Doing an LT5 Full Rebuild, Should I replace the Cylinder Liners?

[spork2367]

Opinions needed on this one.

I own a 1990 and decided to buy a spare motor when one came up for sale on here for a good price.

It's a 1991, the motor out of Dave Davis's wrecked Black car.

The last time it ran was when he had his accident (2008) and it sat garaged with all the original oil leaks and grime since.

I got it last week and tore the entire thing down. Since this is the first time I've had one of these apart, I was looking for opinions (hopefully backed with some knowledge...) on a few things. I've attached pictures of the liners. I don't think they look bad for having over 100,000 miles on them. Once has a noticeable gouge, but I'm unsure of whether I should replaced the gouged one, re-ring, and go, or replace them all while the motors apart. If I replace one or two, I'll try to find some low mileage liners. If I replace them all, I'd like to go with OEM liners. I do have a complete set of liners/pistons/rings that I bought from Jerry's less than a year ago, but should I just throw liners in, re-ring, and use reuse the pistons if they look alright?

Also, on the main bearings, I know Jerry's sells a stock kit and .0005 oversize kit. What journal/bore size would dictate the oversize kit.

I'm a manufacturing engineer who was a machinist before I finished my degree, so I tend to be picky.

Thanks for the help.

[spork2367]

Other 4 bores.

[spork2367]

Mains.

[Scrrem]

The liners don't look bad and honestly the nikasil coating on these liners is tough stuff. Unless you were doing a stroker build I would stick with the stock liners.
Rich

[A26B]

About 0.0005 oversize main bearings:
Occasionally, when checking assembly clearances with new, STD sizs bearings, the main clearance on some journals may be right at the maximum. Some engine builders prefer to be under the maximum or "top-side" of the clearance spec. That's where the 0.0005" bearings are used. It's likely that only a couple of journals may make use of the oversize bearing. We don't sell partial sets or single bearings, so buying two full sets would be necessary.
I would emphasize that because final clearances are at the top side of the spec, does not dictate the need to move the clearance tighter by 0.005". Only if the final clearances were greater than spec, I would recommend using the oversize bearing.

About the scored sleeve/liner:
Replace it. We have good, used ones.

Reusing your pistons:
Inspect the cylinder and ring groove clearances with new rings, measure the piston for wear and the piston pin/rod bushings. If the rod bushings are worn, they can be replaced. If all is good, re-use them.

100,000 miles will probably show some wear although good running LT5's with that many or more are not uncommon. The difficult choice is always "where do you draw the line on a rebuild."

[spork2367]

Originally Posted by A26B

About 0.0005 oversize main bearings.
Occasionally, when checking assembly clearances with new, STS bearings, the main clearance on some journals may be right at the maximum. Some engine builders prefer to be under the maximum or top-side. That,s where the 0.0005" bearings are used. It's likely that only a couple of journals may make use of the oversize bearing. We don't sell partial sets or single bearings, so buying two full sets would be necessary.
I would emphasize that because final clearances are at the top side of the spec, does not dictate the need to move the clearance tighter by 0.005". If the final clearances were greater than spec, I would recommend using the oversize bearing.

About the scored sleeve/liner.
Replace it. We have good, used ones.

Reusing your pistons.
Inspect the cylinder and ring groove clearances with new rings, measure the piston for wear and the piston pin/rod bushings. If the rod bushings are worn, they can be replaced. If all is good, re-use them.

100,000 miles will probably show some wear although good running LT5's with that many or more are not uncommon. The difficult choice is always "where do you draw the line on a rebuild."

Thanks. On the second picture, what is the discoloration in the bore?

My dad and I went in on a 1990 zr1 last year, and he purchased one of your complete liner/piston/ring sets last fall. I'd like to keep that on the shelf for now though

[John Boothby]

Originally Posted by spork2367

North Central, Williamsport.

My wife was born and raised in Montoursville and her father was an air traffic controller in the Williamsport tower! Her brother still lives in Montoursville.

Good luck on your rebuild!

[Schrade]

If the DMF springs are loose, or wasted, it COULD mean many miles were done at lower rpm's - hard to know for sure tho'.

Tight DMF likely could mean a little less 'conservative' driving history...

Good snappics too! Always fun to look at builds!

[spork2367]

Originally Posted by Schrade

If the DMF springs are loose, or wasted, it COULD mean many miles were done at lower rpm's - hard to know for sure tho'.

Tight DMF likely could mean a little less 'conservative' driving history...

Good snappics too! Always fun to look at builds!

Car was driven hard at least once....


Truthfully, the only evidence of this demise as far as the motor was concerned was one small gouge in the air horn and a small piece of safety glass in the valley. I'd be curious to know what the story of the car was before Dave owned it, and who pulled the motor. Every single electrical connector on the top of the motor was broken. Someone had the upper intake off and about half of the vacuum lines were missing or broken. Some bolts were replaced with non OEM bolts, and a few of the missing ones were laying in the valley....lol.

The accel injectors Dave put in/had put in were there. Plug wires were replaced at some point, with several being off the coils when I pulled the plenum. And whoever replaced the spark plugs never replaced the back two...

[rkreigh]

this is a VERY good running LT5 and gibby pulled a few 12 OHs with just headers and drag radials

saw him do it and was amazed

liners, rods and pistons are durn near give away on these things

nobody wants the stock parts which is really silly as they are hugely strong and adequate for most builds

as pete and many others have shown getting 500 plus hp out of the stock bottom end is very doable

and based on what I know the limit is likely quite a bit higher as the LT5 is one tough little engine