Found rear balance shaft bearing in oil pan, need opinions.

[LessIsMore]

I was experiencing a nasty noise and vibration coming from my motor so I pulled the oil pan. In it I found my rear balance shaft bearing split at the seam along with some other metal particles/chunks from the bearing craping out. I also removed the 2nd and 3rd cylinder rod caps and the center main cap. The bearings on the rod caps looked good and the crank journal had very small scratches that were only visible and couldn't be felt by running my finger nail across. The main bearing that I pulled had small nicks in it on one side that could be felt and the crank journal had small unfeelable scrathces.

Now my plan is to eliminate the balance shafts by replacing the rear one with the stuby shaft from the mirage and leaving the front balance shaft in the block with no balance belt.

My question is whether or not the wear to the crank and bearings is normal for a motor with 100K+ miles? Can I get away with just eliminating the balance shafts and leaving the rest as is? Is there anything particular that needs to be done when reinstalling the rod and main caps or do I just torque them back down and be done with it? I'm new to engine bottom end work and any insight would be appreciated.

 

[Defiant]

You're going to make Buck a _very_ happy poster. He'll be along any moment now.

 

[RallyGSX]

You need to balance your rotating assembly to eliminate your balance shafts (crank + flywheel together). You need to remove your motor to do this as well. A thorough inspection anywhere oil goes is on order here. Your crank and block need to go to a good machine shop, if your lucky you can just polish your crank amd reinstall it w/ new main and rod bearings. Your cylinder walls may be F#@$ed up as well...

I've done 2 motors now w/ JUN chromemoly flywheels, and those things were both balanced perfectly off the bat... machinist was very impressed.

If your going to remove and teardown a motor w/ over 100k mi., just do a full rebuild, your 90% there anyway.

-Disclaimer- I've done a bunch of domestic motors but I'm new to the 4g63 scene, and things seem to need to be "perfect" if you want your 4g63 to last at all. I failed the first time on my 1st 4g63 build for my Rally Car project, but my 500HP supercharged big block Chevy ran perfectly from the 1st start up...

Also...heard some people were having oil pump failures from balance shaft elimination, sorry to butt in, but can anyone explain this?

Thanks,
Dave
Dave's Welding and Automotive

 

[BUCK]

In it I found my rear balance shaft bearing split at the seam along with some other metal particles/chunks from the bearing craping out.

I'm sure you are aware the rear bearing is Oil fed via the soon to be gone SILENT Shaft.

I also removed the 2nd and 3rd cylinder rod caps and the center main cap. The bearings on the rod caps looked good and the crank journal had very small scratches that were only visible and couldn't be felt by running my finger nail across. The main bearing that I pulled had small nicks in it on one side that could be felt and the crank journal had small unfeelable scrathces.

If the bearings looked REALLY good - I personally would reuse them - If not I'd at least replace the rod bearings.

Now my plan is to eliminate the balance shafts by replacing the rear one with the stuby shaft from the mirage and leaving the front balance shaft in the block with no balance belt.

P/N MD 098626 - $18 - don't forget the Loctite.

My question is whether or not the wear to the crank and bearings is normal for a motor with 100K+ miles?

What your describing is far better than mine were at 100K miles...

Can I get away with just eliminating the balance shafts and leaving the rest as is?

Replace / Inspect Harmonic Balancer, if it's original can it... I'd replace ALL the front Oil seals - including the one on the front balance shaft that will just sit there - replace Timing Belt & Tensioner (use THE GRENADE PIN to set the Tension setting) - replace the Water Pump - don't forget to plug the hole where the front balance shaft tensioner WAS (short bolt, washer & RTV) - Clean Oil Pressure Relief Valve Assembly - I'm SURE you've already canned your water to oil cooler - if not - NOW is the time - which style Oil Filter Housing do you have?

Is there anything particular that needs to be done when reinstalling the rod and main caps or do I just torque them back down and be done with it?

NO OIL on backside of bearings - Synthetic Gear lube, STP, or Engine Assembly lube on face of bearing - Inspect & pack Oil pump with grease - clean & BACKFLUSH the hell out of Oil pickup strainer - Torque Oil Pan fasteners evenly & correctly over & over till all are to spec... I personally would run it without plastic Timing Cover & P/S pump - check for leaks - RE-SET Timing Belt Tension after the initial "stretch" - THEN button it up...

You need to balance your rotating assembly to eliminate your balance shafts (crank + flywheel together).

I didn't - mine runs like a top - idles smoother than most 4 cylinders... the consensus of opinion is that our Cranks, rods & pistons are as balanced as any stock engine components - the Silent Shafts are there for the traditional 4 cylinder vibes.

Also...heard some people were having oil pump failures from balance shaft elimination, sorry to butt in, but can anyone explain this?

My guess would be SOMEONE who didn't properly inspect & or reassemble the Oil Pump OR the Front Case OR the Oil Filter Housing OR plug the front SILENT Shaft Tensioner Hole OR blew the Timing Belt Tension setting OR Timing - etc, etc... IMO those failures have a LOT to do with these "Oil Pump failures" - Honestly the Oil Pump bearings should be very happy to be rid of that heavy balance shaft - the tiny Mirage stub shaft is a PERFECT FIT.

You're going to make Buck a _very_ happy poster. He'll be along any moment now.

You've made my day... & Good Luck