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Plastagage versus bore gauge

General engine tech -- Drag Racing to Circle Track

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engineguyBill
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Re: Plastagage versus bore gauge

Post by engineguyBill » Sun Jan 12, 2020 10:36 pm

Plastigage is surprisingly accurate for what it is - an extruded wax thread manufactured to very accurate diameter. Engine bearing vertical oil clearance should be checked ONLY at a location 90 degrees from the bearing parting line. Any other location will result in wrong clearance due to eccentricity of the bearing shells. ALSO, as mentioned in previous posts, Plastigage is more accurate than inexpensive dial bore gauges that have pointed anvils. Use the Sunnen tool for best and most accurate results. But Plastigage remains a viable alternative to expensive measuring tools, just depend upon how much accuracy you are comfortable with . . . . . . . . .

Plastigage trivia: The machinery used to manufacture this product takes up as much area as a small computer desk. Very simple process.
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af2
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Re: Plastagage versus bore gauge

Post by af2 » Sun Jan 12, 2020 10:44 pm

engineguyBill wrote:
Sun Jan 12, 2020 10:36 pm
Plastigage is surprisingly accurate for what it is - an extruded wax thread manufactured to very accurate diameter. Engine bearing vertical oil clearance should be checked ONLY at a location 90 degrees from the bearing parting line. Any other location will result in wrong clearance due to eccentricity of the bearing shells. ALSO, as mentioned in previous posts, Plastigage is more accurate than inexpensive dial bore gauges that have pointed anvils. Use the Sunnen tool for best and most accurate results. But Plastigage remains a viable alternative to expensive measuring tools, just depend upon how much accuracy you are comfortable with . . . . . . . . .

Plastigage trivia: The machinery used to manufacture this product takes up as much area as a small computer desk. Very simple process.
Funny thing is that I use the plasti-gauge to check my measurements just in case.
GURU is only a name.
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Re: Plastagage versus bore gauge

Post by BLOCKMAN » Mon Jan 13, 2020 10:21 am

engineguyBill wrote:
Sun Jan 12, 2020 10:36 pm
Plastigage is surprisingly accurate for what it is - an extruded wax thread manufactured to very accurate diameter. Engine bearing vertical oil clearance should be checked ONLY at a location 90 degrees from the bearing parting line. Any other location will result in wrong clearance due to eccentricity of the bearing shells. ALSO, as mentioned in previous posts, Plastigage is more accurate than inexpensive dial bore gauges that have pointed anvils. Use the Sunnen tool for best and most accurate results. But Plastigage remains a viable alternative to expensive measuring tools, just depend upon how much accuracy you are comfortable with . . . . . . . . .

Plastigage trivia: The machinery used to manufacture this product takes up as much area as a small computer desk. Very simple process.
Bill

Very good post, I have seen Car Craft and other magazines do articles saying Plastigage is no good. And you look what they are using for a bore gauge its one with wheels or slides which is impossible to get an accurate measurement when your dealing with bearings that have eccentricity. Those gauges are great for measuring bores that are round period.
Here are pics of about every bore gauge made.
https://www.google.com/search?q=bore+ga ... 24&bih=608

This thread has a lot of good info here and there. Funny thing I found Foxwell had to answer every question about every bore gauge made says he using an SPI bore gauge only to find out he uses one with slides LOL. You can use the best ring gauge made but when you check a housing bores with a gauge with rigid fingers its not very accurate with bearings in the housing bores.
https://www.performanceboats.com/gn7-dy ... ances.html

ImageBORE GAUGE by CARL HINKSON, on Flickr

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Re: Plastagage versus bore gauge

Post by n2omike » Mon Jan 13, 2020 10:54 am

In a pinch, or to get a quick reading without having to take several measurements... I've installed dry bearings on only two journals... such as #1 and #5... tightened the caps... then placed a standard dial gauge on the crank next to the bearing.

All you do at that point, is lift up on the crank, and see how much the gauge moves. Is a quick check, and gets surprisingly accurate results when checked against other, more accepted methods.

I do understand its limitations. I came up with this when getting suspicious results using a dial bore gauge with a pointy anvil. It was digging into the bearing slightly, making it appear larger than it actually was (compared to Plasti-gauge). This method agreed with the Plasti-gauge... which placed me in the market for a dial bore gauge without the pointy tip.

I also measured the raw iron bore without a bearing, then the bearing thickness, then the crank... and did all the math. What bothered me, was the more measurements you take, the more 'stacked up' the measured precision errors become. The fewer measurements you can make to get the results, the more accurate the final result. Sometimes, a less precise SINGLE measurement can trump a series of more precise ones.

