Ive decided to stick a Lt1 from s 9c1 crapice into my 94 trans am. Since the only major difference are the different cam and iron heads, i was wondering if it would be better if i used my old aluminum heads instead of the iron ones they come with. Woudl this be a noticable improvement? i was told iron heads will flow better but weight more.

or am i just better of getting pcm tunned to the new cam and heads?

 

I would think it's better to go with the aluminum LT1 heads and have them fully ported. It would be alot more $$ to have the iron heads ported then it would the aluminum ones and like you said there is the weight difference. I'd put the aluminum heads on with the cam and a good tune.

 

I read a test in one of my magazines awhile ago that says the HP gains of Iron heads are not as great as the weight reduction of the Aluminum heads. But if you use Iron heads you don't have to mess with TTY bolts...which is cool...

 

If i decide to to with the aluminum im not looking into porting them, just raplace the iron ones. But if it wont cause to much of a performace difference id want to leave the iron ones on

 

Use the aluminum LT1 heads. They disipate heat better, and they are lighter.

 

Sorry guys, you are all wrong. The iron heads flow much better then the aluminum ones, the only real difference is aluminum allows more compression due to heat dissipation. In every flow test the stock LT1 iron heads flowed much better then the aluminum. Porting the iron heads allowed more material to be removed without sacrificing flow, although aluminum weighs less then iron by about 30Lbs. Iron you can get away with 2.02-1.6 where aluminum can only do 2.00-1.55 without major machine work. Here is a quote from a builder......http://www.automotiverebuilder.com/ar/ar99928.htm

HEADS
There were two heads used on the 350, one aluminum and one cast iron, along with one cast iron head for the 265. GM claimed that the original LT1 aluminum head had a 15% increase in airflow as a result of revised port angles and higher port ceilings when compared to the 1991 L98 head. That was impressive in 1992, but the iron LT1 head that came out in 1994 was even better. It flowed 20% more on the intake side and made more horsepower on the dyno.

 

Thanks alot for the info Grygst76, thats exactly what i was looking for. thanks.

 

That's what I'm here for, good luck with yo
ur project

 

On the "they dissapate heat better" thing. What an engine does is turn heat energy into rotation any heat not used to turn the crank is wasted, so the better heat disapation is wasting more energy. Ever thought of it that way?

On the irons weight hurts performance more than the extra power gains, did you not read the part about the higher flow? 5% more flow plus better thermal efficiency still has to come out ahead. If the heads flowed the same then you might have a valid point.

 

Iron heads wiegh 30 pounds more then aluminum; heat dissipation is critical only to add compression; iron heads hold heat as well.

LT1 Cast Iron Stock 58.0
intake
117.0
174.0
207.0
221.0
exhaust
57.0
107.0
135.0
146.0
150.0
Aluminum LT1
intake60.2
119.1
170.9
198.9
206.4
200.9
exhaust46.1
93.6
123.5
141.2
153.2
156.0

 

If you're trying to make so much power that heat disipation becomes a major point, then spend a few bucks and have the chambers and the piston tops coated by Swain. You could then run more compression and keep the heat inside the cylinders where it can do more work.

 

I really don't think the heat thing is a major issue I just frankly see the belief that pulling heat out of the chamber has to be good as ignorance and try to correct it whenever possible. The physics of what I said are correct right? So why is the heat disapation good?

 

The internal combustion air pump is basically an inefficient mode of generating power. Off the top of my head, obviously a guess, the IC engine is about 35% efficient. The remainder of the 100% goes out the exhaust, into the coolant, friction and oil. The more heat energy that can be contained in the fuel burning chamber, the more of that energy can be utilized to push down the piston. Seal off the exhaust valve (more for durability), the chamber, the exhaust port, and the piston crown. Will these costly mods be cost effective? Probably not, but an improvement in efficiency, nonetheless.

 

I’m going to have to agree and disagree. Yes heat is the energy that drives the piston down, but not all the heat can be used as energy because of the speed of the rotating assembly. So heat disapation is not a waste of energy because the heat can no longer be used for energy. It is there so that the combustion chamber is cooler for the incoming air for combustion.

 

Heat disipation simply allows for more compression with the same amount of timing. The biggest advantage to aluminum heads, IMO, is the light weight of the castings, and the fact that they are much easier to port than iron castings.