OVERHEATING

inertia said
When it's really hot , shoot the temps of the actual metal fitting top and bottom rad hoses.
You need min 30* drop, 50* would be better

I removed my Glen-Ray re-cored radiator and I'll perform this test when I install a radiator that I am borrowing from a friend.

dadsbee said
Did it puke? 220 shouldn't puke with the proper cap and glycol/water mixture.

My radiator overflowed quite a bit with a 16 lb cap, and a 50/50 glycol/water mix, every time I shut her down after it hit 220 degrees.

12many said
If your current pump does not have the anti-cavitation plate, and originality is a concern (I assume as you had it rebuilt) I would install a plate on the vanes.

I can't find any info on a cavitation plate or a plate on the vanes. Can anybody explain this and if I can purchase a cavitation plate? Would a water pump cavitate at 3,500 rpm or only at much higher rpm?

RustyRatRod said
First thing that jumps out at me is, your water pump is being under driven.

Dana67Dart said
...while his is under driven by 5 percent it was done on purpose to stock engines.

Would it make sense to purchase and test a slightly smaller water pump pulley to spin the water pump faster, maybe 6" or 6 1/4"? If so, where would be the best place to purchase smaller pulleys?

moparlvr166 said
Is the radiator sealed to the core support to force air into the rad... When you were driving did you hear the fan clutch roaring?

Since the radiator is stock it should have been properly sealed to the core support. I never heard anything from my 18" clutch fan. Plus, I'm under the impression that the fan wouldn't have much effect at 75 mph.

Oldmanmopar said
Did it overheat before the radiator was done with a new core

I had my radiator restored at Glen-Ray because of the original overheating issue. Since Bob installed a new 3 row core the fins wouldn't be an issue.

Bewy said
Unless I missed it, nobody has mentioned ign timing. Retarded ign timing will very quickly cause o'heating. Make sure your dist centri weights are moving AND that the vac adv unit is working.
Failure of either/both will cause hot running.

My initial timing is 12 degrees and all in @ 33 degrees @ 1,800 rpm (vacuum advance disconnected) and with the vacuum advance connected all in @50 degrees @ 2,200 rpm.

Frank Mopar said
Spark plugs do three things. They provide spark, keep themselves clean and they PULL HEAT OUT OF THE COMBUSTION CHAMBER.

Start two steps colder.

Ricks70Duster340 said
Shouldn't the current plugs be inspected before going to a different heat range?

My spark plugs are Champion RN12YC. Attached are pictures of their condition. There doesn't seem to be a lean condition. The step-up rods for my stock 1969 340 AVS for a 4 speed, are correct. The original 1969 340 spark plugs are Champion N-9-Y. Could the difference in the spark plug heat range cause this much of an overheating issue?

I started this reply yesterday and left the page open. I didn't responded immediately because I was doing more research. I see there are some more replies didn't show up in what I read and responded to yesterday. I will respond to them in another post.

Thanks to everyone for all the feedback.