Why would my timing change?!

[Canadian1968]

I put a post awhile back about some timing issues . I was getting about 48 degrees at 2500 which was obviously a problem . It was suggested that I disconnect the vacuum advance and run just off the springs in the distributor. So with base at 18 I was hitting 38 at 2600 rpm .

I then had some unrelated starting issues, and pulled the distributor out and had a shop test my pick up coil for me. I was told it was workin fine but they mentioned that the distributor had 40 degrees of timing in it??? I thought that was weird . But getting the car started was more important at the time . Car is running / starting good now. I checked the timing again today . Starting with my 18 degrees I am now only reaching a max of 31 degrees??

If I hook the advance up again, it will go up to 45 plus. 

Why would will it only go to 30 with the vacuum disconnected ?  He did not change anything in the distributor .

[Cooter]

How old is the distributor? Have you oiled the hole under rotor button? Not many know thhat this is the lube for weights in distributor.
Could be sticking. Plus, almost all of the reman dist. Today that are sold are set up with mid seventies emission timing. Meaning A LOT of timing.

[Canadian1968]

The distributor is only 3 years old with maybe 15 hours run time on it. Its a MP unit.

[Chryco Psycho]

the newer MP units have an adjustable plate inside using 2 torx screws so you can limit the mechanical advance curve , it coul dhave been disassembled & set differently when reassembled

[69wannabe]

Like said above your distributor has an adjustable advance and can be limited if the engine is pinging. If he took these torx screws loose and didnt put them back in the same exact spot it could have limited your advance and you may have to pull it apart and give it some more advance to get it back to the mid 30's. I got about 20 degrees of mechanical advance in my distributor now and I got initial at 15 for a total of 35 but I could probably use a little more initial timing since its still a little sluggish off the bottom but i'm about as high as I can go since its on the edge of pinging so I may have to limit my advance a couple more degrees so I can maybe pull my timing up to 16 or 17 degrees and I think it would be plenty peppy there.

[firefighter3931]

  He did not change anything in the distributor .

If that is correct then the only logical explanation is that that the advance weights are sticking. 


Ron

[Canadian1968]

I just went back and talked to the guy. It was about a month ago that he had it so, i dont' blame him for not remembering exactly.

But I can peak inside and see the screws that you are talking about, they look like they are at the end of the slotted adjustment?

Also, when he looked at the distrbutor initially, he said something was binding, but he fixed it ??  I had the distrbutor apart jst before I gave it to him so there is a chance I had not put something back right.

Regardless , I dont' think its anything to crazy I will just have to pull it apart and see what I can find. The car is parked for the winter, as I am getting a new trunk floor and frame rails put in.

[firefighter3931]

The screws are visible through the breaker plate....you will have to rotate the shaft around so that the hole in the plate is above the screws. There are 2 screws and you can only see one of them at a time. To adjust with the plate on you have to back one screw off at a time and then adjust the stop and then go back and tighten each screw individually to lock it down.

The stop should be somewhere towards the middle of it's adjustment range to give you 18-20* of mechanical advance. Mallory sells a re-curve kit for the MP distributor with keys and springs to fine tune the timing curve. Takes the guesswork out of it 


Ron

[Canadian1968]

I am goin to have him recurve the distributor for me