So I was driving my Chevelle around today, and I noticed an intermittant 'bog", at part throttle, about 2200 RPMs... basically, at moderate acceleration... Still pulls great, and at either mild accelaration (driving with typical traffic) it is fine, and If its floored, its also fine (no miss, no bog, no hesitation... It was really a quick hesitation (i originally thought i was running out of gas)... feels almost like it woul;d be a transition from one circuit to another...

I did notice the tach dropped (to near zero) when the bog occurred, so i was initially thinking "ignition"... The tach drop is more like a bounce, maybe a half-second to go from 2200-0-2200...

But the more I thought about it, i realized the other day I 'loosened" the secondary Air door on my Edelbrock 800 Thunder Series AVS so the secondaries would open quicker... I am wondering if that part throttle is enough to pull the door open a little too quickly and cause the momentary bog...


So basically, I am asking if it is the carb, would the tach drop so quickly? It doesn't feel like the engine loses that much RPM...

Thanks...

With the tack dropping to 0, I'd say its electrical. Sounds like a loose wire. Check your Dist., starter and battery connections along with your engine and chassis grounds.

Check for worn distributor shaft.

This is a similar symptom I had recently when my points rubbing block wore down to where the dwell was out of spec. Reset the points, problem solved.

Brettd85 had this....called me, "WHAT DO I DO?"
I gave a few suggestions. Turned out his hot wire to the distributor had pinched/worn through and was shorting off and on out as it flopped around. Check your hot wire out.

Brettd85 had this....called me, "WHAT DO I DO?"
I gave a few suggestions. Turned out his hot wire to the distributor had pinched/worn through and was shorting off and on out as it flopped around. Check your hot wire out.

Okay, i'll go look for loose or worn wires...

Ironic that it did not occur when I was really getting on it 5000+ RPMs, etc...

the dirstributor is new (about 8-10 hours of use), its an HEI, with a CD ignition box (so no more module either)...

It sounds like the pick-up coil wires are loose. When you gas on it the vacuum advance mechanism moves and that will pull on the pick up coil wires that plug into the module.

Dave

if you do something like loosen the AV adjustment and then notice something wrong or unexpected first thing to do is go back and un-do whatever that last change was. If it fixes the problem you're home free. If it doesn't at least you know that change wasn't the cause of the problem. It's way too easy to get into a tail-chasing deal in these situations. guys have spent hours and hundreds fixing problems that were actually a downstream effect of some change that was made.

if you do something like loosen the AV adjustment and then notice something wrong or unexpected first thing to do is go back and un-do whatever that last change was. If it fixes the problem you're home free. If it doesn't at least you know that change wasn't the cause of the problem. It's way too easy to get into a tail-chasing deal in these situations. guys have spent hours and hundreds fixing problems that were actually a downstream effect of some change that was made.

I agree, except in this case, the issue wasn't immediate, so I wasn't sure to equate it with that adjustment (I probably drove the car for several hours without the problem)... The car is so "fun" right now, because I took my sticky drag radials off... So it starts spinning the tires at part throttle, with no issues... Driving the same way, but the problems didn't start until much later... And still later, I couldn't get it to reoccur...

True, it could still be the carb, and I am planning on readjusting it back... But the "tach" rpm drop had me questioning if it was "fuel/carb" or electrical...

Thanks

It sounds like the pick-up coil wires are loose. When you gas on it the vacuum advance mechanism moves and that will pull on the pick up coil wires that plug into the module.
Makes sense... I am going to check those wires, probably at the same time I check the carb adjustment...
Thanks...

if there's no module in the distributor often the pickup wires are just plugged into some wires that come from the ignition box. there's no little bracket or anything and they can flop around. Also, as pointed out, when the vacuum advance pulls things move around. have a close look at this stuff including pulling on the pickup wires. sometimes they're "stretchy", which means the copper conductors are broken inside the insulation. This calls for immediate replacement of the pickup coil unless you're fond of tow trucks.

pickup coil replacement involves pulling the shaft out of the distributor, so it's a non-trivial task for most guys.