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> Is there a "how to.." for crank measurement, and bearing verification?
malcolm2
post Dec 16 2019, 11:07 PM
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I am gonna make a 2 liter from my 1.8. So I have a refreshed 71mm crank that I have been told has been ground to -0.010.

I measured as best as I can with a digital mic and got about 59.66 on the mains and 49.65 on the rod journals.

Where can I find the STD specs and ranges ? were they 60 and 50, respectively?

Since I know nothing about this crank, how can I verify the 71 mm measurement?
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Superhawk996
post Dec 17 2019, 06:17 AM
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@malcolm2

My understanding is that this crank that came to you came out of my 2.0L engine GA004310. It will need to be used with a set of 2.0L rods. I provided the crank only to another member for cost of shipping. The engine it came ran (video on my thread) but when I tore the engine down I found rust in the sump. See photos in my build thread for condition of this engine GA004310 (page 5 and 6).

The crank was subsequently hot tanked and had a light polish at my local machine shop.

You should measure using a micrometer it is more accurate than a digitial caliper when we are taling about ten thousandths of an inch (0.0001").

This crank came out of my engine at 0.010" undersize on both mains and rods. It was scored. My local machine shop put a very light polish on it that removed another 0.0001" to 0.0002". If I recall, most journals were actually 0.0101 under size. There was some light pitting at the nose of the crank between where the distributor gear sits and between the main bearing but it was not pitted at all where the bearing actually rides (inclusive of end play).

I was going to use it but subsequently got a used standard size crank from KevinW for not much more than about $200 total and my local machine shop was going to charge $90 to take this worn/polished crank down to 0.020" undersize which didn't make sense to me to pay when KevinW helped me out for not much more than that. My preference was to use a standard crank. Nothing wrong with 0.010" - 0.20" undersize, lots of low buck rebuilders would do that but for only $200 to get a standard crank, that is where I wanted to start from.

I recommend that it be trial assembled and measure with Plastigauge to determine what the actual oiling clearnce is. I just looked to see if I had photos of the journals as I measured them. I'm not finding them quickly. I'll look again after work this evening and then I have the rest of the month off for vacation so I'll look again.

The specifications for journal diameters are in the factory manual, Haynes, or the How to rebuild your VW engine book. I'll dig those out later too.
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malcolm2
post Dec 17 2019, 08:46 AM
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YES, It seems that @jtprettyman has passed it on to me for the cost of a couple IPAs. He told me it was from you. (IMG:style_emoticons/default/piratenanner.gif) Only a few of us 914 guys around in Middle Tennessee. Todd and I have swapped a few parts back and forth over the years.

I did find the crank specs in the Tom Wilson book. So all the type 4 MAIN journals start out at 59.971 to 59.990 mm and #4 specs at 39.984 to 40.000 mm (i forgot to measure this one)

with my measurement technique they were -0.27 to -0.29 mm (-0.01063" to -0.01142")

I will get me a micrometer or take it to a shop and had planned to give plasti-guage a shot.

My last engine was all standard so this is my 1st time with undersized anything.... My case measures straight and true. Measured each side of the saddle with a snap gauge and a straight edge from saddle to saddle with a feeler gauge under it.

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malcolm2
post Dec 17 2019, 08:51 AM
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How about the 71mm measurement? Not that it matters, just curious if I could measure that.

THe rod journals are smaller, but otherwise it looks just like the 66mm from the 1.8. I thought the rod journals were smaller and offset. seems like 5mm offset would be visible.

Any other way to tell it's a 71mm? Markings, etc...
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Mark Henry
post Dec 17 2019, 09:24 AM
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I only use STD cranks or standard (under) cranks I get turned down to .010, reason is I won't use a crank that ever had a burnt journal.

Cheap magnaflux, hold a crank by the nose, give it a solid rap with a hammer and it should ring. If it's just a thud it's cracked. This doesn't replace magnaflux, but I've never had a crank fail that passed the ring test.
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malcolm2
post Dec 17 2019, 09:48 AM
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QUOTE(Mark Henry @ Dec 17 2019, 09:24 AM) *

I only use STD cranks or standard (under) cranks I get turned down to .010, reason is I won't use a crank that ever had a burnt journal.

