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Old 12-11-2002, 06:07 PM
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Post "problems with a crate motor 350/330hp??"

i have a 350/330hp crate motor vortec heads with the GM vortec aluminum intake w/egr, counter balanced flex plate, correct harmonic balancer per catalog, new distributor, fuel pump, knock sensor, temp sensor, oil sending unit, and all other "under hood parts & accessorise are all new including OE GM headers all the way back exhaust system w/magnaflow cats 3" and flowmaster 40'serise muuflers...
********* problem is there is a very *********
pronouced knock from the mid to lower part of eng on passenger side between cyl#4-6!!!! anyone else having or had this problem if so what was diagnoises?? any sugestions as the motor was the on floor display modle at my local GM dealer when purchesed in 04/00 and is so claimed by the dealer to be "out of warranty period" motor has only been ran poss 1hr idle to cruse rpm's...
the knock seems to go away just as the rpms come up and stays gone untill idle returns to normal. eng sounds strong and sees to run good. the eng was recently started after long and costly instalation period as i did not cut corners for my on going building of my truck.

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Old 12-11-2002, 06:18 PM
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sounds like maybe one of the pistons galled a skirt, a common problem on rebuilds that have been in storage for years, the oil that the engine was assembled with has migrated somewhere else leaving a dry cylinder dry piston skirt and when you fire it the skirt trys to weld itself to the wall because of no lube. this lets the piston rock at idle and make noise. also check to see if the piston is clearing the crank counterweight and the crank is clearing the windage or oil pan baffle.
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Old 12-12-2002, 07:12 AM
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I had a simialr problem with my car, but mine was a popping out the exhaust. I later found out that one of my plugs had a crack. I dont know if that mihgt be of help to you
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Old 09-17-2003, 08:34 PM
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Check the easy stuff first. Is the knock coming from the top or bottom?

Sounds like you could have a lifter out of adjustment or sticking. I had a sticky lifter on my V6. I got tired of hearing it so one day I just floored the darned thing. Problem solved....lol
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Old 09-18-2003, 10:38 PM
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I agree with Bob that the problem is in the piston area. You might run a compression test on the engine or a leak down test to see what the problem is. It could even be a broken ring. At any rate it is best to pull it a part now and possibly save some money in the long run. Good Luck,
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Old 09-19-2003, 04:51 AM
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I am assuming the crate engine was new when you bought it, so that rules out any rebuild problem. There have been some reported problems with excessive cylinder wall clearances on certain early GM Performance Parts crate engines. Since yours was purchased in 00, it may be one of the affected ones, Whether or not you can get the dealer you purchased it from to admit it, that is another story. Your description of the noise sounds like a piston slap due to excessive clearance IMO.


Last edited by 302/Z28; 09-19-2003 at 10:25 AM.
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