Working on a '73 340 'cuda that has a Proform distributor. I'm trying to set the timing and cannot get it to run with less than about 30 degrees advance, which also comes in at a very low RPM. Is this typical of them? I'm about to toss in a factory electronic distributor and see. Are these things phased funny or???

I did double check that TDC on the balancer was TDC on the piston. Interestingly enough I ran into a similar problem with a different Chinese distributor in a 273 that has similar timing issues. I was about to blame my nearly 20 yo Craftsman dial timing light except that it timed correct on my 440, but I still borrowed my sons timing light to confirm.

turn the dampener to 15 BTDC #1 compression & turn the housing till the tooth & magnet line up with each other with the rotor under or near under the #1 plug wire & check phasing

Thanks, I'll give that a try...

Well, that looked good UNTIL I looked closely. No gap between the reluctor and pickup. Pulled the distributor and the gap was there and I couldn't duplicate the issue. The bushings didn't feel especially loose, either. Looked in my pile of parts and found, not one, not two, BUT three DC/MP small block distributors. One of them looks clean and ready to go.

BUT, one more question while I'm at it. I pulled out one of "B" motor electronic distributors (one that I have taken apart). I see the pin that locates the reluctor, but the reluctor is loose on the shaft. I'm sure it was tight when I pulled it off. What keeps it tight to the mechanical advance piece?

Reluctor should be resistance fit. The pin helps locate tit and add to the resistance. Try another reluctor, maybe a new one? I think NAPA sells them.

the roll pin needs to be partly in the groove in the shaft & partly in the groove in the reluctor (assuming that is the issue). the reluctor is always tight on the shaft & the little clip up top under the brown circular rubber pad keeps the reluctor from ever coming up on the shaft, just sayin

Yeah, something is wrong with the old big block one. That's not important at this time, though. I did get the small block DC distributor back together this morning, but won't be putting it in until Monday (gonna go work on my son's Dart installing the clutch hydraulic master cylinder this afternoon). Always something to do.

And, no the roll pin isn't the issue with the big block dist. It's in correctly, the reluctor is just loose. I'll address that on a different day.

as mentioned the reluctor fits tight by itself but still somehow loose. When pin is installed this adds the needed presure to make a tighter fitment, like a preload spring. Usually is better try to fit the reluctor and pin already aligned to the shaft provision for the pin to don't need to match them while pressing down the reluctor.

dunno if my opinion helps or not

Yeah, but not on the big block distributor that I took apart a long time ago. I've got plenty of distributors to see what the issue is.

I think once I got a replacement reluctor which fit loose no matter what. Of course I didn't use it.

Put one of my DC distributors in. Timing was considerably more stable, but still doesn't want to idle without 20-25 degrees advance (yes, the mark is confirmed accurate). Cam timing? Carburetor? The cam doesn't seem to be too big, bu t I have no idea on the specs. In all my years working on Mopars I've never encountered one that wouldn't idle at 10BTDC.

I will add that the compression numbers were not ideal, but I doubt that there's a budget to tear the motor down at this time so it will have to live. Best cylinder was around 150-160, worst around 100. This was after adding oil to each cylinder.

That big a spread in the compression numbers tells us that you have mechanical issues.

Yes, I know that. Most likely rings from fuel wash (owner tried way too many to fire it with no spark) and little use over the last 10 years. It still should idle, even if rough, at 10 before. I've had blown head gaskets idle better than this, including a 440 that blew between two cylinders.

Have you pulled the valve covers and looked at the valve train yet ?? Could be a couple of bent pushrods, cam lobes going away ( remember that hard starting ?), Broken valve springs etc.
Helped a guy recently with very similar issues (via phone), wound up being the camshaft going away.

Another thought might be to try a vacuum guage although it will likely just tell you what you already know, you have several weak cylinders. The question is why?
Keep us posted

Nope, haven't pulled a valve cover. I've been resisting that as I am trying to avoid any more project creep. It may be unavoidable, but...