Missing/Backfire

I think the last time I addressed this was on the GSCA BBS. The problem persists.

While cruising at highway speeds, sometimes the engine will begin to miss/cut out and backfire through the carb. It will accelerate and smooth a bit if I step on the gas, but persists at constant speeds. It eventually goes away; on its own time.

Its a 350 with a Holly 600, electric choke (that may not be working).
New: module (converted to HEI), plugs, wires, fuel pump/filter/lines, thermostat. Fluid levels are fine.
No exhaust (it fell off, waiting on student loan to put a new one on).

I rarely drive the car as I'm a grad student, thus I've not had much opportunity to notice the problem. I had put a new module in the last time I brought this up, and it seemed to improve things. However, the problem was never consistent.

 

I would check the voltage to the coil. Make sure you have the correct (12v for HEI) voltage and have taken out the resistor wire that the old points system coil used.
I would also double check the choke, and make sure it's not stuck tight or in a locked position.......It may run great cold, but pop back when warming up because of the temp.

Mike

 

Voltage to the coil is fine - I replaced the resistor wire with a 12 gauge wire.
I'll go over the choke and its wiring. It has been a problem in the past.
How can the choke cause a backfire? Not doubting you, just curious as to the dynamics of it.

 

Truzi,
Without driving the car, I could not be sure, but it sounds to me like a combination of factors causing the problem.

If it only happens every so often, not all the time, the problem is somewhere in the carb or ignition. The coil could have an internal short that only shows up when it's warm, or it may be a mal-functioning choke... But if it is the choke, then there's a bigger problem.

If the timing is off, it could cause a popping thru the carb when the choke sticks, or it could possibly be a burnt intake valve.

Start with the simple [and cheap] stuff... Wire the choke open, put a replacement coil on it... See if that helps. Check the timing.

Let us know what you find, and good luck!

 

Faulty Ignition

I had this problem with the X-Camino that i built. During take off sometimes the car would just fall on its nose. My friends Rich & Tim Garland discovered that the ignition switch on the steering column had burned up the contacts. It was a brand new one. They replaced it with an original taken off an 80's regal and the car runs fine. Duane

 

backfireing

i had that problem, was the pickup. changed the h.e.i. module, helped for a while, then it started popping thru the carb, limped home, thought wth, changed the pickup, ran perfect, also check the advance weights under the rotor. mine were sticking.

 

Ran into something similar years ago, with a 70 Chevelle with a 454 and HEI. Bought the car off my neighbor and the motor off another friend. The car previously had a 427 in it and it popped like crazy. I was using the same distributor that they had in it, so we figured that was the culprit. Turns out to have been the reluctor. I tore the distributor completely down, cleaned it, regreased everything, shimmed the dist. gear for minimal play (put an extra washer in - worked great), put the new reluctor in, etc. After all that, everything ran smooth - revved up great with no popping!

One more thing for you to check out.

Scott

 

Umm, reluctor?

 

Truzi,

Go to www.boardreader.com and type in 'reluctor'. You'll have to weed thru the posts between reluctors for distributors and ABS rear ends. Check out: http://www.boardreader.com/scripts/...irdgen.org/messgboard/Forum7/HTML/005847.html - make sure to read the part about pickup coils with or without the yellow wire!!
The wrong pickup coil will cause fits!:stmad:

Hope that helps,

Scott