Headers or manifolds 351m
 

I'm wanting to get the exhaust done on my truck soon its a 78 f150 4x4 4 speed with the 351m. and am trying to decide if I should get headers or keep the manifolds. which will sound better with true dule exhaust with glass packs Cowboyed out the back. I'm not concerned with performance as I'll be swapping the 351m out for a fairly Stout 460 once the body and suspention are done. so if all I'm looking for is something that sounds good which way would you guys recommend I go thanks.

IMO keep the manifolds, since you have a motor swap on the horizon. If the OEM exhaust manifolds are not cracked or leaking just stick with them. If you think you need headers to get better sound, you will change your mind once you break off a few exhaust manifold bolts. But then you will be committed to at least the repair.

That what I was dreding the most if I went the header route getting the old manifolds off I do think I have a leaked some were dose exhaust come though the stove pipe becouse the pipe connecting it to the aircleaner is gone or dose it just pipe the heat from the manifold to the aircleaner I can weld it shut if exhaust come through there if not I'm guessing one of my manifold gaskets are leaking as they dont appear to be cracked anywhere

If you suspect a crack look for some black exhaust soot buildup, that is a tell tell sign. Most I have seen are a vertical crack right in the middle of the manifold all the way thru. The air cleaner pipe is just connected to the R/H manifold heat shield/cover. Example 9A603 with that cover installed, a crack is hard to see.

I broke 3 bolts on one side and then 2 on the other. Its not bad until you break a easy out AND a drill bit off in there....

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If they look like they will be that difficult to get out i would be happy to live with the leak untill its 460 swap time if I find a crack in the manifold can I weld the crack or are the manifolds made out of a material thats not weld friendly

They are made of cast iron and not easily welded like regular steel. It takes some welding know how to repair them. I think it takes a special welding rod or welder set up????