Unsure what to do with 0.0020" Main Clearance

[gmrocket]

I have ran .0018"-.0020" on SBF circle track engines with 302 main size and over 800HP with zero issues.

I did some more measuring, so a little more data.

I have a Mitutoyo dial bore gauge, so I decided to do some more measurements, and see what I came up with. I measured the clearances three different ways. All mics are nice older Mitutoyo Vernier style.

1. Plasti-gage: 0.0020"

2. Comparator. Measured the crank with an outside mic, locked it in place, then zero'd the dial bore gauge with it. I then placed in in the torqued bearing and came up with +0.0025". I have avoided using the dial bore gauge on bearings before, as it scratches them. These are the MS-590 HX without the flash layer, so they seem a bit harder on the surface, and don't scratch as easily... and it seemed to work just fine. Happy, but decided to try something else to make sure...

3. Used the dial bore to find the main saddle, then subtracted.

Main Saddle: 2.4415"
Top Bearing Half: 0.0953"
Bottom Bearing Half: 0.0953 (have a rounded anvil Mitutoyo 0-1 mic)
Main journals come out between 2.2488 - 2.2490

Subtracting... 2.4415 - 0.0953 - 0.0953 - 2.2489 = 0.0020"

So, plasti-gage gives 0.0020"
Comparator gives 0.0025"
Subtracting shows 0.0020"

Go Figure... lol

I'm not a machinist by trade, but am practiced well enough with the mics to get consistent readings.
Thoughts and ideas?

Thanks!

Clevite specs says the shells are .0952”, not what your getting. I’ve found them to be right on when I’ve checked.

With their spec and your other measurements you should have .0022”

2.4415” - (.0952”+.0952”) .1904” = 2.2511”

2.2511” = 2.2489” = .0022”

If your main saddle was at the max spec 2.442” you would have .0027” with clevites .0052” spec

When I measure a shell for wall thickness, I put the shell on a machined surface, set my dial gauge stand up to read zero on the surface, then lift the gauge rod up, slide the shell under it. Clevites are right on spec

[zums]

I have ran .0018"-.0020" on SBF circle track engines with 302 main size and over 800HP with zero issues.

I did some more measuring, so a little more data.

I have a Mitutoyo dial bore gauge, so I decided to do some more measurements, and see what I came up with. I measured the clearances three different ways. All mics are nice older Mitutoyo Vernier style.

1. Plasti-gage: 0.0020"

2. Comparator. Measured the crank with an outside mic, locked it in place, then zero'd the dial bore gauge with it. I then placed in in the torqued bearing and came up with +0.0025". I have avoided using the dial bore gauge on bearings before, as it scratches them. These are the MS-590 HX without the flash layer, so they seem a bit harder on the surface, and don't scratch as easily... and it seemed to work just fine. Happy, but decided to try something else to make sure...

3. Used the dial bore to find the main saddle, then subtracted.

Main Saddle: 2.4415"
Top Bearing Half: 0.0953"
Bottom Bearing Half: 0.0953 (have a rounded anvil Mitutoyo 0-1 mic)
Main journals come out between 2.2488 - 2.2490

Subtracting... 2.4415 - 0.0953 - 0.0953 - 2.2489 = 0.0020"

So, plasti-gage gives 0.0020"
Comparator gives 0.0025"
Subtracting shows 0.0020"

Go Figure... lol

I'm not a machinist by trade, but am practiced well enough with the mics to get consistent readings.
Thoughts and ideas?

Thanks!

Your not ever going to get accurate numbers by subtracting the shell thickness from the bore, put a light preload on your boregage and stick with that measurement method
Tom

[vortecpro]

I have ran .0018"-.0020" on SBF circle track engines with 302 main size and over 800HP with zero issues.

I did some more measuring, so a little more data.

I have a Mitutoyo dial bore gauge, so I decided to do some more measurements, and see what I came up with. I measured the clearances three different ways. All mics are nice older Mitutoyo Vernier style.

