jayyyw

Working on a car for a friend of mine. Just put together a forged LS3 with AFR Mongoose LS3 heads. Due to hood clearance issues, he decided to go with a rod modded LS3 intake. I just got the car running and it seems to have a pretty good vacuum leak. Car won't idle under 1500rpm. When I installed the intake, it took a little work to get it to sit down on the heads. The aluminum sleeves for the bolts weren't fitting into the provisions on the heads very well. I'm assuming this might have put the intake into sort of a bind and likely causing the leak.

Has anyone modified those sleeves on the intake side? Cut them flush? Any downsides to that? Or should I try to open the provisions on the head side to get it to sit better?

Che70velle

iTrader: (6)

Jonathon, were the heads milled down considerably for compression reasons?

jayyyw

Off the top of my head, I don't think they were milled a whole lot. I'll have to look back at the conversation with the owner.

sewerpickle

iTrader: (3)

What head bolts/studs were used? I ran into issues on a build where the nuts were hitting the intake, not allowing it to sit down on the heads properly.

jayyyw

ARP head bolts. I will look to see if there are witness marks on the intake in that area. The valley cover plate has the OEM bolts.

jayyyw

Dang, good call. Looks like we milled .042” and then did .040” head gaskets.

Che70velle

iTrader: (6)

Those numbers will make intake alignment tougher for sure, but maybe not the entire problem…the Oem valley plate is thick, and along with those valley cover bolts…if he’s trying to run heat masking material like in the pic, it adds to the issue. Could be 2 or 3 things fighting you here.

jayyyw

That was just a picture I pulled from the internet. I did look around the provisions for the bolt heads underneath the intake and didn't see any witness marks. The main issue was the sleeves for the manifold bolts, being extra tight on the head side.

I'll look over everything again and see if I missed anything. Is there a gasket that I can use along with the o-rings or even by itself that might help the alignment?