Hi I'm new hope someone can help I have a 1970 350 sbc I have a rpm gap edelbrock manifold and when I set the timing and tighten down the dist. it kills the motor and from the day I put that motor all in my truck it has had a miss in it that I can't seem to find also I noticed that my dist. while just sitting in the dist hole it still needs a 1/4 inch before it seats on the manifold. Really from the old motor the only thing that was changed was the manifold I have the msd dist. any help would be great .

Have you considered going back to the stock distributor? Years ago, I ripped an MSD distributor out, after having all kinds of stalling problems in traffic. After I installed the stock distributor, I never had another problem. I have been skeptical of MSD, and many aftermarket "performance" ignition products, ever since.

Its fuel injection