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Backfire and carb fire! Advice please

Geff McCarthy

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My 63 SF with a 70 400 and Edelbrock 1407 quit suddently, driving up hill in heat. I thought it might be empty tank, so rolled into station and it took only 13gal.
then it wouldn't start, and somebody yelled "pump it" so i did.
It started, and then backfired and burst into flame. Fortunately the air cleaner was off. A short shot of fire extinguisher put out the fire after 20sec or so.
It then started and I drove home...
So: the carb is covered in soot. Is it damaged? How to clean?
Was this vapor lock? the rubber fuel hose was very hot, so i cooled it a bit with water.
If so, is there external insulation for the fuel hose, to reduce vapor lock?
thanks in advance for the help!
 
My 63 SF with a 70 400 and Edelbrock 1407 quit suddently, driving up hill in heat. I thought it might be empty tank, so rolled into station and it took only 13gal.
then it wouldn't start, and somebody yelled "pump it" so i did.
It started, and then backfired and burst into flame. Fortunately the air cleaner was off. A short shot of fire extinguisher put out the fire after 20sec or so.
It then started and I drove home...
So: the carb is covered in soot. Is it damaged? How to clean?
Was this vapor lock? the rubber fuel hose was very hot, so i cooled it a bit with water.
If so, is there external insulation for the fuel hose, to reduce vapor lock?
thanks in advance for the help!



Years back I tried many different Holley carbs on a 390 Ford. One worked extremely well for about two weeks, then failed as the others. Holleys would back fire through the carb and catch on fire.

Friend with doctorate degree in Mechanical Engineering from MIT says too lean will cause backfire.

Edelbrock and Carter didn't ever do that on any of my Mopars....'69 RR, 70 GTX, 70 Barracuda all big block.

Carb is likely not damaged depending on how long the fire was burning. Maybe take it off, clean it with carb cleaner and inspect for damage. Check your exhaust pipes. Are they light grey and very clean? If they are black I think your mixture is not too lean. Possibly a float level too low inside the fuel bowls? I think Eddy has a float on each side of the carb. Check these.

I know you can rejet Edelbrock for leaner or richer. After 40 years of fiddling with these things I would say to approach problem solving with moderation and lots of thinking. Patience will save you tons of money and frustration.

Heat passes more quickly through metal than rubber, so the rubber hose might already be insulated.

If you stay with it, you will solve the problem. Many people get frustrated and give up sometimes sell their car. That isn't you.

Think how great it will be when you solve this one. You'll feel like a car genius because that is what you will have become.

All the best-

Z



Don't think you need to insulate the fuel line because stock car/engines did not had no fuel insulation

People would tell me about a "power valve" problem.
 
Sounds like it was running lean, one way or another.. Do you have an electric fuel pump by chance? I just had a similar situation happen recently where: car was dying up hill, struggling under load sometimes, etc... Turns out my 20 year old electric fuel pump finally quit. Popped a new one in and works great now. Good luck!
 
Are you running a newer MSD ignition box by chance? Reason I ask is I was and same thing happened minus the 20 second fire. It only lasted a few seconds. I was running a Holley 650 and had just upgraded(?) to msd ignition. It backfired couple times at the pumps. Able to get it out of the pump area and backfired again.Turns out after checking everything carb, it was the New MSD box!
 
Might want to check float levels if you never have. I had a brand new Edelbrock, thoughtn I would remove the air horn and double check the float levels prior to install. When these are shipped ( and probably rough handled in shipping ) there is no support for the floats that can flop from one extreme to the other. One would think that were correctly set from the factory, but mine were way off. On a big block, mechanical pump ? If you have never replaced the fuel pump push rod, it's worth pulling to inspect and check the length, could have effect on consistent fuel delivery. Thermal insulation on fuel lines would not hurt, nor would a phenolic or insulating carb spacer.
 
