Need a Mopar guru: 273 part-throttle ping driving me crazy!

fazeka said
OK. I am a little confused as you are saying no EGR valve but did have EGR... Let me see if I understand your point: Are you saying my 273 has an intake manifold with a "hole" in it that is allowing/leaking exhaust into the intake? If so, how would I plug it (looks like a thread plug? in your pic above) and would it even be possible with the carb removed?

It would have to have a later manifold installed. The first couple of years (around 72) that Ma implemented EGR, they did not use a VISIBLE EGR valve on the external part of the manifold. They simply drilled the "floor jets" as outlined in the drawing.

I've never tried to plug these, don't know.

fazeka said
what else would cause a knocking sound at part throttle to improve when I used a mix of 100 octane with 91/92 octane? Feel silly for asking in light of your question, but... could there be an issue with valve adjustment?

Could be a number of things, depending. The engine torking over under throttle and "rattling' against something, IE header or broken engine mount, etc. Any chance it's a rod, piston pin, broken piston?

"What do you think" the compression ratio is? Did the pistons have valve reliefs? Does it seem to have good power, that is, the cam must be in time?

How big a role does engine temp play?