Cheap magnaflux, hold a crank by the nose, give it a solid rap with a hammer and it should ring. If it's just a thud it's cracked. This doesn't replace magnaflux, but I've never had a crank fail that passed the ring test.



I definitely have tools to do that test. (IMG:style_emoticons/default/shades.gif)
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Superhawk996
post Dec 17 2019, 02:13 PM
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QUOTE(malcolm2 @ Dec 17 2019, 09:51 AM) *

How about the 71mm measurement? Not that it matters, just curious if I could measure that.

THe rod journals are smaller, but otherwise it looks just like the 66mm from the 1.8. I thought the rod journals were smaller and offset. seems like 5mm offset would be visible.

Any other way to tell it's a 71mm? Markings, etc...


Stroke of the crank 71mm is measured from the centerline of the main bearings to the centerline of the rod journal. That dimension should be 35.5mm or 1/2 the stroke.

It will be difficult to measure perfectly without putting the crank between centers, doing some set up of height gauges and some math to account for journal radius offset.

A 1.7L/1/8L is an offset of 33mm from crank centerline. A difference of 2.5mm to the 2.0l crank. That 2.5mm is 0.100” and could easily get lost in an eyeball or tape measure type measurement.

Easier way would be to mock up, and then measure the actual stroke of a piston. That should be 71mm.
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Superhawk996
post Dec 17 2019, 02:34 PM
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Also for what it’s worth, I provided this crank thinking it was going to a low buck down and dirty rebuild or low buck refresh of some sort.

From your previous posts I think you have invested in new AMC heads and may be building this for a Bus IIRC. I wouldn’t use this crank as-is for for a top notch rebuild. This crank is was polished beyond the 0.010 undersize to remove light scoring. That polish basically equals WEAR. As long as it’s between the tolerances it’s usable but some life was lost and oil clearances would be increased with the polish. Plastigage would tell you where it actually is at.

If you don’t want to spend dollars for a standard crank, at least take this one down to 0.020” under, get 0.020” under bearings and start with fresh unworn bearing clearances.

Factory manual allows for 0.030” undersize but I personally wouldn’t go that far undersize.

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malcolm2
post Dec 17 2019, 06:30 PM
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OK it passed the hammer test. very high pitched tuning fork ring. The 1.8 has an even higher ring and lasts longer. If that means anything... (IMG:style_emoticons/default/piratenanner.gif)

I have a set of micrometers coming from a workmate tomorrow. If he forgets, there is always Harbor Freight for $40.

With my method of measuring last night, I got a consistent 49.65 on all 4 rod journals.
Book says std is 49.97 - 49.98. That puts them at 0.33mm under which is -0.01299. Seams excessive.

More accurate measurements tomorrow, I guess.

So @Superhawk996 , did this crank ever run in it's current state? Or you took it out and polished it, but never installed?
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Mark Henry
post Dec 17 2019, 11:26 PM
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QUOTE(Superhawk996 @ Dec 17 2019, 03:13 PM) *

QUOTE(malcolm2 @ Dec 17 2019, 09:51 AM) *

How about the 71mm measurement? Not that it matters, just curious if I could measure that.

THe rod journals are smaller, but otherwise it looks just like the 66mm from the 1.8. I thought the rod journals were smaller and offset. seems like 5mm offset would be visible.

Any other way to tell it's a 71mm? Markings, etc...


Stroke of the crank 71mm is measured from the centerline of the main bearings to the centerline of the rod journal. That dimension should be 35.5mm or 1/2 the stroke.

It will be difficult to measure perfectly without putting the crank between centers, doing some set up of height gauges and some math to account for journal radius offset.

A 1.7L/1/8L is an offset of 33mm from crank centerline. A difference of 2.5mm to the 2.0l crank. That 2.5mm is 0.100” and could easily get lost in an eyeball or tape measure type measurement.

