exhaust manifold

[vinnytruck]

Thanks guys for your help, Silly question...***What happens if I drive the truck with a crack? do I damage anything? what about JB weld? a friend told me to try,I wondered Why the truck sounded somewhat loud, there is some air passing out of the manifold. Can I live with it... can vt&1/2 get hurt? thanks again VT

[WarrenD]

Well, for myself, I wouldn't. CO can get into the cab and even though there may be outside air moving around (these things are less than air-tight ) CO can do bad things if inhaled. Search the internet, lots of info on the bad stuff CO can do to you. I certainly would not want to expose my offspring to it.
On a seperate front, exhaust valves rely on backpressure to operate properly. With lower backpressure you risk damaging the valves. Granted, it may take time and with the limited use these trucks see it might not happen for a long time, but the bottom line is, it's not safe to operate like that. Fix it right and it should last for a long time to come.

[k8icu]

You can try JB weld, but in my life time I have found JB weld to not work worth a dang! It stays soft and on exhaust manifolds it tends to burn out soon after put in. You can try finding someone who might be able to weld it up but again that's tricky at best. I would recommend start searching for a good used manifold to replace the one you have. Replace it with new gaskets and you should be good to go.

[w30bob]

Hi Vinny,

You can forget the JB Weld.....won't work. JB Weld a cute fix for things that don't see any thermal expansion. There's nothing in JB Weld to give it any resistance to tension....it's basically a tough plastic when it dries. The only way to fix is either have it professionally welded or replace it. My M has two cracks in the exhaust manifold and about 4" of exhaust pipe attached to the manifold. That's it. No header, no muffler, no tailpipe. That's the way I bought it. I drove it when I bought it and can drive it now. It's not nearly as loud as I would have expected....sounds like my garden tractor with a bad muffler. Fix it when you can, but don't lose sleep over it if you can't get to it tomorrow.

I would think that since these trucks were designed for water fording the exhaust manifolds would have been bit beefier. I'm sure that when soldiers drove them with nice warm engines into nice cold water they replaced exhaust manifold frequently. The cast iron just can't handle the rapid change in temperature without cracking.

regards,
bob

[hbb]

Vinny
what can be done as far as repairing the manifolds is by relieving the cracks by grinding the area to accept a weld,then bolt it up to a old engine block or make fixture for holding the manifold in place. once it is secured then the manifold will need to be heated to a cherry red color at the crack and a couple inches back on both sides of the crack. At that point you are ready to weld with a high nickle rod and it will hold very nicely. It is really good to have a extra hand when heating so you can get after the welding and not loose heat.
I have welded many manifolds and engine blocks in this Mainer and they have all held up and not cracked in the broken areas again. You do have to keep the parts from shifting when heating and welding. and if this is not your cup of tea then take it to a machine shop and they will most likely fix it up for you or buy a replacement.

good luck and let us know what you end up doing with it.

hb