Moral of the story... I'll check clearances with a variety of methods... and always double check them with Plasti-gauge! You never know when you'll make a math error, or something else may happen. :)

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Re: Plastagage versus bore gauge

Post by bentvalves » Mon Jan 13, 2020 6:31 pm

incredible.

remember when you guys yelled at me for asking about poking a hole in a seat counter bore and it not being a racing engine?

welp, here you have it.

best wishes to all in the new year.

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Re: Plastagage versus bore gauge

Post by gmrocket » Tue Jan 14, 2020 1:30 am

My latest clevite bearing catalogue explains how to check bearing clearance using clevite plasti gauge.

Clevite does sell plasti gauge under their own name...

It's no different than any other plastic gauge, except the price.

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Re: Plastagage versus bore gauge

Post by engineguyBill » Tue Jan 14, 2020 12:02 pm

Actually, Clevite/MAHLE Aftermarket is the manufacturer of Plastigage, at their facility in Olive Branch, MS. They sell it to several other manufacturers who sell it under their own label. Plastigage product was developed and owned by Perfect Circle division of Dana Corporation for several years. PC and Clevite divisions were sold to MAHLE in 2007.
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Re: Plastagage versus bore gauge

Post by engineguyBill » Tue Jan 14, 2020 12:07 pm

engineguyBill wrote:
Tue Jan 14, 2020 12:02 pm
Actually, Clevite/MAHLE Aftermarket is the manufacturer of Plastigage, at their facility in Olive Branch, MS. They sell it to several other manufacturers who sell it under their own label. Plastigage product was developed and owned by Perfect Circle division of Dana Corporation for several years. PC and Clevite divisions were sold to MAHLE in 2007.

As I mentioned previously it is a very simple manufacturing operation and takes up about the same space as your kitchen table. The table at MAHLE is over by the restrooms, I think the janitor runs the machinery at night while he is cleaning the offices . . . . . . . .
Bill

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Re: Plastagage versus bore gauge

Post by engineguyBill » Tue Jan 14, 2020 12:08 pm

Actually, Clevite/MAHLE Aftermarket is the manufacturer of Plastigage, at their facility in Olive Branch, MS. They sell it to several other manufacturers who sell it under their own label. Plastigage product was developed and owned by Perfect Circle division of Dana Corporation for several years. PC and Clevite divisions were sold to MAHLE in 2007.

As I mentioned previously it is a very simple manufacturing operation and takes up about the same space as your kitchen table. The table at MAHLE is over by the restrooms, I think the janitor runs the machinery at night while he is cleaning the offices . . . . . . . .
Bill

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Re: Plastagage versus bore gauge

Post by tenxal » Tue Jan 14, 2020 5:57 pm

A few weeks ago I was assembling a SBC and got curious how Plastigage would measure compared to the dial bore method. As expected, it was very accurate. You can't get to the .0001's, obviously....but it's pretty easy to split the difference between .0005's.

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Re: Plastagage versus bore gauge

Post by Dave Koehler » 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.
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Re: Plastagage versus bore gauge

Post by Kevin Johnson » Wed Jan 15, 2020 10:03 am

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.
https://www.yellowbullet.com/threads/pl ... t-56447370

Yes, there is a difference. Photobucket wants to be paid if you would like to see the images or write directly to the poster.

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Re: Plastagage versus bore gauge

Post by BLOCKMAN » Wed Jan 15, 2020 10:20 am

https://www.yellowbullet.com/threads/pl ... t-56447370

Yes, there is a difference. Photobucket wants to be paid if you would like to see the images or write directly to the poster.
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Re: Plastagage versus bore gauge

Post by Ks Fats » Wed Jan 15, 2020 10:27 am

Dave,
About 20 years ago I was doing a resto on a 235 chevy for a customer. I decided to do a quick check with pg on the mains.
When I removed the caps the material had not compressed completely and actually left indentations in the bearing. As you say; there is no born on date so I don't know how old it was or the storage conditions. Bought the customer a new set of mains and have never touched the stuff again. Could have been a fluke but I can live with the quirks of the d.b. gauge.

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Re: Plastagage versus bore gauge

Post by David Redszus » Wed Jan 15, 2020 7:13 pm

A recent head sealing project and the mention of Plastigage brought an idea to mind.

Suppose we were to take a nice clean block surface, lay down several strips of Plastigage, install a nice clean head and
torque to specs.

What range of clearances are we to expect? Does the head/block surface remain parallel or does it distort when clamped?
Where does the distortion occur? Do the surfaces move with respect to each other?

Didn't mean to hijack this thread but could not resist the temptation.

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