1970 C-10 knocking sound - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ghill901 · 03-27-2013, 10:57 AM

I changed the carb on my 70 c10 with a Eddlebrock performance series 4 barrel. Char was running fine then i noticed a knocking sound as i accelerate. Any ideas?

**Ol Blue K20** · 03-27-2013, 11:33 AM

Carb may be lean and now it's pinging? just first thought to pop into my head and that hurts this early LOL

~Whitey~ · 03-27-2013, 11:40 AM

sounds like the timing is off... probably advanced too far causing pre-detonation.

ghill901 · 03-27-2013, 11:51 AM

the timing is what i thought was off also, I had the timing adjusted but still the same rapid knocking noise. Also when i decellerate my truck backfires. it sounds like it is coming from the carb itself. What controls the spedometer cause when i hit 60mph the needle goes crazy and drops.

truckster · 03-27-2013, 12:09 PM

Quote:

Originally Posted by ghill901

the timing is what i thought was off also, I had the timing adjusted but still the same rapid knocking noise. Also when i decellerate my truck backfires. it sounds like it is coming from the carb itself. What controls the spedometer cause when i hit 60mph the needle goes crazy and drops.

I would look for a lean mixture as well.

The speedometer is run by a cable coming from your transmission. If it works correctly up to 60, it's likely the speedometer head (the part behind the dial you see on your dash) needs to be repaired.

ole dollor · 03-27-2013, 06:58 PM

i would pull all the plugs out and see if they have been hit by anything ...a bolt or nut could have been in the intake or fell in while you had the intake off, right now it could be holding a valve open, also run a compression check and see whats going on...i sure hope i am wrong..but it want take a lot of time to do this , before more damage could be done..

03-27-2013, 10:57 AM	#1
ghill901 Registered User Join Date: Mar 2013 Location: Phoenix, AZ Posts: 2	1970 C-10 knocking sound I changed the carb on my 70 c10 with a Eddlebrock performance series 4 barrel. Char was running fine then i noticed a knocking sound as i accelerate. Any ideas?

03-27-2013, 11:33 AM	#2
Ol Blue K20 Proprietor of Dale's Corner Join Date: Nov 2012 Location: Vacaville , CA Posts: 16,271	Re: 1970 C-10 knocking sound Carb may be lean and now it's pinging? just first thought to pop into my head and that hurts this early LOL __________________ "Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man R.I.P. FleetsidePaul

03-27-2013, 11:40 AM	#3
~Whitey~ Registered User Join Date: Jun 2011 Location: Springfield, MO Posts: 677	Re: 1970 C-10 knocking sound sounds like the timing is off... probably advanced too far causing pre-detonation. __________________ Jimmy .69SWB Build.

03-27-2013, 11:51 AM	#4
ghill901 Registered User Join Date: Mar 2013 Location: Phoenix, AZ Posts: 2	Re: 1970 C-10 knocking sound the timing is what i thought was off also, I had the timing adjusted but still the same rapid knocking noise. Also when i decellerate my truck backfires. it sounds like it is coming from the carb itself. What controls the spedometer cause when i hit 60mph the needle goes crazy and drops.

03-27-2013, 06:58 PM	#6
ole dollor Registered User Join Date: May 2012 Location: Anton, Texas Posts: 2,364	Re: 1970 C-10 knocking sound i would pull all the plugs out and see if they have been hit by anything ...a bolt or nut could have been in the intake or fell in while you had the intake off, right now it could be holding a valve open, also run a compression check and see whats going on...i sure hope i am wrong..but it want take a lot of time to do this , before more damage could be done..



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