Misses at High idle or high speed

[poorman]

I've got a small question on the ignition system on my 1975 SII. At High Idle or traveling down the highway the ignition system is missing very badly. I've checked the vacuum lines and the spark plugs, the cap and carburater settings. I did find one vacuum line that was in the wrong place, but the wires and carb look real clean. What could be causing the miss at high speed or high Idle???

[Creepy196]

Does it pop back through the carb? Has this problem been gradually getting worse instead of a sudden change? After running it for a while with the 'missing' is the air filter wet with fuel? If so, then your problem may have nothing to do with the ignition. I had these symptoms with my 304. It turned out that the cam's #7 exhaust lobe was flat, and the mating lifter was badly dished. I swapped out the cam/lifters/timing set and the problem was solved.

Do a compression check of each cylinder. I'll bet one or more of the jugs gives a much lower reading than the rest. If so, you should check the rockers for the bad jug(s). Disconect the coil lead, and pull the valve cover for the cylinder bank that the bad jug(s) occupy. Have a helper crank the engine while you watch the rockers. If one or more of them is moving less than the rest, your troubles lie there. Watch to see what parts aren't moving (lifter, pushrod, rocker).

Of course, it's still possible that you have an ignition problem after all. Check your distributor shaft for play in the bushings (wobble). Check the pickup in the distributor (little white cube held down by one screw, whith a wire coming out of the side). Remove the gold colored ignition box from the firewall and clean its mounting surfaces, ground wire ring terminal, and the mounting screw that goes through it. I removed the paint on the firewall where the Gold Box mounting tabs touch and coated them with a little dialectric grease. It should get sufficient ground through the scew into the firewall, but I'm anal about grounds... If the Gold Box isn't grounded it won't work right (They don't work that well anyway...I eventually replaced mine with a Pertronix).

Go check out www.binderbulletin.org for more help. Someone there will probably tell you to get a service manual (not a Haynes/Clymer/Chiltons piece of shit but a REAL IH service manual). Said manual will have detailed info about your ignition, as well as needed info for a camshaft swap.

[poorman]

Thanks for the info, and now that you mentioned it the "gold" box was replaced and probably not grounded correctly, I shall comb through this situation today. the engine was recently rebuilt 30K mi. ago, so I am certain that the compression is up there. I'm gonna lean more towards an electrical issue with the ignition or advance......Thanks for the insight.

[Darel]

I had this same problem several times with bad points sets, but from above it sounds like you have the GB system. If I were you I would get rid of that and put in a points dizzy, and if you want to drop the extra $100 or so put a Pertronix in the points dizzy. That will solve your problem once and for all.

Darel