Getting front exhaust manifold to seal 2.hate

The Dark Side of Will · Mon Sep 01, 2008 10:27 am

I've never been able to get the front manifold on my Formula to seal correctly.

When I bought the car it had a manifold leak. When I replaced the clutch, I discovered that one of the flanges had broken off the tube. There was no gasket, but there was a sheet metal heat shield between the manifold and cylinder head.

I had it welded, but my usual welder wasn't available when I needed it done; the guy who was available sucked. I added a gasket to the stack. The manifold warped and still wouldn't seal for very long. It would seal for a short period of time, but the bolts would work loose in as little as a week.

I had the manifold faced, but it was inadvertently damaged beyond easy repair.

I acquired another manifold that was almost straight. It still won't seal. The bolts work loose in a few days.

The '88 shop manual shows a gasket but no heat shield on the front manifold. I'm thinking that I need to wire brush everything, copper-cote the heat shield and put it back together with no gasket.

Has anyone else had this issue (except lowlux)?

Xanth · Post by **Xanth** » Mon Sep 01, 2008 10:34 am

Ditch the shield and use just a gasket, thats what I did on my Formula.

Mine looked like shit, whole engine looks shit actually but the shield was pretty bad.

The shield was one of the paranoid recall measures I believe, so if you send a rod flying through the block your oil won't spray on the cat. Problem is it doesn't stand up to well to the conditions on the manifold.

Scrap the shield, have the surfaces of the manifold machined flat and you should be good to go. My manifold is bent slightly where the Y-pipe spread it apart, I just machined all the flanges flat and it worked great.

Xanth · Post by **Xanth** » Mon Sep 01, 2008 10:41 am

I did actually have one alternative in mind though, now that I think about it. Chop off the upper portion of the shield, leaving only the lower mount holes, then bolt it down over the manifold flange rather than under. Perhaps need to make a small bracket to retain the bottom edge, but this would relieve the exhaust leakage issue.

Shaun41178(2) · Post by **Shaun41178(2)** » Mon Sep 01, 2008 11:23 am

if the bolts work loose then isn't that why its not sealing right? Retighten the bolts and won't it seal back up?

The Dark Side of Will · Mon Sep 01, 2008 12:35 pm

For about 3 days, then the bolts work loose again.

The Dark Side of Will · Mon Sep 01, 2008 12:37 pm

Xanth wrote:The shield was one of the paranoid recall measures I believe, so if you send a rod flying through the block your oil won't spray on the cat.

Yeah, I didn't know anything about the nature of that heat shield and how people were doing without it. I figured that if GM put it there, it was probably worth a few minutes of my time to figure out how to keep it... but not at the expense of my car sounding like a lawn mower.

Shaun41178(2) · Post by **Shaun41178(2)** » Mon Sep 01, 2008 12:49 pm

retighten and wait 3 more days? weird they keep backing out. use lock washers.

Aaron · Post by **Aaron** » Mon Sep 01, 2008 1:24 pm

Lock washers and Locktite aren't doing it?

The factory nuts on most GM exhaust manifolds are the oblong type, so they are difficult to install and remove. Maybe try replacing those?

jelly2m81 · Post by **jelly2m81** » Mon Sep 01, 2008 4:18 pm

I ditch that heatshield too, never had nothing but issues with them.

Dunno why your bolts are working loose, I've never had to retighten them, but I do crank them down really tight to start with, I always use new bolts also. I have no idea what the torque spec is susposed to be for them, but I guarantee I make then quite a bit tighter, to the point where I feel like I don't want to break them off.

I pulled the back shield on my 2.8 and installed a brandnew manifold back in 1995 that I ported , it's just now starting to leak ever so slightly, 13 years, I'm happy.

p8ntman442 · Post by **p8ntman442** » Mon Sep 01, 2008 9:19 pm

Will, get some new bolts, yours may have deteriorated enough that they are not getting enough friction on the mating surfaces. Ditch the heat sheild, and put some star torque on the new bolts (torque it till you see stars).

The Dark Side of Will · Mon Sep 01, 2008 9:27 pm

I've been using stainless bolts, but no lock washers or locktite.

jelly2m81 · Post by **jelly2m81** » Mon Sep 01, 2008 10:08 pm

The Dark Side of Will wrote:I've been using stainless bolts, but no lock washers or locktite.

Stainless steel distorts when heated. I've found that when you us SS bolts, they can be a cunt to get back out and usually fubar some treads.

That may be your problem. I'd also get a mirror there and check the condition of the treads, if they are jacked up, throw some helicoils in there.

Xanth · Post by **Xanth** » Mon Sep 01, 2008 10:17 pm

I'm using Rodney's stud kit, works great. I don't think he sells it anymore but the FieroStore kit is the same deal.

Just crank the studs in there, and the nuts are a locking style. Not sure what the name is, but they're dimpled so they pinch the stud.

Aaron · Post by **Aaron** » Tue Sep 02, 2008 12:03 am

I wasn't aware you didn't have studs. That'd be my first swap. Put studs with the oblong nuts, and they won't ever move again.

Nashco · Post by **Nashco** » Tue Sep 02, 2008 12:36 pm

I've had good success with the studs and locking nuts as well, mine were a part number posted many moons ago that list for a Saturn, I got them from GM. I also use this stuff rather than copper spray...copper spray works pretty good for replacing gaskets in a pinch with flat surfaces, but this stuff has never failed me on questionable surfaces:

It's tough to find in local stores (sometimes you can find it or something equivalent at Napa) but I promise that it's worth ordering over the net if you're ready to try something new. It looks like tar, pretty easy to work with, and stands up to heat better than any other sealant I've ever worked with. If the mating surface is really FUBAR, you might be better off removing the gasket and using this stuff. If it's so-so it's your call on using the gasket+sealant or just sealant.

Bryce

Series8217 · Post by **Series8217** » Wed Sep 03, 2008 4:40 pm

Why do you have stainless bolts? You should be using plated or oxide-coated studs. You should be able to get a set from Autozone.

Stainless steel tends to gall on aluminum and iron. It becomes more problematic at high temperatures due to the different expansion rates between stainless and the other materials it may be threaded into. Your threads are likely damaged so you probably need to drill them out and helicoil them. You could try installing some black oxide or nickel plated steel bolts of high quality. I wouldn't use stainless.

The Dark Side of Will · Fri Sep 19, 2008 10:27 pm

Woops... I got distracted from this for a while.

I can thread the bolts in by hand and they take full torque, so it's not a thread or raw bolt strength issue.

My dad and I have had good results with stainless bolts on *cast* exhaust manifolds on SBC's for quite a while. I don't see why these should be any different.