misfire that won't quit

[DEEPNHOCK]

And remember Ron is 2000'+ in Asheville with today's bad gas...

[Ron Dame]

I'll have you know we are 2400 feet! ;-)

I can drain gas and put fresh in, and there is nothing but E10 here, so what can be done about that and the altitude?

And remember Ron is 2000'+ in Asheville with today's bad gas...

[Dan Timberlake]

What to do about E10 - Generally higher altiitudes require "leaning out" some or all of the 4 or 5 carb circuits to provide correct combustible mix with thinner air. maybe 3% per 1000 feet, so 2400 feet would require nominal 7 or 8% leaner mixture to provide sea level jetting settings ( but power will drop, regardless). The 10% alcohol in the E10 makes the fuel act maybe 5% "leaner". To some extent the effects would tend to cancel, but some enrichening the carb may still be required

[wolfie]

Ron, a simpler test would be to disconnect the line to the fuel pump and drop it into a can of high octane gas that has been medicated with a bit of water remover. Let it run on the can long enough to get the fresh mix through the system (15-20 min) and see if your problem is corrected. If it runs better in the shop with the fresh mix then drop and clean your tank. Steve

[Ron Dame]

AARRRGGGGH!

I've been under the weather a couple of days, but today found some non-ethanol gas, drained the carb and the fuel pump bowl, and fed teh fresh gas in, and it STILL is backfiring and popping!

One more time, it happens when I go from a high vacuum to low vacuum...like fast acceleration (well it is a 6 cylinder) with moderate throttle, it's not too bad, but present, but with fast throttle opening, it will either backfire or stutter, and continue stuttering or backfiring until I let off the throttle, even a little bit. If i very slowly accelerate, it will cruise just fine., and yes the accelerator pump is adjusted, has a healthy squirt, and the nozzle is pointed correctly.
It's got to be that step-up circuit, but why is is going on also with the old RBS that was working fine when I took it off? It makes no sense! BTW, I did check compression again, and vacuum, and both are fine, except vacuum when it stutters and backfires. Everything goes wrong when I drop to 5" of vacuum, as soon as it goes above 5" it smooths out.


I am really stumped, and need help on this badly

[Ron Dame]

is there any chance this could be due to an exhaust restriction? I'm really grasping at straws now

[jclary]

Ron, I might be over my "Pay grade" here but I think something may be amiss in the timing advance circuit vs fuel delivery. As your engine calls for more acceleration the "advance" changes to anticipate the added demand. It seems to me that somewhere that is going awry. I have also experienced something similar when making homemade carb gaskets and leaving out one of those little holes in the gasket that seems to not be necessary, only to find out that it really is necessary. Just a few crumbs of thought on my part.

[wolfie]

I agree with John, I believe its in the advance. Pull the hose from the carb end and try to draw air through it. It should raise the idle slightly. If you can draw air through it the diaphram is bad, No change in idle means something is stuck. If that checks check the vaccuum from the nipple on the carb and see if it increases as throttle is applied. Steve

[Ron Dame]

I'm almost at the point of putting a hose on the exhaust pipe and drawing deeply. FWIW, I did remove the vacuum advance hose, plug it and try again...same dad-gimmed result. Old, but decent dizzy made no difference either.

[Ron Dame]

Dammit, maybe that IS it..there was no change in speed. I've got yet another spare dizzy to try.

I agree with John, I believe its in the advance. Pull the hose from the carb end and try to draw air through it. It should raise the idle slightly. If you can draw air through it the diaphram is bad, No change in idle means something is stuck. If that checks check the vaccuum from the nipple on the carb and see if it increases as throttle is applied. Steve

[Ron Dame]

Dammit, maybe that IS it..there was no change in speed. I've got yet another spare dizzy to try.

dammit, I found one dizzy that I could feel the advance move, set it up and STILL the stupid thing backfires horribly!

[jclary]

Ron, I think Wolfie was trying to be a little diplomatic when he suggested you "pass air through" the vacuum advance. Really, just take the vacuum line loose and "suck" on it! With the distributor cap off, you should see movement of the in the distributor if you "Suck" hard enough. If you don't want to be seen sucking on your car...one of those little "Mighty Vac" pump kits will also work just fine. It only takes a small "pin hole" in that rubber diaphragm to cause the vacuum module to fail. If that is all that is wrong, there is no need to replace the distributor. The vacuum chambers (or modules) are available from lots of sources including eBay. Forgive me if you already know this. I have had this to happen several times. The problem is that it has happened so rarely, I drive myself crazy trying to find and fix the problem because it takes a while for the old memory to kick in.

[Ron Dame]

I appreciate it John, yeah, I went to my Willie Nelson's " girl who can suck the chrome off of a ball hitch" side, and had no luck at all. 0Maybe I'm not girly enough. Tried 3 Auutolites, and could not make nary a one move, but a Delco, I could. I cleaned and set it up, and still the truck does EXACTLY the same thing. I've decided that the AS I rebuilt has problems, and the RBS went wrong somehow. That was the only variable before problems began, now there's been lots of changes.

I've been befoozled by computer injection cars, but never a simple engine like this.

Does anyone have a known good RBS, AS or WE for a Champion engine they'd lend for testing?

Ron, I think Wolfie was trying to be a little diplomatic when he suggested you "pass air through" the vacuum advance. Really, just take the vacuum line loose and "suck" on it! With the distributor cap off, you should see movement of the in the distributor if you "Suck" hard enough. If you don't want to be seen sucking on your car...one of those little "Mighty Vac" pump kits will also work just fine. It only takes a small "pin hole" in that rubber diaphragm to cause the vacuum module to fail. If that is all that is wrong, there is no need to replace the distributor. The vacuum chambers (or modules) are available from lots of sources including eBay. Forgive me if you already know this. I have had this to happen several times. The problem is that it has happened so rarely, I drive myself crazy trying to find and fix the problem because it takes a while for the old memory to kick in.

[wolfie]

Ron, Ive got a carb that was good 2 years ago from a 51 Champion engine and an untested one from a 53 Champion if they will bolt up. Dont know what series they are but definately older than what you have. If all goes well I could bring them up Sun. Ive also got a good full-flow 259 in the 63 lark and a bellhousing and flywheel from the T-cab parts truck..... Steve

[Dan Timberlake]

I'd do a fuel pump pressure and delivery test from a line disconnected close to the carb. Later that night I'd look under the hood with the engine running . If sparks are jumping, stuff needs cleaning, dielectric greasing or replacing to prevent those sissy sparks from taking the easy path when the cylinder pressure is higher under load.