Intake maifold leak problem

Those o-rings might be for the injectors...usually included in an intake manifold kit.

Intake manifold gasket should not need sealant. Hopefully you're using OEM parts. If not.....?

Also, each side's gasket may be "slightly" different. Check that.

Bolt torque order and ft-lb specs are important with these gaskets.

Is the "replaced" head "new" or did you machine and reinstall the old one? Either way, there might be enough of a height discrepancy between the front and back for a leak.

I had to replace the front cylinder head last weekend. Got everything buttoned down and connected and the thing started up and sounds great. Only problem is the engine is idling at around 1300 rpm. Discovered that there is a leak at the intake manifold edges and also at the plenum gasket.

I put new gaskets on and followed the All Data isntructions. There was a bag off rubber o-rings that I couldn't find any mention in the assembly instructions so I didn't use them. Now I'm thinking that these o-rings are the cause of the air leaks.

But where on the bolts do the rings go? Under the bolt head or between the manifold and the cylinder head. If the latter, how do you keep them in place while installing the manifold. I doubt they would go there since they would keep the manifold from a flat contact with the head.

Also, other than adding sealant where the heads meet the block , there's nothing that says I should use any kind of gaslet sealer on these gaskets. Should they go on dry or would a thin layer of sealer help?

Any advice would be greatly appreciated.

Thanks for the quick reply.

There are 12 o-rings and there are 12 bolts total on the manifold and plenum. There are only 6 injectors which makes me think the rings are for the bolts. The head was new and the gasket is a one-piece metal unit that covers both heads and the valley in between. I followed the torque specs and the pattern when installing.

The really weird thing is there's a leak around the plenum gasket. Both of the surfaces were clean and flat and the fiberboard gasket should have done its job.