another knock noise ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

blazer2007 · 10-09-2019, 11:28 AM

5 yr. old motor 350/350 stock low miles only driven in the summer, small town mostly in town and on the hiway now and then to stretch it, legs so to speak. Good Lucas Hot Rod hi zinc oil. Anyway I was going to work about 20 MPH and heard a heavy ticking noise,checked oil press. and was 60 psi,pulled over to see if something was hitting but nothing but the noise was down in the bottom of the engine and not a valve train sound ,was heavier than the usual valve noise. Engine ran fine ,nice and smooth,RPM,s were consistent. Took it home and took my Jeep to work,came home and started the truck,the noise was gone. Will try again this morning and see,cold right now 3 below Celsius. I did some reading and the 3 things that came up was rod ,fuel pump and flex plate and someone mentioned looking under dist. cap ,I don,t know why. Couldn,t see anything in the flex plate area for cracks but could be small. I did put in a new carter fuel pump 2 weeks ago when looking for random stall which was the ign. sw. Checked fuel pump with a broom handle and couldn,t hear anything strange. Can these 3 items pump,rods and flex plate be random? I would think the rod knock would be all the time especially when cold. Hope I explained everything.

geezer#99 · 10-09-2019, 11:38 AM

Collapsing lifter can be random.
I had one on my 65 like that.
Made noise at odd times.
If I shut it off and started it a couple times it would quit and come back again maybe a couple weeks later.

blazer2007 · 10-09-2019, 09:06 PM

Took it for a drive and no bad noise but heard a bit at the beginning but not loud, seems a ta off but could be my imagination. I think I will change the fuel pump as the old one was OK. Do you think something fell off on the fuel pump and rattled but would still work ? Will keep a ear out for the collapsed lifter as geezer said. I hate these random issues

**truckster** · 10-10-2019, 05:32 PM

You don't say what year 350 you have, but if it's a Vortec, it could be piston slap. Some of the earlier ones were especially noticeable.

blazer2007 · 10-10-2019, 09:02 PM

Quote:

Originally Posted by truckster

You don't say what year 350 you have, but if it's a Vortec, it could be piston slap. Some of the earlier ones were especially noticeable.

I thought I had everything covered but the year,is 75 L-48 stock rebuilt about 5 yrs. ago, low mileage in a 80 2 wheel truck

Dead Parrot · 10-10-2019, 11:14 PM

Power steering pump going bad can sound a lot like an engine noise.

*YoungPup1977* · 10-14-2019, 09:16 AM

Take off the belts one at a time, fire it up and see if it has a noise.

10-09-2019, 11:28 AM	#1
blazer2007 Registered User Join Date: Jan 2007 Location: vernon b.c. Posts: 3,022	another knock noise ? 5 yr. old motor 350/350 stock low miles only driven in the summer, small town mostly in town and on the hiway now and then to stretch it, legs so to speak. Good Lucas Hot Rod hi zinc oil. Anyway I was going to work about 20 MPH and heard a heavy ticking noise,checked oil press. and was 60 psi,pulled over to see if something was hitting but nothing but the noise was down in the bottom of the engine and not a valve train sound ,was heavier than the usual valve noise. Engine ran fine ,nice and smooth,RPM,s were consistent. Took it home and took my Jeep to work,came home and started the truck,the noise was gone. Will try again this morning and see,cold right now 3 below Celsius. I did some reading and the 3 things that came up was rod ,fuel pump and flex plate and someone mentioned looking under dist. cap ,I don,t know why. Couldn,t see anything in the flex plate area for cracks but could be small. I did put in a new carter fuel pump 2 weeks ago when looking for random stall which was the ign. sw. Checked fuel pump with a broom handle and couldn,t hear anything strange. Can these 3 items pump,rods and flex plate be random? I would think the rod knock would be all the time especially when cold. Hope I explained everything.

10-09-2019, 11:38 AM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,516	Re: another knock noise ? Collapsing lifter can be random. I had one on my 65 like that. Made noise at odd times. If I shut it off and started it a couple times it would quit and come back again maybe a couple weeks later.

10-09-2019, 09:06 PM	#3
blazer2007 Registered User Join Date: Jan 2007 Location: vernon b.c. Posts: 3,022	Re: another knock noise ? Took it for a drive and no bad noise but heard a bit at the beginning but not loud, seems a ta off but could be my imagination. I think I will change the fuel pump as the old one was OK. Do you think something fell off on the fuel pump and rattled but would still work ? Will keep a ear out for the collapsed lifter as geezer said. I hate these random issues

10-10-2019, 05:32 PM	#4
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,805	Re: another knock noise ? You don't say what year 350 you have, but if it's a Vortec, it could be piston slap. Some of the earlier ones were especially noticeable. __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson

10-10-2019, 11:14 PM	#6
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,486	Re: another knock noise ? Power steering pump going bad can sound a lot like an engine noise.

10-14-2019, 09:16 AM	#7
YoungPup1977 Account Suspended Join Date: Jun 2015 Location: No longer here Posts: 1,000	Re: another knock noise ? Take off the belts one at a time, fire it up and see if it has a noise.



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