Oversize/Undersize bearings ????

[BlueRolex007]

Not sure if I am posting in the right place but here goes. Im rebuilding a 7mgte the rod bearings say .5 im assumming that i need bearings that are 5 thousanths over. When i go to parts store Autozone/Advanced/Pepboys, They all only have undersize bearings 25/50/75. Why would anyone need an undersized bearing? Did they get larger journals put on there crank?? Am I missing something? Someone please shed some light :runaway:

 

[hvyman]

The crank is under sized.

I would take the crank to a machine shop and have him look at it and see what size bearings you need. then plastigauge each one to make sure its the proper clearance.

 

[BlueRolex007]

I was kinda thinking that but um the crank is already in the block and all buttoned up. And the bearings say .5 so im pretty sure i need a .5 over bearing but the stores say under size so i dunno, are they refering to crank or bearings or i dunno :1zhelp:

 

[hvyman]

If the crank is under sized then you need a under sized bearing. The size of the bearing is related to the size of the crank.

Did you get rod knock or something and your just replacing the bearings?

What brand of bearing is it?

 

[BlueRolex007]

What happened was i bought the car from this dumb ass kid. the car wasnt running right, did a compression test no pressure in number 2. tore it down there was a hole in piston, im sure he detonated, took pistons out cleaned block internals throughly. the rod bearings that were in it were perfect, but of course im not gonna re-use em, the bearings say ACL im pretty sure thats the brand and next to that it says .5 ,I am doing a partial rebuild.

 

[airhead04]

Over size would mean that the crank is LARGER then when it came from factory. Soooooooo I really dont think you need over sized bearings. But I could be wrong. But most of the times when you need new bearings, youll need undersized bearings bc your crank wont magically be larger then it once was from factory. XD lol

 

[BlueRolex007]

Yea i know, lol but the oversize of the bearing would compensate for what was ground off the crank. But i dunno maybe you guys are right and i am just a dumbass.:kickinthenuts:

 

[CyFi6]

There's no such thing as an oversize bearing, people say it but it is the wrong terminology like these guys mentioned. Undersized bearings are used on a crank that has been machined. If it is stamped .5 that means the crank was cut .5mm or .020", which is a lot.

 

[BlueRolex007]

Ok cool thanks guys..

 

[Nick M]

Have you seen the markings on the block that say something like 0110210?

 

[BlueRolex007]

No i have not, but then again i wasnt really looking. why what do the numbers mean?

 

[hvyman]

What the original toyota select fit bearings were in there.

 

[te72]

I was kinda thinking that but um the crank is already in the block and all buttoned up. And the bearings say .5 so im pretty sure i need a .5 over bearing but the stores say under size so i dunno, are they refering to crank or bearings or i dunno :1zhelp:

"Pretty sure" and "knocking again" sound pretty similar don't they?

Not to be rude, but bearing sizes and things that need to be that precise are the territory of a machinist. You can do it once and do it right, or take your chances, that's up to you.