Plasti gauge measurement

[Dsm559]

I am putting together my 7 bolt 4g63t block. I am not getting any readings from the plasti gauge after plasti gauging the main bearings. Torqued the girdle to 16ft Ibs and followed it with a 90 degree turn just like how the service manual said. After that i remove the girdle and do not get measurement readings from the plasti gauge. Did this twice. Idk if using arp main studs have to do with anything. Also the crank has machine work done to it due to a spun bearing. Am I needing a new crank, is that why I am not getting any plasti gauge readings?

 

[pauleyman]

So do you have the matching oversize bearings Installed to go along with the machine work?

 

[Mech Addict]

Sounds like excessive clearance. You might need the next large size of plastigage, or borrow the proper mics and bore set. You might speak with your machine shop, too. Hopefully a thicker set of bearings will do the trick, but you’ll need to know what size.

 

[Dsm559]

So do you have the matching oversize bearings Installed to go along with the machine work?

Yes I got the bearing size I was told to get by the machine shop

 

[Dsm559]

Sounds like excessive clearance. You might need the next large size of plastigage, or borrow the proper mics and bore set. You might speak with your machine shop, too. Hopefully a thicker set of bearings will do the trick, but you’ll need to know what size.

hmm. Sounds like I have to call or make a stop to the machine shop.

 

[1990TSIAWDTALON]

Can you feel any up and down movement of the crank AT ALL when the caps are tight, like pull up on the snout. If you feel ANYTHING, then have the crank checked again. I totally agree with the others here.

 

[Dsm559]

Can you feel any up and down movement of the crank AT ALL when the caps are tight, like pull up on the snout. If you feel ANYTHING, then have the crank checked again. I totally agree with the others here.

Can you feel any up and down movement of the crank AT ALL when the caps are tight, like pull up on the snout. If you feel ANYTHING, then have the crank checked again. I totally agree with the others here.

I just retorqued the cranked to 16 ft Ibs then followed it with a 90 degree turn. The cranks turns smoothly and the is no play. Here is a picture of how it looks torqued the plasti gauge specs.

 

[Mech Addict]

Which plastigauge are you using? The principle behind it is fairly simple: a rectangular strip of deformable plastic of a given section volume starts with a specific height and width. When squeezed into a space of lesser height, the width expands proportionally. Then the “gauge” is used to compare the width, and reports the corresponding height (clearance). If the width doesn’t change after torqued, then the height started out too short, and you need “taller” plastigauge to start with. That would be cheaper than trying a thicker set of bearings.
Assuming the main bores are standard still, was your machinist able to tell you the diameter of you crank main journals?

 

[1990TSIAWDTALON]

I would have the crank miked and see what its true OD is on the journals. Very possible it is cut and will require a thicker bearing which is no big deal.

 

[Dsm559]

Which plastigauge are you using? The principle behind it is fairly simple: a rectangular strip of deformable plastic of a given section volume starts with a specific height and width. When squeezed into a space of lesser height, the width expands proportionally. Then the “gauge” is used to compare the width, and reports the corresponding height (clearance). If the width doesn’t change after torqued, then the height started out too short, and you need “taller” plastigauge to start with. That would be cheaper than trying a thicker set of bearings.
Assuming the main bores are standard still, was your machinist able to tell you the diameter of you crank main journals?

I’m using the green plasti gauge.

 

[Dsm559]

Which plastigauge are you using? The principle behind it is fairly simple: a rectangular strip of deformable plastic of a given section volume starts with a specific height and width. When squeezed into a space of lesser height, the width expands proportionally. Then the “gauge” is used to compare the width, and reports the corresponding height (clearance). If the width doesn’t change after torqued, then the height started out too short, and you need “taller” plastigauge to start with. That would be cheaper than trying a thicker set of bearings.
Assuming the main bores are standard still, was your machinist able to tell you the diameter of you crank main journals?

no I didnt get the diameter of the cranks main journals. I only the what bearing size I neede from the machinist.

 

[Dsm559]

I would have the crank miked and see what its true OD is on the journals. Very possible it is cut and will require a thicker bearing which is no big deal.

yes the bearing was scarred and that required cutting the crank, I went with the bearing size told by the machine shop.

 

[Mech Addict]

And what size did you get?

 

[Dsm559]

And what size did you get?

I had to get 0.010 of an inch. Only thing I could think of that went wrong is maybe I shouldn’t have had oiled the crank journals and should’ve just plasti gauge it dry. I’m going to try that and see if it changes anything. I was watching videos and doesn’t seem like anyone was piling it for plasti gauging.

 

[Mech Addict]

Yes, I believe you are supposed to do it completely dry. You place the crank in the block without rotating it at all, lay in the plastigauge on each journal, place the caps, torque the bolts, remove the caps, measure. If there is no change, then you need a different plastigauge that is for a larger range of clearance. Eventually you’ll determine how much clearance you have, and which bearing size should be used. I’d still do a final check when you get the new bearings, and write it down if you need to compare in the future.
Ever figure out how your crank got scored in the first place?

 

[AWD-Tony]

Dry assembly for plasti gauge.

 

[Dsm559]

Dry assembly for plasti gauge.

I’m hoping that’s my issue. Going to give that a try.

