Have a few they were adjustable also on the mechanical side with easy keys Rob
MP distributor - reducing mechanical advance
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I welded in pieces of 1/8" rod in the top of the slot and ground slightly to get 0.355" slot length. The engine is idling at 20 degrees and I get 35 degrees total advance / 53 degrees with VA. The advance seems to come in reasonably quickly. I have yet to plot a curve but there is a fuel leak near the pump that needs to be fixed first. I think I am good for now.
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I took some advance readings (no VA of course) and it looks like I have 30 degrees advance by 1300 rpm (10 degrees mechanical) which hangs around until close to about 1900 rpm. Its pretty flat after that as max timing is at about 2100-2300 rpm (15 degrees mechanical). Is this considered acceptable? I haven't noticed any pinging. Plugs look ok. I haven't driven it after welding the slots but that shouldn't be a factor here.
If I look back at Troy's @CFD244 graphs its looking a lot like the OEM curve (just like the 30 deg mechanical OTOB). I think I will send a note to Mancini and see what they claim this distributor's set-up is supposed to be not that I expect a good answer.
If I look back at Troy's @CFD244 graphs its looking a lot like the OEM curve (just like the 30 deg mechanical OTOB). I think I will send a note to Mancini and see what they claim this distributor's set-up is supposed to be not that I expect a good answer.
Thanks, by the look of the springs I figured full advance would be in by about 2000 RPM. I will be putting a timing light on mine this weekend and report back on the factory settings. I will likely weld up the slots over the winter myself. I am aiming for about 20 initial and 35 total as well.
I’m not well versed in Mopar advance curves (last distributor i dealt with you could design your own advance curve on a laptop and upload to the distributor) but i think it comes in too quick. Perhap I will drive it some more before I consider changing anything. I assume i will need to swap the light spring for something a bit heavier?
I wonder if you had welded the other side of the slot how it would have come out. Little more preload on the springs.
A factory distributor has one heavy spring and one light spring. When I redid my current distributor I used two factory light springs, and the curve is all in by about 2500. The MP distributor appears to have one spring the same and one a bit lighter, which is why I guessed it would be in by about 2000. The spring is nowhere near as light as some of the old kits that looked like a spring from a ballpoint pen.
I wondered about that. I'm no expert on how the advance works but I think the advance would start a bit later but by how much? Or do you end up having to turn the distributor as its advanced too much at idle? The curve would otherwise be the same I think. The other issue is that max advance would come in quite late because the slot is way out there. If I do fiddle with it I have a few springs off of my parts distributors to try. I will have to try and measure the springs, spring tension and see if there is something a little heavier. Perhaps Halifaxhops can help if that time comes.
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I did some timing checks today. When I set the advance to 35 degrees at 2500 rpm, I ended up with 25 degrees at 1000 rpm. The problem is when I increased the rpm it slowly kept advancing and ended up at almost 42 degrees at over 3500 rpm. My conclusions are that the light spring is giving me extra advance at idle and the stiffer spring is not giving me full advance until over 3500 rpm. This seems to agree with what other people have noted as sticking slots.
I believe that. Just look at the OEM curve above. Its my (perhaps educated) opinion that if your going to weld the outside of the slot and run a lot of initial advance (20 degrees) the mechanical advance will need to be slowed down some. I said I wasn't going to mess around with the distributor after welding the slots until I ran it but I had to pull the distributor to drop the tranny so I did. From what I can tell the little spring allows for rapid initial advance to about 10 degrees (per the OEM curve above) and the big spring doesn't do anything until well after 15 degrees advance which the distributor will never see with a 15 degree (crank) slot. This means the distributor is only running on the light spring. What I am going to try is replacing the heavy spring with another light spring out of my old 340 distributor. It will slow things down but by how much?
I have a couple of extra distributors, so I will look for a lighter spring as well.
I mapped out the advance curve more carefully today.
1000. 15
1500. 18
2000. 22
2500. 26
3000. 29
3500. 33
4000. 37
I connected the vacuum advance and it was pulling 22 degrees for 48 total at 2500. I need to change the springs to get the centrifugal in quicker, and limit the vacuum advance over the winter.
1000. 15
1500. 18
2000. 22
2500. 26
3000. 29
3500. 33
4000. 37
I connected the vacuum advance and it was pulling 22 degrees for 48 total at 2500. I need to change the springs to get the centrifugal in quicker, and limit the vacuum advance over the winter.
Looking at your curve and I do not know why you want to speed it up any more than that.
Unless it’s horribly low on compression or it has a big cam (or both) I’d slow it down a skosh and try and get 35-36 at peak rpm.
Its got a little slower curve than in my MP distributor.
Yeah, those MP curved distributors definitely have a fast curve in them.
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