Exhaust manifold leak (no gasket style?)

[AlseaAssassin]

Hi Guys,

When I originally bought my boat 3 years ago I knew it had a slight exhaust leak around the manifold (Ford 302) (I could here the tisk, tisk, tisk) but put it off figuring the leak was slight. Well 3 years later sounds isn't much worse but i've got the time to fix and thought I would. First step, or so I thought, was to secure some new manifold gaskets like I did my old Ford pickup I owned years ago. Well I called KEM and they told me that my canister style mainifolds didn't require a gasket between the head and manifold. I guess the manifolds are aluminum and the heads are steel so they heat up at a different rate causing a gasket to fail. He recommended pulling the manifold and taking a peice of emory(?) cloth wrapped around a block of wood to smooth the contacting surface. Does that sounds right to you guys? I was going to give it a whirl but thought I might be able to get away with tightening(checking) the bolts securing the manifold. Would it be a waste(or a bigger headache) to use a gasket? Thanks in advnace.

[fishkisser]

I think if you did not get the surface perfectly flat you would have a bigger leak ... I would not try and sand it with a block ...
Your best bet would be to remove them and have them professionally surfaced using a belt sanding table then you know they are flat ...
re - torquing the manifolds might help but some bolts might snap off creating more problems ... its up to you ... Heres some info ... Barney :wave:

http://fomoco.phpbbnow.com/viewtopic.php?t=2306&sid=d970d58ff2d120575a312fcaf032bd1a

http://www.federal-mogul.com/en/AftermarketSolutions/Asia-Pacific/SealingSolutions/Products/LeakRepair/Fel-ProManifold/Exhaust/

[riverhawk]

I have a 351 in my boat had a small leak. I had the manifolds surfaced and installed a set of Mr. Gasket header gaskets. The ones I could never blow out on my hot rods with headers. Still going strong three years latter.

[DK]

I would think that the two different metals expanding & contracting at different temp's would be more incline to have a gasket than not,no matter how flat you get them they will still leak,

[dabbad]

I agree. I would use a gasket. Doesn't an aluminum head on castiron block have a headgasket. They do expand at different rates and will over time wear out gasket. Aluminum heads ussually make it to 100k-150k and beyond. Make sure you use a heavy header gasket as stated above. Later Dan

[1pump]

I wouldn't sand anything aluminum by hand. It's too soft and before you know it you've taken off way too much metal.
I used to run a machine shop, and the platen (belt) type sanders are OK for cast iron, but IMHO they're too agressive for aluminum unless you change the belt, and that's a big job just to do a couple of manifolds. And the machinist needs to know what he's doing or he'll destroy them in an eyeblink.
A rotary broach or surface grinder would be a lot better since they have more control over the amount of metal being removed.
And yeah, I'd use a gasket. Ford and a few others made some engines that didn't use gaskets from the factory, which is fine until they start leaking. The heads can warp just enough on the manifold side to where the manifolds won't seal up (without a gasket) no matter how flat you get them. :twocents:

[AlseaAssassin]

Thank you very much guys!!! The amount of great advice I recieve on this board never ceases to amaze me!!!!!!!!!!!!!

[Pelhament]

I use to have this problem in my old car... I used a gasket as explained above and coated the whole damn thing in high temp Red RTV... Never leaked again.