Exhaust Manifold Gaskets......Again

[Ian Osborne]

I know I'm not the only one who has dealt with constantly failing exhaust manifold gaskets but I have the heads off for a valve job and I'm trying to fix the issue once and for all. Well, maybe for a long time would be more realistic.

I know the topic has been discussed here but I am wondering if anyone stumbled onto a great fix.

In general, the manifolds are solid with no cracks or defects. I believe they are in pretty good shape for 56 year old parts. Years ago I had the manifold mating surfaces machined flat and checking them now, they still look good.  The surfaces are solid, without any deterioration and the flatness is still good checking them with a straight edge and on a flat surface plate. I will check the cylinder head surface as well but they are less prone to problems.

I will attach them to the heads before installing so this is my chance to get everything right. Obviously I will install new gaskets and figure on using a non-hardening, high-temperature sealer. I also plan to use some Loc-Tite on the threads as the bolts don't use lock washers and they have had a habit of backing out.

The gasket sides are different with one side being more perforated looking. Is there a correct way to install them?

Any other observations or suggestions?

[Jason Edge]

Having the exhaust manifold machined / planed flat is a must and sounds like this as been addressed. You want to use new gaskets and I tend to put the shiny side out ... but since they compress don't think it matters.

What does matter is to make sure the bolt & cylinder head threads  are nice and clean and a good torque sequence is followed. I always chase the bolts with a die and the thread holes with a tap and blow out the thread holes with compressed air, and make sure the bolts turn freely.  When torquing down the bolts you want to gradually ramp up the torque... in at least 3 stages. I would probably torque toe bolts as follows: snug, 20 ft lb, 40 ft lb, 58/60 ft lb.  Many people recommend increasing by 10 ft/lb increments. It can only help spread the load and flatten the gasket. It is also generally agreed that an inside to outside torque sequence is bet to help flatten out the gaskets ... think of it like grandma rolling out those home made buttermilk biscuits. With that in mind, I start at the inner to then work may way out going back and forth until you reach the 2 end bolts, then repeat again starting at the center with the next torque increment.

I rebuilt my engine in 2012 and have maybe checked the bolts once or twice with no issues. Of course exhaust manifolds were machined, cleaned and torqued down as indicated. As far as coating the bolts I know I used the Permatex Anti-Seize Lubricant, rated up to 1600 degrees, on the cylinder head bolts and am pretty sure I also coated the exhaust manifold bolts with it, but need to go back over my notes.

[Russ Austin]

The exh manifold gaskets can go on upside down. They are just offset enough to give you problems, but they look like they are installed correctly.

[Mark Geertsma]

Also used to have problems with the exhaust manifolds. Had them machined flat twice, but the problem persisted. The fix for me was new bolts and copper gaskets. Never had any problems since. 

[Ian Osborne]

Thanks to all for the input. Mark, I have heard about copper gaskets. Are they just cut from a sheet and if so, how thick? Were you able to locate new bolts identical to stock, with the smaller head?

[Mark Geertsma]

Seller told me they are cut from copper sheet, in my case 0.046” thick. His standard thickness is 0.042” but I like my gaskets a bit thicker. Please note that copper gaskets must be annealed before installation.

As for the bolts, they were custom made by a local company. Couldn’t find the original bolts anywhere (metric only here). They fit nicely though, so I assume they are an exact copy of the original.

[Jason Edge]

You can see the original bolts and see specs on my parts page by Clicking Here

[Ian Osborne]

Thanks Mark, I think I will go with a compromise. I have ordered a sheet of .043" soft annealed copper and will fabricate my own gaskets but I have a good set of original bolts that I will use. I will also carefully torque the manifolds to the heads before installation as suggested by Jason. This may be the first time that has happened since I've owned the car. My memory is a little fuzzy but I believe when I rebuilt the engine in about 1989, I put the engine in first and then installed the manifolds. I have learned since that the manual tells you to do the opposite but that was just how I did things back then so they may have never been torqued correctly leading to the cycle of replacing gaskets with the heads in place.

[Mark Geertsma]

Good luck! Hopefully this will solve your problem.

[Ian Osborne]

Got them done today. I'm feeling pretty confident this is going to work but we'll have to wait and see. I was looking through my extra parts for a pair of exhaust flange gaskets which I was pretty sure I had. I found six pairs - which means that's how many times I've replaced them. Isn't that pretty much the definition of insanity?

The process:

[Jason Edge]

They look fantastic!!! Very Professional. 

[Mark Geertsma]

Nice!

[Ian Osborne]

So far so good. Here is what they look like installed. Carefully torqued to 5 ft-lbs more than the manual calls for (just because I really want to be done with this)