Custom sized rod bearings? Help
- Thread starter mk1spyder
- Start date
- Status
basically I bought a new crank from toyota and I got it all in and realized the #6 rod journal is smaller than the rest. I would just use a #5 bearing which is the biggest stock size variance bearing you can get from toyota but its not enough to make the proper clearance. I need to get in contact with a company that can make me a 7M rod bearing in a custom thickness, itll need to be fairly precise metric as well, none of that .010" standard bullshit.
Couldn't you also just have the rod resized to allow the correct clearance with a 'standard' thickness bearing?
I don't even trust the crank work Toyota did. LOL .010" standard is not bullshit btw.
I would have it ground .010" under, shot peened, tear drop the oil holes, re-balanced, micropolished, and put a set of Clevite bearings in it. The whole multiple bearing sizing thing always seemed like a joke to me. It's just a way to make up for poor manufacturing processes on the crank and/or block if you ask me. If the crank was done right, and the mains all were standard, and the rods were all sized standard, you would not have any clearance issues.
I would have it ground .010" under, shot peened, tear drop the oil holes, re-balanced, micropolished, and put a set of Clevite bearings in it. The whole multiple bearing sizing thing always seemed like a joke to me. It's just a way to make up for poor manufacturing processes on the crank and/or block if you ask me. If the crank was done right, and the mains all were standard, and the rods were all sized standard, you would not have any clearance issues.
bigaaron said:
I don't know for sure what the method to the Toyota bearing madness is but my 7M crank pins measured EXACTLY (like right in the middle of the tolerance range of a few ten-thou) as it was blueprinted. To me that's pretty damn good work. Even though their blueprint sytem can be a little convoluted, it works (but only with 'genuine toyota parts'
).
Boostedstr8six said:I don't know for sure what the method to the Toyota bearing madness is, I would guess to save time/cost during (re)assembly, but my 7M crank pins measured EXACTLY (like right in the middle of the tolerance range of a few ten-thou) as it was blueprinted. To me that's pretty damn good work. Even though their blueprint sytem can be a little convoluted, it works (but only with 'genuine toyota parts'
Repeatability is key. If they all were like yours then they wouldn't have different sized bearings.
You're talking about resolution of a single ten thousandth. Toyota has a range of 2.0472 - 2.0463 on the rod jouranls. That's a span of .0009. Less than a thou. It's even less for the mains. I'd say a tolerance of less than a thousandth is pretty good for a production line.
People are spinning bearings in brand new shortblocks these days, so I'm not so sure all the cranks are falling in between those tight bearing specs.
My best guess is that the cranks/blocks that were used in production cars are probably the best quality wise. My block was a pre MK3 engine, the production number on the side of the block is like 00001014, it was supposed to be used for training purposes (hence the messed up journal spec). Makes me wonder what else might be wrong, the head casting number is 2. All the other journals came in real close to 2.048 give or take .002, the #6 journal came out at 2.036 which in the TSRM is called a U/S .25. Toyota has special bearings specifically for that size, I thought for sure I was gonna need a custom bearing cause with the old regular bearing on you could actually move the rod enough to get a click against the crank. It woulda made some hellish rod knock from the very beginning, what amazes me is that I missed it. I swear I plastigaged every damn one, musta just had too many beers. I would have just gotten a U/S .25 from toyota but you can only buy a whole set and even with my employee discount it was still $70. So I ordered a .010" from clevite for $5 lol. Hey if it puts the clearance in the perfect range like the rest I have no problem running it. In my experiences a bearing is a bearing, as long as its accurate and somewhat quality you should be fine. Nothing is supposed to touch the bearing anyways.
- Status