Easier way would be to mock up, and then measure the actual stroke of a piston. That should be 71mm.


The T4 crank is a flat-plane crank, just use a vernier caliper and measure from the bottom of one throw to the top of the next throw. You can use a straight edge or just eyeball it. It will even work telling the difference between a 78mm and 80mm but it might be hard to tell between a 78mm vs a 78.8mm crankshaft.

It's not a dead accurate way, but quick and easy to identify if it's a stock 66mm or 71mm crank.
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Superhawk996
post Dec 18 2019, 08:53 AM
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QUOTE(malcolm2 @ Dec 17 2019, 07:30 PM) *


With my method of measuring last night, I got a consistent 49.65 on all 4 rod journals.
Book says std is 49.97 - 49.98. That puts them at 0.33mm under which is -0.01299. Seams excessive.

More accurate measurements tomorrow, I guess.

So @Superhawk996 , did this crank ever run in it's current state? Or you took it out and polished it, but never installed?


No the crank was never run in it's current configuration after the polish. I measured it roughly 0.010" under with my micrometer toward the high end of the tolerance. My machine shop said they did a light polish of .0001" - 0.0002". I cannot find any record of my having remeasured the crank after return because by then I had the standard size crank from Kevin. So in my mind, measure it, see what it is but more than likely it will need to to to 0.020" under to get it to be exactly on-size toward the high end of the tolerance.


Here's the bottom line: I never intended for this crank to go into an engine as-is and had assumed it would get plastigage'd for verification and/or taken down to 0.020" undersize.

I had no intention of representing this crank as being a a great crank. If this crank doesn't suit your purposes or you have any reservation about taking it to 0.020" under before use, I'll gladly refund the shippping cost that was paid to me.
My only intention was to help a low buck rebuild with a free crank for the cost of shipping. The shipping cost is trivial and I would feel terrible if you tried to use this crank as-is and had a poor outcome. If you're OK to have it ground 0.020" under you could do that but given you have invested big$$ in the new heads, I can't see why you wouldn't try to find a good standard size crank.

Note: the tolerance on jounal diameters is only 0.02mm which is 0.0008". Eight ten thousands of an inch is the total tolerance between new and worn!

Quick note on caliper vs. micrometer accuracy for anyone that is interested in measurement of preciesly machined parts:

My 6" Mitutoyo digital calipers are accurate to +/- 0.001" with a resolution of 0.0005". This is not accurate enough to measure a crank with. Resolution is not the same as accuracy. If you play with a set of calipers like these and try to get a reading of 0.0006" it is not possible. The caliper will jump to 0.001".

https://www.mitutoyo.com/wp-content/uploads...8/07/15003A.pdf

My vernier micrometers are accurate to +/- 0.0001" with a resolution of 0.00005".

That is a comparison of 1/1,000th of an inch accuracy (larger than crank tolerance) vs. 1/10,000th of an inch (still 1/8 of the tolerance and not ideal). That is an order of mangnitude (x10) imporvment with the micrometer. Digital micrometers can be even more accurate to within 1/20,000th of an inch. A micrometer is what you need to accurately measure the crank and I can only say I wish I had a set of digital micrometers but that is too much $$ given how infrequently I use them.
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malcolm2
post Dec 18 2019, 10:03 AM
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QUOTE(Superhawk996 @ Dec 18 2019, 08:53 AM) *

QUOTE(malcolm2 @ Dec 17 2019, 07:30 PM) *


With my method of measuring last night, I got a consistent 49.65 on all 4 rod journals.
Book says std is 49.97 - 49.98. That puts them at 0.33mm under which is -0.01299. Seams excessive.

More accurate measurements tomorrow, I guess.

So @Superhawk996 , did this crank ever run in it's current state? Or you took it out and polished it, but never installed?


No the crank was never run in it's current configuration after the polish. I measured it roughly 0.010" under with my micrometer toward the high end of the tolerance. My machine shop said they did a light polish of .0001" - 0.0002". I cannot find any record of my having remeasured the crank after return because by then I had the standard size crank from Kevin. So in my mind, measure it, see what it is but more than likely it will need to to to 0.020" under to get it to be exactly on-size toward the high end of the tolerance.


