Hey all, How do I permanently seal off the flange between the pipe and the manifold. On my 72 350 with dual exhaust. It is always leaking. Maybe I don’t have the alignment perfect. But I am always trying to get a good seal, and it is always leaking. I’ve tried aligning the mailing surfaces and high temp sealant… I know it didn’t come with a gasket, but is there a gasket that fits? many solutions you guys recommend?
Try a liberal amount of copper permitex high temp on the sealing surface, align and tighten the stud nuts to 20 foot pounds. Leave it overnight and then fully tighten. https://www.amazon.ca/Permatex-8187...ocphy=9001292&hvtargid=pla-434612799579&psc=1
I tried the permatex again. And it’s still leaking. Super clean surfaces. I just can’t get the exhaust to stop leaking. Maybe I’m just not getting the exhaust to sit flush on the manifold. Any recommendations? Any tricks?
Might be time to find an exhaust shop near you. There might be a hole you can't see under there! I'm lucky to have a shop near me that can still 'free-hand' an exhaust system, most of the Midas type shops can't do anything othere than bend pipe according to the comptuter!!
You sure its at the flange? Is there a gasket between the manifold and the head? A little hole in the gasket between the head and the manifold may be the sound you hear.
Am I wrong to think the manifold outlet is tapered and the pipe that mates to it flared? I feel like this this spot has never been an issue at all for me with regard to leaks? Is the '72 different from '68/'69?
I don’t hear the leak. But can feel it. I even put a shop vac to the exhaust pipe and blew through it. It’s a very obvious leak. I put the manifolds on a year ago after my local exhaust shop sanded them flat. I installed without a gasket. They sealed up pretty good. Indeed, it is flared and assembled without a gasket. I can’t figure out why it’s not sealing properly. You’re probably right. I’ll visit the guys here when I can.
[QUOTE=" I put the manifolds on a year ago after my local exhaust shop sanded them flat. I installed without a gasket. They sealed up pretty good. /QUOTE] Good!
I had problems with my manifold and head leaking. Someone here recommended Rem-Flex gaskets. I took the manifold back to the original machine shop for resurfacing one more time and he said they looked fine but did it anyway. I then put on the remflex and have not had leaks since. I think it may be a common recommendation to not use a gasket but that wasn't working for me and the remflex were superior to what came in my engine rebuild kit. The remflex is soft and easily damaged but I tried to be careful and it worked. They were about $50 plus shipping but worth it to me.
I used them on my GS 350 as well, at Sean's recommendation and they worked well... Of course this thread isn't about a leak between the head and the manifold, it's about a leak between the manifold and the downpipe...
I setup my heads on a auto travel surface grinder and took a light cut across the full length of the flanges. Run headers. No leaks.
