exhaust noises on deceleration
Thread Starter
Instructor
Joined: Jun 2002
Posts: 145
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From: Downtown
HELP - backfire type noises particulary when using the engine to decel
i'm running an edelbrock performer carb on a generic 350 and have had pretty good luck with it. recently i've been experiencing mild low-rpm hesitation, and also slight exhaust noises during deceleration, - almost a backfire , but much milder.
i'm thinking carb obviously, but could it be timing?, ive got an HEI going too.
[Modified by 14-Paul, 9:25 PM 7/30/2002]
i'm thinking carb obviously, but could it be timing?, ive got an HEI going too.
[Modified by 14-Paul, 9:25 PM 7/30/2002]
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Re: HELP - backfire type noises particulary when using the engine to decel (14-Paul)
I'm chasing around a somewhat similar problem. I have done a lot of checking so far on mine. Next thing I'm going to check is valve spring pressures. I'm thinking I may have a broken valve spring. Maybe you might want to also consider that? Good luck.
Melting Slicks
Joined: Jul 2000
Posts: 2,112
Likes: 2
From: Peoria IL
Re: HELP - backfire type noises particulary when using the engine to decel (Bob86ZZ4)
Burbling when you decelerate in gear is normal. Stock exhaust systems muffle it, but with free flowing systems you can often here it. I kinda like it :)
Tech Contributor
Joined: Aug 2001
Posts: 472
Likes: 39
Re: HELP - backfire type noises particulary when using the engine to decel (korvetkeith)
I get the same thing on my '58 and I love the sound. It's funny, almost the exact same topic came up in the C1/C2 section. Here is Duke's answer...
http://forums.corvetteforum.com/zerothread?id=354113
He says that the idle mixture may be a little bit lean. I'll probably be messing with my idle screws tonight.
http://forums.corvetteforum.com/zerothread?id=354113
He says that the idle mixture may be a little bit lean. I'll probably be messing with my idle screws tonight.
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Re: HELP - backfire type noises particulary when using the engine to decel (aobrien)
I wouldn't mind it if that was the only problem. But, if I'm cruising along and holding it about 3000 rpms there is a definate miss there. I'll letya know if I find a broken spring.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: HELP - backfire type noises particulary when using the engine to decel (14-Paul)
When you see stock cars deccelerating in the corners and see flames comming out of the exhuast it is an improper carb setting. The throttle plates are open too much allowing fuel to be pulled in from the transfer slots. I'm not saying this is your problems but too rich a fuel mixture at idle can cause backfiring.
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Re: HELP - backfire type noises particulary when using the engine to decel (norvalwilhelm)
Well, I just finished checking all the valve springs and they all seem good. I bought a Moroso valve spring guage and they all average about 160lbs of force. Now I'm dumbfounded.
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Re: HELP - backfire type noises particulary when using the engine to decel (BB wowbagger)
If your experiencing popping/backfiring on deceleration, check you timing, both vacuum and centrifigul. I had a dead vacuum can, replaced it, adjusted the initial timing and the problem went away.
