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Help identifying my new (to me) LS1 (pics included)
I'm trying to figure out what year/make/model this new (to me) LS1 is.
The block casting number is 12550592 (97-98).
The valve covers are center (00+) and not the perimeter pattern (97-98).
The PCV seems to be (99+) since the actual PCV is just a few inches from the intake hose and not located in the center of the hose along the passenger valve cover.
Here are some pics of the motor. As you can see I've removed the EGR and AIR lines from the exhaust manifolds in the later pics:
The valve covers are center (00+) and not the perimeter pattern (97-98).
Just an FYI....center bolt valve covers actually started in the 1999 model year (with 853 casting heads), not just '00+. Based on the other items (exhaust manifolds, PCV system) it seems to be dressed as a '99 engine (2000+ would share the same PCV, but come with different exhaust manifolds originally). Not sure why the block casting number would indicate a '97-'98 though, unless it's a '98 that's had a head and PCV swap to the '99+ setup. Have you heard the engine run at any point (i.e. does it sound stock)? Not sure why someone would do a head swap and then reinstall the factory exhaust manifolds, but it's possible. What is the casting number on the heads?
If the engine is totally stock, then it would have to be a 1999 model year as that's the only year which would have used this (visible) specific combo of parts originally.
I think you may be right on the 1999 year. I have read that some early 1999's may have used the same casting number (12550592). This was a junkyard pull so I have not heard it run yet. I'll check the casting number on the heads when I get home today. Really appreciate the advice!
I think you may be right on the 1999 year. I have read that some early 1999's may have used the same casting number (12550592).
This is the most likely explanation then.
Originally Posted by AndyLS1
I am not seeing a number stamped here on the head
When looking at the front of an assembled engine (as in this picture), you'd need to look at the pad on the driver's side head to see the casting number. Correct head casting number for all 1999 LS1s would be 853.
It's a 99. I have the same thing in my car. The centerbolt covers and egr are the giveaway. Most likely it was an early run using up what was left of the 98 blocks. Not uncommon for gm to use a part into the next model year if they have a surplus.
It's a 99. I have the same thing in my car. The centerbolt covers and egr are the giveaway.
Just to expand on this a bit further for anyone who may be searching this in the future: The fact that it has EGR (and the EGR valve itself) with center bolt valve covers doesn't really tell us specifically that it's a '99 because this would be exactly the same for a 2000-spec F-body engine. In this case it's more about the exhaust manifolds; because we can see the exhaust manifolds plus those other items, we can tell it's a '99 assuming all parts are stock/original (2000 cars used cast iron manifolds with a different appearance and different EGR port location.)
Just to expand on this a bit further for anyone who may be searching this in the future: The fact that it has EGR (and the EGR valve itself) with center bolt valve covers doesn't really tell us specifically that it's a '99 because this would be exactly the same for a 2000-spec F-body engine. In this case it's more about the exhaust manifolds; because we can see the exhaust manifolds plus those other items, we can tell it's a '99 assuming all parts are stock/original (2000 cars used cast iron manifolds with a different appearance and different EGR port location.)
02-07-2019, 04:42 PM
Help identifying my new (to me) LS1 (pics included) 
