thought. The Heads Before we began, we decided to look around for a pair of small-block heads that were identical in port size, shoe size, airflow, and valve diameters. Our search took us to World Products where the folks who crank out dozens of iron castings an hour revealed that they offer a pair of Motown 220 heads in both iron and aluminum that work for our comparison. The original Motown heads initially appeared in iron with 220cc intake ports, 2.055/1.60-inch stainless steel valves, and 64cc combustion chambers. The heads are available with either 1.437- or 1.550-inch valvespring diameters, with the larger springs intended for mega-lift roller cams. There’s also a choice of 67cc or 72cc chambers. Both Motown 220 heads are machined for both perimeter and centerbolt valve covers. The Motown 220 Lite aluminum version is almost a clone of its cast-iron cousin with the addition of CNC-ported combustion chambers. The aluminum heads also differ in that they use a 14mm gasket-style spark plug while the iron versions employ a 14mm tapered seat plug. These large-port heads are best matched with larger-displacement small-blocks like 383ci, 406ci, or 415ci engines that can really move some air. Given this, we decided to construct a 383ci small-block for our test. The 383 is a stroker version of a 350, using a 400ci small-block, 3.75-inch stroke crank in a 0.030-over 350 block. With the 64cc chambers, a 0.005-inch negative deck height, and a 0.039-inch Fel-Pro 1014 head gasket, the compression computed to 9.9:1.

The Engine To ensure this effort came together quickly, we called upon our trusty engine-builder Ed Taylor of Ventura Motorsports to assemble the small-block. Starting with a properly relieved, bored, and align-honed block, ably machined by Pete Christensen of Jim Grubbs Motorsports, Taylor chose to drop in an interesting rotating assembly from Scat Industries. Scat has recently produced a kit offering an internally balanced cast-iron crank matched with a set of 4130 steel, 6-inch I-beam connecting rods and a set of SRP forged aluminum pistons. Chevy originally built the 400 crank as an externally balanced unit to reduce the size of the crank counterweights. This requires a more expensive externally balanced harmonic balancer and flywheel when building a 383ci small-block. Scat moves the weight around to create a neutral balance package that allows the engine-builder to use a standard 350 balancer and flywheel/flexplate and also to avoid using expensive Mallory metal to balance the rotating assembly. Taylor combined these parts with a Milodon oil pump and pan assembly to finish off the bottom end, sealed with a slick one-piece Fel-Pro oil pan gasket. Even though this is a comparison test, we wanted to see how much power we could squeeze out of this 383, so we added a healthy Crane mechanical roller camshaft. With 232 degrees of duration at 0.050-inch tappet lift and 0.525-inch intake lift, we estimated this would help the peak horsepower while still building a respectable torque curve for street use. The remainder of the valvetrain is also all Crane: Gold 1.5:1 roller rockers, Crane-spec’d roller style dual valvesprings, steel retainers, hardened pushrods, and a Crane dual roller timing set. All of this fits under a set of World Sportsman II cast-aluminum valve covers. For the intake side, World sent one of its dual plane manifolds that we felt would work best as a street combination when teamed with a Holley 750-cfm mechanical secondary carburetor. A Moroso DuraFire HEI distributor and a set of Moroso wires light the spark. Finishing the engine off is a neutral-balanced 6.6-inch diameter harmonic balancer from Summit Racing and a set of Hooker 1¾-inch headers feeding into a pair of 2-½-inch Borla stainless mufflers. The Test Taylor assembled the engine, pressure-lubed it, and set it on Ken Duttweiler’s dyno. After a suitable break-in and warm-up period, it didn’t take long before we were making steam. The first test was with the iron Motown 220 heads to ensure that we didn’t have a problem with detonation on 91-octane pump gas with the iron castings. Taylor idealized the timing at 37 degrees of total timing and then started yanking the dyno handle.

