multiple small backfires during deaccleration from high rpms - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Dropt72Shortbed · 07-08-2002, 11:19 PM

got my new goodrwench crate motor in. this is a stock engine with just edelbrock performer intake and edelbrocks qjet. has headers and dual flowmasters.

now the problem, say im going 75mpg or faster on the freeways and i let off the gas pedal to slow down i will hear multiple little back fires through the exhaust. theyre not loud at all, pretty soft.

im sure this relates to the carb since it is not new. is it just running to rich? and ideas?

Suicide-D · 07-08-2002, 11:24 PM

or an exhaust leak... my headers would do that when I had paper gaskets... I went to copper and solved it...

Dropt72Shortbed · 07-08-2002, 11:34 PM

just put new gaskets both sides of the headers with the new engine. if it were an exhaust leak wouldnt i hear it more when i was flooring it at high rpms rather than when i just let off the gas? it never does it under 75mph no matter what rpms i let off at, only on the freeway at higher speeds

Suicide-D · 07-08-2002, 11:46 PM

are you sure they are back fires? If they are soft and you don't hear them any other time... maybe it's just the way the exhaust sounds... I had to learn my new exhaust... they sound totally different than flowmasters that i'm used to...i sound like a harley under heavy acceleration now.

mikep · 07-08-2002, 11:52 PM

You are leaning out when the throttle plates are closed. Probably need to richen up the idle mixture screws a bit or richen up the transition circuit if that doesnt do the trick, How is your plug color? You may just be running too lean on your primary circuit and going down a wee bit on your rods might do the trick. try the idle mixture first. set it with a vascuum gauge to get it right the first time.

Dropt72Shortbed · 07-09-2002, 12:16 AM

Quote:

Originally posted by Dropt72Shortbed
just put new gaskets both sides of the headers with the new engine. if it were an exhaust leak wouldnt i hear it more when i was flooring it at high rpms rather than when i just let off the gas? it never does it under 75mph no matter what rpms i let off at, only on the freeway at higher speeds

yea theyre definetly backfires, guy who put the engine in for me also said they were backfires and that he would check the carb

07-08-2002, 11:19 PM	#1
Dropt72Shortbed Registered User Join Date: May 2002 Location: Huntington Beach CA Posts: 678	multiple small backfires during deaccleration from high rpms got my new goodrwench crate motor in. this is a stock engine with just edelbrock performer intake and edelbrocks qjet. has headers and dual flowmasters. now the problem, say im going 75mpg or faster on the freeways and i let off the gas pedal to slow down i will hear multiple little back fires through the exhaust. theyre not loud at all, pretty soft. im sure this relates to the carb since it is not new. is it just running to rich? and ideas?

07-08-2002, 11:34 PM	#3
Dropt72Shortbed Registered User Join Date: May 2002 Location: Huntington Beach CA Posts: 678	Re: multiple small backfires during deaccleration from high rpms just put new gaskets both sides of the headers with the new engine. if it were an exhaust leak wouldnt i hear it more when i was flooring it at high rpms rather than when i just let off the gas? it never does it under 75mph no matter what rpms i let off at, only on the freeway at higher speeds

07-08-2002, 11:52 PM	#5
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	You are leaning out when the throttle plates are closed. Probably need to richen up the idle mixture screws a bit or richen up the transition circuit if that doesnt do the trick, How is your plug color? You may just be running too lean on your primary circuit and going down a wee bit on your rods might do the trick. try the idle mixture first. set it with a vascuum gauge to get it right the first time. __________________ No truck :-(

07-08-2002, 11:24 PM	#2
Suicide-D Registered User Join Date: Jan 2001 Location: Katy, TX...but the love of my life resides in Dublin,OH. Posts: 1,408	or an exhaust leak... my headers would do that when I had paper gaskets... I went to copper and solved it...

07-08-2002, 11:46 PM	#4
Suicide-D Registered User Join Date: Jan 2001 Location: Katy, TX...but the love of my life resides in Dublin,OH. Posts: 1,408	are you sure they are back fires? If they are soft and you don't hear them any other time... maybe it's just the way the exhaust sounds... I had to learn my new exhaust... they sound totally different than flowmasters that i'm used to...i sound like a harley under heavy acceleration now.



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