cc-rider

So I built a supercharged LS3 and used Frankenstein M311 heads. And then used Holley valve covers. Had an oil leak that took me forever to find. Finally noticed that gasket on the back valve cover slipped off the head mating surface. Of course…had to rip my blower completely off to get at the valve cover (Kenne Bell blower). Not fun. But I did it. Thought I had it fixed but now I still have a little leak going?

Just looking to see if anyone else has experienced this with the M311 heads and Holley valve covers? Maybe the M311 heads are just different enough from stock LS3 heads? And finally…looking for valve covers that are known to work with the M311 heads?

JRFed

Sorry you ran into that issue, the way the M311s are design are to run the OEM or whatever valve cover fits an OEM head. Now we have had issues with Holley's valvecovers where the gasket provided isn't sealing on both OEM and M311s yet they take OEM style valve covers.

cc-rider

Ok. Well…I appreciate you responding here on this and confirming. Guess I’ll have to look at switching back to OEM valve covers.

cc-rider

Just in case anyone else finds this thread and has the same problem…I’ve learned that Yella Terra makes a thicker/wider gasket for the LS heads. It is actually designed to raise the valve cover for more clearance for aftermarket rockers. But it looks like it might seal much better due to having a wider flange contact.

So with that…I’ve ordered it, but can’t vouch for it working. Will update when I get it on. But took me some research time to find these things so thought I’d post here in case people like to search these posts for fixes like I do!

pannetron

I used YT rockers on my build so the kit came with their thicker gasket. Using Holley valve covers and the YT gasket, no leaks in over 9 years.