71 C10 backfiring and loss of power after changing distributor

[tino0217]

I have a 71 C10 350 small block found out I had a short in my aftermarket tack ended up changing my distributor, module, and coil now that I've done that it's backfiring and there's no power when I get it up to 30-40 mph. I have retimed it at 12° past advance I've checked all the spark plug connections to make sure they're tight I have noticed where the vacuum connects to the distributor cap that the cap is leaning and I can't get it to fit any tighter but it is on tight and when I did do the timing I did plug up the vacuum hose I have adjusted the gas air mixture on the carburetor which is your typical four barrel Edelbrock. Before I realized I had a short the truck was running perfectly fine. Now that I've gone through all the wiring to see if I had a short because my stupid parking lights weren't working this occurred and I couldn't get the truck to start for no rhyme or reason that's when I started to look for a short in the wiring and found out it was in the aftermarket tachometer. Any ideas what I may have missed I would appreciate the help got to get this puppy back on the road.?

[REDROCKER652002]

You sure you have it set in right? The distributor may be off a tooth or two and that could be the issue. A novice just trying to think about the stuff i did when I was doing it. Also, 12 degrees past TDC doesn't seem right. I cannot remember, but I thought standard timing was somewhere before TDC. Unless I am thinking of something else.

[fdbdw]

First thing to do is verify TDC on #1, there’s a couple ways to do it. I’ve found the easiest is to turn the motor by hand and let a long screw driver ride on top of the piston ( lightly), also make sure you’re on the compression stroke. Then make sure the rotor is pointed at the #1 terminal when at TDC. Numbers mean nothing if your TDC isnt accurate. I think stock timing on a 350 is 8 BTDC. I would be surprised if it started let alone run at 12 ATDC. last but not least triple check your plug wires, I’ve had them out of order more times than I’d like to admit.

[Sheepdip]

Backfiring up thru the carb or out the exhaust?

[bry593]

You need to make sure that the rotor is pointing at the cyl 1 terminal in the distributor cap when the harmonic balance is rolled over to 0 degrees. That will tell you if you are off a tooth or two. It isn't 180 degrees out, or you'd never get it to run.

The next thing is to make sure the plug wires are in order, going clockwise from cyl 1 terminal -> 18436572

Next, make sure you are actually getting 12v to the bat terminal on the HEI coil. A lot of guys fail to replace the stainless steel resistance wire from the firewall bulkhead to the distributor. You need Pink 12 AWG GXL (cross link thermoplastic).

If the above won't fix it, I'd be looking at the HEI itself. Was it one of the $90, Chinese specials? If so, those are trash. You are better off finding an OE distributor and putting a new cap and rotor on it.

[tino0217]

�� l appreciate the tip, will do.

[tino0217]

Exhaust

[tino0217]

Great tip I forgot about this I did it a couple years ago when I timed it and it did work perfectly so I will go through those steps again and as far as I know it's the original hei it's not an aftermarket import. Thanks brother

[garyd1961]

You said something about the cap leaning? Make sure the cap is on right before you do anything else.

[tino0217]

It looks like I might have a intake manifold leak so I'm replacing the gasket today