I have a 355 with HEI electric ignition and a 107 cam (lobe ctrs.) The specs. on this cam are 10 deg. BTDC. My problem is I have set static timing anywhere from 10-16 degrees and somedays the car runs good and others it is just right frustrating. I was running an edelbrock 750cfm but I felt is was too big so I did some homework and decided on a 650 speed demon. I put it on 2 days ago with the same timing I had with edelbrock(16 BTDC) and it ran wonderful. I jumped in today and went to get in the gas a little and she started popping (out exhaust?) I figured it may be timing so I set it at 10 deg. and still popping when you get on it. It seems now after 2 carbs having same type of problem that it may be something else(distributor or vacuum)? I pulled the vac hose off vac advance on dist. and plugged it and still ran like mud. Any ideas?

The mechanical advance is too slow to come in, or sticking. HAve you put in the "mechanical advance spring kit" yet? Only costs $5. Put in the lightest spring possible. I had to re-use my old (stock HEI) bushings because the new ones didn't spin well and caused my advance to not move at all.

Higher base timing (~16*BTDC) is less likely to pop out the exhaust than the 10*BTDC.

Also make sure you're getting spark to each cylinder. When you pop the cap to put in the new springs (or to check mechanical advance movement)take a flat tip screw driver and clean the 8 contact point around the inside of the cap. Also be sure the rotor is in decent shape. Both the cap and rotor are cheap, so just change them too if they are old.

Thanks BB_Mike,

I'm learning about this stuff all backwards and with lots of $$, but it sure is fun especially when it comes together...My problem is I jump the gun and need solutions immediately...Well, I pulled distributor and first noticed a "white flash" coating on the 8 distributor contact points and on some there seemed to be a small circular spot on these contact points where a lot of spark was received? One of the 2 bushings on the mechanical weight posts is "broken"(half missing) and 2 wires that go to the control module labeled W and G had what seems to be "bubbling" of the insulation on those small wires where they were touching eachother. This particular HEI is an Accel with the coil in the cap. Would I be better off purchasing a new HEI distributor with external coil and an adjustable mechanical advance?