V6 305 distributor issues

[randy.joe.drew]

When I purchased my 63 1 ton it came with an after market electronic distributor that had not been installed. It ran pretty good but since I had this shiny new aluminum distributor, I removed the old distributor and installed the new one last summer. New wires, new plugs, looks great, timed at idle and purrs like a kitten. Problem is as soon as you give it some gas it back fires. Replaced vacuum advance hose still undrivable. I would have already put the old one back on but I had to remove the gear, which is rivoted on with some little shims, for the new distributor and didn't want to go thru that pain again. Any thaughts, experiences, advise would be appreciated.
Randy

[jrmunn]

I have nothing but questions at this point. Much has been posted on this site about distributors and tune-ups that you could search for. It would help to know if the truck backfires immediately when throttle is pressed or after the engine revs up? Both vacuum and mechanical advance would be different in these two situations. Also, is your vacuum advance hose connected to ported or manifold vacuum? And did the new distributer come with install and tune-up directions, or do you have to figure things out as you do them?

JRMunn

[AZKen]

........and is it backfiring thru carb or exhaust pipe? NEW MEMBERS: Monitor your post. If not, helpers will lose interest in helping. If you want help, act like it. You got a response in 3 hours, that was two days ago.

[TJ's GMC]

Originally Posted by randy.joe.drew

When I purchased my 63 1 ton it came with an after market electronic distributor that had not been installed. It ran pretty good but since I had this shiny new aluminum distributor, I removed the old distributor and installed the new one last summer. New wires, new plugs, looks great, timed at idle and purrs like a kitten. Problem is as soon as you give it some gas it back fires. Replaced vacuum advance hose still undrivable. I would have already put the old one back on but I had to remove the gear, which is rivoted on with some little shims, for the new distributor and didn't want to go thru that pain again. Any thaughts, experiences, advise would be appreciated.
Randy

Might check the mechanical advance to see if it's sticking. Would help to know where the back fire is coming from though.

[George Bongert]

Originally Posted by randy.joe.drew

When I purchased my 63 1 ton it came with an after market electronic distributor that had not been installed. It ran pretty good but since I had this shiny new aluminum distributor, I removed the old distributor and installed the new one last summer. New wires, new plugs, looks great, timed at idle and purrs like a kitten. Problem is as soon as you give it some gas it back fires. Replaced vacuum advance hose still undrivable. I would have already put the old one back on but I had to remove the gear, which is rivoted on with some little shims, for the new distributor and didn't want to go thru that pain again. Any thaughts, experiences, advise would be appreciated.
Randy

Greetings Randy!

Did the engine backfire with the original distributor? Or is this a condition that just developed after you installed the new distributor? If your engine is backfiring through the carb on acceleration, it could be an indication of the engine not getting enough gas, in other words a lean mixture. It can also be an indication of late ignition timing. It's been so many years since I tuned up my old 305 (which I no longer have) that I've forgotten the exact specs on ignition timing, but a good place to start is 6 degrees before top dead center. The vacuum advance should be disconnected and the vacuum source plugged or capped off when setting the timing. I could be of more help if I were there and could observe the engine's behavior up close and personal. Hope this helps you.

[massey478]

I agree with Mr, Bongert. Take a look down the carb throat, choke open, engine off, work the throttle lever and see if you get s shot of gas out of squirters going into the carb venturies. The accelerator pump in the carb can be bad, not giving this shot of enrichment when needed until the main jets come in when you first depress the accelerator. If no squirted fuel, carb rebuild is needed. It can also cause hard starting cold because when you do the typical pump the accelerator a few times to enrich the mix in the intake before cranking, you will not get that pre-start enrichment if the accelerator pump is bad.

[LEWISMATKIN]

If the backfire problem started only after distributor replacement, chances are that the initial ignition timing is too low. 1963 was the first year for the 305E, and the initial timing for the engine was 7 1/2 degrees BTC with the vacuum line removed and plugged. IMHE, backfire problems usually are caused by low(slow) initial timing settings after distributor replacement. If the engine was backfiring before distributor replacement, chances are that the accelerator pump circuit in the carb. has failed, requiring a rebuild of the carb. I hope this information has been helpful.

cordially,
Lewis Ellis Matkin, Jr.
Ridge Manor, Fla.
1965 1002 305E-v6

[tommr]

Don't forget if your fuel is older than 6 months its probably timed out. If that new distributor is a Cardone rebuilt just pitch it in the trash.