Hello...I bought a Dart LS Next short block. I was told to use Cometic head gaskets. I called Cometic and the guy seemed a bit confused about which gaskets to use. At first he said to use the Cometic Dart gaskets, but I pointed out the bore on those was 4.200" versus the 4.125" of my block. Then he said use LS3 gaskets with the 4.125" bore. The Dart gaskets are LH/RH whereas the LS3 gaskets are either. Then he wasn't sure what to use.

Anybody use the 4.200" bore diameter gaskets on a 4.125" bore block? Or, have you used the LS3 gaskets without issue? I plan on running low boost under 12 psi if that makes a difference.

 

If your using an LS7 style head, I’d go with a Cometic C5702-052 gasket. In all cases, always match the headgasket with the heads chamber, not the bore size per-say. Hers a link…
https://www.summitracing.com/parts/c...SABEgLM3PD_BwE

 

if you have boost go for the MLX.
They will hv them in a 4.130 , if not order the size you want and they’ll make for you

 

Do what this guy said above. He knows.....

 

LS3 style head.

 

I was going with the MLX, but that isn't the question. There are gaskets for an LS3 with a 4.130" bore, and then they show gaskets for a Dart block at 4.200". The Dart blocks show LH and RH gaskets, whereas the LS3 gaskets do not show that. Which gaskets do I need to use?

 

You need to run the dart 6 bolt gaskets if that's the block you have. Cometic can make you whatever custom bore size you want, or just run the 4.200

 

Che70velle nailed it......