exhaust thumping and a knock inside the block

nsjames · Apr 15, 2011

chriskarel said:
ok thanks man. like I said I'm waiting for a new manifold. Would a week of driving lean do permanent damage to my engine??

possibly. If your knock is detonation then it will certainly damage the motor. I melted piston #3 in a mazda B series motor like that. The splatter on the connecting rod was welded to it. It was impressive...

See here:
http://www.misterfixit.com/deton.htm

You might try filling it up with some super premium gas, or just dump some octane boost in it. If you boost the octane and the noise goes away/changes it's detonation and you should probably stop driving the car, or you will damage the internals.

If you hop it all up on octane booster and the noise doesn't change, you're probably hearing the crack in the manifold and I would run it. Just be aware of the risks with a lean running motor and don't run the dog piss out of it.

chriskarel · Apr 15, 2011

I'm gona slap some JB Weld on it and see if it quits

nsjames · Apr 15, 2011

chriskarel said:
I'm gona slap some JB Weld on it and see if it quits

JB won't stick when it gets hot.

Find some stuff called thermosteel

it's copper colored stick in a tube.

It will stick for a week or two, but will fall out eventually.

chriskarel · Apr 15, 2011

JB says it'll hold up to 600 degrees F. Exhaust manifolds get hotter than that? GD....

nsjames · Apr 17, 2011

the cat doesn't even start working until manifold temp is 350 or above. I've never checked the temp of mine, but most gas motors range from 600-1000 degrees depending on manifold material and load.

The EGT's on my diesel get up to 1200. I had to back out of the throttle towing 11K pounds in my brother's 3/4 ton ford when it hit 1400 doing the Vail pass in CO.

yeah, it's hot ****.

http://www.amazon.com/CarGo-18003-ThermoSteel-High-Temp-Repair/dp/B000HABA3O

that's what you're looking for. You should be able to get it at any local parts store.