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Author Topic:   v/6 engine knock
rico 08
Dirt Freak

Total posts: 372
posted December 11, 2002 02:20 PM
This is actually in a blazer i just bought not really a topic for this forum but i wasn't getting any responses elsewhere,it's a 92 4.3 vortec and i bought it cause the owner said it had thrown a rod but it runs ok and nothing is sticking out the block or pan listening to it it sounds as though it's a collapsed lifter or something else in the valvetrain when you drive it it's hard to hear except when you put a light load on it and it gets louder but step on the gas a little more and it totally disappears,a so called mechanic said these are famous for this if it is a rod or main it's the quietest one i've ever heard but the noise does sound low in the engine,any ideas?

jhon hollomon
Dirt Maniac

Total posts: 181
posted December 11, 2002 03:54 PM
Are you sure it's not a spark knock like from some low grade gas or something? Is it firing all six cylinders ok?

Racer14K
Dirt Freak

Total posts: 247
posted December 11, 2002 05:22 PM
You can try pulling one plug wire off at a time and see if the noise goes away or gets quieter. If so then it is more than likely in the lower end, but this does not always work, just an easy check.

stockcar5
Dirt Full Roller

Total posts: 63
posted December 11, 2002 08:08 PM
i work at a chevu dealership and we do have lifter problems. they can almost sound like a bottom end problem if they get bad enough. i'd just get some lifters for it if i were you. you'd know if it was a rod or main

luke

Flatlander
Dirt Freak

Total posts: 310
posted December 11, 2002 09:25 PM
If you pull the valve covers you'll probably be able to see the problem if it's a collapsed lifter

daniell
Dirt Full Roller

Total posts: 31
posted December 12, 2002 04:22 PM
Racer14k is right on about the plug wire check, you can also take a piece of old air hose or something similar and stick one end to ear the other along the valve cover and isolate the area if it is in the valve train. Another thought is timing chain and I have seen a cracked flexplate cause a knock that sounds like a bearing. Just some thoughts.

rico 08
Dirt Freak

Total posts: 372
posted December 16, 2002 02:04 PM
thanks for all the responses,another weird thing about it is that it is really quiet when cold and a lot louder when warm,so i guess that rules out piston problems and points more to bearing related problems.

b4racing
Dirt Maniac

Total posts: 180
posted December 16, 2002 09:22 PM
I bet it is a lifter

rico 08
Dirt Freak

Total posts: 372
posted January 06, 2003 02:42 PM
well i guess it was a rod sent it to the auction,thanks for the responses the other forums didn't respond which proves this is one of the best forums out there even though the topic didn't fit,i'm proud to be a member!

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