engine overhaul question. expert advise needed

[kabanimk3supra]

I recently aquired a jspec 7mgte. I want to deck the block and head for a good seal. I know this may seem like overkill to some, but I want it done one time.

I'm using an HKS hg and ARP studs.

my question is:

can I reuse the stock bearings in the bottom end IF they are in good condition?

If you don't know for sure, please don't tell me "what you think". I want this to as painless as possible.

thanks

 

[HommerSimpson]

yes

 

[CajunKenny]

Did these bearings come out of the same engine and were marked accordingly to insure that they get reinstalled the EXACT same way they came out?

If yes, then yes.

Did these bearings come out of a different engine?

If yes, then tecnically still yes; but, not recommended. Not at all recommended!

 

[kabanimk3supra]

yes, they will be marked and put back in the same order.

so has anyone successfully done this?

 

[HommerSimpson]

yes.. if you keep each bearing in each rod and it goes back on each journal it came off of.. its not a problem at all..

 

[Txsupra]

Not just mark them, but mark the direction that they were facing. Also i would mark the bolts too, if your not replacing them. Be sure to check them for stretching before reusing them.

 

[kabanimk3supra]

Not just mark them, but mark the direction that they were facing. Also i would mark the bolts too, if your not replacing them. Be sure to check them for stretching before reusing them.

up and down, right?

 

[lowtaco]

^ Yes.

 

[IBoughtASupra]

Bearings Are A Cheap Investment. I Always Replace Them Even If They Look Good Just For Safety.

 

[CyFi6]

Why would you EVER want to re-use the same bearings? As prone as the 7M seems to be with bearings problems, its the last thing i would do. You are rebuilding the rest of your engine, absolutely no reason not to put another $100 or so for new bearings. I hope you are going to at least hone/re-ring as well.

 

[CajunKenny]

^Ditto...

 

[hvyman]

also if its a jdm engine you might want to trow plastigauge and see if any were out of clearance and possibly knocking. a lot of jdm engines either have rod knock or a bhg.

if your decking the block you might as well just put new bearings in.

 

[kabanimk3supra]

The cylinders still have the cross-hatch marks. and the bearings look excellent, this is why I'm thinking to just reuse these parts.

 

[hvyman]

it is better practice and piece of mind to put new ones in still. clevites are cheap and much cheaper insurance. have you heard the engine run before? hone the cylinder walls too.

 

[HommerSimpson]

The cylinders still have the cross-hatch marks. and the bearings look excellent, this is why I'm thinking to just reuse these parts.

you have to atleast hone it and break the glaze.. even if you use the old rings... or it wil smoke like a train.. so if you going to do all that work.. its best to use new rings and bearings and know you have a motor that will have oil pressure and compression when done...

 

[funky_monkey58]

DaveH on supraforums did this with his old engine. Which held up to 900+rwhp. Then again it was a jz.

 

[kabanimk3supra]

you have to atleast hone it and break the glaze.. even if you use the old rings... or it wil smoke like a train.. so if you going to do all that work.. its best to use new rings and bearings and know you have a motor that will have oil pressure and compression when done...

smoke? why would it smoke? do you mean if the piston rings are in poor condition?

I understand what everyone is saying, I'm just trying to make an educated decision. It looks like I'll be doing a full rebuild by the time I'm finished.

The biggest issue I didn't want to deal with is break-in period, that's why I wanted to reuse the original parts.

 

[KicknAsphlt]

Why would you EVER want to re-use the same bearings? As prone as the 7M seems to be with bearings problems, its the last thing i would do. You are rebuilding the rest of your engine, absolutely no reason not to put another $100 or so for new bearings. I hope you are going to at least hone/re-ring as well.

I learned my lesson on that one -- if the pistons leave the block, then re-ringing and honing the cylinders is MANDATORY.....

 

[KicknAsphlt]

The cylinders still have the cross-hatch marks. and the bearings look excellent, this is why I'm thinking to just reuse these parts.

Don't kid yourself dude -- if you're decking the block, then the pistons are coming out. This GUARANTEES that you'll need to rehone the cylinders and put new rings on the pistons...trust me, I JUST went through this. It doesn't matter if there's cross-hatch still in the cylinders....the walls are shiny, so it needs rehoning. You'll also need to have the piston-to-wall clearances checked, cylinder bore roundness, and have your rods checked for roundness. I had the rods checked on my 70k block on a recommendation...I wasn't going to initially because I thought with that low of mileage, the rods would still be round....NOPE! Had to have those fixed as well.


Here's a list of things you'll need to do if you're stripping the block down:

Sonic clean the block
have cylinders, pistons, and rods checked for roundness and clearances
buy new rings
buy new bearings (might as well, they're $300 or less for mains AND rods)
have cylinders rehoned and rods brought back into round
have crank journals polished
have head checked for warpage, hardness, etc.
have block and head decked (make sure the head isn't too short already)


Anyone else (Jdub?) feel free to pitch in on anything I missed...this was just a quick run-down based on the shit I just went through with my motor.

 

[KicknAsphlt]

it is better practice and piece of mind to put new ones in still. clevites are cheap and much cheaper insurance. have you heard the engine run before? hone the cylinder walls too.

Clevites are extra machine work, it's a bit cheaper and easier to match the index numbers on the bearings and replace with factory ones.