Help - Carb Backfire - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72moneypit · 06-27-2003, 03:35 PM

I was driving to work today and started hearing/feeling carb backfires. I got nervous and exited the highway, and it seemed to drive OK. When I re-entered the highway, it started again... at about 55-60 MPH.

My question: What would cause a carb backfire at 55+ MPH, but otherwise it runs fine? I have to wonder if the outside temp (about 105) is contributing - I've not driven the truck in such hot weather since rebuilding the engine and installing the new carb.

Any ideas? Thanks!

stelth2002 · 06-27-2003, 04:20 PM

fuel to hot? you sure its back firing or is it just like quiting. Could be vaporlock

Southpa · 06-27-2003, 04:33 PM

Have a looksee inside your dist. cap.

72moneypit · 06-27-2003, 04:40 PM

Quote:

Originally posted by stelth2002
fuel to hot? you sure its back firing or is it just like quiting. Could be vaporlock

It makes a popping sound, and the engine lurches a little bit. Kind of like it's running out of gas (it's not).

hanssolo · 06-27-2003, 05:01 PM

Does kinda sound like fuel vaporization. I read somewhere the Edel. carbs need a heat insulator when things get hot, weather and engine, cause the fuel can boil in the bowls. Carbs like Holleys have the bowls hung on the outside but Edel/Carters have the bowls right on top of the hot engine. Dang! 105!

lukecp · 06-27-2003, 05:15 PM

You sure it's not running out of gas?

A clogged fuel filter will give you problems like that. I would go ahead and try it....a new filter is about $3 and takes 10 minutes to put in.

cableguy0 · 06-27-2003, 08:27 PM

also check the air filter i hadnt cleaned my foam filter in who knows how long and everytime i got to about 60 mph it would start hesitating realllllllllll bad on the highway stay under 60 and it was fine

'72 Shorty · 06-27-2003, 10:58 PM

Mine used to do that in the summer until I put the plastic spacer under the carb. That's with an Edelbrock 1407. I agree to check under the dist cap though, it could be carbon tracked and cross firing.

06-27-2003, 03:35 PM	#1
72moneypit Registered User Join Date: Jan 2003 Location: Mesa, Arizona Posts: 125	Help - Carb Backfire I was driving to work today and started hearing/feeling carb backfires. I got nervous and exited the highway, and it seemed to drive OK. When I re-entered the highway, it started again... at about 55-60 MPH. My question: What would cause a carb backfire at 55+ MPH, but otherwise it runs fine? I have to wonder if the outside temp (about 105) is contributing - I've not driven the truck in such hot weather since rebuilding the engine and installing the new carb. Any ideas? Thanks! __________________ Paul 72 Cheyenne Super Custom Camper greenaz@hotmail.com

06-27-2003, 04:20 PM	#2
stelth2002 Young Gun wth Fast Inline Join Date: Jan 2002 Location: Idaho Posts: 1,475	fuel to hot? you sure its back firing or is it just like quiting. Could be vaporlock __________________ 1967 Chevrolet LWB with built 292! 415 ft. lbs of torque, 4 speed :O with 27% overdrive too, 3.73 Posi. Frame and body done... getting painted!!!

06-27-2003, 04:33 PM	#3
Southpa Registered User Join Date: May 2000 Location: Victoria, BC, Canada Posts: 2,410	Have a looksee inside your dist. cap. __________________ 1970 GMC 1500 Custom Original 350/TH350 Victoria, BC, Canada You can wish in one hand and crap in the other. See which one gets filled first.

06-27-2003, 05:01 PM	#5
hanssolo Registered User Join Date: Sep 2001 Location: central Ill. USA Posts: 447	Does kinda sound like fuel vaporization. I read somewhere the Edel. carbs need a heat insulator when things get hot, weather and engine, cause the fuel can boil in the bowls. Carbs like Holleys have the bowls hung on the outside but Edel/Carters have the bowls right on top of the hot engine. Dang! 105! __________________ 69 C10 longbed: 357c.i. /TH400/3.73s/AC/ beige primer/saving $ for paint ______________________________

06-27-2003, 05:15 PM	#6
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	You sure it's not running out of gas? A clogged fuel filter will give you problems like that. I would go ahead and try it....a new filter is about $3 and takes 10 minutes to put in. __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

06-27-2003, 08:27 PM	#7
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	also check the air filter i hadnt cleaned my foam filter in who knows how long and everytime i got to about 60 mph it would start hesitating realllllllllll bad on the highway stay under 60 and it was fine __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

06-27-2003, 10:58 PM	#8
'72 Shorty I finally got an avatar Join Date: Jan 2003 Location: Cheney, WA Posts: 180	Mine used to do that in the summer until I put the plastic spacer under the carb. That's with an Edelbrock 1407. I agree to check under the dist cap though, it could be carbon tracked and cross firing. __________________ -72 C-10 short step (straight line only) 12.922/102.28 -69 C-20 on Propane (DD) -69 C-10 -56 Mack B-753LS (tow rig) -94 Chev K2500 Short Ex-Cab -89 Isuzu Trooper...Kinda -03 Kawasaki KFX-400 -05 Suzuki DRZ-400S



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