He made a few tweaks to jetting and timing, but the power didn’t really change very much, cranking out 449 lb-ft of torque at 4,200 rpm with a horsepower peak of 407 at 5,600 rpm. While these numbers are powerful, we were only halfway through the test. Now it was time to do the head swap to see where the differences would come in. While Taylor was swapping heads, the bench-racing discussion centered on where the power difference would occur. Some estimated that the entire power curve would be down ever so slightly while others postulated that there would be less of a difference at higher engine speeds because the heads would have less time to transfer the heat. Some engine-builders plug as much as another full point of compression in their aluminum-head engines compared to iron head engines. Not everything goes the way you expect it, however. Soon after we began wailing on the aluminum head combo, it was clear the aluminum version made more power! Comparing the best power curve from the iron heads against the aluminum heads produced a significant difference, so we decided to take an average of three runs from each combination to create the two curves produced here. These runs were the result of several tests to optimize the timing and jetting. The aluminum heads made an average of 8 lb-ft of torque more than the iron heads throughout the entire curve, which contradicts our theory that iron heads should produce more power. For this to work, the theory assumes the heads are identical. There was a slight difference in flow between the iron and aluminum castings when Todd McKenzie flow-tested both sets of heads. This demanded some minor tweaking on the aluminum heads to bring them within a few cfm of the iron. We attributed this slight flow discrepancy to a minor lip created when the hardened steel seats are driven into the aluminum heads. But after McKenzie’s tune-up, both sets of heads flowed very similar numbers. The other significant difference between the iron and aluminum heads was the CNC chamber machining on the aluminum Motown heads. The CNC’d chambers are the same size as the iron heads, but CNC work did reshape the chamber slightly. Chamber shape is a difficult item to quantify, so it’s tough to state with any certainty that the chamber mods contributed to the difference in power, but this appears to be the most likely explanation for the aluminum head power increase. Conclusion We still believe that iron heads have the ability to make more horsepower than aluminum heads, but we also think that the difference is probably less than an average of 5 lb-ft of torque. Given this, the power difference is slight enough that other variables can contribute as well. In this case, the two sets of heads were not identical enough to reveal the basic inherent advantage of the iron heads.



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383 Speed-O-Motive stroker kit with Holley 750DP, RPM intake,MSD6a box,World Products Sportsman II heads, ported and polished with 2.02/1.60 valves,64cc,TRW forged pistons with 10.7:1 compression, Comp Magnum 294s solid cam,Crane pushrods, Comp Cam 1.6 full roller rockers,MSD Pro Billet,ATI damper, 40 series Flowmasters, 4.11 gears with TH350 and Hughes 3000 stall.

CamaroNOTcamero
Dec 9th, 02, 10:24 AM
Ok, Keep using your ALUMINUM heads http://www.camaros.net/forum/biggrin.gif
I've said it before but i believe i'm done caring.

Lonnie,
Eric likes to exaggerate, I work in an autotive machine shop part time, and spend MUCH time at the track learning from Stock Eliminator Racers, Ed Bigley, and both owners of the BSE small blocks, amongst many others.
I take there advice, becuase they're the ones at the track, proving what they know.

If you dont want to listen to me, fine, dont Bull**** though. I can see right through it. If your aluminum heads are so much better then why arent they running up there with Ed's Big Block and the BSE small block with just as streetable components.
Thats the real proof to me!

Lonnie67
Dec 9th, 02, 11:10 AM
<BLOCKQUOTE>quote:</font><HR>Originally posted by Lonnie67:
So if I build my 383 with iron heads and 6.5:1 compression, it will run the same? How about 8:1,

<HR></BLOCKQUOTE>

So does that mean you're not going to answer my question?

I don't question that small or big BSE runs as claimed, I never said my aluminum heads are better than ported BSE iron, if you'd actually read my posts, you'd know that. You can't compare 170cc to 200cc ports. I think a comparison between SR's and RPM's is valid.

Just the porting on my Bowtie heads cost $600 by a reputable head porter 17 years ago. I know it is more now, that is my point.

Exactly what BS do you "see" through? I'm not asking these questions to be a jerk, I really want to know.

Lonnie



------------------
67 Camaro, strip/street 410sb 11.63 @117.6
67 Camaro, daily driver 388 12.07 @112
website (http://www.geocities.com/lonnie67_1966/index1.html)
SHUT UP AND RACE!

Eric68
Dec 9th, 02, 11:24 AM
Thanks Tracy http://www.camaros.net/forum/smile.gif I was thinking it was HRM for some reason - maybe thats why I couldn't find it.

CNC - 3 points compression change alone is worth roughly 56 HP according to DD2k when going from 9:1 to 12:1 on a run-of-the-mill 400 HP 383 small block. Now who's exaggerating?

travis
Dec 9th, 02, 12:06 PM
Since when is a 4500-5000 stall, 4.56 gears, and a 'glide considered truly streetable??? http://www.camaros.net/forum/rolleyes.gif

I don't even want to get started on this...

CamaroNOTcamero
Dec 9th, 02, 12:14 PM
Hmm, We could ask the Big guy himself, but Oh wait he got Kicked off the board!
10.85 with a 1.45 sixty foot is not exaggerating,
I've yet to see a comparible Aluminum headed combo do that! With exception to 40 coupe's combo (That's nearing it!), but his is a stroker.
So yeah maybe there is a difference of about 56HP when compairing to of the same combos with the difference being the cylinder heads.
Just becuase i havent seen Any 10:1 355ci small blocks with a flat tappet cam in the high 10's with a 1.45 60ft time.