 

[Dsm559]

Yes, I believe you are supposed to do it completely dry. You place the crank in the block without rotating it at all, lay in the plastigauge on each journal, place the caps, torque the bolts, remove the caps, measure. If there is no change, then you need a different plastigauge that is for a larger range of clearance. Eventually you’ll determine how much clearance you have, and which bearing size should be used. I’d still do a final check when you get the new bearings, and write it down if you need to compare in the future.
Ever figure out how your crank got scored in the first place?

I’m hoping that’s my issue is that I am not plasti gauging the journals dry. I am trying to stay within standard clearances to keep things simple.

 

[Mech Addict]

So you said green plastigauge: like this one? It is designed to measure up to .020”. Perhaps a different brand of “plastigauge” has a different range for “green”. The service manual specifies a clearance of 0.0008” to 0.0016” for new bearings, with a limit on used bearings of 0.004”. I would think you should use the “red” plastigauge as shown in the second photo, which measures 0.001” up to 0.007”. Presumably this would be after you get thicker (“under-size” in reference to the crank journals) bearings.

 

[1990TSIAWDTALON]

My cranks ALL have assembly lube on them. I NEVER EVER put a crank in dry. You can easily scar bearings. The lube helps hold the plastigauge in place and also makes it easier to remove. Assembly lube or oil will only leave a slight film on the journals and that is good.
Remember, those journals SHOULD be as full of oil as they can get when the car is running and that oil takes up just a tad bit of space but its supposed to be there.
I shoot for .0015-.002" on mains and .002-.003" on rods. If it is tighter, that is good to a point, but in all my years, if you want a motor to "run", they like a little bit of looseness. (Cylinders too). Too loose of bearings and you have low oil pressure and that is bad. I use those tolerances on every motor, not just a 4g,.... Saturn, Dodge, Chevy, all of them.
To each their own, just the way I have done it for over 40 years and haven't had a failure yet. My DD Saturn with those tolerances has 40000 miles on it now 3 years later.
I have a new "secret" build going on in one of my profiles, it will get those specs also. You can find it under "My Other Baby", if interested.
Marty

 

[DSMPT]

I just retorqued the cranked to 16 ft Ibs then followed it with a 90 degree turn. The cranks turns smoothly and the is no play. Here is a picture of how it looks torqued the plasti gauge specs.

Hard to tell but judging by the pic you uploaded, it looks like it has too much clearance. Anyways ask the machine shop to measure the journals and let us know the measurements. They cut .010" does not always mean you need .010" thicker bearings. If the journals have already been cut .010" then you needed .020" thicker size. If you still have the old bearings that the block previously had, then check what size they are. The size should be stamped on the back side of bearings. In case if the old bearings show .010, then you now have the crank .020" cut and you have .010" excess clearance.

 

[Mech Addict]

My cranks ALL have assembly lube on them. I NEVER EVER put a crank in dry. You can easily scar bearings. The lube helps hold the plastigauge in place and also makes it easier to remove. Assembly lube or oil will only leave a slight film on the journals and that is good.
Remember, those journals SHOULD be as full of oil as they can get when the car is running and that oil takes up just a tad bit of space but its supposed to be there.
I shoot for .0015-.002" on mains and .002-.003" on rods. If it is tighter, that is good to a point, but in all my years, if you want a motor to "run", they like a little bit of looseness. (Cylinders too). Too loose of bearings and you have low oil pressure and that is bad. I use those tolerances on every motor, not just a 4g,.... Saturn, Dodge, Chevy, all of them.
To each their own, just the way I have done it for over 40 years and haven't had a failure yet. My DD Saturn with those tolerances has 40000 miles on it now 3 years later.
I have a new "secret" build going on in one of my profiles, it will get those specs also. You can find it under "My Other Baby", if interested.
Marty

Thanks for that perspective. When I read the plastigauge instructions, it does mention checking bearing clearance in an engine simply by dropping the pan, and wipe off excess oil, so your method would be no different for an fresh assembly. Not quite what the FSM instructs, but there are often multiple valid approaches. I would think a dry assembly would not cause damage As long as the crank was not rotated at all during the process, but wiping everything with fresh motor oil first seems like good insurance.

 

[arrowhead]

If crank had been cut, the machine shop should have stamped the new size on the crank.
I think there is a misunderstanding between parties.
Mandy

 

[1990TSIAWDTALON]

I am only pointing out that the crank should never ever touch the bearings as it "floats" on a film at all times. Assembly should always be done with correct lubrication after all parts are clean and dry.
As @arrowhead points out, the machine shop USUALLY marks the crank as M - .010 R - .010 or whatever work the crank has had performed, onto the crank on a throw, normally throw #1.

Edit. Here is what one of my other projects has stamped on it.
Sorry its upside down. But you can see the markings.
Pops

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[1990TSIAWDTALON]

I would think a dry assembly would not cause damage As long as the crank was not rotated at all during the process, but wiping everything with fresh motor oil first seems like good insurance.

That is the "trick", keeping the crank from moving AT ALL When taking main caps and rod caps off, it is tough to keep the crank absolutely still, with no movement. The slightest movement with metal on bearing will marr the surface (and smear the plasti-gauge) so you need to be extra careful to not let the crank move if assembling dry for measurements, but I don't recommend it is all.