Anyone else have problems with this leaking on their trucks? I never did with any of my other trucks, but this 78 keeps leaking there. I've tightened it down a few times, but when I pulled the manifold a few days ago, the nuts had loosened up, and the metal ring gasket was charred and falling apart.

I feel like this is a spot where you'd want anti-seize on the threads, not thread lock...but what would you suggest if these keep loosening up?

 

Are the engine and tranny mounts loose?

 

First check to see if the bottom of the exhaust manifold needs to be milled some. Those gaskets fail because the ring cut is too deep. Me I just use a big mill file and carefully cut it down some, so the gaskets actually get compressed.

Next you need new studs and the squeeze or pinch nuts along with "Nickel" based anti-seize for them.

http://www.summitracing.com/parts/RNB-03142?seid=srese2

 

Whats loose the treaded stud or nut. I always try to use a new lock washer. A staked/crimped lock nut shouldn't get loose like said above but there kind of a pain putting on and off. Doubt the problem is the gasket itself. Also try using a torque wrench, you might not be getting it tight enough or uneven tightness?

 

Alright I'll check that out. I don't know if I can get a torque wrench in there...It's tight. Especially when there's snow on the ground. And it's a 2wd, so I can slide under it, but I've got about 1/2" between my nose and the frame. We'll see...

Thanks.

 

I know, almost wasn't going to say try to torque it. If you're using a wrench thats giving good leverage you should be ok, its an awkward area to work in for sure, I think extensions and ratchet work....

I've used brass nuts before on my Corvairs but think I not only used a lock washer but might have double nutted them but cant remember, makes it easier to remove but there much easier access also on the Corvair.

Being you're so close to the frame you might be getting reflective radiant heating

 

I also noticed today on LCEngineering that they sell this gasket.

There hasn't ever been anything in there other than those metal rings. And I've never seen anything call for that. But maybe that's part of my problem...? I don't know. I guess it sounds like it's for their headers, maybe not stock exhaust.

Either way, I'll be getting new studs and bolts with lock washers, and we'll see. Talked with the machine shop guy today and got the news on my head, and it should be done next week. All new threads for the exhaust manifold surface will be part of the work. Maybe my truck will actually be quiet from now on..

 

20R manifolds call for two exhaust gaskets stacked. I would suggest new stainless lock washers on all three studs. You can also try three grade 8 locking nuts (not nylock type, all metal). Periodic retightening is a good idea too. Every two or three oil changes. I would not use thread lock.

 

Alright, thanks. Yeah I'll definitely stay away from threadlock. I never really thought about retightening for some reason...probably because I've never had to on any other truck. I just assumed something must be "wrong" if mine keep loosening.

But I'll start checking them now and them and retightening if needed.

I did order two of those rings. I think I only had one in there this last time...which might explain why it was black and crumbling when I pulled it out...

I'll be interested to see how my engine sounds when it's back together. I've always assumed that the reason it sounds like a V8 is because of the exhaust manifold leak I knew I had (stripped studs). But then it never sounded like the manifold leaks I'm used to, which sound more like a Harley or helicopter. I keep forgetting that this truck has no muffler...I don't know if they couldn't fit it somehow, because of the camper body, or if someone just did away with it at some point. The tailpipe goes all the way and sticks out the side of the camper. There's just no muffler in there.

 

It was likely removed. I'm unfamiliar with camper trucks, but I have a hard time believing a truck would be sold sans muffler.


My 20R also loosened up a lot. Locking metal nuts would help a lot. And yes, anti-seize. Be careful tightening when using lubricants on threads because it can make it easy to over-tighten. Especially with two gaskets. Tighten it, then re-tighten a few weeks later due to the extra crush from two gaskets.


When your head bolts for the manifold strip out and you're looking for replacements I would suggest grade 8 stainless, course-threaded oversized studs. Maybe only available at specialty shops. I got some off of a diesel engine (big Cummins) and threaded them into the old bolt-holes and they work fantastically. Course threads are taller than fine threads and in this application are a far better choice than the fine thread. If you oversize by one size you should be able to lube the stud and thread it into the head without drilling/tapping. These trucks have a real weakpoint on exhaust mounting/sealing.