Stumped with backfire from carburator

[claysmoker]

Does anyone else see some detonation flecks on those plugs in the last photo? And does the strap look like maybe there's too much timing?

[Kevin Johnson]

When I looked at the video I could tell that you painted the engine components separately and then bolted everything together. Is it possible that you applied paint to the spark plug thread area inadvertently? Try a thread chaser and use the material below:

Post by Warp Speed » Fri Jun 18, 2010 12:21 pm. We use Coposlip high temp anti-sieze on the threads of all of our spark plugs. We have done extensive testing with Bosch on this, and this is about the only lube that provides the best grounding and temp transfer, while still providing the needed lubrication

[naukkis79]

Runs and drives well. Coughs hot or cold.
Tried timing at 8-18 dtdc and verified timing mark
pumped gas pedal before start still no help

White mist from carb after shut off means that carb is boiling. Are you using mechanical or electric fuel pump? With mechanical you are lean at start as carb is boiled it's fuel off.

[huero]

Mechanical fuel pump. Have a 1/2” phenolic spacer. Bowls are not hot to the touch

[naukkis79]

Mechanical fuel pump. Have a 1/2” phenolic spacer. Bowls are not hot to the touch

Bowls stay cool as long as there's fuel to evaporate. Bowl can also leak and fuel is evaporating in intake.

If you cut ignition off and start few seconds to fill up bowl and start then you see if problem is empty carb.

[va454ss]

After you shut it off, look down into the carb and see if its leaking around the squirters.

[huero]

No fuel leaking past the squirters. But I am looking into the fuel system carefully.

[Kevin Johnson]

Idles nice, engine revs nice but on start up (cold or warm) the engine backfires out of the carb. No fire just fuel. Ignition can be set anywhere from 12-18 btdc and the engine reacts the same.

In one of your videos there are momentary glimpses of the spark plug wires to the 2-4-6-8 bank being ziptied together and run parallel and in direct contact with each other for an extended distance. This could cause spark loss as the wire intended to fire is inducing a current in a parallel wire or wires. Spark loss could help explain why unburned fuel is being aspirated from the carb.

Try separating the wires.

When I looked at the video I could tell that you painted the engine components separately and then bolted everything together. Is it possible that you applied paint to the spark plug thread area inadvertently? Try a thread chaser and use the material below:

Post by Warp Speed » Fri Jun 18, 2010 12:21 pm. We use Coposlip high temp anti-sieze on the threads of all of our spark plugs. We have done extensive testing with Bosch on this, and this is about the only lube that provides the best grounding and temp transfer, while still providing the needed lubrication

[huero]

I will work on separating the wires. I thought insulation on modern wires was sufficient. Thank u

[MadBill]

Non-conductive insulation doesn't suppress radio frequency interference. The magnetic field around one secondary wire can induce voltage in another if it runs parallel to the first.

[huero]

Separated wires, still coughing. Talked to my carb builder. It maybe the carb. I’ll fill everyone in when I get an update.

[huero]

Gentlemen, we found the problem!!!!!!!! Actually, my carb builder did.
And I am so mad I could not find such a simple error.
The car is a 56 Chevy and it was originally wired with points and ballast resistor (separate wires). I had a switched 12V wire source to the distributor but not a 12V ignition switched and ignition crank source!!!!
So there was no voltage going to the distributor when cranking the engine over!! I am so upset that I could not diagnose the problem and chased my tail for so long!
I want to thank everyone that tried to help. I feel so foolish. I am new to tri-fives and didn't realize how they were wired. Now I have to find out how to wire the distributor to the ignition switch as it appears there is no 12V run and crank wire. They are separate wires.
Does anyone know if I can join these two wires together and feed it to the distributor + terminal and not damage the distributor? Is this safe?
Thank you all again.
I am so glad this is over!!!

[My427stang]

Gentlemen, we found the problem!!!!!!!! Actually, my carb builder did.
And I am so mad I could not find such a simple error.
The car is a 56 Chevy and it was originally wired with points and ballast resistor (separate wires). I had a switched 12V wire source to the distributor but not a 12V ignition switched and ignition crank source!!!!
So there was no voltage going to the distributor when cranking the engine over!! I am so upset that I could not diagnose the problem and chased my tail for so long!
I want to thank everyone that tried to help. I feel so foolish. I am new to tri-fives and didn't realize how they were wired. Now I have to find out how to wire the distributor to the ignition switch as it appears there is no 12V run and crank wire. They are separate wires.
Does anyone know if I can join these two wires together and feed it to the distributor + terminal and not damage the distributor? Is this safe?
Thank you all again.
I am so glad this is over!!!

That makes perfect sense. I did a couple of Tri-5s and we often swapped out the ignition switch to get cranking power. It'd basically try to fire as you released the key

I cannot remember for the life of me why we didn't just pick up off the solenoid, but there must have been a reason

[sidestep]

On a 55-56 Chevy ignition switch you have to run a small jumper from ign1 - ign2 if you eliminate the ballast resistor, Chevy trifive.com for an original wiring diagram for a 56, you'll see how they wired it.

[huero]

On a 55-56 Chevy ignition switch you have to run a small jumper from ign1 - ign2 if you eliminate the ballast resistor, Chevy trifive.com for an original wiring diagram for a 56, you'll see how they wired it.

Done!! I actually wired it using a relay. To not stress the original old wiring. Car fires right up every time!!! Thank you all!