I did a search but still a little unclear as to what the different casting numbers mean? i have a 97ss that i am rebuilding the motor to a 355 and i want to buy a set of used ported heads what should i be looking for as far as casting numbers? what are the differences between them? and what about the intake manifold? will only certain year intakes bolt up too certain casting numbers heads? thanks everyone

 

there is 3 casting numbers i know mine are 643 came off 94, i believe the 97's had the thinner walls which are not as good for porting but can still be done.

 

Rumor has it that the 374's off the 93's have the thickest walls and the most room for porting. This is just what I've heard.

 

96-97 had 561s,,slightly thinner ,but LE told me they were still ok for porting.

 

Only some of the 96's had those, mine had 643's.

 

I stand corrected....I know my 97 had 561s

 

The head porter at LPE told me that the 643s are ok for porting with the 374s being the best because the 374s have a bit of extra material for porting especially in the intake runner opposite the push rod hole...

--Alan

 

10128374 Starting in 92 is one of the 2 "sweet" castings for porting- came on my 94.
10207643 found from 94-96 is the other "sweet" casting.

10205245 from 1993, and 12551561 from 1996-97 are not especially desirable, but can still be worked to some degree if you want to have them done.

 

okay preaty clear on the heads now what about intake manifolds?

 

they're all pretty much the same. The only difference is the 93's have the crossover tube in the back, supposedly helping airflow. Personally I don't know if it makes that much of a difference.

 

so any year intake will fit? what about like vaccum lines and all that other nonsense that goes to the intake manifold? thanks everyone

 

That's a steam pipe on the back, joining the heads' cooling passages together, hard as hell to find. Nook & Tranny has a pipe/bolts/seals set for about $116.00 that will fit a 97. The intakes are all the same except 93 where the fuel rail cuts across the top front; 93 there is no pipe over the front, just U-shaped. Fuel rail and Intake need to go together. Not a problem for you since it's a 97...

 

If you want you can put the 92/93 intake on the 94+ motors but you need the fuel rail as well. Aside from that it should bolt on, infact the rails will slide right into the fuel lines as well so there really is no hinderance in swapping to the 93 intake. Some even say it helps the airflow since there is no dip in the roof of the intake. I'm glad I own a 93, I don't have to worry about converting anything.....I'm not even going to go vented opti.....the original has been in there for 17 years and 94K miles now, so there really isn't a reason to change it yet.....I'm more interested in getting rid of the spare parts I've got right now.

 

yep 97s are 561 castings but still awesome for porting, The only thing is they are thinner than other castings. So major abuse such as boost or spray with high amounts it may not like.

 

The intake shows NO difference with power as stated by L.e and A.i themselves when I asked them last year. Even a local shop did this just to see if there was a gain and Nothing.

 

And everything I heard was hearsay, I personally didn't think it would do anything anyway. I'm sure it's not noticeable until the very top end of the scale in terms of HP levels. Even then I don't see anyone hitting that point before they swap to say a single plane. So there really is no cause for concern.

 

Lots of lumps and bumps to keep the air in a rolling turbulent state for best atomization mix with the fuel as it enter the intake runners (avoids fuel puddling as the mix goes into the comb. chamber). 2nd pic is looking in the left bore- there is a ridge across the roof of the intake about where the rail crossover is, but it might be on the inside of the casting on both styles of intake- could be there for same purpose as above. Have to see the inside of a 92-93 to say either way... this is a 94. Kitteh digs the intake.