I have a tpi 350. As far as i know the internals are stock. The runners are slp. I was thinking of getting higher flowing heads. But then i was thinking of getting the l98 aluminum vette heads and having them ported. But can't I get my stock heads ported the same as I was going to get aluminum heads ported. They were both on the same motor. What is the difference other than the fact that one is aluminum and the other is cast iron.

 

Well i did see a website that said. aluminum heads to produce more horsepower than cast iron. But will buying the l98 aluminums and having them ported be that much better than having my stock heads ported?

 

It all depends on the money in which you have to spend.
L98 aluminum heads are very economical and very easy
to find at local shops and salvage yards.

however, ull end up spending more money getting the
car to perform the way you want..

In my opinion, take the time and money to research
aftermarket aluminum heads that have be proven already.
(AFR or Trickflow, even edelbrock)

As for the question up above, aluminum heads will
always perform better because they stay cooler, than
iron .. but they are alot more prone to cracking and
warping if abused.

there is no real difference in the iron and aluminum
model other than the cast material, everything else
should be the same.

 

The aluminum heads have 58cc chambers, the iron have 64cc. That will boost your compression ratio noticeably.

 

I don't understand that statement.

That's not exactly true. Aluminum transfers heat more rapidly than iron, true, but that doesn' t mean they stay cooler. It does mean there is more energy loss (heat = energy), therefore aluminum actually performs slightly lesser, not better, than cast iron.

Also true, but only the static compression ratio. See paragraph above. The net result is the aluminum-headed engines need a higher static compression ratio to produce the same power as an all-other-things-being-equal iron-headed engine.

Bottom line: Aluminum weighs less than cast iron. There's your performance increase. Getting more power out of aluminum Vette TPI heads requires good porting work. They also don't tend to benefit from as large of valves as cast iron 083 castings will (diminishing returns thing).

 

A distinct advantage of the Aluminum head is the ability to utilize a higher compression ratio without inducing pre-ignition or detonation by allowing for a more rapid dissipation of heat to the cooling system. That said with todays fuels the aluminum heads will offer a greater performance at a higher compression ratio than Iron heads. Using fuels with higher Octane raitings negates the aluminum advantage visa vi the heat=energy. so the real question is how much compression do you plan to run and do you want to drive the the airport every morning to fill up your car on avgas?


Just a thought (weight advantage aside folks we all know aluminum is lighter than Iron)

J

 

Again, backwards thinking. Yes, you can use higher static compression ratios with aluminum heads, but the very reason you can also means you need to run higher CR to obtain the same power output (all other things being equal).

 

Two more things to think about. The corvette 113 head has a "d" shaped exhaust port that is .100 higher than stock cast heads which can create a problem with manifolds or certain headers. Also you will have to convert your egr operation as the corvette heads don't have the heat passage.

 

Again, backwards thinking. Yes, you can use higher static compression ratios with aluminum heads, but the very reason you can also means you need to run higher CR to obtain the same power output (all other things being equal).


I toitally agree with you however my point was to outline that fuel has a bigger part to play than head material. All simantics aside I agree that the advantages and disadvangages of both are proportional and when combined with induction and cam selection some of your higher HP cams tend to require higher compressionn ratios leaving the aluminum head at a slight advantage on todays fuels over an equal iron head. However this discussion could go miles and miles into advanced tuning cam selection fuel pressure advanced fuel injection(the list goes on).

so short and sweet , I agree that both havd their advantages and disadvantages.

Thanks
J

 

whats the casting number on the aluminum L98 heads?

 

last 3 #'s are 113

 

"What is the difference other than the fact that one is aluminum and the other is cast iron."


Correct me if I am wrong ( which is often), didn't the aluminum corvette l98 heads retain the pre-87 intake bolt pattern? Thus using the pre-87 tpi intake?

 

That is correct.

58cc chambers, no exhaust cross-overs, D-ports on the exhaust, '86-earlier intake mount bolt pattern.