Struggling to understand bearing selection
06-26-2017, 11:10 AM
#26
Re: Struggling to understand bearing selection
Engine rebuilding is a dying art in the repair bays now. It simply isnt cost effective in the shop anymore.
However it was done for years and years in the bay. and almost ever manufacturer indicated that plastigauge was precise enough for measurements and that was how it was done. Millions of engines have been rebuilt using plastigauge, with out any issues. There is a tolerance allowed.
For what its worth, I know quite a few engineers, master technicians and transmission rebuilders that Ive met over the past 20 years.
Ironically I dont know 1 professional engine rebuilder., I mention that because you indicate that youve spoken to more than one and Ive got to wonder what type of engines they are building that plastigauge isnt good enough......
However it was done for years and years in the bay. and almost ever manufacturer indicated that plastigauge was precise enough for measurements and that was how it was done. Millions of engines have been rebuilt using plastigauge, with out any issues. There is a tolerance allowed.
For what its worth, I know quite a few engineers, master technicians and transmission rebuilders that Ive met over the past 20 years.
Ironically I dont know 1 professional engine rebuilder., I mention that because you indicate that youve spoken to more than one and Ive got to wonder what type of engines they are building that plastigauge isnt good enough......
06-27-2017, 06:07 AM
#27
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Re: Struggling to understand bearing selection
However it was done for years and years in the bay. and almost ever manufacturer indicated that plastigauge was precise enough for measurements and that was how it was done. Millions of engines have been rebuilt using plastigauge, with out any issues. There is a tolerance allowed.
For what its worth, I know quite a few engineers, master technicians and transmission rebuilders that Ive met over the past 20 years.
Ironically I dont know 1 professional engine rebuilder., I mention that because you indicate that youve spoken to more than one and Ive got to wonder what type of engines they are building that plastigauge isnt good enough......
For what its worth, I know quite a few engineers, master technicians and transmission rebuilders that Ive met over the past 20 years.
Ironically I dont know 1 professional engine rebuilder., I mention that because you indicate that youve spoken to more than one and Ive got to wonder what type of engines they are building that plastigauge isnt good enough......
In that world, plastigage is "fine enough". It meets the bare minimum requirement which is that you have .0008" per 1" of bore size or whatever that particular manufacturer desires.
In the world of race engines and machining, plastigage is like using a tape measure to check what's coming off the surface grinder . . . it's in no way accurate enough AND even worse off, it introduces a subjective error since it relies on the user to match the width to a scrap sheet of paper.
You made mention that you don't know 1 professional engine builder . . . if you did, I doubt you would be able to find plastigage in their engine shop. The only place I've seen it used is for setting up backlash on the ring and pinion.
I've worked for Warren Johnson (NHRA pro stock), Jon Kaase (IHRA pro stock), and Roger Burgess/R2B2 (NHRA pro mod). I "volunteered" my time for Andy Kelley and Jeff Diehl (NHRA nitro funny car). I also currently machine parts for JRD Rallysport (RallyAmerica) and Panoz and having been in several race shops (Hendrick, Fulton, ProLine) I have never ever seen plastigage being used on any engine part.
In most cases, setting up tight clearance does a number of things not to mention the strain 15+" of vacuum put on the oil. In that world you absolutely need to know clearances down to the .0001 place.
So yes, maybe most guys on this site don't need to know . . . maybe +/-.0005" is "good enough" for you or someone else's build for a daily driver stock motor. The point is the measuring devices are relatively inexpensive for the potential disaster averted when the motor is put together and you are racing on it every other weekend.
06-27-2017, 10:23 AM
#28
Honda-Tech Member
Re: Struggling to understand bearing selection
From an OEM/street car standpoint, give the tolerance a -.0000/+.0005" window and no one will ever notice. You can run bearing clearances +.001" or more and never notice it outside of a dyno or race application.
In that world, plastigage is "fine enough". It meets the bare minimum requirement which is that you have .0008" per 1" of bore size or whatever that particular manufacturer desires.
In the world of race engines and machining, plastigage is like using a tape measure to check what's coming off the surface grinder . . . it's in no way accurate enough AND even worse off, it introduces a subjective error since it relies on the user to match the width to a scrap sheet of paper.
You made mention that you don't know 1 professional engine builder . . . if you did, I doubt you would be able to find plastigage in their engine shop. The only place I've seen it used is for setting up backlash on the ring and pinion.
I've worked for Warren Johnson (NHRA pro stock), Jon Kaase (IHRA pro stock), and Roger Burgess/R2B2 (NHRA pro mod). I "volunteered" my time for Andy Kelley and Jeff Diehl (NHRA nitro funny car). I also currently machine parts for JRD Rallysport (RallyAmerica) and Panoz and having been in several race shops (Hendrick, Fulton, ProLine) I have never ever seen plastigage being used on any engine part.
In most cases, setting up tight clearance does a number of things not to mention the strain 15+" of vacuum put on the oil. In that world you absolutely need to know clearances down to the .0001 place.
So yes, maybe most guys on this site don't need to know . . . maybe +/-.0005" is "good enough" for you or someone else's build for a daily driver stock motor. The point is the measuring devices are relatively inexpensive for the potential disaster averted when the motor is put together and you are racing on it every other weekend.
In that world, plastigage is "fine enough". It meets the bare minimum requirement which is that you have .0008" per 1" of bore size or whatever that particular manufacturer desires.
In the world of race engines and machining, plastigage is like using a tape measure to check what's coming off the surface grinder . . . it's in no way accurate enough AND even worse off, it introduces a subjective error since it relies on the user to match the width to a scrap sheet of paper.
You made mention that you don't know 1 professional engine builder . . . if you did, I doubt you would be able to find plastigage in their engine shop. The only place I've seen it used is for setting up backlash on the ring and pinion.
I've worked for Warren Johnson (NHRA pro stock), Jon Kaase (IHRA pro stock), and Roger Burgess/R2B2 (NHRA pro mod). I "volunteered" my time for Andy Kelley and Jeff Diehl (NHRA nitro funny car). I also currently machine parts for JRD Rallysport (RallyAmerica) and Panoz and having been in several race shops (Hendrick, Fulton, ProLine) I have never ever seen plastigage being used on any engine part.
In most cases, setting up tight clearance does a number of things not to mention the strain 15+" of vacuum put on the oil. In that world you absolutely need to know clearances down to the .0001 place.
So yes, maybe most guys on this site don't need to know . . . maybe +/-.0005" is "good enough" for you or someone else's build for a daily driver stock motor. The point is the measuring devices are relatively inexpensive for the potential disaster averted when the motor is put together and you are racing on it every other weekend.
I would expect a hand built/race engine would be measured much more precisely.
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