Cascade Crew

redlava

I have a problem my car stumbles when I get to 5200 rpm. I have the Holley blue mechanical pump. I replaced ignition with the mallory HEI unit a few years back. I have the timing set at 35 or 36 degrees at 2500rpm. I used a stock style in carb replacement fuel filter. Could this be a problem? I do not remember what octane of gas i put in but it was most likely 87. Could the car pull hard and run good till higher rpms then detonate and stumble at high rpms because of gas octane? Could running to hot of spark plugs do this? I have been running bosch platinums HR9BPX.

Any input would be great thanks.

chevymad · Posted: Mon May 14, 2012 4:42 pm Post subject:

Does it stumble/quick jerk/miss or is it a bogging sensation? Bogging sensations would be fuel delivery, the other is ignition trouble.

I'm thinking ignition trouble. First thing is to go through the tuneup and make sure everything is good. Bosch and/or platinum plugs would not be my choice for a domestic v/8. You don't really want the long lasting plugs like platinum or gimmick multiple electrode plugs. In a performance car you should be pulling the plugs probably once a year anyway so just run regular copper core plugs. I like ngk myself but delco and autolite are both good plugs as well.

My luck with bosch in domestics.. i'd almost think thats your issue. But make sure your cap/rotor are in good shape. You could also have a weak coil as well that doesnt put out enough at high rpm.

Twilightoptics · Posted: Mon May 14, 2012 5:12 pm Post subject:

Ignition, fuel delivery, valve float, flat cam.

Need more description as stated on "stumble"

You should also have a big fuel filter, not just the "in carb" one.

redlava · Posted: Mon May 14, 2012 5:18 pm Post subject:

It is more like a bog and it makes a popping sound (not loud like a back fire though). If you WOT in first gear it can drive/rev though it quickly so it is less noticeable. However the 2 to 3 shift it bogs like something is wrong so my natural instinct is to let off then it pops.

I definitely could see the wires needing replacement as well with the plugs, because they are older and have been pulled on/off a dozen times at least.

The actual distributor i have is

http://www.jegs.com/i/Mallory/650/8548201C/10002/-1?parentProductId=752904

What coil would be a good replacement? What do i look for in a coil?

This is probably a dumb question, but will the spark plug wires touching each other cause a problem? Are jegs or summit brand wires from accel?

aaron_sK · Posted: Mon May 14, 2012 5:38 pm Post subject:

redlava · Posted: Mon May 14, 2012 7:36 pm Post subject:

What heat range should I get hot, cold or in the middle?

Alphius · Posted: Mon May 14, 2012 8:36 pm Post subject:

redlava · Posted: Tue May 15, 2012 6:53 pm Post subject:

Update: I swapped out the bosch plugs with some unused ac delcos I had lying around. It made a large difference, the engine is much smoother. The stumble is still there, however it is much better. There is less of a stutter and the pops are smaller. Following the same track, I went and got some wires and some wire guides. I will get these installed tonight or tomorrow and keep you guys posted.

Thanks again for the help. You guys were right on the money. I have been using those stupid plugs forever and dealing with that rough idle assuming it was the cam. Lets see if these plug wires have this thing idling like a kitten.

redlava · Posted: Wed May 16, 2012 4:50 pm Post subject:

More semi good news. Keeps getting better but still there. So on to cap, coil, and rotor.... Do all HEI distributors have interchangeable parts?

redlava · Posted: Wed May 16, 2012 5:21 pm Post subject:

Just found the problem while browsing summit, for the coil I currently own summit states. Note "Effective up to 5500 RPM."

redlava · Posted: Wed May 16, 2012 7:07 pm Post subject:

I can get this coil at oreily's for 50 bucks. http://www.summitracing.com/parts/ACC-140003/ Has anyone heard anything bad about accel?

Twilightoptics · Posted: Wed May 16, 2012 11:02 pm Post subject:

Coils not the problem.

redlava · Posted: Fri May 18, 2012 4:38 pm Post subject:

Replaced the coil yesterday, but was unable to test drive because of rain. Just got back from the drive, the coil appears to be at fault and the problem is fixed. In case anyone is wondering I bought the bwd select coil for a 86 camaro and then bent the metal connection wires to fit in the hei cap.

Problem solved nice job crew.

Twilightoptics · Posted: Fri May 18, 2012 5:00 pm Post subject:

Never seen this.

Alphius · Posted: Fri May 18, 2012 9:22 pm Post subject:

Very odd. Good fix.

83Z28BlackBetty · Posted: Fri May 18, 2012 9:44 pm Post subject:

Nice work!