newer 300 manifold
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Freshman User
Joined: Aug 2007
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newer 300 manifold
i found a set of manifolds off a newer 300..do they work well on older 300s for putting dual exaust? what do you have to do to the intake if you change the older exaust manifold?
Postmaster
Joined: Feb 2003
Posts: 3,441
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From: Muskegon, MI (home)
The newer "EFI" manifolds will fit an older 300 six with some slight modification. One of the forward ears on the rear manifold requires some trimming. Other than that the ports line up perfectly, you can expect a noticable gain in power and mileage. As for running dual exhaust, I discourage you from trying it... unless you want your truck to sound like a rice burner. The intake manifold requires no modification.
Postmaster
Joined: Feb 2003
Posts: 3,441
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From: Muskegon, MI (home)
You won't be able to bolt the manifolds together. When I did it on mine I installed the exhaust manifolds first bolted on loosely so I could get the ears on the intake interlocked with the exhaust manifold. It's kinda tricky, just take your time and get everything lined up before you tighten everything down.
Senior User
Joined: Jun 2004
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Pkupman82 is right, you'll have to trim a little, do a test fit first. Mike, if you look carefully at the newer exhaust manifolds, you'll see that the 2 manifolds don't bolt together as there are extra holes in the cylinder head for the intake & exhaust to bolt to. I put studs along the underside of the mounting area to help with alignment, seemed a little easier. Regardless, make sure you use very thick, hardened washers of some sort on the manifolds or they will leak.
Edwin
Edwin
Postmaster
Joined: Feb 2003
Posts: 3,441
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From: Muskegon, MI (home)
While your at it might as well double up the gaskets for better sealing, and just for a little added insurance you could lay a thin coat on the gaskets with Permatex Ultra Copper Hi-Temp silicone. I use it on header gaskets and any part of the exhaust system that is clamped together, it holds up to the heat really well; otherwise I usually weld all my pipes... I never have leaks.