It could have been vapour lock - and you can get insulation for the fuel lines and make sure they are not resting on heater hoses etc.
The carb should be OK you could wash with carb cleaner or just leave it.
 
It is a fairly new E 1407, which i rebuilt, mostly to clean out years of crud. I had trouble setting the new floats, so i used the old, which seemed perfect. I shall re-adjust choke and idle jets, and insulate...and carry fire extinguisher! Thanks to all!
 
Just a word of caution if an ABC type was used start cleaning now. Stuff will destroy aluminum
 
For 20 second burns just open the throttle all the way unless of course the engine isn't running.
 
just one of the reasons running rubber hose for fuel line on the engine is part of a safety inspection "no".
 
In all my years of doing this stuff, I’ve never had a car engine running well and then “become lean”. Done it with crusty log splitter engines because some piece of crud got in the jet but not a car that was previously working.

All the coughs, backfires, spits etc I’ve seen I previously good running engines came from either ignition or mechanical timing related issues. (Including bent pushrods, needed valve jobs, timing chain issues etc).

So if this car is one you’ve been driving some reasonable amount with generally good results don’t go chasing lean mixtures. If it’s been sitting then go ahead but I’d start with the fuel delivery system and not the carb / mixture.

The heat part, then the cough / spit make it sound more like a engine that needs a valve job. It’s easy to forget how frequently this was needed back in the day.
 
Why would you be driving w/o a filter on?? That would have suppressed the fire. Vapor lock leaves no fuel in the bowls and will not restart without help. Start with the timing light and verify the timing.
 
I took the air filter off in the gas station to verify that the accel jets squirted. They did. Why would the air filter suppress the fire? Oxygen can certainly get in.
I made a mistake, I think, by continuing to crank during the fire, with the engine not running. Reason: in General Aviation, if an engine fire occurs, "Shut off fuel" and crank to draw fire thru carb, and not set engine bay on fire. In cars...no fuel shutoff!
the car ran fine today here in PDX in moderate summer temps. Again, thanks to all!
 
In all my years of doing this stuff, I’ve never had a car engine running well and then “become lean”. Done it with crusty log splitter engines because some piece of crud got in the jet but not a car that was previously working.

All the coughs, backfires, spits etc I’ve seen I previously good running engines came from either ignition or mechanical timing related issues. (Including bent pushrods, needed valve jobs, timing chain issues etc).

So if this car is one you’ve been driving some reasonable amount with generally good results don’t go chasing lean mixtures. If it’s been sitting then go ahead but I’d start with the fuel delivery system and not the carb / mixture.

The heat part, then the cough / spit make it sound more like a engine that needs a valve job. It’s easy to forget how frequently this was needed back in the day.

Just how often were valve jobs needed, back in the day?
 
Just how often were valve jobs needed, back in the day?

I remember picking up maybe 6 cars for cheap, all late 60’s, because they ran like crap. Good cold then as they warmed they got crappy. Would spit and cough as described, sometimes stall. Gave them all valve jobs and they ran great. Not every car needed One but they weren’t uncommon. OP symptoms are similar. Should be on his list to evaluate.
 
I took the air filter off in the gas station to verify that the accel jets squirted. They did. Why would the air filter suppress the fire? Oxygen can certainly get in.
I made a mistake, I think, by continuing to crank during the fire, with the engine not running. Reason: in General Aviation, if an engine fire occurs, "Shut off fuel" and crank to draw fire thru carb, and not set engine bay on fire. In cars...no fuel shutoff!
the car ran fine today here in PDX in moderate summer temps. Again, thanks to all!
Next time keep the pedal to the floor and keep cranking.
 
It is a fairly new E 1407, which i rebuilt, mostly to clean out years of crud. I had trouble setting the new floats, so i used the old, which seemed perfect. I shall re-adjust choke and idle jets, and insulate...and carry fire extinguisher! Thanks to all!
Carry two fire extinguishers, I do.
 
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