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Old 04-06-2007, 05:33 AM   #1
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Default Head casting #s for LT1 and LT4

I picked up a set of aluminum heads that have a casting # of 12551561 - does this # mean an LT1 or LT4 head? I can't find a listing for this #, L99, LT1 or LT4. I assumed, as did seller, that they are LT1s from a "96 'vette.
The heads are in transit so I can't just go measure the valves. I've seen the 1255 on a lot of LT4 parts.
Thanks guys!
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BMR SFCs,LCAs, PHR and TQA, S60 w/3.54s
Coming soon: Lunati 60122, 3200 stall

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Old 04-06-2007, 10:25 AM   #2
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I think Car Craft has the casting numbers in their cylinder head databank, its pretty cool because they also have the stock flow numbers
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Old 04-06-2007, 10:29 AM   #3
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There's two LT1 aluminum head part numbers too. 92-95 and 96-97. The later heads flow a touch more, but don't have quite as much meat in them for porting.

10207643 92-95
10128374 96-97
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Old 04-06-2007, 10:30 AM   #4
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I can check tonight if you do not find out sooner. I have a book that lists all the casting numbers for each. Stay tuned.
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Old 04-06-2007, 11:49 AM   #5
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Thanks, Mark - I'd appreciate it!
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'11 GMC Sierra

'94 Trans Am 383 LT4, A4
690 heads, TrickFlow Elbow, Lingenfelter CAI, Accel 32#, Summit 58mm TB and bypass, Edelbrock LT4 Airgap, LT4 notsoHotcam / 1.6 RRs, MSD Pro-billet, Blaster, Superconductors OTVC, 6A box, Aeromotive Adj FPR, 160*, LT4 KM, Pacesetter LT / ORY, Magnaflow catback / bullet, PCM for Less tune
BMR SFCs,LCAs, PHR and TQA, S60 w/3.54s
Coming soon: Lunati 60122, 3200 stall

American Legion Post #569

The few, the proud, the slow. The LT4 Owners
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Old 04-06-2007, 04:13 PM   #6
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www.mkmann.com/cyclinderhead.html shows this casting number as a 1996 LT1 aluminum head. One year only. I wonder who made them.....
Thanks, dudes!
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'11 GMC Sierra

'94 Trans Am 383 LT4, A4
690 heads, TrickFlow Elbow, Lingenfelter CAI, Accel 32#, Summit 58mm TB and bypass, Edelbrock LT4 Airgap, LT4 notsoHotcam / 1.6 RRs, MSD Pro-billet, Blaster, Superconductors OTVC, 6A box, Aeromotive Adj FPR, 160*, LT4 KM, Pacesetter LT / ORY, Magnaflow catback / bullet, PCM for Less tune
BMR SFCs,LCAs, PHR and TQA, S60 w/3.54s
Coming soon: Lunati 60122, 3200 stall

American Legion Post #569

The few, the proud, the slow. The LT4 Owners

Last edited by myersfw; 04-06-2007 at 04:16 PM.
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Old 04-06-2007, 04:18 PM   #7
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561 casting are LT1 heads off of the 96 or so, i don't know if they used that casting during 97.

damn dial up.... takes almost 5 minutes for the page to load and for my slow self to reply..

Last edited by CKJ; 04-06-2007 at 04:22 PM.
 
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Old 04-06-2007, 09:30 PM   #8
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Default Cylinder Head Casting Numbers

LT-1 350 cast iron 92-93 12554290
LT-1 350 cast Iron 94-97 10125320
LT-1 350 Aluminum 10128374
Lt-4 96 Vette 12363287
265ci cast iron 10208890

Turns out that is all I have listed.
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Old 04-07-2007, 01:39 PM   #9
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so here I go (sorry)...I have a 95z and want to buy used heads to send to AI and have them port the heads.
Do I need to find heads with the 95 casting #s to be able to put on the block I have in my car now or will any LT1 heads be fine?
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Old 04-07-2007, 04:34 PM   #10
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You should be good with any LT1 heads. Just check the casting numbers to make sure you don't get the iron ones. (unless that is what you want)

Don't worry about LT-4 heads U are not going to find them around likely.
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Old 04-07-2007, 07:14 PM   #11
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Quote:
Originally Posted by AtotheJ3 View Post
so here I go (sorry)...I have a 95z and want to buy used heads to send to AI and have them port the heads.
Do I need to find heads with the 95 casting #s to be able to put on the block I have in my car now or will any LT1 heads be fine?
You either want a 374 or 643 casting head when you send them off for somebody to port them. Those are the two castings that has the most meat on them for porting. I'd say the heads on your 95 now probably are 643.
 
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Old 04-07-2007, 07:19 PM   #12
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when you say '374' are you talking about the LT-1 350 Aluminum 10128374? Where would I look for the casting number and do I have to have the heads off?
Thanks chris, you've helped a lot
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Old 04-07-2007, 11:41 PM   #13
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Quote:
Originally Posted by AtotheJ3 View Post
when you say '374' are you talking about the LT-1 350 Aluminum 10128374? Where would I look for the casting number and do I have to have the heads off?
Thanks chris, you've helped a lot
Just pop off the driver side valve cover and peek down and read the last 3 numbers on the head, the casting number should be after the 1st or 2nd set of springs. The drivers side is a lot easier to take off
 
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