Help pls - 427/425 Exh Man Bolt Lengths

[John L.]

My 427/425 engine has developed a leak at the exhaust manifold where it meets the head at #4 cylinder. The substance appears to be a mix of raw gas and carbon. I have tried tightening the bolt however it is still leaking. I am afraid to tighten it too much as I may strip the threads. There is no gasket. As I remember the torque specs are 30 ft lbs. I have a feeling the bolt may be bottoming out in the head. Could someone pleaase help me with the correct bolt lengths. Also what you be the recommendation on buying new bolts.

thanks

john lolli

[Mike M.]

Re: Help pls - 427/425 Exh Man Bolt Lengths

Suspect the exhaust manifold has warped over the years. Take it off and straight edge it and if it is warped, a local machine shop can surface it . good luck mike

[Larry S.]

Re: Help pls - 427/425 Exh Man Bolt Lengths

Hi John that is the one thats supposed to have the french locks on it?Is the bolt backing out or is it the bolt stays tight and it still leaks? I will pull one of mine and measure it tonight if no body post's the information.

[Bill Stephenson]

Re: Help pls - 427/425 Exh Man Bolt Lengths

-------Also you can order a complete set from Long Island Corvette with correct head and length.
-------Speaking of length,you can check out the bottoming theory easily enough with anything narrower than the bolt hole.Just stick it in to the end and mark it.Then compare it to the bolt...........Bill S

[Joe L.]

Re: Help pls - 427/425 Exh Man Bolt Lengths

John------

The first thing to do is to do as Mike says and remove the manifold for checking with a straight-edge. Exhaust manifold warpage is not uncommon and would account for the "syndrome" that you're experiencing.

As far as the bolts go, there are several possibilities. For the most part, and aside from "special" bolt positions (e.g. p/s pump, etc.), the bolts on your engine should be 1-1/4" long.

The torque for the exhaust manifold bolts should be 20 lb/ft. Don't use more.

[John L.]

Re: Help pls - 427/425 Exh Man Bolt Lengths

Larry

No, the French Locks are on the ends. The leak is in the middle on #4 cylinder.

john

[John L.]

Thanks everyone -- I appreciate it !! *NM*