General Tech Carburetors Backfiring

[KVH]

So frustrating. I dismantled and cleaned my carbs. It ran great. Now it's already back to its old behavior. Rough start, needs heavy choke, then starts missing and backfiring. I'm sure my plugs are fouled again with heavy carbon--but I haven't looked just yet.

The thing I keep recalling here is adding a Pertronix Distributor. That's when this all seemed to start. However, I do notice that my rear carb float bowl looks wet and appears to have overflowed.

I'm just not finding a clear answer here. Once I get it running, it's fantastic. But if I'm not careful, the plugs foul out.

This car used to start right up. I'm inclined to start playing with the timing, but thought I'd see what more experienced folks think.

 

[dklawson]

You said the car was backfiring and you mentioned the carbs. Which way is the engine backfiring, out the carbs or out the exhaust?

If the Pertonix is new to the car, did you set the ignition timing? If you did not, you need to. Without adjustment the Pertronix is not going to fire the coil at the exact same time as the points that were removed/replaced.

If after setting the ignition timing you find the backfiring continues... and is out the carbs... work on the float level in the carbs and followed by correcting the mixture. Carb backfires are common when the mixture is very lean.

Backfiring out the exhaust can be associated with ignition timing. If setting the Pertronix timing does not help and the backfire is out of the exhaust, look carefully again at the float level and look for leaks in the exhaust system. A rich mixture entering a hot leaky exhaust can result in backfires, particularly on deceleration.

 

[Geo Hahn]

...my rear carb float bowl looks wet and appears to have overflowed...

I think that condition pretty much accounts for what you describe. Most likely culprit (since you just rebuilt them) is the valve.

Did you replace the valve & in any case which type of valve do you use? Even new ones can stick - I always clean new ones well with carb cleaner or acetone as there can be some sort of residual on them from the manufacturing process.

 

[Sarastro]

.... However, I do notice that my rear carb float bowl looks wet and appears to have overflowed.

I think you just answered your own question. Probably you have a sticking float valve or the float level is way off. Fuel pump pressure might be too high, also. Are you using the stock fuel pump or do you have an aftermarket electric one?

 

[JerryVV]

Some Pertronics units only work with resistor Spark Plug wires. Try changing if you have solid core wires.

 

[dklawson]

Some Pertronics units only work with resistor Spark Plug wires. Try changing if you have solid core wires.

That's the first I have heard of the need for resistor wires. Is this unique to the Ignitor-II and later modules? It was not a limitation of the original Ignitor product.

 

[charleyf]

I can not say for the Pertronix unit. But I had a True Spark unit on my TR4 and it ran fine with the newer type wires. But shortly after changing the wires to old style copper-- the unit died. And when I say died I mean on a trip about 200 miles from home while driving down the road. Can't verify that the wires are what caused it to die. But I did later find where it is not recommended to use solid core wires. I now run regular points and solid core wires.
Charley