Intake problems

So finally got a new exhaust manifold and bolted everything down to 25ft lbs per specs and the second runner from the back on the offenhauser intake still has a vacuum leak even with exhaust and intake gasket any ideas I have been trying to get this thing running for 3 weeks. I was told to put blue locktite on the bolts to make sure they don’t back out but if there already tight, I am about ready to just buy a factory intake and carb and just trash this intake and sale the Holley.

 

It sounds like the manifold is warped and/or the heads. You should check the straightness of mating surfaces with a machinist rule. If there is a machine shop near by they can also check.

Ed :tea:

 

The last gasket set that I brought came two gaskets one was long one that has the intake and exhaust. it say that some engine came without exhaust gasket and you need to use both on those engine to make up for warped manifold and prevent vacuum leaks

 

This is what i'm thinking too...

 

I used both and even used a little Hight temp RTV gasket maker, now i see why people put chevy v8s in these things

 

I had my intake and exhaust manifold machined, and they were WHEY off!!(+-3mm!)

It's not running yet, but they were a lot off, so I hope for the best!

 

Any engine has its faults and virtues. None are perfect. SBC included.

Manifold sealing can be a problem with the 232/258 manifolds. Where is it leaking, between the manifolds (the 4-bolt gasket) or between the manifold and the head?

Silicone is a bad idea on an exhaust manifold. I would use spray CopperCoat, if anything. The 4-bolt gasket needs to be loose when you bolt up the manifolds. Tighten it last.

 

The leak is on the head on the 3rd intake port from the back its a single runner and yes i bolted down the 4 studs on the intake/exhaust last.

 

It's a pain, but I suggest you remove it and check it for flatness. I know that the original manifolds on my J10 were badly eroded by exhaust gas leaking for a long time... even the head surface was eroded. My exhaust manifold had a crack - maybe not all the way through - so I replaced them both.

If you have the manifold surfaces machined, you should be able to put them back with no exhaust gasket. That's how the factory did it. An exhaust gasket will make a leaky manifold seal for a while, but it will blow out eventually. However, you need the 4-bolt gasket between the manifolds. The Felpro gasket has tabs between the intake and exhaust parts so you can separate them ... you may be able to buy just the intake gasket.

There's also a steel doughnut gasket for the pipe. The soft doughnuts will seal for a while but eventually blow out. The later manifolds have the gasket surface cast into the manifold, eliminating a gasket to the pipe entirely.

 

Yeah i think i am just going to pull it back down and have it machined seems like the right thing to do then i think this winter i am going to do the 4.0 liter head swap i seen the wright up on that yesterday. Thanks for all the help from everyone