Need a Mopar guru: 273 part-throttle ping driving me crazy!
======================================================
From the page you mentioned: Is this what you are referring to?
"The manifold was made from cast metal. The molten metal was poured into a mold through a little hole and when the manifold was finished, the little hole was plugged up with a little rubber plug. Well, after a few years this little plug would dry up, shrink, and fall out, leaving a hole in the manifold."
======================================================
I've never heard of such a thing as a factory rubber plug. YOU MIGHT HAVE an early (72) intake which DID NOT use an EGR valve, BUT DID have EGR. The first year or two that Mopar used EGR, Ma just drilled into the bottom of the intake, into the heat crossover, which of course is exhaust, and "jetted" it for a continuous leak of exhaust into the intake. On those early manifolds, YOU MAY or may not be able to see them with a flashlight down through the carb throats. You may have to look down through the bores with the carb removed, see below
Once again, these early EGR manifolds HAVE NO external EGR valve. No external clues that I know of
http://i54.tinypic.com/29w4wtz.jpg
You mentioned very high octane fuel. ARE YOU CERTAIN that what you hear is spark knock and not some other noise?
======================================================
From the page you mentioned: Is this what you are referring to?
"The manifold was made from cast metal. The molten metal was poured into a mold through a little hole and when the manifold was finished, the little hole was plugged up with a little rubber plug. Well, after a few years this little plug would dry up, shrink, and fall out, leaving a hole in the manifold."
======================================================
I've never heard of such a thing as a factory rubber plug. YOU MIGHT HAVE an early (72) intake which DID NOT use an EGR valve, BUT DID have EGR. The first year or two that Mopar used EGR, Ma just drilled into the bottom of the intake, into the heat crossover, which of course is exhaust, and "jetted" it for a continuous leak of exhaust into the intake. On those early manifolds, YOU MAY or may not be able to see them with a flashlight down through the carb throats. You may have to look down through the bores with the carb removed, see below
Once again, these early EGR manifolds HAVE NO external EGR valve. No external clues that I know of
http://i54.tinypic.com/29w4wtz.jpg
You mentioned very high octane fuel. ARE YOU CERTAIN that what you hear is spark knock and not some other noise?