Msd pro billet in a small block 360 backfire at idle
I flipped the 2 wires in the dist connector and went for a drive yesterday and let it idle for a while. No issues. Now need to figure out springs and hot start hard crank. Had timing set at About 14 deg at idle. Light silver and blue in there now and a 14 deg bushing.
Verify that the bushing is actually 14 degrees. I have handfuls of them and it’s hard to find two the same.
That 14 degree bushing gives you 28 degrees of mechanical advance, and that’s a TON. I’d you really have 14 initial, at some RPM you’ll have 42 TOTAL. That’s a TON.
Depending on several things, the smallest bushing is use is the 10 degree part, and I forget what color it is and verify it’s actually 10 degrees.
With that bushing you’ll have 20 mechanical and you can get 15-16 initial.
I make my own bushings quite a bit. A 9 degree bushing gives you 18 mechanical and 17-18 initial.
An 8 degree bushing would give you 16 mechanical and 19-20 initial.
If the converter is loose, you can bring the curve in pretty quickly. If the RPM drop from neutral to in gear is too much, you need get more initial from your starting tune up.
Any ignition box will retard with RPM. When it starts to retard, and how much is always a guess because two identical boxes will start retarding at different RPM and may not retard the same amount.
I’ve seen as high as 6 degrees retard at 7500 (I’ve seen more retard but most guys don’t even turn that much RPM) so if you set your total when the distributor stops advancing at say...2500 RPM and you don’t check total timing at whatever max RPM it will most likely have less total than what you think.
EDIT: crackedback pull my head out of my can so in the above if you have the 14 degree bushing, that means you’ll need 21-22 initial to get 35-36 total. If you need that much initial than that’s what it needs. You have to give it what it wants.
Working on the bench I use distributor degrees and do the math in my head, but crackedback is correct. I prefer to do it that way, but it can be confusing...it just caught me.
