Plastigage, How to use.

[herm111]

For many years now, there are still a lot of people that don't know how to use Plastigage, to check the amount of clearance they have in a bearing they want to reset. The instructions say to clean the crankshaft, and bearing before you use the Plastigage. What they leave out is, you have to use oil, on the shaft, and on the bearing to get any kind accuracy, especially a Babbitt bearing.

If you do not use 2, or 3 drops of oil on the shaft, and in the bearing, the plastigage will not spread out to its full width, for the pressure that is put on it, from tightening the bolts. In a babbitt bearing, what normally happens is the Plastigage pushes itself in to the babbitt, and does not spread out, for a reading.

A modern engine is a little better off, as the insert is a little harder then babbitt, but you can still improve the Plastigages use, by using oil.

To remove the used Plastigage from Shaft, and Bearings, Lacquer Thinner, will take care of it fast.

Picture No. 1 Shows oil being spread on a shaft, to receive the Plastigage.

Picture 2 Shows what Plastigage looks like for some that do not do their own engines.

Picture 3 Shows, the plastigage set in the oil on the shaft, and it also keeps the Plastigage in place, while you put on the cap.

Picture 4 Shows, a cap with oil ready to be put on.

Picture 5 Shows, the Plastigage flattened out on the crank, ready to be size checked. And again, always read the crank, and not the bearing.

Picture 6 & 7 Show, Reading the Plastigage on different Journals.

Picture 8 Shows, that with oil, Plastigage does not embed in the babbitt.

Thanks Herm.

[poci1957]

Good tips, thanks Herm

[Guest GaWajn]

Good information. Thank you.

[edinmass]

Question, if the crank is round, and the rod bored to the correct clearance from measurments taken off the crank, why is there any talk of shims? I have never seen a factory bearing job with shims, and was taught by an old time babbit man they are not correct and are a band-aid. Would like to hear comments on shims on rods and mains. Ed

[Dandy Dave]

Question, if the crank is round, and the rod bored to the correct clearance from measurments taken off the crank, why is there any talk of shims? I have never seen a factory bearing job with shims, and was taught by an old time babbit man they are not correct and are a band-aid. Would like to hear comments on shims on rods and mains. Ed

Band Aid.... That's a lot of BS. A lot of early automobiles, stationary engines, and tractors came right from the factory with shims, and had shims right up into the 1930's. After the 30's they started to go away with the more modern insert bearing shells. Dandy Dave!

[edinmass]

Hi Dave, I only work on the big cars, and have opened up quite a few, and have never seen shims. (Pierce, Rolls, Dusenberg, Stutz, ect) I was taught to pour babbit by a factory Springfield Rolls Royce engine builder who was in his 80's about 30 years ago. The P1, P2 and P3 didn't have shims, and when new babbit was installed you had to re lap all the timing gears by hand. It took quite a bit of time. And I still ask, if the crank is round, and you bore the bearing correctly, why shims? I was also taught the only way to get a correct reading on the bearing is a bore gauge. Yes, it's expensive, but it was what I was taught, so you could get an accurate reading of the entire bearing. Ed

Edited January 18, 2012 by edinmass (see edit history)

[Dandy Dave]

Yes, if everything is bored correctly then you will not need them. With that said, I can't say that Caterpillar, Allis Chalmers, IHC, Ford, John Deere, Economy, Mack, or any of the many others was wrong to include shims either. Dandy Dave!

[herm111]

Question, if the crank is round, and the rod bored to the correct clearance from measurments taken off the crank, why is there any talk of shims? I have never seen a factory bearing job with shims, and was taught by an old time babbit man they are not correct and are a band-aid. Would like to hear comments on shims on rods and mains. Ed

Your old time babbitt man was wrong. More then not, when he got rods in to rebuild, the rods that he seen didn't have shims left to see, as they were all used up. Evidently, he didn't have access to Factory rebuilding Rod, and Main insert Specs. Just about all rods, and mains on engines from 1900 to 1953, as in all Chevys from 1953 down had 6 to .008 thousands shim packs, Rods, and Mains. and if he was any kind of rebabbitter, he would have certainly done a very common Chevy rod??? Most Buicks had .006 thousandths, and on, an on. I would say here, that there were some Bearing building Companys, that didn't use shims, as a cost saving measure.

The reason the bearings need shims, is for nothing, but adjustment, and wear. On a modern engine yes the correct shaft, and bearing size should match, but you could miss both sizes, easily just between Mics. there could be a 1/2 thousandths! So if a shaft is off 1/2 thousandths tight, and the inserts are off 1/2 thousandths, tight, you have a whole .001 to tight a bearing, and if it was a babbitt rod, or main, you adjust with shims, if it was modern inserts, you go get a +, or - set to corect the problem, of remove more metal from either, or both.

Any thing else Ed, feel free, Thanks Herm.

[edinmass]

Hi Herm, The old time babbit man only did babbit on the high end cars and aircraft. I'm sure he worked on Ford and Chevy products, but he did not pour babbit for them. In the shop I work with (I don't own it, they do my work and I help out around the shop.), bearings are right on the money, or they need to be redone. Accurate measurement of all components, and cutting bearings is a very time consuming and expensive process. It takes up to 45 hours to line bore a 9 main bearing engine in this shop, and the results are controlled down to the 1/10 th. In the 20 years I have been there, NO ENGINE left with shims in the rods or mains. I have seen them make new shells when necessary. The last 9 main bearing engine that was done all mains were kept to 3/10 ths across the board. Examples of engines that left the shop include Rolls, W O Bentley, Stutz, Pierce, V-16 Cadillac, Dusenberg, Cord, Pope Hartford, and many others. As far as using a shim to adjust for wear, wouldn't the bearing be out of round? I ask these questions not to be critical or difficult, but to understand the process. Maybe on production run mass produced cars, shims were an option to keep costs down? Could you post photos of applications of shims like you have done on other posts? I would be interested in rods as well as main bearing shims. Thanks, Ed.

