I know this question has been asked over and over again, but what do I look for on my block to see if it's an LS6. Isnt it a bullseye or something. There was a good post a few months ago with pics, but I cant find it

 

Only some 01 and 02 cars had LS6 blocks. You have a 00.

 

Yep, sorry. Your '00 definitely doesn't have an LS6 block from the factory.

 

How to tell anyway??

 

the block itself has holes up on the main walls to help equalize the pressure, if im not mistaken. the casting numbers should also be diffrent, but i cant remember what they are. some blocks came from diffrent plants as well but this is a bad indication.

 

If the heads are on the LS6 check the ports. LS6 is D shape, Ls1 is not. (Unless modified with head swap)
Another way but its not for all F-bodies. most LS1 are 2 bolt mains except for corvettes and SS. If u have a 2 bolt its and Ls1.

 

Both LS1s and LS6s have 6 bolt mains. The 2 bolt/4 bolt thing was with the SBC. If you have the bullseye pattern you have an LS1. If The PCV comes out of the valley cover, you have an LS6 unless someone put an LS6 valley cover on the engine. The D shaped port is the exhaust so you would have to take the exhaust manifold or header off to see that. Also, I've heard that no Fbodies come from the factory with an LS6 block, don't know for sure if that is true but there is very little difference between them anyway. The important thing about an LS6 is it's heads.

 

Cal, GM High Tech Performance said that GM said there were 10% LS6 blocks in 2001 and 25% used in 2002 F-bodies. I'm still wondering where to find the "bullseye".

 

All LS1s are 6 bolt... I believe you're thinking about LT1s where I believe (correct me if i'm wrong) most were 2 bolt and vettes got the 4 bolt or something to that effect.

 

Yes, I believe you are right! And here's how to tell for sure, including the number:

 

Still not sure about the 6 bolts, I'm researching.
The pic above shows 4. But it is not complete.
I'm so old I get confused sometimes. LOL.
If I'm really mistaken on the 2 VS 4 bolt thing, I apologise but I would have learned a new thing. I was right about the exhaust ports though, hey I'm half way there

 

The 5th and 6th bolt are crossdrilled through the side of the block and main caps.

 

Yep, that's the answer: crossdrilled. Unlike the SBC, LSx motors have a deep-skirted block simialer to diesel engines giving them a very strong low end and a place to put two more bolts/main. See Sharky, what you can learn on the internet!

 

they are also called Y blocks but not any more. my dads old 292 in his '55 t-bird had a Y block. they thought they needed the strength, but really didn't. and you can see, in the picture, the cross drilled holes, look close.

 

Yes I see the light OOPs thats why I love this site thanks guys, I know better now. I confused it with LT1.
Also after research (considering my weakness is I've never taken or seen a LS1 apart) I learned that LS6 heads have 60cc combustion chambers VS 68cc for LS1. Which means a raise of 0.5 in compression for LS6 (10:1 LS1 VS 10.5:1 LS6). So a simple compression test should tell the difference. That is if it is not an LS1 with milled heads or an LS1 with LS6 heads.
Ah I'm so hungry for LS1 knowledge. Thanks for the lesson Ya All.

 

Another thing (from what my local deals tell me) is that all LS1's after 00 have the LS6 rods in them. They are supposed to be the same except they have stronger rod bolts for the higher rpm limit on the ZO6's. Any one know if that is correct or if I am mistaken? I wonder if a person who has an LS1 block can modify it to have the breathing holes through the webs like the LS6 blocks?

 

I think u can, I used to do this on SBC's in the late 80's when I'd do a performance rebuilt to prevent crank oil starvation.

 

i figured since i was really bored i'd take a look, i don't recomend this unless you have really small hands and arms. it took me longer to get them damn miorror out than it did to get it back there. and i couldn't see shiet anyways so all in all it was a well wasted hour.

by the way, is there a way to prove it's not by some other numbers, cause i have no idea how dull or bright the shine is to the block compared to others

 

The only real way to tell if you have the LS6 Block is to....

Get under the car....On the drivers side rear of the block where the head meets the block you will see the casting number....

If it reads 12561168 it is an LS6 Block if it reads any other number then it is an LS1 Block....



....PSJ Marc ( I am over from the LS1.com site)

 

As far as I know, having an LS6 block DOES NOT net you the LS6 cylinder head, if that were the case I would consider selling the '99 for a '01 or '02! Someone please confirm.