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View Full Version : Couple questions, oil pump shaft bearings, cylinder size

CyFi6
06-06-2009, 04:59 PM
Hello everyone i just have a few small questions. Basically i have a bare block that has already been hot tanked and i noticed it still had the original oil pump drive shaft bearings in place. I have read that they need to be replaced if they have been hot tanked. I installed my drive shaft and it rotates smoothly with no "play". I am wondering, if i measure the bearings inside diameter and the outside diameter of my shaft, if the clearance is in spec does the bearing still need to be replaced? If so i wont even bother measuring them. What exactly is removed from the bearing during hot tanking?

Another question i have is the block i am getting machined has a scratch in the number 1 cylinder. I can just catch my fingernail on it. My plan is to have them all bored out .020", my only concern is i dont know if that will be enough to remove the scratch. I need to buy the pistons before i get the machine work done, so how do i know which pistons to buy? I am using a machine shop that is about 5 hours away from here, so its not very possible to have him determine this and then have me buy the pistons and keep going back and forth. I have a picture of the scratch, maybe you could give me your opinions.
http://img.photobucket.com/albums/v313/cyfi/Car/Shortblock%20rebuild/IMG_1342.jpg

This was after a light honing with a ball hone. My bet is .020" over could get rid of that, but i don't want to take any risks. Also, does NPR make piston oversizes anything over .020"? I was hoping to use NPR pistons, but if .020" doesn't do it, what other piston options am i left with besides Toyota OEM (I want to stay with stock style pistons). THanks
IJ.
06-06-2009, 07:09 PM
If they're in spec and there is no surface degradation they're fine to use.

That needs boring due to the vertical scar.
KORYTOYORTA
06-06-2009, 09:32 PM
I just bought a set of npr pistons for my engine. the place i got the from sold them in std and .50 over(ebay- domestic gaskets) i would just get .50 and it would almost for sure remove the scratch. just my opinion i dont know that much about engine work though.

An hopefully someone else will fill us in on the oil pump bearings i have been wondering the samething.
CyFi6
06-07-2009, 03:16 AM
.50mm over is the same as .020" over. Thats all i am concerned with, if .020" over is enough to remove the scratch.
TooGoode
06-08-2009, 05:46 PM
well, we don't know how deep the scratch goes. you will have to take it to the machine shop and have them hone it .20 over. then check to see if the scratch is still there. go .30 over and so on. then, order your pistons.
CyFi6
06-08-2009, 11:43 PM
Everything i have read has told me i need to buy the pistons before the machine shop can properly size the bores. Not to mention i am using a machine shop 5 hours away, so back and fourth to the shop is not a possibility. I honed the bore out as much as i could with a ball hone and the scratch is now barely there. If i can get my hands on a dial bore gauge i can measure the cylinder and determine if .020" will be enough or not.
IJ.
06-09-2009, 01:59 AM
Have them bore that cylinder to +17 and see if it cleans out the gouge before buying pistons, if it does get the +20 slugs and have them bore to size and you're golden, if it doesn't buy either another block or +40's.
CyFi6
06-11-2009, 12:44 AM
Have them bore that cylinder to +17 and see if it cleans out the gouge before buying pistons, if it does get the +20 slugs and have them bore to size and you're golden, if it doesn't buy either another block or +40's.

Thats what i would like to do, the only problem is that they are located far from me, so i wouldn't be able to go back and give them the pistons. I could mail them, but that seems like a lot of hassle for the machine shop to deal with. Also, another thing i am concerned about is the price would go up because they would have to mount it more than once to bore it, because of the downtime waiting for pistons after i get the news.

I am thinking i will just buy .040" pistons and have them bore it to that. Are there any real downfalls of going .040" over besides the fact that the block wont really be able to be rebuilt/bored over at a later time? I don't plan to need to do that (street motor, wont see high hp), and these blocks are so easy to come by that it seems its not really a big concern. Only concern i would have would be taking away from the structural integrity of the block. It is an 89+ block by the way.
IJ.
06-11-2009, 01:01 AM
No real downside to +40 other than what you mentioned but I believe you can get +50's that would work in your thick block if needs be so it's not all bad.
gofastgeorge
06-12-2009, 11:15 AM
I have bored/honed a lot of cylinders,
and would be very suprised if that didn't clean up with sizing for .020" pistons.

But why waste time here ?
Take it to your favorite machine shop, and ask them.
They do it every day, and could inspect the scratch themselves,
instead of a bunch of people trying to do it over the internet.