Still chasing the knock
Thread Starter
Intermediate
Joined: Jun 2015
Posts: 49
Likes: 4
Still chasing the knock
76 l48 350 automatic with air knocking from front of engine at idle the ac does not work so belt has been removed new water pump and alternator and belts I used a rubber hose and thought it was the timing chain after I removed the belts I started the car I do not hear a knock I put just the power steering belt back on and have a little knock maybe 1\4 of the original pulled the belt back off yanked on the crank pully nothing feels loose I could use some feedback where to go next I drive this car 2-3 times a week since I bought it in may and keep fixing what goes bad it sat for quite a while
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
None of the acccesories are loose or hitting something adjacent? Is the harmonic balancer in good shape? The inertia ring can disbond from the hub and make noise.
Last edited by SH-60B; Nov 29, 2015 at 09:27 AM.
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
You said you removed all the belts and it went away. Since you have checked the damper look for movement from the water pump pulley/shaft. Also if you replaced the belts, try it with the old ones and see how that works.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
76 l48 350 automatic with air knocking from front of engine at idle the ac does not work so belt has been removed new water pump and alternator and belts I used a rubber hose and thought it was the timing chain after I removed the belts I started the car I do not hear a knock I put just the power steering belt back on and have a little knock maybe 1\4 of the original pulled the belt back off yanked on the crank pully nothing feels loose I could use some feedback where to go next I drive this car 2-3 times a week since I bought it in may and keep fixing what goes bad it sat for quite a while
Maybe the three 3/8" bolts that hold the pulleys on are loose.
Thread Starter
Intermediate
Joined: Jun 2015
Posts: 49
Likes: 4
Found it
The bolt for the harmonic balancer was just loose enough that I could spin the washer with my finger I have no idea why it would loosen up but I plan on doing the timing chain with a new cover and gaskets when I up grade to an aluminium radiator and electric fans I will replace the balancer at that time until then thank you for the help tops off and throttle down.
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Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 113
From: Michigan
Check the fuel pump, I went thru 2 stock replacements. 1st blew the diaphragm and last one still worked good but always knocked. Use a stethoscope, piece of pipe or long rod and put it on the pump. Aftermarket pumps have a spring to keep it from happening, but no return so you gotta be creative. Could also be just wear on the pump pushrod.
Instructor
Joined: Dec 2011
Posts: 159
Likes: 12
From: Bushnell Florida
Just for what it is worth. My 80 C3 with an L48 had a knocking noise at idle also. As soon as you gave it gas the knock went away. The smog pump and ac have been removed, it has an Edelbrock carb and performer intake, true dual exhausts. After spending weeks chasing it we found the flex plate was cracked. Replaced it and knock is gone. Good luck with your car. (Now time to fix the C4's Optispark, arghh!).
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
You seem confused
[QUOTE=toobroketoretire;1591008286]Yes, I'm well aware of what he has. I was just pointing out the previous V8's had their dampers driven on with no bolt/washer to hold them on.[/Q
All of no use to the OP.
All of no use to the OP.
Last edited by SH-60B; Nov 30, 2015 at 04:26 PM.