1. Plasti-gage: 0.0020"

2. Comparator. Measured the crank with an outside mic, locked it in place, then zero'd the dial bore gauge with it. I then placed in in the torqued bearing and came up with +0.0025". I have avoided using the dial bore gauge on bearings before, as it scratches them. These are the MS-590 HX without the flash layer, so they seem a bit harder on the surface, and don't scratch as easily... and it seemed to work just fine. Happy, but decided to try something else to make sure...

3. Used the dial bore to find the main saddle, then subtracted.

Main Saddle: 2.4415"
Top Bearing Half: 0.0953"
Bottom Bearing Half: 0.0953 (have a rounded anvil Mitutoyo 0-1 mic)
Main journals come out between 2.2488 - 2.2490

Subtracting... 2.4415 - 0.0953 - 0.0953 - 2.2489 = 0.0020"

So, plasti-gage gives 0.0020"
Comparator gives 0.0025"
Subtracting shows 0.0020"

Go Figure... lol

I'm not a machinist by trade, but am practiced well enough with the mics to get consistent readings.
Thoughts and ideas?

Thanks!

Your not ever going to get accurate numbers by subtracting the shell thickness from the bore, put a light preload on your boregage and stick with that measurement method
Tom

Yes......but if the OP is locking the mic after reading the journal he is skewing the number, do not lock the mic! Another thing: Make dam sure that crank is strait before any checking is done, because it probably ain't strait.

[gmrocket]

I have ran .0018"-.0020" on SBF circle track engines with 302 main size and over 800HP with zero issues.

I did some more measuring, so a little more data.

I have a Mitutoyo dial bore gauge, so I decided to do some more measurements, and see what I came up with. I measured the clearances three different ways. All mics are nice older Mitutoyo Vernier style.

1. Plasti-gage: 0.0020"

2. Comparator. Measured the crank with an outside mic, locked it in place, then zero'd the dial bore gauge with it. I then placed in in the torqued bearing and came up with +0.0025". I have avoided using the dial bore gauge on bearings before, as it scratches them. These are the MS-590 HX without the flash layer, so they seem a bit harder on the surface, and don't scratch as easily... and it seemed to work just fine. Happy, but decided to try something else to make sure...

3. Used the dial bore to find the main saddle, then subtracted.

Main Saddle: 2.4415"
Top Bearing Half: 0.0953"
Bottom Bearing Half: 0.0953 (have a rounded anvil Mitutoyo 0-1 mic)
Main journals come out between 2.2488 - 2.2490

Subtracting... 2.4415 - 0.0953 - 0.0953 - 2.2489 = 0.0020"

So, plasti-gage gives 0.0020"
Comparator gives 0.0025"
Subtracting shows 0.0020"

Go Figure... lol

I'm not a machinist by trade, but am practiced well enough with the mics to get consistent readings.
Thoughts and ideas?

Thanks!

Your not ever going to get accurate numbers by subtracting the shell thickness from the bore, put a light preload on your boregage and stick with that measurement method
Tom

What happens when you do the math so that you never get accurate measurements?

Clevite gives you a housing bore diameter, a shell thickness, and a crank diameter... then they give you a running clearance

It all adds up to the running clearance they spec.

Exactly like I showed in my last post.. it’s their numbers. The bearing crush when installed and torqued does not change those numbers... that I’ve ever found

I got tired of checking everything individually and then installed and torqued to always get the same numbers.

[Bob Hollinshead]

This easily fixed.........you sand the back of the bearing counting sand strokes. You want to sand the bottom 1/3 of the radius, so as too increase the vertical clearance. This is done all the time. Of course you want to CK clearance with a Sunnen bore gauge. You can easily get 4 tenths......easy.

A friend assembled pro-stock engines for Jason Line and they did that all the time.

[gmrocket]

This easily fixed.........you sand the back of the bearing counting sand strokes. You want to sand the bottom 1/3 of the radius, so as too increase the vertical clearance. This is done all the time. Of course you want to CK clearance with a Sunnen bore gauge. You can easily get 4 tenths......easy.

A friend assembled pro-stock engines for Jason Line and they did that all the time.

