Popping noise need help!!!! - Chevelle Tech
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post #1 of 9 (permalink) Old Apr 9th, 15, 5:14 PM Thread Starter
Lamar
 
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Popping noise need help!!!!

Hey guys,

Got a 71 chevelle. 350 c.i. Th350. Starts fine runs fine but when I get between the speeds of 55-70 I hear a popping sound under the good. I did install new distributor (summit racing HEI) and spark plugs (Accel spark plugs). Doesn't knock or do the popping sounding until I reach that speed range. Any ideas??? I'm lost.


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post #2 of 9 (permalink) Old Apr 9th, 15, 5:25 PM
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RonO.
 
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Re: Popping noise need help!!!!

Carb may be running lean at higher speeds, could very easily be a minor adjustment to remedy. If your not sure how to do this you can always go to a shop and have them adjust carb as they increase rpm's. (AFR, air to fuel ratio) is probably weak, needs more juice. Did you put a timing light on it after Dist. install?

1970-LS5, #28- Fathom Blue,TH400, original motor car.
1970- NOM, 496, M21, #48 Forest Green.
1972- Malibu, 350. TH350- original motor car, #43 Gulf Green.
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post #3 of 9 (permalink) Old Apr 9th, 15, 6:11 PM Thread Starter
Lamar
 
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Re: Popping noise need help!!!!

My HB didn't have the timing marks on. You think I should start over. Get the TDC mark the HB and go from there? And also I have as Holley 750 4 barrel. And only the front float had gas in it. Is that a problem too?


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post #4 of 9 (permalink) Old Apr 9th, 15, 6:41 PM
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Darren
 
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Re: Popping noise need help!!!!

I have never seen a harmonic balancer with no markings on itÖ I think you should get a wire wheel that fits into a cordless drill and do a little cleaning on it. What would be the point of a part that is useless, Iím sure they are there you may just have to dig for themÖ

EDIT - Obviously timing is a critical part of your overall tune, and it MUST be done.

If you donít push the limits how are you going to find the weak spots?
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Factory 12 bolt /4-Speed Malibu -Dual stage wet nitrous with heater & purge - Holley Strip Dominator, Speed Demon 750 CFM - (All MSD distributor, blaster 3 coil, 6AL, & 3 stage retard) - 4 wheel disk brakes - Aeromotive Fuel system Ė Boss 338 18ís - BMW 5.25 true HID projector mod - and of course... the FLAPPER - bla, bla, bla.. lots of other expensive stuff I canít remember
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post #5 of 9 (permalink) Old Apr 9th, 15, 7:55 PM Thread Starter
Lamar
 
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Re: Popping noise need help!!!!

Good to go. Thanks


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post #6 of 9 (permalink) Old Apr 9th, 15, 7:58 PM
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Charlie
 
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Re: Popping noise need help!!!!

Quote:
Originally Posted by Lmrmiller View Post
My HB didn't have the timing marks on. You think I should start over. Get the TDC mark the HB and go from there? And also I have as Holley 750 4 barrel. And only the front float had gas in it. Is that a problem too?


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Yes, the rear bowl must have fuel. How did you determine that fact? Through the brass plug in the bowl, or did you remove the rear bowl?

Charlie

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post #7 of 9 (permalink) Old Apr 9th, 15, 8:19 PM
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G.B.
 
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Re: Popping noise need help!!!!

Hope it is not...... but a wiped cam will pop through the carb...if the exhaust lope is wiped it will force the exhaust out the intake...carb..

GB
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post #8 of 9 (permalink) Old Apr 9th, 15, 8:42 PM Thread Starter
Lamar
 
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Re: Popping noise need help!!!!

The bowl. I'm a novice at this. I noticed the gas trickle through the front 2 Venturi. But not the back 2. I had a mechanic " tune my carb" that's when the knock occurred.


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post #9 of 9 (permalink) Old Apr 9th, 15, 8:45 PM Thread Starter
Lamar
 
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Re: Popping noise need help!!!!

And I checked the float levels the front bowl was good. But the back bowl was empty. Any ideas?


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