Here's the bottom line: I never intended for this crank to go into an engine as-is and had assumed it would get plastigage'd for verification and/or taken down to 0.020" undersize.

I had no intention of representing this crank as being a a great crank. If this crank doesn't suit your purposes or you have any reservation about taking it to 0.020" under before use, I'll gladly refund the shipping cost that was paid to me.
My only intention was to help a low buck rebuild with a free crank for the cost of shipping. The shipping cost is trivial and I would feel terrible if you tried to use this crank as-is and had a poor outcome. If you're OK to have it ground 0.020" under you could do that but given you have invested big$$ in the new heads, I can't see why you wouldn't try to find a good standard size crank.

Note: the tolerance on jounal diameters is only 0.02mm which is 0.0008". Eight ten thousands of an inch is the total tolerance between new and worn!

Quick note on caliper vs. micrometer accuracy for anyone that is interested in measurement of preciesly machined parts:

My 6" Mitutoyo digital calipers are accurate to +/- 0.001" with a resolution of 0.0005". This is not accurate enough to measure a crank with. Resolution is not the same as accuracy. If you play with a set of calipers like these and try to get a reading of 0.0006" it is not possible. The caliper will jump to 0.001".

https://www.mitutoyo.com/wp-content/uploads...8/07/15003A.pdf

My vernier micrometers are accurate to +/- 0.0001" with a resolution of 0.00005".

That is a comparison of 1/1,000th of an inch accuracy (larger than crank tolerance) vs. 1/10,000th of an inch (still 1/8 of the tolerance and not ideal). That is an order of mangnitude (x10) imporvment with the micrometer. Digital micrometers can be even more accurate to within 1/20,000th of an inch. A micrometer is what you need to accurately measure the crank and I can only say I wish I had a set of digital micrometers but that is too much $$ given how infrequently I use them.


Thanks for your input. I certainly hope you don't take this personally, I never thought you or Todd represented this part as good or bad. It is my responsibility to verify. So I thank all who have chimed in here.

I started this post, just to find out about HOW to measure and check a crank. My plan was to pick your brain about the crank once I had some measurements, regardless of their accuracy. It looks like I would prefer to spend time working to find a std crank (new or used) vs getting this one fixed to use. Maybe one day I will find someone that has a trusted machinist to do it right. And we can make a trade for a few beers.

I have time to search and learn, so all is well.

Thanks,
Clark
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Superhawk996
post Dec 18 2019, 02:58 PM
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QUOTE(malcolm2 @ Dec 18 2019, 11:03 AM) *


Thanks for your input. I certainly hope you don't take this personally, I never thought you or Todd represented this part as good or bad. It is my responsibility to verify. So I thank all who have chimed in here.

Thanks,
Clark



@malcolm2
@jtprettyman

No worries. Nothing personal at all and no offense taken on my part. I just want to be completely upfront that if anyone is unhappy, I'll work to make it right.

For all practical purposes, we are talking about beer money here. I just don't want any one to feel they got stuck with a door stop. That crank has a viable purpose to someone, it just might not be the right crank for this engine build under discussion.

Glad to see the posting on WTB for a Std. 2.0L crank. Someone help a brother out!
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malcolm2
post Dec 21 2019, 02:47 PM
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OK, maybe not the super duper accurate tools but I feel better after these measurements. They are the Mitutoyo brand... so this is what I got.

#1 main is 0.0072 under
#2 main is 0.0076 under
#3 main is 0.0072 under
#4 main is 0.00925 under

Rod journals are all 0.0084 under

So I had already bought some 0.010 under (0.25mm) main bearings, so I am gonna get some plasti-gauge and see where the clearance ends up.

What are the thoughts of the group??
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Mark Henry
post Dec 21 2019, 03:24 PM
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Sounds like a lot. If you're right about #4 you'll be lucky to get it ground at .010 under.
You need to send it to a crank shop, once done they will tell you (tag) what sizes you need. I never use plastigage, nether does Raby IIRC. Your rods should at least have the big ends done.

