396/375 hp/motor issues

[christopher teed]

thanks for the help so far...removed the carb and checked all the idle circuit for blockage etc.and checked the carb in general ..noticed that the diaphragm front pump... appeared to be sticking.changed it appears to run better...two things i really notice is the first is with the timing light ; at idle or throttle up the timing mark is steady ,then all of the sudden it jumps back about 20 degrees and then moves back to the stationary mark on timing tab this happens about every five seconds,,,the other is the fact that the bullet flat tappet cams is not much above the stock 396/375 cam...it does have a alittle tighter duration and a tight valve lash...but should have a good vacuum right at idle.....have drained the oil and removed the filter and will cut into the filter and see what is up.i live in orlando florida and the motor was dyno tuned on Bo Laws dyno by a guy named Dave Crunes ,Dave used to run stock eliminator years ago

[christopher teed]

well. drained the oil and cut away the oil filter to be on the safe side...everything looked good..drove the car down the road at 3000 rpm and up it runs fine...starting to think it may be a distributor issues..stock gm distributor with a advance curve kit and a pertronix ignitor ignition in distributor...have the same setup in my 396/350 camaro with no issues...will keep plugging ,but at low speeds and idle it runs and sounds like sh...will put my AFR innovative motorsports gauge on it ,and work on getting the air fuel ratio correct

[Jeff Lee]

Last time I had a car with that Petronix in it it ran pretty much as you are describing. It was in the car when I bought it. I went to auto zone, paid about $55 for a rebuilt single-point distributor and the AMX instantly ran perfect. Also picked up about 800 RPM.
Pull one plug wire at a time, ground it and see if you have spark out of all 8.

[christopher teed]

i will give it a try Jeff.thanks...with the timing light hooked up ,timing mark it is steady for about 5 or 10 seconds them its instantly jumps about 20 degrees.starting to make altittle more sense.

[stage1scott]

Originally Posted by Jeff Lee

Last time I had a car with that Petronix in it it ran pretty much as you are describing. It was in the car when I bought it. I went to auto zone, paid about $55 for a rebuilt single-point distributor and the AMX instantly ran perfect. Also picked up about 800 RPM.
Pull one plug wire at a time, ground it and see if you have spark out of all 8.

Me too-went through 2 of those junkers then bought a ford dura spark dist to power an msd box-cured months of frustration! now I just say no to pertronix

[pmrphil]

Chris - try swapping distributors and see if the problem goes away

[christopher teed]

changing distributors this weekend will let you guys know what happen...

[Mike Pearson]

I have used the Pertronics conversion for years on my boat. It has worked perfect. I doubt that is your problem. Google the wiring for your unit online. I cant rember but I think you have to eliminate the ballast resistor. If the ballast resistor is still in the system that could be causing some issue. Also some ignitions used a resistor wire. Run new wiring to the coil and pertronics unit.

[Mike Taylor 3601]

The way you say your timing is jumping around,it sounds like ignition control/box problem.
I have used alot of pertronix on restoration projects have'nt had any problems,I use ignitor 3 has protection circuit and built in adjustable rev limiter,pertronix tech line has always been helpful when I have called,oddball installations, I would probaly give them a call.
I keep a hei w/wires so I can test and elimnate whole ign. system@ one time then have hei setup for msd so can determine box or dist.
Don't take for granted that any part can't be or go bad.
Mike Taylor 3601

[Run to Rund]

Definitely check out the ignition as noted above. As a last resort, the carb to intake, or intake to head gaskets could be leaking vacuum.