Thread: bearing clearance

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What is the most accurate way to check bearing clearance?

Pat would know best, but I believe its measuring the crank journals with a mic. in about four places. Then you need to set the dial bore gauge to this measurement. Install your main bearings and torque the main caps down. Then whatever the difference between the two measurements is the actual clearance. What I don't know is exactly what clearances you want, I'm thinking between .0020 and .0030. Pat builds em' for a living so hopefully he will chime in on this one, i could be forgetting something.

OK, you asked "most accurate".
That would be with an experienced machinist, using his own tools, the proper tools for the job, that he is used to using and has used day in and day out for years in a controlled environment with the same temperature and humidity conditions day in and day out.

If you are talking about a person who builds one motor a year in his garage, then plastigage works pretty well. I'll put it as simply as I can, this stuff ain't rocket surgery.

the best way is the way i do it. i will tell you. i size the clearance for the job at hand NOs drag .street street /strip . hi RPMs big engine and other things come in to play . i mic the crank put the number down on paper . i set my mic and then set my dial bore gauge to read bearing when its in the housing bore . some play this off say any thing will work on rods you have 0001.5 to 0003. about the same on mains by the book. i hold every thing no more then 0002 and that is from were i want it .not were it come s out so to build them at the leve were i hand fit bearings were i want to see them. your not going to get there with plastigage. but at the end of the day i like to think i build engines like rockets so i may not be the guy to ask i spend alot of time here more time then most and housing bore size,s . i think at pays off.. my stuff works

Pat, you are the experienced machinist that I outlined in the first part of my reply. Not everyone has the experience or the tools or the controlled environment like you have to work in. Some of us have to work on dirt floor garages in the cold, where, even if the mic was just zeroed, it ain't gonna be accurate for very long, not to within 2 tenths anyway, even if the average guy knew how to measure and read 2 tenths. He'll be lucky if he's within 6 or 8 tenths and in the end, it won't matter anyway because he's probably not trying to build a precision motor like you would build one and I hope he has the common sense to realize that.

Just trying to be real here. You can put a motor together using plastigage and it will pull your beater down the road and hold oil pressure if you used the plastigage correctly. If you want or need a precision motor to compete in some venue of racing or if you simply have the money to buy the best motor you can, then contact Pat and let him build it. End of story.

well ok i spend way to much time on bearings have a cabnet at the shops with $100s of bearings i just did not like or split to get size i wanted . even on the stock stuff its a big deal with me so i do not get a call thats .she runs fine but its low on oil psi for stock engine with a stock pump . if the rods come out on the big end your going to get that .i first check the housing bores so there were i want them on rod bores and mains .guys like me may check your size for nothing or abit of money if they did all the machine work .that why you never want to piss off the guy that machines your stuff if your not paying him to short block or long block your engine

The reason i bring this question up is i have been thinking about crank journals being out of round. I think it is possible to mic a journal and miss that it is'nt round. If a journal is out of round but not symetrically out of round i think the mic could still read good. I am wondering if i should have my new crank checked and a dial indicator put on it to check all the journals for round? On a different note, Why do guys take offense to others building there own stuff? If you have to ask questions i think more of that persons intelligence than the guy who thinks he knows it all.

Originally Posted by dmarrs

The reason i bring this question up is i have been thinking about crank journals being out of round. I think it is possible to mic a journal and miss that it is'nt round. If a journal is out of round but not symetrically out of round i think the mic could still read good. I am wondering if i should have my new crank checked and a dial indicator put on it to check all the journals for round? On a different note, Why do guys take offense to others building there own stuff? If you have to ask questions i think more of that persons intelligence than the guy who thinks he knows it all.

offenes ? i did tell you how to do it ? or not i never said you could not do it hell i do not know what you can do .a mic will check for out of round but most cranks are round . mains can not be on center line and have a whip to them as well as the rods can be off as well on stroke and then tapper on the rods . then there size on rods /mains down the line for size .then crank finsh .i check most of this stuff but not really in this order finsh is first . i buy cranks i used in the past that i had good luck on for over all size and finsh .there has been some in the past that were poor and needed to be ground to start with a true crank

I know you did'nt say i could'nt, thanks for the info.

Another option is to drive north about 425 miles and pay Pat to do your crank

My heads were done in mi, i don't know if i have enough money to get more mi hp