Hey Moparheads, Got a question, installed a later smogger 318 into my 55 Fargo Pickup. But here's my question, i have the bigger exhaust port heads on this engine. I have frame clearance issues so bought early LA 318 exhaust manifolds. They bolt on no problem but the ports are slightly smaller. Its the same as using 273 or 318 manifolds on a 360. Anybody done same, will there be any issues? I have already plugged smog holes on the engine
Unless you intend to do drag racing where tenths of a second matter, any small block exhaust manifold will work. If you were drag racing, using any exhaust manifolds in the 1st place would put you at a handicap, unless the class required them. In that case there are some manifolds that flow better then others. On the street, for normal driving purposes, any manifold will work great for you. Some have a lot more back pressure then others, but if your connecting the manifolds to a good exhaust system, you won't know or feel the difference. Gene
Thanx Gene I was concerned about seal as the older 318 ports are a bit smaller than my later ports on heads. Its like putting 318 manifolds on 360 heads.
Not a Mopar expert but I'd lay the gasket that exactly matches the heads on the exhaust and mark the outline You could get all fancy with Prussian blue and a scratch awl or just trace the gasket with a sharpie and take your die grinder and blend the manifold ports to the line. No need to get carried away you primarily want to take that sharp edge off
I'd say no major "issues" except decreased exhaust flow capacity and a little less horsepower, especially at higher RPMs. No big deal. But I think I'd at least blend the exhaust manifolds to match.
I did both sides same earlier LA 318 manifolds Oops i just used both sides. I did not remove material on manifolds to match as of yet.
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