Need Help Dont No What Else To Do

[Deer_hunter_088]

Originally Posted by C.20

hm i didnt think of that it is a offbrand distributor

had an atv that did that, but the coil sparked bc of stator position, and it jumped timing, and it did EXACTLY what yours is doin. jumped like 3 teeth. pull dist and check On that style of atv, a lil raised pad acted as the rotor on your dist, so when it struck a certian point it fired, when the timing jumped, the valves would open at the wrong time, so it sparked wrong and ran like CRAP at idle, get up in rpms and it went away, but was a lil down on power.

[volksworld]

ok the backfire...is backfiring out the exhaust or popping back through the carb? back through the carb is typically a lean condition...what carb is on it? its possible that while cranking it when it was wet it crossfired and spit back thru the carb and damaged something...blew off a vacuum hose, damaged pcv valve or hose, power brake hose, carb gasket etc...now that its dry its running lean...also did you check the timing? if its way off or all over the place the timing chain could have skipped (original style plastic tooth ones were famous for that)...

[Alex V.]

What about the coil? I had similar symptoms after running my '85 out of gas - replaced everything but the coil (the fairly expensive part) and rebuilt the carb. to no avail, but IIRC a new coil fixed it right up.

[C.20]

Originally Posted by volksworld

ok the backfire...is backfiring out the exhaust or popping back through the carb? back through the carb is typically a lean condition...what carb is on it? its possible that while cranking it when it was wet it crossfired and spit back thru the carb and damaged something...blew off a vacuum hose, damaged pcv valve or hose, power brake hose, carb gasket etc...now that its dry its running lean...also did you check the timing? if its way off or all over the place the timing chain could have skipped (original style plastic tooth ones were famous for that)...

Its a demon and we bought a new carb also and we checked the timing and it was fine
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[C.20]

Originally Posted by Alex V.

What about the coil? I had similar symptoms after running my '85 out of gas - replaced everything but the coil (the fairly expensive part) and rebuilt the carb. to no avail, but IIRC a new coil fixed it right up.

Put a new coil in it
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[67 chevelle]

check timing before you do anything

[C.20]

Originally Posted by LongBox

A backfire strong enough to blow a muffler means unburnt gas was in the exhaust. this is because the engine was turning, but not firing. When it started firing again, the hot exhaust ignited the unburnt gas in the muffler. We used to do that on purpose when we was kids.

Since the last thing worked on seems to have been the ignition, time to go over the distributor very carefully, in an organized way. Is the wire from the coil connected correctly? Is the rotor seated on the plate on the top of the shaft. Is the centre contact in the cap there, and in good order. Is the centre contact on the rotor in good shape. I know these are new, but they can get out of whack.

Next, is each plug wire firmly seated in the cap? And at the plugs? Are the wires in good shape, with no issues with the insulation? Etc.Etc. Etc.

will check on this tommorow im running out of ideas

[71CHEVYSHORTBED402]

Bad distributor is my guess.

[dmjlambert]

I read through the thread and don't think you mentioned yet, are you powering the HEI distributor with the stock resistor wire, or have you done the 12V solid wire modification to your wiring when you installed the HEI?

[C.20]

Originally Posted by 71CHEVYSHORTBED402

Bad distributor is my guess.

thats what im thinking

[C.20]

Originally Posted by 67 chevelle

check timing before you do anything

pulled the first plug cranked it till it shot out of first looked at the rotor and it was pointing to number one

[C.20]

Originally Posted by dmjlambert

I read through the thread and don't think you mentioned yet, are you powering the HEI distributor with the stock resistor wire, or have you done the 12V solid wire modification to your wiring when you installed the HEI?

i did the mod to 12v

[67 chevelle]

Originally Posted by C.20

pulled the first plug cranked it till it shot out of first looked at the rotor and it was pointing to number one

has almost nothing to do with timing , check your timing

[C.20]

Originally Posted by 67 chevelle

has almost nothing to do with timing , check your timing

I can't test it with a light because it doesn't have a mark were you can check it with the light
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[C.20]

So took the truck out this morning and when it shifts or gets to a certain rpm it backfires when I keep it at that certain rpm it backfires ALOT
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[C.20]

Originally Posted by Alex V.

What about the coil? I had similar symptoms after running my '85 out of gas - replaced everything but the coil (the fairly expensive part) and rebuilt the carb. to no avail, but IIRC a new coil fixed it right up.

Put a new coil in it
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[geezer#99]

Originally Posted by C.20

I can't test it with a light because it doesn't have a mark were you can check it with the light
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Sure it does!
Clean off the balancer and find it.
THen check where your timing tab is. It'll be at 2 oclock or at 12 oclock. At 12 oclock you need to look behind the water pump for it.

[71CHEVYSHORTBED402]

Originally Posted by 67 chevelle

has almost nothing to do with timing , check your timing

Now there's a good starting point.

Let us know what it is OP.....Thanks

[firedemon]

had a 74 monte carlo with a 350 it had a bad cam and it backfired through carb and exhaust had 3 or 4 bad lobes on it at 85 thousand miles . not saying its it but if all else fails something else to check

[Steelheader]

I had a similar situation last year , thought I fouled a plug so I did a tune up ( plugs and wires ) still same issue , replaced cap and rotor still the same issue , started looking into everything and I couldn't figure it out , and I tried evething before tearing into the internals , so for the hell of it I pulled all the plugs and found one that wasn't firing (new plug )replaced it with another new one and it fired right up no more issues , so it is possible to buy bad new parts .
I would also double check the to make sure all your plug wires seated properly , I've seen that multiple times . I like to feel a nice solid snap , and if it's not squeeze the connector down with some plyers for a good fit .
Just a few suggestions , probably stuff you already tried , but I know how frustrating things get , some times the easiest fix is to take a step back and let some fresh eyes take a look at it , might be something stupid . Good luck .
Sincerely, Doug

[dmjlambert]

Originally Posted by Steelheader

...I pulled all the plugs and found one that wasn't firing (new plug )replaced it with another new one and it fired right up no more issues , so it is possible to buy bad new parts .

How did you do the test to determine it wasn't firing?