Timing ? AGAIN!!

[mjr45]

Zed, all the hose PCV etc. are all new < 12 mos. old, but that's a good idea for me to go and check them over again. I re-calibrated the AFM(per Atlantic Z), its been driven after that with no issues other than it still runs very rich so I'm not sure about the A/F mix being changed, I'll also check the vacuum again, it is usually low per the specs(steady at 13), but I also live at 9000' so when adjusted for altitude it is right on, as far as I understand vacuum readings.

[Mark Maras]

Glad to hear that you're going to check a few of the basics first. Reading your description of the engine stumbling a little above 4500 RPM & the timing problem, I suspect that the oil pump shaft was installed wrong a while back & the PO got it to run to his satisfaction & gave up. That is an an easy fix. Was there anything else that you worked on when you adjusted the valves or did you possibly bump an elec. connection.(personal experience) Random thought- What position are the cam lobes in when you're adjusting? Mark in Portland

[Zed Head]

The standard timing setting for the 1975 engine, warm, was 7 degrees. Many people bump it up for a little better overall engine performance but it should still run fine at 7.

There's the ignition module possibility. They tend to show signs of failure at high RPM. Could just be coincidental that it happened near the time you adjusted the valves. You probably went out and ran up the RPM to see how things were working and might have pushed it over the edge. Usually the tachometer gets goofy also when the module goes bad though. The modules tend to fix themselves when they cool down, then go bad again when they get warm. Makes them hard to diagnose.

[mjr45]

Zed and Mark, I went and pulled the oil pump to put the oil pump spindle in the correct 11:25 position, I did this after I rechecked valve clearances, checked compression (ranged 118 to 130) with #3 being the lowest, check all the lines and hoses and made sure they were all tight, put the dizzy back in place, and plug wires, turned the key and it burped and banged and wouldn't run, went back and doubled checked and sure enough, had the plug wires on 180° off, changed that and she fired right up, messed with the timing and took it out for a short run, went to 6000 RPM, no stumble no backfires, no nothing, no high idle on decel, no nothing. Somehow my timing marks got either wiped off or something, so I don't really know what degree the timing is set(I'll figure that out later), it runs very very well right now, smooth revving all the way up. Thanks for all the help.

I'll be keeping my eye on the ignition module as I've read in several places about it getting a bit wonky and hope for the best in the meantime. Thanks again.