All the time? I can understand if your in a points race and need the engine together ASAP and no other parts available...

But why have a crank that’s the wrong size “all the time” ?

That would happen once with me...or I would find a new crank grinder who gives me the specs I want

[Bob Hollinshead]

He said it was common for them to fine tune the bearing clearance by sanding the bearing backside-never any problems.

[zums]

I did some more measuring, so a little more data.

I have a Mitutoyo dial bore gauge, so I decided to do some more measurements, and see what I came up with. I measured the clearances three different ways. All mics are nice older Mitutoyo Vernier style.

1. Plasti-gage: 0.0020"

2. Comparator. Measured the crank with an outside mic, locked it in place, then zero'd the dial bore gauge with it. I then placed in in the torqued bearing and came up with +0.0025". I have avoided using the dial bore gauge on bearings before, as it scratches them. These are the MS-590 HX without the flash layer, so they seem a bit harder on the surface, and don't scratch as easily... and it seemed to work just fine. Happy, but decided to try something else to make sure...

3. Used the dial bore to find the main saddle, then subtracted.

Main Saddle: 2.4415"
Top Bearing Half: 0.0953"
Bottom Bearing Half: 0.0953 (have a rounded anvil Mitutoyo 0-1 mic)
Main journals come out between 2.2488 - 2.2490

Subtracting... 2.4415 - 0.0953 - 0.0953 - 2.2489 = 0.0020"

So, plasti-gage gives 0.0020"
Comparator gives 0.0025"
Subtracting shows 0.0020"

Go Figure... lol

I'm not a machinist by trade, but am practiced well enough with the mics to get consistent readings.
Thoughts and ideas?

Thanks!

Your not ever going to get accurate numbers by subtracting the shell thickness from the bore, put a light preload on your boregage and stick with that measurement method
Tom

What happens when you do the math so that you never get accurate measurements?

Clevite gives you a housing bore diameter, a shell thickness, and a crank diameter... then they give you a running clearance

It all adds up to the running clearance they spec.

Exactly like I showed in my last post.. it’s their numbers. The bearing crush when installed and torqued does not change those numbers... that I’ve ever found

I got tired of checking everything individually and then installed and torqued to always get the same numbers.

You can alter the clearance with clamp load regardless of the math
Tom

[vortecpro]

This easily fixed.........you sand the back of the bearing counting sand strokes. You want to sand the bottom 1/3 of the radius, so as too increase the vertical clearance. This is done all the time. Of course you want to CK clearance with a Sunnen bore gauge. You can easily get 4 tenths......easy.

A friend assembled pro-stock engines for Jason Line and they did that all the time.

All the time? I can understand if your in a points race and need the engine together ASAP and no other parts available...

But why have a crank that’s the wrong size “all the time” ?

That would happen once with me...or I would find a new crank grinder who gives me the specs I want

Typically I find myself in the bearing sanding mode when I get a crank from lets say Scat and its big and I don't want to grind the crank or open up the housing bore outside of spec, and I need a few tenths extra clearance to sleep good. I have a friend that machines and builds engines and there no end of the -hit I get from him over sanding bearings in rare instances, but again he really knows very little of anything............

[vortecpro]

Mike, just my opinion

1 - Plastigauge...like a moped, fun to ride, but that's about it, heck it's not even as good as a moped LOL. I don't even buy the crap anymore, and I used to use it all the time in the 80s and 90s. Here's a punch line, the least accurate it ever was, was on small block Fords too, no idea why

2 - Using the dial bore gauge against the mic..that's how I do all, and I trust it. However, you can tweak those numbers if you wrench on the mic, if it's a good mic, checks to the standards and you can repeat your numbers, I can that the best way. I will say though, each brand is different, FM seems to be the loosest, Clevite the tightest, but literally splitting hairs

3 - Fun with math...I also like it, but bearings aren't a constant shape, I much prefer using method #2 to also look for taper.

If you are worried about less than .001 per inch, can't you just hit it with a polish? or is that crank something that cannot be polished? You can't reshape it, but you can take a little edge off

Which is why I refuse to sand them.

