kobayashi

I am in the process of rebuilding an engine. Just reached the rod bearings and was wondering about the amount of wear on the bearings. Is this a little or a lot of wear?


This is the #1 bearing. The #2 bearing had slightly more wear. The coating that is on the bearing is mainly intact.

beentherebaby

It's difficult to tell much from the photo quality other than a piece of debris passed thru and scratched the bearing. I can't detect any serious wear issues from the photo. You'd need to actual measure the crank/bearing wear to see what has occurred unless the bearing is trashed and it doesn't show well in the photo?

odurandina

my rod bearings will be done right after i refresh the suspension.


the implications of rod bearing failure are eerily similar to the following video clip - Mein Fuhrer.




http://www.youtube.com/watch?v=Soc7S...eature=related




the unseen, forces of darkness must be destroyed...

krystar

u can't visually tell...other than "holy **** i'm down to copper". u need to properly measure the clearance using plastigauge. go to Autozone/PepBoys/Oreilly and get a pack of plastigauge. you want the green kind.

turn crank so #2 is accessible
wipe clean the bearing and journal surface of all oil.
tear off a strip of plastigauge about 1" length. as wide as the bearing shell.
lay the plastigauge strip across the width of the bearing shell.
install the rod cap back onto the connecting rod with crank journal in middle
thread on your OLD rod nuts and torq to spec ( i think it was 43 ftlb?)
undo the rod nuts and take the cap off again.

the plastigauge strip will be squished wide. compare how wide with the scale from the plastigauge package. it should be no more than 0.07mm on the scale. the scale is in reverse so thinner the squish, the wider the clearance. wide clearance is bad.

if it is more than 0.07mm and less than 0.10mm, buy new bearings.
if the amount of squish is not even across the strip and it's wavey, but the skinniest portion of the squish is still within 0.10mm , you need to get your crank polished at machine shop. and you also need new bearing shells

odurandina

K, would you be interested in hearing my exhaust or taking her out for a go-round on Friday ?

gonna be passing through your town in the late afternoon, after i visit Carl Fausett's shop.


Allan.

kobayashi

Cool - I'll stop and get some plastigage. Just wondering what the wear is before I put in the new bearings (or if I even need new bearings). The engine is not being rebuilt for rod bearing failure, so they may still be pretty good.

Thanks!

kobayashi

Stopped by to pick up the Green Plastigage. It looks like the wear on the #1 cylinder is 0.038mm. Should the rod bearings be replaced at this clearance?

Jeremy Himsel

That's not your wear, that's your total clearance. The specs for a 944 rod (IIRC) is 0.034-0.092 mm's so they're in really good shape.

EDIT: Be sure to check them all and if you have new bearings it's not a bad idea to install them if you are this far into the project already.

krystar

by the amount of squish, your plastigage is showing actually a hair wider than 0.038mm scale. which means the clearance is <0.038mm . that's really good.

kobayashi

Yeah, they are all showing <0.038. It was consistently wider than the 0.038 mark on all the rods. I'm thinking about not changing these out because they could have been changed recently. Will that bite me in the a$$ later?

I have another engine that I am rebuilding and that one definitely needs rod bearings. Thinking about using the bearings on that engine.

krystar

i'd say these are just fine. since u have the engine part anyway. might wanna pop off the main caps and look at the main bearings too. those see alot less wear than the rod bearings so it should be perfect too.

M758

If you are rebuilding the engine use new main and rod bearings. Even if they look ok use new ones. It is not worth the risk of bearing damage by using old bearings. They new ones are easy to install at this point and the cost is minimal in the grand scheme of things.