Excessive valvetrain noise?
03-22-2004, 07:23 PM
#1
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Excessive valvetrain noise?
I've got an 02' REX w/ about 10k on a fresh built shortblock w/ forged internals. The valvetrain just recently has started making the loudest damned tapping and clanking that is totally not normal. It sounds like one real loud metal on metal tap per revolution and it seems to be originating from the passenger side valve cover if I can tell correctly.
The motor does not eat excessive oil and it is not dirty and is not dilluded w/ fuel. The coolant is fine and is not dilluded w/ oil. The compression tests w/ a variance of at most 5 psi. Now although I did not remove the entire front cover, I did remove either side except for the middle and the crank pulley. The teeth and belt are not worn and both sides line up correctly as per the indicated marks on the gears. Not to mention both the belt and tensioner were replaced 10k miles ago, right after the rebuild. I just reinstalled the entire exhaust, header and all, it does not leak visually and I cannot hear it, even when I'm under the car with it running.
The heads are totally stock, but were totally went through and re-assembled when the motor was rebuilt. What else can I do at this point short of pulling the motor and tearing the heads off? What would cause this noise, bad shims and or buckets, cam, etc.? Any help or advice would be greatly appreciated as I'm pulling my hair out. Oh ya, the car does not knock at low RPM or idle, but picks up knock up in the mid and upper RPM band even at very light throttle and or load.
This car is heavily modified and the dealer is not an option.
Thanks much,
-Adam
The motor does not eat excessive oil and it is not dirty and is not dilluded w/ fuel. The coolant is fine and is not dilluded w/ oil. The compression tests w/ a variance of at most 5 psi. Now although I did not remove the entire front cover, I did remove either side except for the middle and the crank pulley. The teeth and belt are not worn and both sides line up correctly as per the indicated marks on the gears. Not to mention both the belt and tensioner were replaced 10k miles ago, right after the rebuild. I just reinstalled the entire exhaust, header and all, it does not leak visually and I cannot hear it, even when I'm under the car with it running.
The heads are totally stock, but were totally went through and re-assembled when the motor was rebuilt. What else can I do at this point short of pulling the motor and tearing the heads off? What would cause this noise, bad shims and or buckets, cam, etc.? Any help or advice would be greatly appreciated as I'm pulling my hair out. Oh ya, the car does not knock at low RPM or idle, but picks up knock up in the mid and upper RPM band even at very light throttle and or load.
This car is heavily modified and the dealer is not an option.
Thanks much,
-Adam
03-22-2004, 07:51 PM
#2
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Join Date: Apr 2003
Location: kaneohe
Posts: 140
Car Info: 2002 silver rex
Valves move twice per revolution, rod knock sounds like only once per rev. If it were me I wouldn't drive or start it until I found out whats causing the sound. Start with the valve area and work your way to the crank. Some people would change motor oil to some 50W If the sound lessens or goes away a tear down is in order. With what you got invested I would just start with the heads and work my way in.
Last edited by curbait; 03-22-2004 at 08:06 PM.
03-23-2004, 12:38 PM
#3
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Join Date: Feb 2003
Location: busy writing log of best roads in CA.
Posts: 568
Car Info: 2002 WRX Sedan
How is the oil pressure? If you have a rod bearing going away, you'll see low pressure.
What kind of clearances did you see rod-bearing-to-journal?
And the valvetrain runs at half the speed of the crank.
720 crank degrees = 360 cam degrees.
I think a valvetrain problem would be noisy regardless of rpm.
Take the plugs out of the motor and set each piston to TDC. When said piston is at TDC, use a plastic stick or wooden dowel and try to push piston back to BDC thru plug hole. If you feel no resistance and then resistance, you've found the rod bearing that is dying.
Sorry buddy,
Jim
What kind of clearances did you see rod-bearing-to-journal?
And the valvetrain runs at half the speed of the crank.
720 crank degrees = 360 cam degrees.
I think a valvetrain problem would be noisy regardless of rpm.
Take the plugs out of the motor and set each piston to TDC. When said piston is at TDC, use a plastic stick or wooden dowel and try to push piston back to BDC thru plug hole. If you feel no resistance and then resistance, you've found the rod bearing that is dying.
Sorry buddy,
Jim
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