You probably wouldn't like it when I oval hone rods either............LOL

[gmrocket]

A friend assembled pro-stock engines for Jason Line and they did that all the time.

All the time? I can understand if your in a points race and need the engine together ASAP and no other parts available...

But why have a crank that’s the wrong size “all the time” ?

That would happen once with me...or I would find a new crank grinder who gives me the specs I want

Typically I find myself in the bearing sanding mode when I get a crank from lets say Scat and its big and I don't want to grind the crank or open up the housing bore outside of spec, and I need a few tenths extra clearance to sleep good. I have a friend that machines and builds engines and there no end of the -hit I get from him over sanding bearings in rare instances, but again he really knows very little of anything............

I send it out for a .010” correct grind $150

How long does it take you to a complete set ?

[gmrocket]

Your not ever going to get accurate numbers by subtracting the shell thickness from the bore, put a light preload on your boregage and stick with that measurement method
Tom

What happens when you do the math so that you never get accurate measurements?

Clevite gives you a housing bore diameter, a shell thickness, and a crank diameter... then they give you a running clearance

It all adds up to the running clearance they spec.

Exactly like I showed in my last post.. it’s their numbers. The bearing crush when installed and torqued does not change those numbers... that I’ve ever found

I got tired of checking everything individually and then installed and torqued to always get the same numbers.

You can alter the clearance with clamp load regardless of the math
Tom

That’s designed into the bearings by the manufacturer.

I dont see any different when I physically measure or math out the clearance. Maybe with a laser mic there would be something in the .0000x range

What kind of difference have you seen?

[vortecpro]

All the time? I can understand if your in a points race and need the engine together ASAP and no other parts available...

But why have a crank that’s the wrong size “all the time” ?

That would happen once with me...or I would find a new crank grinder who gives me the specs I want

Typically I find myself in the bearing sanding mode when I get a crank from lets say Scat and its big and I don't want to grind the crank or open up the housing bore outside of spec, and I need a few tenths extra clearance to sleep good. I have a friend that machines and builds engines and there no end of the -hit I get from him over sanding bearings in rare instances, but again he really knows very little of anything............

I send it out for a .010” correct grind $150

How long does it take you to a complete set ?

We grind cranks in my shop so thats not a issue, and we can grind .0005 off our grinds no problem, but sometimes you don't want to change the surface of a aftermarket crank for one reason or another, so in that case I pull out a bearing holder fixture I made and sand away, I measure with a ball mic and count sanding strokes, of course you don't sand the whole radius. To answer your question: the last set of mains I had to do maybe took 20 minutes, I've never had to do the rods, and really I hate doing this, but its a means to an end.

[zums]

What happens when you do the math so that you never get accurate measurements?

Clevite gives you a housing bore diameter, a shell thickness, and a crank diameter... then they give you a running clearance

It all adds up to the running clearance they spec.

Exactly like I showed in my last post.. it’s their numbers. The bearing crush when installed and torqued does not change those numbers... that I’ve ever found

I got tired of checking everything individually and then installed and torqued to always get the same numbers.

You can alter the clearance with clamp load regardless of the math
Tom

That’s designed into the bearings by the manufacturer.

I dont see any different when I physically measure or math out the clearance. Maybe with a laser mic there would be something in the .0000x range

What kind of difference have you seen?

Ive seen .0002-.0003 with a 5-8 lb tq difference, quickest way to prove it to yourself would be to torque a rod up in a vise, measure the bearing clearance, check the stretch, which never seems to pull up on the first tq, then pull it to stretch at whatever tq it may take and check again. You can see main bore dimensions change going from stock bolts to aftermarket bolts/studs, all you changed was the clamp load, knowing the bearing thickness is good for altering the clearance up or down{once you have a known data point} but not for assuming clearances, but if it works for you thats all that counts.
Tom

[BigBlocksOnTop2]

Are you setting the dial bore gauge to zero on the journal (using a mic) and then measuring the corresponding bearing? May make you feel a little better....