Heads

[Intlcutlass]

OK, we all know that the Gen III heads are better than Gen II, (better flow), and somewhere along the way we found out that the Gen II heads are better than the Iron heads say off of a Fiero. But I just found out that the Fiero heads from a 2.8 (HO) had larger valves that the Gen II aluminum heads. Now granted, you could do head work on any of the above. But what made the gen II heads better than the High Output Iron heads from a Fiero???

PS Forgive my ingorance....

[Vegeta]

Fiero heads dont have larger valves than the gen 2 aluminum heads.

[Intlcutlass]

This was the quote I had snagged off the Fiero board, and was not aimed at this board, this was a couple of guys bs'n back n 4rth on the Fiero board.

"No that is incorrect. The 2.8L with fuel injection used in the Cavalier based cars and Pontiac 6000 based cars in the mid 80's were the small valved heads. Only the Fiero and the F-bodies had the H.O. heads. The H.O. heads were first used on the 1983 F-bodies with TBI injection. I think it was 1988 when the Cavalier based cars had 2.8's with aluminum heads and the next year is when the 2.8's were replaced by the 3.1L engines.

 

The cast heads can be ported to supply enough flow to match the stock GenII aluminum heads. (about a 18-20% increase) But the GenIII's have 37% flow. Plus both aluminum heads can be ported for more flow."

 

Now after reading this the second time I realize he is still refering to the Iron heads.

 

Now what I need to know is what is the volume of Gen II heads. The tech at Ross told me that he needed this in order to properly cut my pistons.

And if I do any work to the heads I would assume He would need that too. I WILL GET larger valves and get the heads proted & polished.. If anyone has Gen II heads and has done the porting and polishing and the larger valves, could you respond to this and tell me what the head volume is....or tell me how to calculate this???

[Guest]

Now I like this topic, unfortunately I have NO experience in this. But I have to ask, and again excuse my lack of knowledge as well.

 

What engines received the Gen III heads?

[Vegeta]

3100 and 3400 engines have the gen 3 heads. The gen 3 heads have changed from 94-present but its slight. 3400s have larger intake valves (1.76 vs 1.72) till 2000 when the 3100 and 3400 got the same larger intake valves. You wont be able to fit much larger valves in there and the shrouding against the cylinder wall may even be bad (aside from teh shrouding on the exhaust valve that is there stock on a gen 2 head, let alone from a larger valve).

 

GPXSS has probably measured the volumn of the gen 2 combustion chamber stock. You should measure it yourself though on your particular heads after you do the work.