Team Camaro Tech banner

1 - 8 of 8 Posts

·
Registered
Joined
·
2,946 Posts
Discussion Starter #1
My 468, mild camed engine runs fine and has good power with the 4 SPD, 342 gears. The issue is it has a knock that does not go away for all the 5 years I have owned the car and 5-6 hundred miles. I have done nothing to the engine as it was "rebuilt" when I bought the car. If it is a "rod" how do I know and what is the easiest way to fix? If not what could it be?
 

·
Registered
Joined
·
1,194 Posts
Have you listened through a stethescope (or broom handle) to see exactly where the knock is coming from? I thought that I had engine knock, only to find out that the shroud was being hit by a wobbling fan, but could have sworn that it was coming from the back of the motor. The harmonics inside that engine bay can be tricky.

How's the oil pressure and have you dropped the pan to see if you have anything inside?
 

·
Registered
Joined
·
8,349 Posts
Rod knock will often change tone or almost go away when you pull the plug wire off the bad cylinder while running. Like Chad indicates, don't be sold on it as worst case right off the bat if you're not sure what it is. Auto Zone has a good mechanic's stethoscope over in the tool section for about ten bucks.
 

·
Premium Member
Joined
·
1,157 Posts
If you have forged pistons, they will sometimes knock due to tighter tolerances and thermal expansion compared to hypereutectic or cast pistons. I don't know if that is your issue or not but it is a possibility. I would first do as the others have suggested and get a cheap mechanics stethoscope and see if you can narrow down where it is coming from. I once thought that I had a rod knock, but it turned out to be a loose torque converter bolt. Hopefully it isn't a rod knock. Good luck.
 

·
Premium Member
1968 Z28
Joined
·
617 Posts
^^^*looser* tolerances. Forged pistons will rattle if they are set too loose.
X2.....It is usually worse when the engine is cold and the block to piston tolerance is the greatest. But, the knock should lessen as the piston heats and expands causing the tolerance to decrease.
 

·
Registered
Joined
·
2,946 Posts
Discussion Starter #8
Changed the oil to 20w50 and the knock went away. My buddy said that over the last few years, gas while pumping to start changed the viscosity of the oil, been 3 years on a change!
 
1 - 8 of 8 Posts
Top