any ideas on what may be the cause? timing? my husband thinks there may be arching of something .. I hear that once but did not cause the back fire thru carb though?
Help with backfire thru carb?
wudju2
any ideas on what may be the cause? timing? my husband thinks there may be arching of something .. I hear that once but did not cause the back fire thru carb though?
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look at the plug wires carefully, see if any are touching the headers. start it up at night, see if you can see any arcing around any of the plug wires. have a dry stick handy so you poke around on them a little.
What is the timing set at? sounds like it may be set too low or retarded.
What is the timing set at? sounds like it may be set too low or retarded.
Ditto about the method for looking for plug wire arcs at night time where there aren't any street lights nor light of any kind (just keep your hands outta there when you're looking around in the dark!!! that goes for long hair too. 
). Another thing might be the carb can be running way too lean. A very lean condition can and will cause backfires like that. I'm not a fan of those Edelbrock carbs, but it can occur with any carb if it isn't jetted right. If I remember right, those Edelbrock carbs use some type of tuning rods. You might want to check what one you have in there. But I'd check the plug wires in the dark first. If they're arcing, you'll sure see it in the absense of light.
If you haven't put a timing light on it, you'll definitely need to do that to rule out an initial ignition timing setting that isn't advanced enough (should be atleast 10 degrees BTDC).
). Another thing might be the carb can be running way too lean. A very lean condition can and will cause backfires like that. I'm not a fan of those Edelbrock carbs, but it can occur with any carb if it isn't jetted right. If I remember right, those Edelbrock carbs use some type of tuning rods. You might want to check what one you have in there. But I'd check the plug wires in the dark first. If they're arcing, you'll sure see it in the absense of light. If you haven't put a timing light on it, you'll definitely need to do that to rule out an initial ignition timing setting that isn't advanced enough (should be atleast 10 degrees BTDC).
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The timing too far retarded will cause it. Set the timing at 12 degrees to start with.
I also agree on the Edlebrock carbs. I have one on a Cuda and I can't get the thing to run right to save my life. If it's too lean it will backfire.
The only other thing that causes that to happen that I know of is a wiped cam lobe. Is it making a ticking noise?
I also agree on the Edlebrock carbs. I have one on a Cuda and I can't get the thing to run right to save my life. If it's too lean it will backfire.
The only other thing that causes that to happen that I know of is a wiped cam lobe. Is it making a ticking noise?
I thought of a wiped out camshaft lobe at first, but I ddn't make mention of it, because I think that if it was a cam lobe being wiped out, the backfiring would be worse and more frequent than that. When I wiped out #6 exhaust lobe on my SBC engine, the only time the engine would run without constantly pooping out of the carb is at idle. Anything above idle RPM, and it would pop real bad.
It's an easy diagnosis for a wiped out cam lobe though. Just remove the coil wire so the engine won't start up, and remove the valve covers, and while one person holds the key in the start position for 5 or 6 seconds at a time, the other watches for all the rocker arms moving up and down while the engine is being turned over by the sterter motor. If one of them isn't moving and just lays there, then the corresponding cam lobe is worn down to just a perfect circle or close to it.
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5,065 Posts
What they don't mention is - anything you do to the carb is a waste of time until AFTER your timing is correct. 10°? 12°? No - go to 16-18° and be done with it.
Yep 16-18 no doubt, but what I meant by my "atleast 10 degrees BTDC" comment is that although 16-18 BTDC is a whole lot better, if it's currently atleast 10 degrees BTDC, then the initial timing setting isn't what's causing the backfire. :noway:
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:noway:
In requards to checking for arching..We did try that last night and we only could see the glow from the headers but no arching..also it seems that it overheated when i took that video and it wasn't running all that long..??
Mudflaps will be removed.. lol
Mudflaps will be removed.. lol
OK, this above^ is a clue. Headers should NOT be glowing red. :noway: That's an indication of either a clogged exhaust system (not likely since you aren't running catalytic converters I'm sure, unless you drove over something and collpased part of the exhaust) or the ignition timing is too far retarded (or more accuratly put, it isn't advanced enough).
Have you put a timing light on the engine yet, and checked the initial timing advance???? It's easy enough to do.
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669 Posts
I think the lady gave a good clue "the brakes are messed up"
I see the brake booster line has a T in it with the extra line going to what looks like vented oil cap. That would result in a large vacuum leak and very poor brakes.
Thanks
Randy
X2. No tees in the vacuum line to the brake booster, especially plugged into a valve cover. Use something to squeeze that line shut on the carb side of that tee and see if the problem settles down.
but dude,it gets muddy in Iowa....
rth
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