Funny that they never figured out what a true comparison is, compaire to similar heads, where one has the CHAMBERS WORKED!
Why did they Work the IRON chambers to make everything ACTUALLY EQUAL.

407 at 5,600 rpm It took them 220cc heads, a Solid ROLLER cam and 383 cubic inches to make 407HP? Seems pretty lame to me!
Sure now that they didnt do any tweaking to the aluminum Engine that they Forgot to do to the other engine???
I guess we'll never know,
What i do know is that the Iron headed combo's that I know of Work, they Work Well and they're streetable, so I've done and said my Peice http://www.camaros.net/forum/biggrin.gif
I guess its for you guys to decided!

Eric68
Dec 9th, 02, 02:14 PM
<BLOCKQUOTE>quote:</font><HR>Originally posted by CamaroNOTcamero:
Hmm, We could ask the Big guy himself, but Oh wait he got Kicked off the board!
10.85 with a 1.45 sixty foot is not exaggerating,
I've yet to see a comparible Aluminum headed combo do that! With exception to 40 coupe's combo (That's nearing it!), but his is a stroker.
So yeah maybe there is a difference of about 56HP when compairing to of the same combos with the difference being the cylinder heads.
Just becuase i havent seen Any 10:1 355ci small blocks with a flat tappet cam in the high 10's with a 1.45 60ft time.


Funny that they never figured out what a true comparison is, compaire to similar heads, where one has the CHAMBERS WORKED!
Why did they Work the IRON chambers to make everything ACTUALLY EQUAL.

407 at 5,600 rpm It took them 220cc heads, a Solid ROLLER cam and 383 cubic inches to make 407HP? Seems pretty lame to me!
Sure now that they didnt do any tweaking to the aluminum Engine that they Forgot to do to the other engine???
I guess we'll never know,
What i do know is that the Iron headed combo's that I know of Work, they Work Well and they're streetable, so I've done and said my Peice http://www.camaros.net/forum/biggrin.gif
I guess its for you guys to decided!<HR></BLOCKQUOTE>

Just admit you are wrong for once and get on with life. CNC chambers ARE NOT worth 56 HP over as-cast, iron heads ARE NOT worth 56 HP over aluminum and you know it. The aluminum vs iron comparison done in CHP is valid testing so don't try to discredit it just because it doesn't support your theory. Instead maybe you could produce some other test that supports your idea. Maybe I should get pistons with the ceramic coating to reflect heat and make another 56 HP. http://www.camaros.net/forum/rolleyes.gif

There's no doubt Ed has put together some good combos. BUT it's the COMBO (including the chassis) that works, and to say its the iron heads does a disservice to Ed's hard work finding and tweeking a combo that works together. I'm sure Ed could build an aluminum head combo just as good as his current iron head small block if he wanted.

BTW Any particular reason you insist on arguing so much? I'm sick of your argumentative posts and wish you'd quit bragging about someone else's accomplishments. You ain't Ed.

ps. What does your combo run?

pdq67
Dec 9th, 02, 02:45 PM
You know, one thing that people seem to overlook when comparing heads is that weak ports CAN be crutched with a GOOD cam pick!!

You can add duration and/or lift to even out flow rates intake to exhaust if so desired so if you come across a low priced bargain in a set of not the best/newest-high-zoot heads then take advantage of the low price deal and tune them using a good cam pick!!! pdq67

PS., I think you can coat the water passages of aluminum heads with baked on waterglass, (i.e., sodium silicate), to keep them from bleeding too much tewmperature out of the chambers, but may be off here???

Just coat, harden and try and coat again until you get what you want!

69RS/SS350
Dec 9th, 02, 03:23 PM
CNC, remember why Ed got kicked off the board? He started flame wars, I think you may be headed in the same direction!

CamaroNOTcamero
Dec 9th, 02, 03:35 PM
Ok dude, this time why dont YOU prove that your right?
I want some numbers.
BTW, my appologies for not making enough money to quickly build up my engine. But then again that gives me plenty of time to Think things out.
Eric, Ed's not doing Himself a disservice by using Iron Heads, IMO. I think (wait i KNOW) they work well!

Argue all you like, that "comparison" dyno pull doesnt mean a thing! One pair has Worked chambers, PERIOD!
Eric, i really didnt want to make this personal, so i'm going to stop posting on this post.
I'll Agree to disagree.

Lonnie67
Dec 9th, 02, 04:47 PM
The power figures in that article are pretty lame, but they are just as lame for the iron heads though. Someone missed that part I guess. It just supports what I said earlier, port design is more important.

