I installed my Duraspark Distributor/MSD 6AL combo during the winter and noticed I had a high speed miss when the motor was revved over 4000 RPM--in neutral. I changed plugs and added MSD wires and the problem persisted.
While playing with a vacuum gauge and timing light today I discovered the cause of the miss--too much total advance caused by the Crane vacuum advance canister. If vacuum is unplugged from the unit, I get a clean rev to 6000+. Once hooked up, the engine will again miss at higher speed. The advance is hooked to ported vacuum.
I set timing to 36 degrees total (initial+mechanical advance) which is all in a 3500rpm (vacuum unhooked.) With the vacuum advance hooked up, the total timing appears to hit 65-70 total degrees (although with the miss it will jump around alot.) I thought that total (initial, mechanical, vacuum) should be a max of about 50 degrees.
My first question is will this be a problem when I put it back on the road? Will vacuum be so high when cruising that I will have the miss?
Should I limit the amount of travel that the vacuum advance can add?
If so, how is this done in a Duraspark? Anyone have a picture?
I wish to retain my vacuum advance for street driveability since the strip is about an hour away.
While playing with a vacuum gauge and timing light today I discovered the cause of the miss--too much total advance caused by the Crane vacuum advance canister. If vacuum is unplugged from the unit, I get a clean rev to 6000+. Once hooked up, the engine will again miss at higher speed. The advance is hooked to ported vacuum.
I set timing to 36 degrees total (initial+mechanical advance) which is all in a 3500rpm (vacuum unhooked.) With the vacuum advance hooked up, the total timing appears to hit 65-70 total degrees (although with the miss it will jump around alot.) I thought that total (initial, mechanical, vacuum) should be a max of about 50 degrees.
My first question is will this be a problem when I put it back on the road? Will vacuum be so high when cruising that I will have the miss?
Should I limit the amount of travel that the vacuum advance can add?
If so, how is this done in a Duraspark? Anyone have a picture?
I wish to retain my vacuum advance for street driveability since the strip is about an hour away.