MSD 6AL missing

[vector1]

supposed to use non-magnetic feeler when checking also.

[Eljaro]

I finally think I found what was wrong. I modified a distributor cap making a big square hole in front of one of the terminal points for cylinder #1 and checked with the timing light
The spark would jump while the rotor point was past the #1 terminal. I did loosen up the screws holding the magnetic pickup and pushed it as far as I could to the most advanced position.
Now the point and terminal match perfectly at idle and at max engine speed.
Apparently MSD does not do a perfect job in phasing the rotor as they claim.

Now the timing is consistent and does not jump around above 3500 rpm.
I also made myself a larger stop bushing (10mm diameter) in order to be able to set 21º initial advance with a max advance of 36º.
The black stop bushing MSD provides did give me with a 21º initial a 42º maximum advance. Some wear of the interior diameter and a not very tight fixing was giving me 3º more advance than the 18º advertised.
I am using the two heavy silver springs.
Runs very well now.

[FatBoy]

I have almost identical symptoms with my engine. I am also running and MSD 6AL and MSD Pro Billet distributor.
At lower revs, it feels fine, but when cruising at around 3,000rpm, it sounds like it is misfiring and will hesitate and pop if asked to accelerate. Once accelerating, it feels fine again until it settles to an even cruise rpm.

Having read this thread, it sounds like I have to ruin a cap by drilling a large hole in it just to check if the phasing is the problem.

Oh well, needs must I suppose.

One more point, the central terminal in the cap is recessed below the level of the steel ring around it. That doesn't seem right to me, but can someone please confirm. Everything is just over 1 year old and has done less than 3,000 miles.

Paul