Honestly if you're not doing that then it's a recipe for disaster.
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Superhawk996
post Dec 21 2019, 07:36 PM
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QUOTE(malcolm2 @ Dec 21 2019, 03:47 PM) *

OK, maybe not the super duper accurate tools but I feel better after these measurements. They are the Mitutoyo brand... so this is what I got.

#1 main is 0.0072 under
#2 main is 0.0076 under
#3 main is 0.0072 under
#4 main is 0.00925 under

Rod journals are all 0.0084 under

So I had already bought some 0.010 under (0.25mm) main bearings, so I am gonna get some plasti-gauge and see where the clearance ends up.

What are the thoughts of the group??


I assume this is the .010" under crank we are talking about. If that is correct, it sounds to me like you're tightening the micrometer too much. The crank from GA004310 was definately AT LEAST 0.0100" undersized and was running in 0.010" undersize bearings when I tore it down. The clearnace would but super "tight" in 0.010" undersize bearings. Micrometers can be a bit fickle to learn to use if you are not used to using them. Mitutoyo usually have a small ratchet knob to help set the "feel" and keep from overtightening.

Three suggestions.

1) Make sure you're only tightening the micrometer until you have only the slightest friction feel when the Micrometer slips off the journal. Keep measuring until you're getting repeatable measurements +/- 0.0001". It's definately a feel thing. Practice measuring a human hair if you have to. You should be able to measure the hair and pull it out of the micrometer without it breaking but yet still feel the friction on the hair.

2) If you are consistently coming in above 0.010" undersize, then check the micrometer calibration. They should have a calibration gage. 1", 2", 3" etc. whatever is appropriate to the range of the Micrometer. Make sure the micrometer is calibrated to that gauge meaning that if for example it is a 2.0000" gauge block, that the micrometer comes in right at 2.0000". Google how to do that calibration if not familiar, likewise there should be a very small special wrench with the micrometer to do this. If it missing don't even try.

3) If you can't seem to get the feel and/or you don't have calibration gage blocks, then have a machine shop measure as Mark suggests. No harm and they will probably do it for free.
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malcolm2
post Dec 23 2019, 10:08 AM
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Both micrometers were checked prior to the last measurements. I believe you are correct on me being a little aggressive on the dial.... I have re-checked both tools and taken new measurements with just a tad of friction....

#1 2.3518 vs. the mid-point of the spec'd range = 0.0095 under
#2 2.3520 " " = 0.0093 under
#3 2.3517 " " = 0.0092 under
#4 1.5662 " " = 0.00815 under
ROD Journals day 2 measurement all equal at 1.9595 = 0.0084 under

I had planned to take the crank to a shop that I had forgotten about and had heard was reputable, but they are closed 'til January 2nd.

I guess I will move on to another project.


2ndly, Why not use plasti-gauge? How do you know what your oil clearance is without it?
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Superhawk996
post Dec 23 2019, 10:34 AM
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QUOTE(malcolm2 @ Dec 23 2019, 11:08 AM) *

Both micrometers were checked prior to the last measurements. I believe you are correct on me being a little aggressive on the dial.... I have re-checked both tools and taken new measurements with just a tad of friction....

#1 2.3518 vs. the mid-point of the spec'd range = 0.0095 under
#2 2.3520 " " = 0.0093 under
#3 2.3517 " " = 0.0092 under
#4 1.5662 " " = 0.00815 under
ROD Journals day 2 measurement all equal at 1.9595 = 0.0084 under

I had planned to take the crank to a shop that I had forgotten about and had heard was reputable, but they are closed 'til January 2nd.

I guess I will move on to another project.


2ndly, Why not use plasti-gauge? How do you know what your oil clearance is without it?


Plastigage is not well liked by some. Like all tools it is a bit subjective and can be used improperly.

