Question on engine rebuild 4.2 2006 trailblazer

CASHKJ

Original poster
Member
Feb 4, 2013
28
I have a 2006 trailblazer with a 4.2 it had a bad knock so I pulled the engine and found the number 3 rod bearing bad.I was going to replace all the rod bearings but the question that I have is there any other bearings or any other preventive maintenance I should do while I have at this point.

Thanks!
 

C-ya

Member
Aug 24, 2012
1,098
Main bearings. About the only other thing left in the motor itself after that is the rings. I would get the cylinders deglazed at least, then put new rings in. If you have the time and cash, maybe send the head out to get the valves and seats cleaned up and new stem seals. Someone on here had some porting work done (clean up, mostly, IIRC) on a head they picked up.

Might not be a bad idea to have the cylinders checked if the rod bearing was bad. The piston could have wobbled in the cylinder, making it out of round. I bought a junkyard motor for my SBC swap and one hole was so bad due to a bad bearing, the shop had to bore the cylinders oversize. As bad as it was when I tore it down, it really cracked me up when I thought of the guy at the junkyard saying he heard the motor run. I was LOLing!
 

mrphoenix80

Member
Jan 1, 2013
251
CASHKJ said:
.I was going to replace all the rod bearings but the question that I have is there any other bearings or any other preventive maintenance I should do while I have at this point.!

I would do a Crank kit with the main and rod bearings. Also check the connecting rod for propper size and out of round, and replace if needed. But if you are this far you want to look at everything. If you have the crank out to do bearings I would go with a full rebuild. You don't want to get back in because of something you missed while it was apart.
 

CaptainXL

Member
Dec 4, 2011
2,445
If the cylinder head was out I would just replace the sleeves, pistons, wrist pins and rings. I'm not sure if the sleeves need to be machined once installed.
 

CASHKJ

Original poster
Member
Feb 4, 2013
28
Thanks for all the input as it turns out I need a new crankshaft in search of one now.
 

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