340 Exhaust Manifold Help

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bobscuda67

bobscuda67

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HELP! I have a 340 motor with magnum heads and I want to put my 69 340 manifolds on it. They bolt up just fine,but the port size mismatch will cause a huge exhaust leak. The magnum ports are about a 1/2 " smaller in height and causes a gap on the bottom of the exhaust manifold. Has anybody else ran into this, I can't believe I'm the first one.
 
Someone else was talking about the same problem either here or another site.I believe thay wound up using magnum exhaust manifolds.I have been told that the mid 80 ish magnum exhaust manifolds flow as good or beer than the 340 manifolds. I bought a set of them for my project I hope the magnums fit my X heads.
 
Dodge dakota and Durango exhaust manifolds are very free flowing and as good as the 340 manifolds.... however you have to watch for firewall clearance depending on what you are putting them in...

if you cant use the 340 mans... i will buy them off ya .... ha ha

-RPM
 
Hey Guys, I think I can make the 340 manifolds work on my magnum heads. I am cutting 16 gauge steel plates with 340 manifold outside dimensions and a magnum port size hole. Question is, should I use a magnum gasket on the head and a 340 gasket on the manifold? Or should I just not use any gaskets and just use some high temp sealer?
 
I Would Use The Magnum Gasket On The Head Side,and A Thin Layer Of Sealer On The Other Side! Just A Thought!
 
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