77 440

[newport440]

Hey guys got a question. I have a chance to buy a set of Stealth alum heads with 74 cc combustion chamber. They will be going on a 1977 440 which looks stock piston are down in the hole pretty far. My question is will these make a big difference in my compression ratio. I'm a little unimpressed of the power my motor makes and was just wondering if these would help. Any advice would be great thanks

 

[1978 NYB]

If it's closed chamber heads it will raise the compression about a full point.

 

[Badvert65]

I thought the Stealth heads were 84cc.

 

[commando1]

80cc as cast, same as smogger heads.

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[has300]

I've always been told switching to aluminum heads is the same as lowering the compression one full point. (ie) 10.0 to 9.0. sucks out that much heat.

 

[commando1]

Bullpuckey!!!!!
Material make zero difference in volume.
CR is based purely on volume.

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[Catfish]

I've always been told switching to aluminum heads is the same as lowering the compression one full point. (ie) 10.0 to 9.0. sucks out that much heat.

Aluminum heads allow you to run the same octane fuel as an engine with roughly 1 point less compression. i.e., you can run 1 point higher compression on your pump gas engine if you have aluminum heads.....give or take.

 

[heyoldguy]

Interesting reading refuting common misconceptions about iron vs aluminum.

http://www.carcraft.com/techarticles/ccrp_0602_iron_versus_aluminum_cylinder_heads_test/viewall.html

http://www.chevyhiperformance.com/techarticles/83858_iron_vs_alloy_engine_heads/

 

[70bigblockdodge]

Those 452s are close to 90+ cc in most cases and the slugs are down over .100 , I would open up exhaust, change cam ditch lean burn if not done already, buy a air fuel ratio gauge and fix jetting on carb. Will have performance and mpg increase, still be able to run 87 octane with full advance. This can just about all be done for the price of switching to stealth heads and you will see a noticeable increase.

 

[commando1]

Those 452s are close to 90+ cc in most cases and the slugs are down over .100 , I would open up exhaust, change cam ditch lean burn if not done already, buy a air fuel ratio gauge and fix jetting on carb. Will have performance and mpg increase, still be able to run 87 octane with full advance. This can just about all be done for the price of switching to stealth heads and you will see a noticeable increase.

The specs I have show 452's with 84cc.

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[heyoldguy]

Having been cc'ing Chrysler factory iron heads for 40 years now I have yet to find one stock factory big block open combustion chambered head that measured less than 88 cc's. Most are in the 90 cc area and some measure 94 cc.

 

[bajajoaquin]

You two are saying different things. One is quoting specification, and one is describing experience with production pieces. I have no idea what is correct, but just thought I'd point that out before you argue about it.

(Cause let's face it, it's FCBO, you're going to argue about it.)

 

[Catfish]

Interesting reading refuting common misconceptions about iron vs aluminum.

http://www.carcraft.com/techarticles/ccrp_0602_iron_versus_aluminum_cylinder_heads_test/viewall.html

http://www.chevyhiperformance.com/techarticles/83858_iron_vs_alloy_engine_heads/

Interesting in that both tests are non conclusive. The first link even states that they were no where near detonation point even with 91 octane (and running 118 octane)
and on a dyno where detonation is less prevalent than real world.

 

[bajajoaquin]

Having been cc'ing Chrysler factory iron heads for 40 years now I have yet to find one stock factory big block open combustion chambered head that measured less than 88 cc's. Most are in the 90 cc area and some measure 94 cc.

And that makes sense if you think like a factory: what's their main goal? Optimize performance? Nope, minimize complaints. If someone thinks his car isn't fast enough, he'll buy glasspacks. If someone's car detonates under load, he'll bring it back for warranty service.

 

[commando1]

Having been cc'ing Chrysler factory iron heads for 40 years now I have yet to find one stock factory big block open combustion chambered head that measured less than 88 cc's. Most are in the 90 cc area and some measure 94 cc.

There's nothing like real world experience. Thanks. So all this time I've been doing calculations based on faulty data. I feel so dirty now....

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[bajajoaquin]

Commando, no argument? You're such a disappointment.....

Re-reading the original post, he says he found Stealth heads with 74cc combustion chambers. That implies he's not buying new, and they advertise that they have plenty of material for milling. Assuming the numbers in this thread are correct, and the pistons are .100 below deck, and a stock combustion chamer is 90cc, your current compression ration would be 8.9:1. If the Stealth heads have 74cc chambers, your compression ration would be 10.1:1.

For the sake of argument, if the Stealth heads are stock (and remember they have production tolerances of their own) your compression ratio would go up to 9.4:1

So strictly speaking, in answer to your question, yes, the Stealth heads will increase your compression ratio. They will probably also increase your performance. Will they increase your performance more than making other mods suggested for the same money? Don't know. How does that calculation change if you plan on making other mods in the future (like cams, intakes, exhaust)? It probably makes the heads look better. But only you can decide how you want to spend your money.

For the record, I am favorably disposed towards the Stealth heads. My current plan is to buy a set when it's time to rebuild my engine. But I have no experience with them myself.

 

[commando1]

Commando, no argument? You're such a disappointment.....

Heyoldguy has more experience in his pinkie finger than I'll ever have total in a lifetime.
Do a SEARCH on his other posts...

Having been cc'ing Chrysler factory iron heads for 40 years now I have yet...

 

[heyoldguy]

Some information about the Stealth heads that we reported a few years back.

http://forums.moparmusclemagazine.c...40-source-stealth-heads/#13930876179841&8,tss

Yes the Stealth heads will increase the compression but the greatest power increase will come from the better airflow.

Things bother me though, 74cc? The earlier Stealth heads we 84 cc and when they constantly had the head gaskets hanging into the combustion chamber they were change to 80 cc. If they really are 74cc now they must have been milled. If they were milled you may find that your pushrods are too long now. If they started as the early 84cc heads and were milled to 74cc that would have been about .060" worth of milling. Then the intake surface of the heads would have needed to be milled .075" so the intake ports and bolt holes would still line up with the intake manifold.

Best to make some further inquiries before purchasing those heads.

 

[newport440]

So would I be better off running a set of 915 heads They at closed combustion camber right ? I already put a Hughes cam in her and am running high flow exhaust manifolds with a holley intake and 750 carb

 

[commando1]

452 heads with dome pistons might get you to around 10:1