I know that the 93 heads have a different GM part number then the 94-97 heads. What I have not yet found is why. I do not know if they have a different casting number or what but I am looking for a reason that they are a different number. Perhaps it's just superseded?

Does anyone know the difference in the head? The reason I ask is because I have one 95 head that was given to me. I was never able to collect the other one. I need one more head to send them off for porting. I have found someone with one head to sell but it's from a 93. I highly doubt that there is any internal difference, but maybe an accessory difference? I would just like to know for sure first.

 

im wondfering the diffrence to couse i have a whole 93 lt1 motor sitting around.

 

I bought a pair of 374s that I sent off to AI for porting instead of sending my 643s. The 374s and 643s are both good for porting. The 10207643 casting seems to have less material than the 10128374 casting.

 

see, that's the thing. I cant find anywhere that tells any difference between the 2 casts. I have seen some speculation but nothing for sure. I just don't want to run into any issues when it comes time for porting.

Thanks so far.

 

Shoot an email to Ron at AI. I am sure he will be happy to answer your questions. The folks at AI are nice guys and they do great work too.

AI 190 full port done on 374s







My old 643s.

 

The ports are different among the different LT1 castings and the accessories the same. You want to use two of the same casting number heads.

 

under a perfect situation I would love to use the same casting number, but if I can get away with it there is no need to.

I sent emails to both Lloyd Elliot and AI before I posted this. Lloyd responded, so far no word yet from AI.

In Lloyd's words, the differences are "very minimal" and after porting they would be "identical".

I am hoping for an email from AI to get a consensus but if not i'll get that head anyway.

 

There was a post about this within the last month on here in one forum or another with side by side comparison.

One has more material around the pushrod area was the conclusion. As for which I cannot remember but in the pics it is obvious. Sorry but do not have time to search for it.

Also the 93 intake paths are different as well besides the fuel crossover that is obvious.

 

The '92 and '93 head castings have a little more "meat."
Not enough difference to write home about.

Tom Piper

 

AI responded saying that it would not hurt at all. The same CNC port program that they use works on both heads. It will be just fine

 

Are the '94-'97 castings all the same then?

Dan