[herm111]

Hi Dave, I only work on the big cars, and have opened up quite a few, and have never seen shims. (Pierce, Rolls, Dusenberg, Stutz, ect) I was taught to pour babbit by a factory Springfield Rolls Royce engine builder who was in his 80's about 30 years ago. The P1, P2 and P3 didn't have shims, and when new babbit was installed you had to re lap all the timing gears by hand. It took quite a bit of time. And I still ask, if the crank is round, and you bore the bearing correctly, why shims? I was also taught the only way to get a correct reading on the bearing is a bore gauge. Yes, it's expensive, but it was what I was taught, so you could get an accurate reading of the entire bearing. Ed

Ed, I have done about , give, or take 10 Rolls Royce, rods, and main sets in the last 44 years, and all those had at least 1/8 packs, with babbitt on the ends, that you machined with the Rod, or Main, and that made the center a oil well. Another thing I remember is the packs were all numbered, for each Rod, and Main. I also done rods from an early Stutz, they had shim packs, may be you havin't worked with enough earlier cars in those makes. Thanks Herm.

[herm111]

Hi Herm, The old time babbit man only did babbit on the high end cars and aircraft. I'm sure he worked on Ford and Chevy products, but he did not pour babbit for them. In the shop I work with (I don't own it, they do my work and I help out around the shop.), bearings are right on the money, or they need to be redone. Accurate measurement of all components, and cutting bearings is a very time consuming and expensive process. It takes up to 45 hours to line bore a 9 main bearing engine in this shop, and the results are controlled down to the 1/10 th. In the 20 years I have been there, NO ENGINE left with shims in the rods or mains. I have seen them make new shells when necessary. The last 9 main bearing engine that was done all mains were kept to 3/10 ths across the board. Examples of engines that left the shop include Rolls, W O Bentley, Stutz, Pierce, V-16 Cadillac, Dusenberg, Cord, Pope Hartford, and many others. As far as using a shim to adjust for wear, wouldn't the bearing be out of round? I ask these questions not to be critical or difficult, but to understand the process. Maybe on production run mass produced cars, shims were an option to keep costs down? Could you post photos of applications of shims like you have done on other posts? I would be interested in rods as well as main bearing shims. Thanks, Ed.

I would be interested in the shop you use, that you talk about, as I know all the shops in the U.S. that do babbitt, and have seen there work, one way or another. Even if you put shims in a Rod, or main, we still bore the hole on clearance size, we don't just bore a hole, and use up the shims to get top, and bottom to Spec's. The only set of rods I have ever done with out shims, was a set of racing rods, that was hi oil pressure fed, and the part lines were built up. When you get a rod, or main that has .006, to 3/16's shim packs in, you can't just pour the bearings, and bore, as the hole with out babbitt, would be egg shaped in side, and you would most likely hit steel in the cap. If you don't like the prospect of shims, just use the rod, with out using the adjustment, and when wore out, replace it. If the bearing didn't have the shims, or if a guy don't want them, then we wouldn't use them, I don't see is as any hurdle.

To use shims to adjust bearings, yes some would be some what out of round, but you are talking a cap on a worn splash bearing, dropped .002 thousandths, at the part line you would be a .001 over the .001 thousandths per inch Spec's, but still with in Max. Spec's., for any given bearing, and there is little amount of pressure on the sides of the bearings, Rods, or Mains. Before 1950's, if you had your motor bearings worked on, you didn't have a complete motor rebuild, you had bearing adjustments, and that was choice for the times.

The last thing Ed., is you said you use a Bore Gauge to find a bearing hole size. I too have tried that, along with snap Gauges, and inside Mic's, and have found that they are very inaccurate! I find that a Post Mic. used on the inside of a Bearing, or any hole, will give me a 0 reading, meaning not a 1/10, of .001 thousandths difference ever time, and you have to use a Out Side Mic. on the Post Mic. Try it, you will like it.

Thanks Ed, Herm.

[herm111]

I have only taken pictures lately with something be sides a One Step, so I will be taking some as they come in. Most of our bearings are done for other engine builders, and if we don't Align Bore, we don't see the main shims.

1936 Buick Rods, and Bearings.

1923 Aluminum Rods, and Main caps, from a Air cooled Franklin.

Thanks Herm.

[Dandy Dave]

With what Herm has said, Shiming bearings in the farm tractor, and heavy earth moving equipment industry from the begining, though the 30's, 40's, and beyond can hardly be called a "band aid." Many of these machines have been subjected to thousands of hours of work without a teardown and rebuild. Some as high as 8,000, to 10,000, or more hours. I know of a Caterpillar D-7 that had over 20,000 hours on it and the lower end has never been apart. As Herm has said, it was common practice to remove a few shims to get the bearing clearence correct if the bearings and crank were still in good condition. As with aircraft engines, they need to be torn down and gone though in a much shorter period of time as mandated. Many as low as 500 hours of flight time. Many Rods were designed to have shim packs, and if not included, would not have enough room for a proper bearing thickness. Dandy Dave!

[Rusty_OToole]

In the old days it was common to remove shims and scrape bearings as part of an overhaul. You could return a worn bearing to factory clearance this way without the trouble and expense of rebabbiting the bearings.

Maybe you don't have to do this today because of better oils, filters, less dusty roads, and lower annual mileages. But if the bearing does wear what will you do?