The Stovebolt Site Forums The Shop Area Engine Shop Overhaeting-not typical fix

I have not seen this on here, and thought it may be of interest. A friend of mine has a 60 Corvette, with a stock 283 Fuel Injected engine. He has run it for years without any problems, driving cross country and all. Last year we had a run down here, and on his way home to LA( it was a triple digit weekend heat wise ), it overheated, and after cooling down would still quickly overheat. After going through all the normal business trying to fix it, nothing seemed to work. One day he had it up on his rack, and looking around, he thought, those mufflers have been on there for over 15 years, I think I'll replace them. Bingo, heating problem fixed, run's better, etc. The car doesn't burn oil or run rich, so it seems odd that they started plugging up. Its a true dual ehxaust, and they both were still pumping fumes alright.

I suppose if I have a question, since it would happen slowly over time, is there any way to check or inspect for clogging before they get totally plugged?

My guess: it's not plugged with deposits. One of the baffles finally vibrated or rusted loose, and went into the outlet pipe.

I have seen a partially plugged cat converter actually limit the RPMs of the engine. That must have been hard on it for sure.

I've seen this. The ceramic stuff inside the cat broke loose and basically limited exhaust flow so much that it would barely run over idle. Took me forever to figure out what the problem was.

A vacuum gauge can/will identify an exhaust restriction.

Are your talking Intake manifold vacuum? What and how will this record or show up on a guage?

With the engine running at moderately high RPM in neutral, no load, the intake manifold vacuum will drop after a few seconds, indicating an exhaust restriction. The engine is actually being loaded down like it was pulling a long hill just from the effort of pushing the exhaust gas out. The diagnosis procedure is pretty simple- - - -just create an exhaust leak by loosening a pipe flange, and repeat the no-load vacuum check. If the vacuum stays high with a leak, you can assume the restriction is further downstream. I've seen a catalytic converter empty itself into the muffler, and the no-power symptom remained after the cat was replaced. A new muffler cured the problem.
Jerry

Thank you for your response, I had not heard of this before.

If air can't get out, it won't go in so the vacuum will be low.

We just sent a school bus in for warrenty work due to a blocked intake. The new diesels use a EGR valve to introduce exhaust gas back into the intake system to help meet the new emission standards. The EGR system uses engine coolant to cool the gas before intering into the intake. The cooler was leaking a bit of coolant whick mixed with the exhaust soot to form a sticky mess. Overtime the intake manifold just filled up and the engine just died out on route. We not sure how long it took to fill up. The Mercedes dealer never seen one do it before. Whats odd is these things will suck your shirt off your back if you get near the intake hole.

Joe