Machining an Intake Manifold

[Orange65]

I have an old aluminum intake for a BBC that is pitted around the water jackets. I filled the pits with JB Weld and am getting ready to put it on the engine. But I got to wondering if it would be better to machine off the mating faces a little. Ever had a manifold machined on the mating faces? How much can I go without trouble? Or should I use thick gaskets, plenty of sealer, and install it like it is?

[JeffMcKC]

That will depend on port line up, I like as thin a gasket as I can have, and get the clamp so it does not suck in or have a gasket shift, even when glued. I just wipe a small amount of silicone on the water passages and trim adheasive the ports on one side. anti seaze the other

[anotheridiot]

If the JB weld is on the clamped surfaces you should be fine to just draw file the mating surface flat and choose a good gasket.

[DanStokes]

I frequently use my straight line sander to flatten everything. But then, I have 2 straight line sanders (pawn shop buys). 80 grit works for me, followed by the sealer of your choice.

Dan

[Bob Holmes]

I second the flat file idea.

[Loren]

If you're good with a powered sander, that'll do but some guys round off the ends of whatever they're sanding. I have a course file I use but...

I hope the rotten parts were cleaned out real good before the epoxy job. Like with dental work, you got to get in there and grind out the crap first. Better yet would be to tig-weld the repair, and have it done for good. In any event, intakes (at least naturally-aspirated) seem pretty tolerant of non-flat mating surfaces, within limits.

I once had a brand-new intake manifold machined to correct very poor factory machining (Offenhauser disappeared for good reason IMO) but the machinist couldn't seem to do it right either. Then you got to not remove too much material, just take down the high spots.

Back when I used to fix those things for guys, the way to really annoy me was to bring something to weld up that already had a bunch of old JB Weld in there. Jeez, that stuff is a drag to get out and you can't weld if there's any present...I'd send them back home with it to cut/burn/pick it out themselves. Otherwise, I spend an hour picking at that crap and then they don't understand why they should have to pay for that part. You're better off trying to weld at raw oxidation, at least you can get it to float to the top and grind it off then go back to welding.

So don't do the epoxy if you suspect at all it won't work, and it might wind up at the welder's later.

[JeffMcKC]

I use Splash Zone Epoxy