SBC - main bearing clearance question

[panic]

An error @ .00075" causes the crank to appear in your mirror.

[Warp Speed]

Are you getting your clearances from measuring assembled or doing math for a theoretical?

[Belgian1979]

Measured. Mic on crank. Bore mic set to zero on the mic and measuring the clearance. When done and set I will check it a final time with plastigage to verify.

BTW: I was just informed that the Clevite HXX's are out of stock. Is this correct? Anyone have a set?

[Dan Timberlake]

"The original bearing set that came out, had marks on the number 3-2 and a little on the number 1 (marks in the location where the journal is the smallest)."

Hi Belgian1979,

Got pix of the bearings that came out?
Were the marks on the insert from the block side of the bearing, or the cap side?
How small was the journal where it was "smallest" ? That location would have largest oil clearance, I;m guessing.

[BCjohnny]

That said I had:

- std bearing on the rear: .00275", which seems ok.

hx on everything else, which gives:

- number 4: .00275, bit large but acceptable since the trust face needs extra oil.
- number 3: .00215, too tight
- number 2: .00215, too tight
- number 1: .00235, a bit tight

Those measurements just look weird ...... you're actually measuring to one hundred thousandth of an inch ? 1/100000 or 0.00001" ?

And they're all ending five one hundred thousandths ? 5/100000 or 0.00005" ? Not zero or something other like three one hundred thousandths ?

Anything less than a 'tenth' (one ten thousandth / 0.0001") gets rounded in most peoples' reality

[Belgian1979]

"The original bearing set that came out, had marks on the number 3-2 and a little on the number 1 (marks in the location where the journal is the smallest)."

Hi Belgian1979,

Got pix of the bearings that came out?
Were the marks on the insert from the block side of the bearing, or the cap side?
How small was the journal where it was "smallest" ? That location would have largest oil clearance, I;m guessing.

Lower (cap) half of the bearings. Sorry, was a wrong statement. Meant to say biggest as in the largest diameter. 62,19 to 62.205 mm
Will make a couple of pictures later, but the problem is showing them here since photobucket stopped doing it for free.

[Belgian1979]

That said I had:

- std bearing on the rear: .00275", which seems ok.

hx on everything else, which gives:

- number 4: .00275, bit large but acceptable since the trust face needs extra oil.
- number 3: .00215, too tight
- number 2: .00215, too tight
- number 1: .00235, a bit tight

Those measurements just look weird ...... you're actually measuring to one hundred thousandth of an inch ? 1/100000 or 0.00001" ?

And they're all ending five one hundred thousandths ? 5/100000 or 0.00005" ? Not zero or something other like three one hundred thousandths ?

Anything less than a 'tenth' (one ten thousandth / 0.0001") gets rounded in most peoples' reality

I have 2 mic clocks. One in .01 mm (0.0003937"), on in .001 mm (0.00003937"). With the .01mm you can more or less estimate when it is between 2 marks (.005mm). I converted it from mm to inches.

[Belgian1979]

An error @ .00075" causes the crank to appear in your mirror.

https://www.mahle-aftermarket.com/media ... -40-14.pdf

P.16

[rebelyell]

In addition to a mic clock in .001 mm, do you also have an array of certified Grade AA (or similarly appropriate) gage blocks?
Have you also performed Gage R&R studies to demonstrate & verify capabilities? I don't and have not, but have rather good MTI gaging.
With my capabilities, I don't consider anything less than half a tenth. And, due to significant figures, seldom quote/report out to greater accuracy than 0.001"

[rebelyell]

An error @ .00075" causes the crank to appear in your mirror.

https://www.mahle-aftermarket.com/media ... -40-14.pdf

P.16

^^^this^^^ reliable, credible tolerances on next to last page.

[steve cowan]

Hi,

Clutch car, 350 SBC, oil is 10W40. What kind of oil clearance would you recommend on the main rear bearing? Currently have .00275".

Have you checked rear main cap clearance with oil pump bolted up ?

[BCjohnny]

I have 2 mic clocks. One in .01 mm (0.0003937"), on in .001 mm (0.00003937"). With the .01mm you can more or less estimate when it is between 2 marks (.005mm). I converted it from mm to inches

Which IIRC is 1 micron !

Having the tools to measure to that metric, and being able to repeatably achieve the same measurement is something else ...... you're pretty much into a lab type environment to do that

There may be a place for doing so but IMO for what most people are doing here, anything less than a rounded 'tenth' is for the birds

[Belgian1979]

Hi,

Clutch car, 350 SBC, oil is 10W40. What kind of oil clearance would you recommend on the main rear bearing? Currently have .00275".

Have you checked rear main cap clearance with oil pump bolted up ?

No

[Belgian1979]

An error @ .00075" causes the crank to appear in your mirror.

https://www.mahle-aftermarket.com/media ... -40-14.pdf

P.16

^^^this^^^ reliable, credible tolerances on next to last page.

It says on that place to take machining tolerances into consideration and more or less conclude that .0026 is ok. .0031 is too much.

[Belgian1979]

I have 2 mic clocks. One in .01 mm (0.0003937"), on in .001 mm (0.00003937"). With the .01mm you can more or less estimate when it is between 2 marks (.005mm). I converted it from mm to inches

Which IIRC is 1 micron !

Having the tools to measure to that metric, and being able to repeatably achieve the same measurement is something else ...... you're pretty much into a lab type environment to do that

There may be a place for doing so but IMO for what most people are doing here, anything less than a rounded 'tenth' is for the birds

I almost never use the .001mm. Mostly the .01mm.
Again conversion from mm to inch gives a lot of decimals and I agree that there is no need to measure in microns.
Anyway, there is a difference between .0022, .0026 and .0031.
As Clevite states, .0031 is not what you want in something also used on the street.