1939 Special - Replacing Manifold Gasket...How Big A PITA?

[JRHaelig]

I have an exhaust manifold leak on the #8 cylinder.  The last stud is loose & has wobbled for a while.  Soot is showing and fiber gasket material missing.

 

In short - I need to replace the gasket, so I bought a nice copper one to coat with graphite/oil and mount on up - including the belleville/spring washers..

 

I am planning (hoping) to either grab a few good threads on the bottom of that #8 stud hole (preferred), or tap it a size up.

 

The job is inevitable (I could live with it, but why?) but I do have to ask - how big of a Pain In The Asterisk is this job?

 

My first review looks like there are no holes in the manifolds by which to hang them on the studs....only the half-round tabs.  Looks like that makes alignment and snugging a 6 handed job.

 

This is a single-carb unit, so are the intake and exhaust portions linked together?

 

My little bit of research so far indicates that manifold gasket replacement is common enough so that is shouldn't be overwhelming for me.

 

Any words of encouragement?

 

 

 

[Morgan Wright]

I took the manifold of my '40 to the shop to get milled. They charged me $200 but there is no more leak. I had:

 

1. Exhaust leak, makes car sound like a Formula 1 and turns heads

 

2. Intake leak, makes a whistle sound and car runs lousy

[Matt Harwood]

The hard part is going to be removing the old nuts if they're rusty. Hopefully none will break off. Use penetrating oil and heat and take your time. If they fight you, quit and come back later with more heat and more oil, not a longer wrench. I'm fighting the head studs on one of my cars and there's nothing more maddening than a broken stud. Take your time and avoid that particular headache.

 

As for the gasket, I just replaced the manifolds on my '41 Limited and removed a copper gasket that I installed two years ago when I replaced the manifolds the first time. It had already started coming apart. These gaskets have about 2000 miles on them and they're completely cooked:

 

 

From the factory there was no gasket, just graphite paste that let the manifolds move around a bit, which is important (that's why you use the bellville washers). But if your mating surface isn't 100% perfect, it won't seal even with the copper rings in place. I have been using Remflex gaskets on all my cars for the past two years and really like them. They're a composite that doesn't burn or shrink and they're a bit thicker than regular gaskets so they will seal up irregular surfaces really well. They don't blow out and they can be re-used. I have them on my wife's '56 Chrysler wagon, used them on my Limited header install (they have straight-8 Buick gaskets on the shelf), and am having them make a set for my '35 Lincoln. They only need 20-30 lb-ft of torque, which is ideal for using with the bellville washers. I'm only a customer, but I've been very pleased with their performance. Sometimes a new idea really is better.

 

Installation isn't as hard as you think because the manifolds will hang on the studs even though they're only half-round. The cast iron doesn't flex so it'll sit on the studs without falling off. It might be worth replacing the studs as long as you're in there, but that's up to you. Here's my Limited when I did the manifolds: 

 

 

Hope this helps!

 

[Jolly_John]

THANKS for the super tip about using the Remflex Gaskets, Matt. I've been messing with straight eight Buicks for 50+ years, and have never heard of them before.  I just checked out their website, and saw the straight eight Buick set runs just $50. A real value....if they keep a guy from having to go back in on this PITA job after a couple of years! John

Edited April 4, 2019 by Jolly_John (see edit history)

[Morgan Wright]

Sometimes it's just easier to take a glob of stove putty (furnace cement) and put it over the leak. Works perfectly for small leaks, whether exhaust or intake.

[JRHaelig]

I did try the stove putty.  It was a good effort,  but the soot and whatnot kept it from lasting.

All nuts came loose ok, save for one that backed the stud out instead.  I torqued them back after determining that they weren't going to be a problem. 

 

We'll see how it goes in a couple of weeks. 

 

Thanks all!

[rodneybeauchamp]

John,

if you want some practice, you can do mine! I have the gasket set and tools, bed and breakfast supplied!

 

Be interested in what you discover, I have put penetrating oil on mine a few weeks ago, knowing it was going to be done sometime soon.

cheers RODNEY 😀😀😀😀😀

[Morgan Wright]

The nuts that attach the exhaust manifold to the header pipe are brass, so be careful with the wrench. I use the box end of wrenches on brass nuts to avoid damaging them.

[Mark Shaw]

Be sure to install new manifold rings too....