Interesting find! Way to go! I had a similar situation about a year ago. I found that the 'hot' wire going into the distributor had a worn area near the little brass strain relief clamped onto it. At times, it would short out with the body of the dizzy casting and quickly "go south". It was a pain to find it. Old cars.....

 

Started cutting out again under hard acceleration. Took everything apart and found the 3rd set of points were starting to burn, even with a new condensor. Called Lectric Limited and asked them if the resistor wire could burn the points. The tech said no, that any failure mode of the wire could only further restrict current (or burn open...I suppose). Told him my problems started after rebuild and use of a new GM Delco repro coil from China. He GUARANTEED me that the coil was the problem, that he has heard of many problems with these imported coils. He told me their internal construction, electrical characteristics and quality are NOTHING like the OEM part.

Looked in the Paragon catalog and noticed they still sell the imported repro 287 coil for $95, but it is no longer under the GM Restoration Parts logo. I bought mine in the summer of 2009 but noticed it has a date of Sept 2004 printed on the bottom. Hope my supplier will take it back and get a credit from whomever he bought that POS from.

The new GM Restoration Parts 287 coil, now made in the USA, goes for $140. I'll bet they had so many failures with the Chinese coil that GM pulled the license and sold it to an American company. I just want a quality "Made in the good ol' USA" coil with the correct impedances and turns ratio, made for a standard points ignition system and fits inside both my original coil bracket and shielding box. Paragon sells an American made '55 to '74 standard ignition performance upgrade coil (106:1 turns ratio) for $55 but I have to check it out. I saw where Pro Team Corvette has (1) used original 287 coil for sale at $200. Sheesh.

I know all about Pertronix and MSD so please...no lectures. I'm just not interested in mods. These cars were just fine the way they were originally built and I am trying to keep mine that way.

 

I'm probably boring some of you with this, but I believe the problem has been solved. I put the new Pertronix Flamethrower performance coil back in, new NAPA points, cap, rotor and Champion RN14YC plugs. Set the dwell at 30 and the timing back down to 16/34. Screams to redline in all gears. If I had to guess...the new cap locks down tight to the distributor, the new rotor matches the cap and clean plugs...even though the AC R44XLS plugs only had 1400 miles on them. They were kinda sooty and weird looking...probably from all the messing around.

If the ignition stays the same for a few hundred miles, I can follow Lars' advice and finally start working on the fine tuning of my Q-jet. He is absolutely right when saying that 90% of the time, performance problems have to do with ignition...and they have to be solved first.

 

Still cutting out at higher rpms. Been told I could be running lean and to try non-ethanol 90 octane with an additonal couple gallons of 108 octane leaded C12 race fuel. Also replaced the original gas cap, which was not venting properly. All to no avail.

Also been investigating my carb on-line with Cliff Ruggles and seems that I need to follow the path many others here on this forum have gone down. My new (dated 1986) service replacement carb has huge airbleeds (.120") that need to be replaced, along with possibly new main jets, primary/secondary rods and an adjustable APT screw. This is plan B and on hold for now.

Today I borrowed a known good complete Corvette points distributor, cap and solid wires from the local vette shop. Tomorrow's plan A is to pull my ignition and try this one. If the problem goes away, then something is wrong with my system. Will advise.

 

I had a similar problem once I got to 5 grand the car would lay down and start running out of fuel.

Things I did:

1) I had bought a nice rebuilt correct quadrajet carb, and as you know it has a place for a filter. I also had an inline aluminum aftermarket filter going to the carb. The filter in the carb was restricting the flow. Taking that filter out and just keeping the line filter made a big difference. You may want to just take the carb filter out and see what that does.

2) I Replaced the fuel pump, it was weak for sure.

3) I also raised the float level a little bit, to much and you smell gas, so it is a fine line.

 

Rat,

I had similar problems with my 71 points ignition. Turned out to be a weak spot in the coil resistance wire down by the starter.

My car would crank and idle fine. Would accelerate fine under normal driving. Wot in neutral, no problem. But at wot under a load would spit and sputter, then slowly clear out as rpms climbed.

When I bought my car the wiring next to the starter had been bent into a 180-degree shape and fastened to the starter with a tie wrap. I cut the tie-wrap and straightened the wireing, and it fixed the problem.

Straightening the wiring was a fluke to find, it was an act of desparation after changing carb twice, distributor twice, coil once, replacing points with petronix breakerless system, new plug wires, new cap, new rotor, adjusting timing, blah blah blah.

I new I had a voltage problem by hooking my voltage meter to the coil terminals, and driving the car with it hooked up. Under WOT my voltage dropped down to around 4 or 5 volts. I have an auto tranny and could make it cut out in my driveway by powerbreaking it. Maybe you can do something similar.

Good luck,

Feel free if you want to call me 225 931-7745 and I can give you more info on phone. Tough to write it all down.

Roger3

 

Rob, thanks for the reply. I have no filter in my carb inlet, only the correct inline aluminum filter...which is new. My fuel pump is new also.

Roger, thanks for the reply. Running current to the coil is supplied thru a resistor wire, which comes from the fuse block and is nowhere near the starter...unless your wire from the solenoid to the coil for full points starting current was rubbing somewhere and shorting to ground.

Anyhow, I went for a short run today with the loaner ignition system and it seemed to work fine on the first try to 5200 in 1st and 2nd. Then I decided to go for a longer run and get the engine good and hot. The same thing is happening, cutting out in the higher rpms, both part and WOT. I also noticed a significant increase in chugging and popping in the exhaust, along with stumbling off idle...probably the B20 vacuum can on the loaner distributor. Still running on ported vacuum and timing at 16/36 with vacuum plugged. I just think this service replacement carb is set up too lean over the entire range for my engine, especially after rebuild.

At this point I am going to pull the carb and go thru it per Cliff Ruggles suggestions for jets, metering rods and external APT adjusting screw. Good opportunity to check the float setting, needle and seat, power piston and check the output from the fuel pump with a gauge. If not adequate, then I'll stick my arm in the tank and change the original sock.

 

I know you guys like a happy ending, so here goes...

Look at what I found today...a worn spot on the primary lead from the coil to the points...exactly were the breaker plate would probably contact the wire when at full advance. No wonder the ignition just gave up! After rebuilding the entire rear end and fuel system, the problem was still there. Decided to take a high power flashlight and a magnifying glass and start looking the distributor over again.



This is what a new GM primary wire looks like, with a brass ferrule protecting the lead from the advancing breaker plate. Go figure.



All is well that ends well. Fuel or ignition? Just like Lars says...90% of all carburetor problems are ignition related. How true it is.

 

I'm not the expert here, but you say that the vacuum can checks out fine.

But does the distributor breaker plate rotate smoothly and freely? I have had old distributors with badly gummed up breaker plate bushings that would in effect prevent smooth vacuum can actuation - catching a hitch on the way up as vacuum varied, then freeing up as vacuum varied more.

I've also had distributors where Bubba replaced the factory short breaker plate hold down screws with ones long enough to drag on the base plate and prevent smooth vacuum advance.

Yes, it's odd and unlikely, but it's also super simple to check.

I'm also curious about the very narrow range of the problem, and just how repeatable it is. What happens if you stay right at a steady 1600-1700 rpm? And does your problem occur with 100% repeatability?

 

did you notice how old this thread is??