The LT1 used 3 different heads as far as I am aware of. The early aluminum casting, the later aluminum style casting, and the Iron heads available on Impala's and stuff. O yea and the Vette heads, theyre slightly higher compression. So that makes 4. What are the differences between the heads though, which ones flowed the best, and so on? ...

 

As far as I know the flow numbers of the LT1 castings are very close. The early Vette and Camaro castings are better for porting because they have more meat in them. Other than that they are all very close.

 

the impala iron heads flowed the best averaging like 230cfm peak.

 

But the iron heads owuld suck for how high a F-Bod or Vette's compression is wouldnt it? They wouldnt dissapate heat as well and would detonate like a mofauker ... I think ? What year did they change the castings in on the fbody ?

 

yeah the chambers are big but they flow like a Vortec head. Basically a Vortec port in a revears cool head.

Not a bad deal for a circle track car that lets you run any Iron GM head. Revearse cool block and good flowing stock heads.

Bret

 

The iron heads have press in studs and the alum. are screw in type; I also have heard the iron heads flow best.

 

The iron heads are too heavy though.

 

!!! Dang!! I have several sets of the Iron heads. I have sold several 5.7 LT1s lately from Impalas and Police and nobody wants the iron heads. Maybe there is a use out there for them after all.
1. How do you block the reverse flow in them?
2. They shouldnt have the near detonation problem the aluminum heads face right??
3. Could someone port the heck out of them and get great flow?

 

I'll let you know some results on porting the irons. I have a set of em, I will be porting them out in an upcoming class I have. They have a flow bench at school also, so I'll get some before and after numbers.

 

The irons do flow a tad more than most of the aluminums and still equal to the best of the LT1 aluminums, the compression drop is minor and made up for by the fact that iron keeps heat in the chamber, remember heat is what pushes the piston down so any not used to do that is wasted. The aluminums need the extra compression to make up for lesser thermal efficiency. On the Vette heads having higher compression than the f-body heads, well only the LT4s otherwise the Vette got the same heads as the f-body.

The chambers are around 64cc so they are not "big" it comes out to 10:1 whereas you guys have 10.4:1, but as I stated aluminum needs more compression to make the same power so call that a wash.

To call the iron LT1 head reverse flow Vortecs is backwards, where do you think GM got the ports and chambers for the Vortecs heads? Hint hint the iron LT1 heads were in b-bodies starting in 94 whereas the Vortecs didn't make it into a vehicle till 96.

Forget the performance heads have to be aluminum crap, aftermarket heads are aluminum one for weight and two because it is cheaper to tool up for, the iron heads are good and are just as good a starting point for porting as the aluminums. If you want to argue that aluminum is better give me scientific reasons why, and I don't want to hear the heat disapation thing since as stated that is heat then not used to drive the piston so you would have it backwards.

 

Figure on them not flowing as well as the earlier #374/245/643 heads, depending how far you push the envelope. As far as porting receptability and virgin casting flow is concerned, I'd compare them to the later #561 aluminum head. They flow better out of the box, but have limited potential, due to thinner casting, of the port walls. Earlier castings have thicker port walls, allowing more porting latitude.

I agree with Dwayne's above post, regarding the issue of compression. The iron head has a larger more open chamber, which may lend itself to better flow around the valves and chamber walls. However, I don't understand why GM reverted back to the straight plug in the LT1 iron head, when they proved the superiority of the angled plug in the 70s.

Also, I'll stick my neck out and state Bret is aware, and was accurate in intent, but the wording used, opened the door suggesting correction.

 

Sorry guys, my bad about the Vette heads being slightly different comp from the F-Body heads ... I am now dumber ...

I have a ProCharger catalog ... and I remembered it saying that the Vette had slightly different compression. I jsut checked it to see what it said, and it compares an LS1 Vette head's compression to a LT1 F-bod.

 

casting #s and chamber sizes on all these heads....
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