Crankshaft end play question

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Crankshaft end play question

Postby livetoride60 » Wed Jan 11, 2017 3:58 pm

Got my crank in and end play came out at 0.010. The book says 0.004 to 0.008 are spec, with wear limit at 0.012.

Wanted to see what you all thought about leaving it at 0.010 vs shifting the #3 cap to take up some slack. My machinist said he'd shift it and take up some, but I know that puts the load only on one half. His response to that was Chevy's only use a half thrust bearing. Also know it's pretty commonly done.

Also know lots of places say not to do it, and that's why you seat the thrust bearings when installing the crank, so both halves are taking the load.

My guess is at 0.010 it won't make a big difference either way, especially since I'm not racing and the car will have limited use.

Thoughts?

Thanks,
Rich
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Re: Crankshaft end play question

Postby C6ZZKGT » Wed Jan 11, 2017 6:08 pm

livetoride60 wrote:Got my crank in and end play came out at 0.010. The book says 0.004 to 0.008 are spec, with wear limit at 0.012.

Wanted to see what you all thought about leaving it at 0.010 vs shifting the #3 cap to take up some slack. My machinist said he'd shift it and take up some, but I know that puts the load only on one half. His response to that was Chevy's only use a half thrust bearing. Also know it's pretty commonly done.

Also know lots of places say not to do it, and that's why you seat the thrust bearings when installing the crank, so both halves are taking the load.

My guess is at 0.010 it won't make a big difference either way, especially since I'm not racing and the car will have limited use.

Thoughts?

Thanks,
Rich


I would not have that much concern with the .010 end play in your situation. Also Chevy engines do have full thrust bearings. Their bearings are just wider and their thrust is on the rear main.

-Fred-
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Re: Crankshaft end play question

Postby zray » Wed Jan 11, 2017 10:04 pm

Leave it alone.

But I would want to know why it's on the high end starting out . That doesn't leave you with much room for wear.

Z
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Re: Crankshaft end play question

Postby livetoride60 » Wed Jan 11, 2017 10:26 pm

Yeah, both Z and Fred that's what I'm thinking. (Leave it alone). Thanks for input.
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Re: Crankshaft end play question

Postby livetoride60 » Thu Jan 12, 2017 8:22 am

....and Z, I'm not exactly sure why it has so much play. Well, I'll say this...I haven't "verified" why. I'd have to take it apart and re-measure everything. It is an original crank with 90K on it, so one would expect it to be worn. The distance between thrust faces was good....spec is 1.137 - 1.139, and I measured multiple times getting from 1.1370 to 1.1381. So only possibilities are:

1) My measurement technique needs improvement, which is entirely possible. I took these when I was first starting. Getting much more consistent measurements now. Using a cheap telescoping gauge with a good Mitutoyo micrometer.
2) Thrust bearing sides are too narrow. Didn't measure these, just measured end play with feeler gauges and dial indicator. Both came out to 0.010. They are new STD bearings from King.
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Re: Crankshaft end play question

Postby zray » Thu Jan 12, 2017 9:57 am

Can you feel the crank move forward and backward when you grab he balancer and push it in and out ? If the play feels imperceptible, then the snap gauge measuring technique might be the culprit, more so than anything else I see you are doing.

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Re: Crankshaft end play question

Postby livetoride60 » Thu Jan 12, 2017 10:25 pm

zray wrote:Can you feel the crank move forward and backward when you grab he balancer and push it in and out ? If the play feels imperceptible, then the snap gauge measuring technique might be the culprit, more so than anything else I see you are doing.

Z


Grabbed the snout and can just barely feel it popping back and forth, almost imperceptible, but we're only talking 0.010. I'm pretty confident in the end play measurements. It's harder to mess up a dial indicator, and got the same 0.010 with feeler gauges.
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Re: Crankshaft end play question

Postby livetoride60 » Sat Jan 14, 2017 4:07 pm

C6ZZKGT wrote:Also Chevy engines do have full thrust bearings. Their bearings are just wider and their thrust is on the rear main.

-Fred-


Hi Fred - I got clarification on this from my machinist. He meant modern engines, specifically said many modern engines have only a 180 degree (half moon) thrust bearing now days. That was his point on adjusting the #3 main cap slightly to take up the slack. Not sure I know all the ins and outs of that, like are there any differences in materials, design, etc. between then and now that might make it more reliable now, but apparently manufacturers are doing it regularly. Anyway, an interesting thought.

Apparently even the Corvette motor has a half thrust bearing now...and the modular motors in the new Mustangs....

Per GM mechanic in 1st thread below "This is actually nothing new and has been proven reliable for many years."

http://www.thecorvettemechanic.com/forum/showthread.php?4185-Crankshaft-thrust-bearing

Modular motor discussion on half moon thrust bearing....

http://www.modularrevolution.com/forums/showthread.php?p=43755
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Re: Crankshaft end play question

Postby C6ZZKGT » Sun Jan 15, 2017 8:46 am

livetoride60 wrote:
C6ZZKGT wrote:Also Chevy engines do have full thrust bearings. Their bearings are just wider and their thrust is on the rear main.

-Fred-


Hi Fred - I got clarification on this from my machinist. He meant modern engines, specifically said many modern engines have only a 180 degree (half moon) thrust bearing now days. That was his point on adjusting the #3 main cap slightly to take up the slack. Not sure I know all the ins and outs of that, like are there any differences in materials, design, etc. between then and now that might make it more reliable now, but apparently manufacturers are doing it regularly. Anyway, an interesting thought.

Apparently even the Corvette motor has a half thrust bearing now...and the modular motors in the new Mustangs....

Per GM mechanic in 1st thread below "This is actually nothing new and has been proven reliable for many years."

http://www.thecorvettemechanic.com/forum/showthread.php?4185-Crankshaft-thrust-bearing

Modular motor discussion on half moon thrust bearing....

http://www.modularrevolution.com/forums/showthread.php?p=43755


I guess that if it is good enough for the major manufacturers to change to the half thrust bearing it must be OK. They have to stand behind a warranty on their engines and they would not make a change like this if they felt that it was edgy and now proven OK. I would think it has to do with cutting down on frictional losses for horsepower and mileage. I am just too old school to change.

-Fred-
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Re: Crankshaft end play question

Postby livetoride60 » Sun Jan 15, 2017 11:07 am

C6ZZKGT wrote:I guess that if it is good enough for the major manufacturers to change to the half thrust bearing it must be OK. They have to stand behind a warranty on their engines and they would not make a change like this if they felt that it was edgy and now proven OK. I would think it has to do with cutting down on frictional losses for horsepower and mileage. I am just too old school to change.

-Fred-


Have to agree. They know what they're doing. Like you though, I'm a little leery of less surface area in my hipo's case. I just don't have enough experience to know which is better (or worse)....0.010 of endplay or thrust load on half the thrust bearing. Does the oil leak out too easy? I'm reading those thrust faces don't hold the oil wedge like the bearing itself to begin with. Also reading one of the main cause of bearing failures is misalignment. But he does have about 30 years of experience building and racing all sorts of engines around the region. All the mechanics say he's probably the best around. I think his point is, with my limited driving and planned use, I'll be fine either way.
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