New short block this summer and at 600 miles I noticed the paper type manifold had failed and was leaking and I had a putt putt putt noise. I replaced the manifold gaskets with gland and copper rings. I stopped the manifold leak but I still have putt putt putt when there is a load on the engine or just driving with gas applied. If I back off the gas, the putt putt stops. Any suggestions?
Welcome to the forum Robert, have you checked to see if your exhaust manifold is true? They have a tendency over time to warp and cause problems. I would suggest pulling off the exhaust manifold and putting a straight edge on it to confirm its straightness, if its warped, the vendors sell a great reproduction at a very reasonable price...Good luck, let us know what you find.
Sometimes the spark plugs will leak on compression. Especially noticeable on a hard pull. Usually leak is around the tapered threads. unless you have Champion X then it could be around the porcelain.
Another potential exhaust leak is the packing nut which tends to back off. This is the large brass nut which holds the exhaust pipe to the manifold
Also with the ring type gaskets, you need to torque them down a few times after running the engine. It takes a while to crush them similar to installing a head gasket.
You may still have a manifold leak. Brush on some liquid detergent with the car running and see if you get any bubbles.
Is your head gasket leaking? Did you re-torque after a short run-in?
Also possible that your glands/rings are not seated properly. It's sometimes a lot for two hands to keep lined up.
I would check the Exhaust packing nut first, I had the same issue until I found it also this accessory will prevent it from backing off again
and here is the repro exhaust manifold John was talking about
to check for trueness lay a straight edge along the bottom of the holes the warp tends to show between # 3 and 4 cylinders. hope this helps
Robert -- I had a similar experience a few weeks ago. It sounded like an exhaust leak near the front of the engine. I too replaced all the manifold gaskets, but the noise was still there. Then I noticed a spark occurring at the base of the insulator on the #1 spark plug (a straight-sided Champion X from the 'teens ). It turned out that that insulator had cracked while driving. I replaced that plug and all was well. I guess I should use some of those "stone" plugs mentioned in another thread.
Replaced the manifold. Existing one was warped. New one fit like a glove and I used glands and copper rings. Thanks for your suggestions, interest and support.