If anyone can tell me where to buy new complete iron heads for $900 that will give me 56 more HP, I'll go buy them tomorrow.



------------------
67 Camaro, strip/street 410sb 11.63 @117.6
67 Camaro, daily driver 388 12.07 @112
website (http://www.geocities.com/lonnie67_1966/index1.html)
SHUT UP AND RACE!

Eric68
Dec 9th, 02, 05:06 PM
never mind.

[This message has been edited by Eric68 (edited 12-09-2002).]

1968camaro123
Dec 9th, 02, 07:44 PM
Guys,
So, is the conclusion that iron heads will make slightly more power given the same circumstances?
I have a 406 with a set of Turbo GM heads that have been heavily ported and polished with 2.08, 1.66 valves. Would I see a huge increase with say a set of AFR 210's?
Thanks,
Donnie

run-a-way-69
Dec 10th, 02, 05:45 AM
I opened a new topic. Heads, Iron vs Aluminum -- Myths & Facts I hope this puts an end to the bickering. George

DjD
Dec 10th, 02, 07:32 AM
CNC - What's up with the agressive approach? I'm not going to comment on alum vrs iron or rect vrs oval, I have opinions but for now that's not the issue. The issue is the way your forcing your (dare I say Ed's) views down peoples throats. Say what you have to say, post it and let others decide for themselves. This actually goes for everyone here as it takes 2 to tango.

CNC you are a rookie, (that's not a slur or put down, it's how folks get started) your posting history is here for all to see. One of the things you are doing goes against the grain of everything your mentor stands for. That is speaking from personal experience and not second hand information.

Let's move forward and not regress to some places we've been in the past!!

Lonnie67
Dec 10th, 02, 09:34 AM
68Camaro123, what is your combo and what does it hit now?


------------------
67 Camaro, strip/street 410sb 11.63 @117.6
67 Camaro, daily driver 388 12.07 @112
website (http://www.geocities.com/lonnie67_1966/index1.html)
SHUT UP AND RACE!

CamaroJSU
Dec 10th, 02, 12:23 PM
Litte change of pace, with the proper set up is 10.2:1 in a 400 to much compression for Nos. Maybe anything under a 100 shot. Just your thoughts. Thanks

Tracy Focht
Dec 10th, 02, 01:29 PM
<BLOCKQUOTE>quote:</font><HR>Originally posted by CamaroJSU:
Litte change of pace, with the proper set up is 10.2:1 in a 400 to much compression for Nos. Maybe anything under a 100 shot. Just your thoughts. Thanks <HR></BLOCKQUOTE>

Nope...I plan to have 10.5:1 with my 406, and plan to spray 125 shot......

------------------
383 Speed-O-Motive stroker kit with Holley 750DP, RPM intake,MSD6a box,World Products Sportsman II heads, ported and polished with 2.02/1.60 valves,64cc,TRW forged pistons with 10.7:1 compression, Comp Magnum 294s solid cam,Crane pushrods, Comp Cam 1.6 full roller rockers,MSD Pro Billet,ATI damper, 40 series Flowmasters, 4.11 gears with TH350 and Hughes 3000 stall.

68rs406
Dec 10th, 02, 07:38 PM
<BLOCKQUOTE>quote:</font><HR>Originally posted by 1968camaro123:
Guys,
So, is the conclusion that iron heads will make slightly more power given the same circumstances?
I have a 406 with a set of Turbo GM heads that have been heavily ported and polished with 2.08, 1.66 valves. Would I see a huge increase with say a set of AFR 210's?
Thanks,
Donnie<HR></BLOCKQUOTE>
have you cc'd or flowed those heads of your's? like stated above, it does matter what your combo is, but i will tell you a 406 loves a fairly large cam, and good flowing, bigger runner heads, such as those afr 210's. remember, those are big block cubic inches. and as far as 10.5:1 being too much compression for nitrous, no way. i know several guys that have well in excess of 11:1 w/ 406's that run 200-250 horse shots with no problem. just make darn sure your fuel system is up to it. heck, i built my motor for nitrous, not planning on regular use but wanted the option, and its 11.5:1. and i'm not worried at all. hope that helps

1968camaro123
Dec 10th, 02, 08:39 PM
Lonnie,
It's a 406 small block with the above heads(steam holes drilled), comp solid cam .550 lift. 10.5 to 1 CR, victor jr. intake, holley 800 double pumper, forged internals, shot peened rods. Anything else just ask...I'm also running a 200 shot. It's in an el camino right now that runs 11.70's on the motor and and about 10.6's on the bottle so that'll be about 11.5's in the camaro and 10.4ish on the spray.
Thanks,
Donnie