VCCA Home Forums GENERAL DISCUSSION Forum Questions exhaust manifold leaks

1932 Chevy. out of the 4 exhaust manifold ports,the two inner ones continue to leak,noticeably even after being changed,surfaces thoroughly scraped,and after those two ports were doubled up with gaskets!Currently using the gasket kits from Filling station,need suggestions on how much to tighten if I am overtightening or use a different type gasket.When first changed they are fine for an hour or so,then leak,retightening does no good.Thanx

Check the straightness of the exh outlets with a straightedge and also the manifold. You may need to have them machined. Also be sure the intake is in proper alignment. If necessary loosen the four bolts that attach the two together then retighten after snugging up the exhaust bolts. I do wonder about the thickness of the gaskets and quality as I also had a problem with leakage and did have the head and manifolds planed. Once they are installed recheck after running the engine up to operating temp. I may be incorrect but I thought the original gaskets were composed of an asbestos paper inner with metal on both sides. The "best" gasket is (my opinion) an aluminum foil center with a tissue thick paper on the outsides.

well,where would you get that type of gasket? I have removed the manifolds and they will be planed tomorrow.

Try Obsolete Chevrolet Parts in Nashville, Georgia.

Thanx

I wish to echo what Steve posted. If the two manifolds were separated then re-mated together it is easy for them to be out of alignment, and thus not aligning flat to the head causing leaks. The best practice is to tighten the two manifolds to the head then two each other. If you can not get them to mate then loosen everything up. Start the mating bolts but leave them loose then gradually tighten the bolts to the manifold. You should try to tighten the bolts all a little at a time so they seed the same. Do the mating bolts between the two manifolds a couple of steps behind the others until they are close to tightness. I would also take a child's toothbrush and put a little anti-seeze on each bolt as a lubricant. By little I mean just barely coating all of the threads. Remember you are dealing with cast iron so it would be easy to brake something with too much muscle. I would assume the torque settings could be in the 30 pound range with re-torquing being necessary after driving the car and it being well heated up. My advice comes from working on 216 engines of the 40's. They also have steel ring inserts that seat between the head and manifolds in each of the intake and exhaust ports to help with the sealing leaks, besides the heavy duty gaskets. I think the bolts should be checked for tightness on some regular maintenance schedule. Maybe once every 2-3 years. Some might assume the anti-seeze is causing the problem, but I like being able to remove and tighten the bolts easily.

In most cases the manifolds mated well before they were removed to be painted or the engine repaired so with a little patience they should reattach without a problem. A lot of us have had the same experience as you, so should not be blaming the gasket or even the need for re-milling. Good luck, Mike

P.S. I can post pictures if they would be of any help? In the future consider posting your question in the Forum that covers the age of your car, or in the Forum at the bottom of the Forum page under the heading Mr. Goodrich Mechanical-Engine, Trans, etc. You will find many more viewers there and they can answer your questions, and more will learn from the answers.

Like mike says, forget re-milling...And I'd advise anti-seeze for future removal...He's correct about leaving the manifold coupling bolts loose until the manifolds are tightened down...Don't forget the steel ring inserts...I'd tighten the bolts starting from the center and work your way towards the outside...I've never experienced this much trouble with alinement but I guess there's always a first time...I've never even heard of someone trying to mill a manifold...Can you imagine the trouble it would be to even hold it in the mill to fly cut it without it shifting during the process...? geez. I think I'd try using my belt grinder first...

A garage I worked in a couple of years ago machined manifolds on a regular basis. If it is a 2 piece manifold it was secured together before machining.
Tony

Belt grinder? Well thats exactly how my manifolds were machined. It was a machine with a belt maybe a foot wide and four feet long over a flat bed.

That is a belt machine designed to straighten both manifolds at once. The cost is not too bad and it does a great job.

The situation I was refering to fastened the unit to the head milling machine via adjustable angle bracket and made adverse comments about the belt sanding machines.
Tony

A couple of days ago I reinstalled my manifolds on my rebuilt motor. I did it first without the gaskets to see how out of plane the two were. I could easily slide a piece of paper under all but one of the exhaust ports. So after loosening the manifold head bolts I loosened up the fastners holding the two manifolds together so they could easily move. I then retightened both manifolds to the head and found I could barely slide a piece of paper under any of them. One was so tight I could not. I retightened the fastners holding the manifolds together and then loosened and retightened the manifolds with their gaskets and metal intake ring seals, and said "that was good enough." Thanks, Mike

P.S. I forgot to hit the "that was easy button."