Loud bang in exhaust.... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Edmond · 02-23-2004, 10:11 AM

When I ask more power from the engine, for instance while going on the freeway I sometimes get a loud bang in the exhaust.
Could it be that maybe the ignition timing is off?
It happend yesterday for the first time in almost 18 months. Before that I had it also, but that was due to bad cables to the sparkplugs. After changing the cables the problem was gone.
Back then I did not change the distributor cap or rotor.
It has been on there from the day I bought the truck. Could that also be causing this? Any one of you have any ideas on this?
Thanks

Cya,
Edmond

Longhorn Man · 02-23-2004, 10:13 AM

I would start with a new cap and rotor, and a fresh set of plugs too if you haven't chainged them in the past couple years.

Edmond · 02-23-2004, 10:25 AM

Well then that's what I will do at first.
Plugs were changed when I changed the cables .
But since I run on propane it's not a bad thing to change them again.
Propane runs hotter than gasoline.
Thanks for the quick respone Longhorn Man!

cya,
Edmond

OhioDan · 02-23-2004, 12:52 PM

You could check timing, rotor and cap? Plugs? Vacumn advance sticking sometime? LP timing is different than gasoline. Fuel mixture ? LP converter? Propane is a different beast than gasoline. Low coolant to regulater will cause it to run weird.(LP will freeze-up regulater if coolant is low) Causing it to sometime backfire, miss, spit and sputter. Not reall familiar with LP on auto and truck engine. Can't be much different than the forklifts at work? Hope this helps?

Edmond · 02-24-2004, 12:03 PM

I did check the coolant and it was okay.
Timing is indeed different for Propane. As I run on propane all the timing it is set for propane.
I will use gasoline only on highway when I don't have enough Propane.
Hasn't happend in a long time :-) We have a good network of propane outlets!

Thanks for thinking along OhioDan!

Cya,
Edmond

Edmond · 03-02-2004, 04:44 AM

What a world of difference a new rotor and distribution cap can make

Changed it last night, took the truck for a testdrive and the beast is running better than ever

Just wanted to let you know!!

Cya,
Edmond

02-23-2004, 10:11 AM	#1
Edmond Registered User Join Date: Jan 2000 Location: The Netherlands Posts: 1,063	Loud bang in exhaust.... When I ask more power from the engine, for instance while going on the freeway I sometimes get a loud bang in the exhaust. Could it be that maybe the ignition timing is off? It happend yesterday for the first time in almost 18 months. Before that I had it also, but that was due to bad cables to the sparkplugs. After changing the cables the problem was gone. Back then I did not change the distributor cap or rotor. It has been on there from the day I bought the truck. Could that also be causing this? Any one of you have any ideas on this? Thanks Cya, Edmond __________________ 1971 Chevy C/20 Longhorn, 350/TH400, Edelbrock Performer, IMPCO 425 LPG Carb 1974 Chevy Camaro Z28 (Original) ------------------------- The Netherlands

02-23-2004, 10:25 AM	#3
Edmond Registered User Join Date: Jan 2000 Location: The Netherlands Posts: 1,063	Well then that's what I will do at first. Plugs were changed when I changed the cables . But since I run on propane it's not a bad thing to change them again. Propane runs hotter than gasoline. Thanks for the quick respone Longhorn Man! cya, Edmond __________________ 1971 Chevy C/20 Longhorn, 350/TH400, Edelbrock Performer, IMPCO 425 LPG Carb 1974 Chevy Camaro Z28 (Original) ------------------------- The Netherlands

02-23-2004, 12:52 PM	#4
OhioDan Registered User Join Date: Apr 2002 Location: New Carlisle, Ohio,USA Posts: 1,404	You could check timing, rotor and cap? Plugs? Vacumn advance sticking sometime? LP timing is different than gasoline. Fuel mixture ? LP converter? Propane is a different beast than gasoline. Low coolant to regulater will cause it to run weird.(LP will freeze-up regulater if coolant is low) Causing it to sometime backfire, miss, spit and sputter. Not reall familiar with LP on auto and truck engine. Can't be much different than the forklifts at work? Hope this helps? __________________ LIFE AIN'T EASY WHEN YER FAT AND GREASY! GMC= Got More Class! 1970 GMC LWB, Fleetside, 350/4spd, Flowmaster "40's", 2002 GMC 16" Rallies, cowl hood,and added a bunch of options that weren't there when I started. Last edited by OhioDan; 02-23-2004 at 12:54 PM.

02-24-2004, 12:03 PM	#5
Edmond Registered User Join Date: Jan 2000 Location: The Netherlands Posts: 1,063	I did check the coolant and it was okay. Timing is indeed different for Propane. As I run on propane all the timing it is set for propane. I will use gasoline only on highway when I don't have enough Propane. Hasn't happend in a long time :-) We have a good network of propane outlets! Thanks for thinking along OhioDan! Cya, Edmond __________________ 1971 Chevy C/20 Longhorn, 350/TH400, Edelbrock Performer, IMPCO 425 LPG Carb 1974 Chevy Camaro Z28 (Original) ------------------------- The Netherlands Last edited by Edmond; 02-24-2004 at 06:21 PM.

03-02-2004, 04:44 AM	#6
Edmond Registered User Join Date: Jan 2000 Location: The Netherlands Posts: 1,063	What a world of difference a new rotor and distribution cap can make Changed it last night, took the truck for a testdrive and the beast is running better than ever Just wanted to let you know!! Cya, Edmond __________________ 1971 Chevy C/20 Longhorn, 350/TH400, Edelbrock Performer, IMPCO 425 LPG Carb 1974 Chevy Camaro Z28 (Original) ------------------------- The Netherlands

02-23-2004, 10:13 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I would start with a new cap and rotor, and a fresh set of plugs too if you haven't chainged them in the past couple years.

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