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Plastagage versus bore gauge

General engine tech -- Drag Racing to Circle Track

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MadBill
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Re: Plastagage versus bore gauge

Post by MadBill » Thu Jan 16, 2020 1:22 am

Running with the hijack ball: that would be really interesting! I suspect all the PG strips would end up as near-transparent blots a half inch wide.

Of course for an accurate picture the use of pressure indicating film would be preferable: https://www.sensorprod.com/glossary/pre ... g-film.php
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Re: Plastagage versus bore gauge

Post by Kevin Johnson » Thu Jan 16, 2020 9:55 am

MadBill wrote:
Thu Jan 16, 2020 1:22 am
Running with the hijack ball: that would be really interesting! I suspect all the PG strips would end up as near-transparent blots a half inch wide.

Of course for an accurate picture the use of pressure indicating film would be preferable: https://www.sensorprod.com/glossary/pre ... g-film.php
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Re: Plastagage versus bore gauge

Post by David Redszus » Thu Jan 16, 2020 10:19 am

MadBill wrote:
Thu Jan 16, 2020 1:22 am
Running with the hijack ball: that would be really interesting! I suspect all the PG strips would end up as near-transparent blots a half inch wide.

Of course for an accurate picture the use of pressure indicating film would be preferable: https://www.sensorprod.com/glossary/pre ... g-film.php
Before we had Fiji Film, we made use of carbon paper (like typists once used, now obsolete).
The film would indicate the local pressures but not the clearance gap.

When we get back from Eagle River this weekend, I'm going to try film and Plastigage on a few applications.
Might work better than Prussian Blue.

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Re: Plastagage versus bore gauge

Post by Knight rider » Thu Jan 16, 2020 1:12 pm

I would look at like this, you're trying a measure a clearance which is either from a OEM spec or bearing supplier or even a standard for that engine by engine builders, you must use the same method they used. Let's say you had a even better way of measuring like using a scan tool with lasers and 3D imaging well now you have no reference point to compare to because that's not how it was done to come up the clearance in the first place. Cheers

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Re: Plastagage versus bore gauge

Post by Kevin Johnson » Thu Jan 16, 2020 1:28 pm

I think Plastigage supplanted the use of very thin lead wire (lead wire might still be called out by an OEM).

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Re: Plastagage versus bore gauge

Post by engineguyBill » Thu Jan 16, 2020 2:42 pm

Victor-Reinz used to market impression paper which could be placed between two surfaces, such as between block and heads. The parts were torqued to specification, then removed. The impressions left on the paper would show the consistency (or inconsistency) of the two surfaces involved. Can't remember what they called this product and am not sure if it is still available.
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Re: Plastagage versus bore gauge

Post by engineguyBill » Thu Jan 16, 2020 2:42 pm

Victor-Reinz used to market impression paper which could be placed between two surfaces, such as between block and heads. The parts were torqued to specification, then removed. The impressions left on the paper would show the consistency (or inconsistency) of the two surfaces involved. Can't remember what they called this product and am not sure if it is still available.
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Re: Plastagage versus bore gauge

Post by engineguyBill » Thu Jan 16, 2020 2:45 pm

Don't know why that post showed up twice . . . . . . .
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Re: Plastagage versus bore gauge

Post by Kevin Johnson » Thu Jan 16, 2020 3:10 pm

When we would fit precision investment castings to dies we would mix some pulverized rouge in carbon tet so that high spots would be indicated. Things have certainly progressed.

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Re: Plastagage versus bore gauge

Post by ProPower engines » Thu Jan 16, 2020 3:23 pm

Dave Koehler wrote:
Wed Jan 15, 2020 9:18 am
I used to include some plastigage with ever degreesy unassembled engine that went out.
As such I kept a fair amount on hand.
Even long ago I heard the stories about "fresh" being critical.
Here is the thing.
Since it never had a born on date how the heck do I know what is fresh?
I had/have no idea how long it sat on the warehouse shelf before I bought it..

Has anyone ever done a test with some 5 year old pg against what you assume is fresh?

Is this just another one of those things that became wisdom but has no basis in reality?

Edit: https://www.plastigaugeusa.com/about.html
Other than it is preferred to be used below 95 degrees (melts?) nothing is said about it going bad over time.
I had some PG that was on the back shelf for over 10 years. I had a toyota diesel in the shop a few weeks back and the bearing clearance was very close using PG compared to a bore gauge.

I was teaching a young kid here how to use it as part of the teaching program as he has never seen it used before.

Bottom line is after you have done this for 30+ years you get good at reading certain things in between the lines so to speak but because we mostly work to much tighter tolerance then the OEM's did its hard to accept the PG reading over a bore gauge.
And there is the red or green PG drama as to which to use to get the perfect measurement as the red is .002-.
006 and the green is .001-.003 but it seems most just go with the green PG. but again like Dave mentioned there is no best before date or a suggestion of how long the stuff will last on the shelf.

But with some that was over 10 years old it seems to work just as intended to do =D>

Personally I only recommend the use of a gauge to precisely measure bearing clearance but I have a hard time with the current rods being run today and using PG to check.
Most fit the dowels or bolts very tight and to separate the halves after torqued to check the PG it makes be think the error from disassembly will ad or if you will subtract the clearance from the pressure sensitive PG making the check not as close as it should be then on a stock engine refresh .

That in itself may be why the OP is seeing a reduction in clearance using PG and the same bearing size as started with [-X
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Re: Plastagage versus bore gauge

Post by AC sports » Sat Jan 18, 2020 6:13 am

I too have recently been playing with the conventional type bore gauges in measuring bearing clearances. With 2 different branded Japanese tools I get consistently similar results. With plastigauge I'm getting around 0.005mm tighter readings on a 2 inch journal. This is with a European platigauge equivalent. I learn to live with small bearing mark's. In fact I know if they are still there on tear down all is well with lubrication, clearance and application.

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Re: Plastagage versus bore gauge

Post by gmrocket » Sat Jan 18, 2020 6:43 am

AC sports wrote:
Sat Jan 18, 2020 6:13 am
I too have recently been playing with the conventional type bore gauges in measuring bearing clearances. With 2 different branded Japanese tools I get consistently similar results. With plastigauge I'm getting around 0.005mm tighter readings on a 2 inch journal. This is with a European platigauge equivalent. I learn to live with small bearing mark's. In fact I know if they are still there on tear down all is well with lubrication, clearance and application.
probably because the plastigauge doesn't put pinpoint pressure on the bearing like your gauge does.

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Re: Plastagage versus bore gauge

Post by engineguyBill » Sat Jan 18, 2020 1:08 pm

AC sports wrote:
Sat Jan 18, 2020 6:13 am
I too have recently been playing with the conventional type bore gauges in measuring bearing clearances. With 2 different branded Japanese tools I get consistently similar results. With plastigauge I'm getting around 0.005mm tighter readings on a 2 inch journal. This is with a European platigauge equivalent. I learn to live with small bearing mark's. In fact I know if they are still there on tear down all is well with lubrication, clearance and application.
Your inexpensive bore gauges are measuring the "bearing mark's" as additional vertical oil clearance, therefore it is reasonable that the Plastigage is indicating a tighter clearance. I think you meant to say 0.005", not 0.005mm??
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