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measuring bearing clearance

Engine Building Fundamentals

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Discussion and questions related to the course Engine Building Fundamentals

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Hi Andre,

Whats your opinion on Plastigage? It wouldn't leave scoring or marks of any kind on the bearing surfaces.

Nissan workshop manuals recommend plastigage to measure clearances.

Cheers!

-Shaun

I really don't have a problem with using plastigauge. It's heavily frowned upon by most professional engine builders and there's no doubt it isn't as accurate as a bore gauge and mic.

There's a complete module in the course that covers the correct way of using plastigauge to get the best results possible - https://www.hpacademy.com/dashboard/courses/engine-building-fundamentals/using-plastigauge/

Hello again I've just measured my bearings with the bore gauge and micrometer and as before it's left marks on the bearing faces enough for me to be able to feel them, I've used the back side of the emery cloth and this has made them better but the marks are still there although a lot better, the car is fairly high power being an F10 M5 and the labour if there is any problems is colossal, and on the flip side the bearings are equivalent to 500 dollars in the uk, what's your thoughts? Here's some pics

Attached Files

Hello again I've just measured my bearings with the bore gauge and micrometer and as before it's left marks on the bearing faces enough for me to be able to feel them, I've used the back side of the emery cloth and this has made them better but the marks are still there although a lot better, the car is fairly high power being an F10 M5 and the labour if there is any problems is colossal, and on the flip side the bearings are equivalent to 500 dollars in the uk, what's your thoughts? Here's some pics

Attached Files

You should be able to get the surface finish much better than that with the back side of emery paper and some lubricant. I'd guess that you may have been too gentle on the shells as I'd expect the QR code would probably be removed during this process. I've never had any trouble reusing bearing shells that I have measured clearances using a bore gauge with.

I worry the same about scratching the bearings during measurements. Another way is to measure the bore without the bearings installed. ACL and King Racing and think others specify the thikness of the bearings to very tight tolerances. With a bit of math it should get accurate measurements in theory. In the real world i found the results can differ a bit.

Does anybody else use to measure the bore instead of the bearing? Whats your experience?

I worry the same about scratching the bearings during measurements. Another way is to measure the bore without the bearings installed. ACL and King Racing and think others specify the thickness of the bearings to very tight tolerances. With a bit of math it should get accurate measurements in theory. In the real world i found the results can differ a bit.

Does anybody else use to measure the bore instead of the bearing? Whats your experience?

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