If you have a properly measured ID on the bearing as installed into a properly torqued case, and the OD of the crank, you know the bearing clearance as the difference between the two measurements. You also have to KNOW that the case main bore is perfectly circular for this to be true

What isn't well recognized is the error in measurements that you're now running into just checking the crank OD. Now factor in the error in measurement when checking bearing ID and you get a sense of what error might be creeping into the bearing clearance calculation.

The some of the pro's don't like Plastigauge because:

1) It is time consuming. If you have a highly trusted shop doing your crank grinding and case line boring, AND you trust thier measurement accuracy then Plastigauge is redundant.

1A) If your machine shop's crank grinder is a modern, calibrated CNC crank grinder I'd be willing to take their measurement at face value. If you're using a lesser machine shop with older manual crank grinding equipment, and who knows who doing the measurements, then you're back to quality control, and manual measurement errors. Likewise if your case is line bored with CNC equipment, sure trust the measurent. But if the case is line bored with an old fashioned, bench top, drill powered line bore that has questionable guide busings you have no control over, we'll you might want to question and/or double check how round the case main bearing bore actually is.

Just to ground ourselves on line boring. Ranges from this to full CNC. Nothing wrong with this depending on application but let's not kid ourselves this is not CNC. Not posting this for any other reason that to demonstrate bench top line boring.



Wow! Here's an interesting CNC line bore with a right angle cutter. Right axis cutter adds some variability to things but at the same time a single cutting point is more accurate and CNC virtually guarantees the ability to locate repeatibly along a singular axis. Cool!



1B) Time is money. If you have proper quality control upstream at the machinist you work with for say 20 builds a year, and someone that will financially stand behind their machine work if they screw it up, then why waste your own time with Plastigauge.

2) Plastigage is prone to it's own errors:

2A) it only measures one axis of the crank at a time. If you have an oval case bore, you will need to measure each bearing twice to get a sense of what the ovality is.

2B) Plastigage can "smear" if the part is moved while torqueing it. Especially true of Rod journals since the rods can move easily while being torqued.

2C) Plastigauge like all other measurements has a +/- error and shouldn't be considered absolute.

3) For hobbyists like myself, Plastigage can serve as a sanity check, a redundant backup. I measure both ID, and OD and calculate the clearance. But then I like to use Plastigage as a double check. Remember we are taling about tolerance of 0.0008" between the high end and low end of crank measurement. 0.00025" is a 25% change. Easy to lose sight of how the errors in measurement compound and how the +/- tolerance spread can affect bearing oiling clearances. Plastigage is just cheap insurance.

3A) in the case of an unknown crank like we are taling about here, Plastigauge is a quick way to gague what you're dealing with. I would not suggest that that is all you do but rather it is a double check to what you do.
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malcolm2
post Dec 23 2019, 10:44 AM
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QUOTE(Superhawk996 @ Dec 23 2019, 10:34 AM) *


3) For hobbyists like myself, Plastigage can serve as a sanity check, a redundant backup. I measure both ID, and OD and calculate the clearance. But then I like to use Plastigage as a double check. Remember we are taling about tolerance of 0.0008" between the high end and low end of crank measurement. 0.00025" is a 25% change. Easy to lose sight of how the errors in measurement compound. Plastigage is just insurance.

3A) in the case of an unknow crank like we are taling about here Plastigauge is a quick way to gague what you're dealing with. I would not suggest that that is all you do but rather it is a double check to what you do.


I should have specified that that was what the plan was. I assumed that plasti-gauge was the back-up. I guess some folks might use it as the "be-all end-all".
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malcolm2
post Jan 14 2020, 08:38 PM
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UPDATE>>>>>

Todd is the Director of Quality for an automotive parts maker, and he measured the crank in is lab.... much lighter touch than me. (IMG:style_emoticons/default/blink.gif)

Here is what he measured...

#4 -0.009350
#3 -0.009843
#2 -0.009843
#1 -0.009500

The RODS.... from the fan.

-0.010026
-0.010105
-0.009908
-0.010194

At 1st look, I am thinking, " GO WITH IT". Next step will be a plasti-gauge check.

I need to check the rods now. What is the factory spec for the big end?

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