Exhaust leak on 79 258 engine

[jp79cj]

I recentl putchased 79 CJ7 with an exhaust leak on the exhaust manifold area. Removed intake and exhaust manifolds. Seperated them and cleaned the flages and any mating surface including the head. Chased and cleaned all threads on bolts and the head. Pruchased a Fel-Pro MS9982 gasket set and care fully followd the instructions. Facing the metal side of the gasket toward the manifold. Installed manifolds with anti-sieze on the bolts and torqued to 25 foot pound.Started engine and was very quite. Drove down the road and it started leaking under a load. Returned and checked bolts. thet were ok. The leaks is worse under a load and hot engine. Leak not heard on start up. Cant feel leak ant where . Added Marvel oil in carb to make it smoke but still not sure,
Any ideas or suggestion from someone with same problem or smarter than ME. HA HA

 

[Saddle Tramp]

Do you have a cast iron manifold or more of a “tube” style header? If you have the tube header then most likely it’s cracked at the lower collector area (very common problem) or it could be higher up on the individual tubes. The cracks may also be on the backside of the manifold that you don’t see right off.

You state this happens under hard acceleration. It could be that the extra heat from the motor exhaust expands the cracks enough that you hear the leak or that the twist of the engine rotation on hard acceleration opens up the cracks enough for you to hear it; could be a combo of both. Exhaust manifold cracking in itself is common on jeeps because of off roading. If the exhaust system is not properly secured (sometimes even if it is) the bouncing and twisting leads to the system swinging back and forth which will lead to stress cracking in the manifold. A hot exhaust sytem will expand and any leaks will expand with it making the leak more noticeable.

 

[jp79cj]

Thanks for the reply. One discussion I am having with several people is the facing of the metal gasket. Does the metal side face the manufold or the head. Any thoughts. I have cast iron manifolds
Thanks

 

[Saddle Tramp]

I’m not sure if there is a “correct” side out for the gasket, others may have an answer; I guess I’ve not had to make the choice of metal in or metal out. The one thing that happens with cast iron exhaust manifolds is that they warp ever so slightly requiring that the contact surface be machined prior to reinstall. This may be your problem from the symptoms. A good muffler shop should be able to do it or take the manifold to your local machine shop.

 

[73CJ]

Time out guys. Lets lay a straight edge across the flanges first, then if bad take it to the machine shop.

My guess is a crack. Had one in a V 6 once. Perfect until you stomped on it. Then sounded like it needed attention.