Amb engine clearances???

[EuroxS4]

Hey guy I am looking to check my crank bearing and rod bearing clearances.However I am wondering if anyone has the correct procedure from the repair manual???Anyone use plastigage???


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[diagnosticator]

AMB

Crankshaft main bearing radial clearance: New: 0.02 to 0.04 mm; Wear limit: 0.15 mm.

Connecting rod bearing radial clearance: New: 0.01 to 0.05 mm; Wear limit: 0.12 mm.

Factory repair information specifies Plastigage for measuring main and rod bearing radial clearance.

[Kevin C]

Hey guy I am looking to check my crank bearing and rod bearing clearances.However I am wondering if anyone has the correct procedure from the repair manual???Anyone use plastigage???


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My experience building motors. Every few years I end up building an engine. It seems that over time I do it less and less. It might be that I got better at it and they last longer, or that i bought a house and every free cent seems to go to a mortgage and maintenance. . My experience is that modern motors are factory built to pretty exacting tolerances and just matching what the factory did can be challenging.

In my home shop I have a good selection of measuring tools. I have measured mains using dial bore gauges, as well as snap gauges and a micrometer. Then used a set of micrometers to measure the crank and get the actual clearance.

Comparison measurements are always nice since the calibration of the gauge is not an issue. You're only looking to measure a difference, and not come up with an absolute number (bore diameter). This is why some shops like to fit pistons to the bore. Measure the pistons OD with a micrometer, measure the bore with a snap gauge and use the same micrometer to measure the snap gauge and you have the clearance. You may not have a perfect absolute diameter measuremnt, but you do have the important number, running clearance. Accurate absolute numbers take a bit more work. You need calibrated tools and a controlled environment as well as an experienced operator.

The same thing applies to rod and main bearings.

1 Dial bore Gages: I have a set of Mitutoyo gages. Very nice, but the contact surfaces are small and they sink into the bearing a few tenths. The softer the bearings, the worse the issue. Also, I hated the marks it leaves in the shells. It never seemed to hurt anything, but if it can be avoided, why not? The measured clearance always seemed to end up .0002 to .0004" large (.05 to .01mm) from the actual. A lot of work for the wrong number. On the last motor I was working on, that was enough say I had enough clearance when in fact the mains were too tight.

This was on a motor that was notorious for having bearing issues when the boost gets turned up.

2 Snap gauges: The standard method if your making measurements. It still takes a good feel to get the gauges square to the bore and get an accurate reading. You then need to measure the snap gage with a micrometer. Take the same gauge and measure the crank. Subtract the two to get your clearance. Getting a good repeatable number on the crank is easy. One thing I never liked is on un-hardened steel cranks, how easy it is to leave a mark. Hardened cranks? Easy, Cast iron also seems to be a bit more forgiving. Getting a good repeatable number on snap gauges takes a bit of practice and a good feel.

At work we sometimes refer to gauge R&R studies as a method to determine if a measurement system is acceptable. Mostly because we make measuring devices and we need to know if they really work. When I build an engine, the same thinking comes to mind ( occupational hazard?). The two steps needed to get the ID of the bearing bore provide a couple of opportunities for error if your even off a little with the squareness of the tools.

http://support.minitab.com/en-us/min...age-r-r-study/

Personal experience says that a plastigauge is a great tool and more much less likely to have operator introduced measurement errors. It looks like a shortcut method, but in my experience, it's a great sanity check if you took all your measurements the hard way or fine all on its own.

It may sound like I'm nit picking on tiny details. On the last engine I built the measurement error was enough to say my mains were in spec when they weren't. On a performance turbo engine know for bearing problems (non 1.8T), it's not a risk I wanted to take. The upside, is it's easy to open up clearances, getting them to be tighter, not as easy.

Short story? Plastigauge.

[EuroxS4]

AMB

Crankshaft main bearing radial clearance: New: 0.02 to 0.04 mm; Wear limit: 0.15 mm.

Connecting rod bearing radial clearance: New: 0.01 to 0.05 mm; Wear limit: 0.12 mm.

Factory repair information specifies Plastigage for measuring main and rod bearing radial clearance.

Thanks!!I have those specs.I was more interested if the clearances need to be measured with the old bolts torque to 65nm or with the new bolts torqued to 65nm to get and accurate measurement.From what I know and believe.I think I just should good with the old bolts torqued to 65nm.As the bolts dont really strech until you do the additional 90 degrees correct??

Readings with the old bolts looked to be on the money.The front bearing just above the NEW spec.

Front crank bearing : .051
2nd crank bearing : .038
3rd crank bearing : .038
4th crank bearing : .038
5th crank bearing : wasnt able to beasure as I didnt pull the rear main seal.Cant get a socket on it at this time.Will measure once its off the stand but at this point its safe to say its within spec.

From personal experience almost always the front crank bearing is always higher than the rest.

I gotta say im pretty surprised being that this engine has over 176k miles on it.

[Kevin C]

Thanks!!I have those specs.I was more interested if the clearances need to be measured with the old bolts torque to 65nm or with the new bolts torqued to 65nm to get and accurate measurement.From what I know and believe.I think I just should good with the old bolts torqued to 65nm.As the bolts dont really strech until you do the additional 90 degrees correct??

Readings with the old bolts looked to be on the money.The front bearing just above the NEW spec.

Front crank bearing : .051
2nd crank bearing : .038
3rd crank bearing : .038
4th crank bearing : .038
5th crank bearing : wasnt able to beasure as I didnt pull the rear main seal.Cant get a socket on it at this time.Will measure once its off the stand but at this point its safe to say its within spec.

From personal experience almost always the front crank bearing is always higher than the rest.

I gotta say I'm pretty surprised being that this engine has over 176k miles on it.

To get an accurate measurement, you need to have the housing torqued to its final value. The upside is that it will only reduce the clearance slightly, so your good. The initial torque on a TTY bolt set the preload. In that range the fastener is supposed to deform elastically ( stretches and will return to its original length). The 90° turn is supposed to put the fastener into its inelastic range. The clamping force increases to a level where it permanently deforms.

Since you using old bolts, yours have obviously deformed once. The issue is they lose repeatability and will deform at a different clamping force. As a bolt deforms, its initial strength goes up as it work hardens. Past a certain point, the bolt starts to neck down and looses clamping force. The strength per square inch of material is still increasing, but not as fast as the bolt is losing diameter from deforming.

If your old bolts have not deformed past the steep fall off from necking down, you can still continue to tighten them to increase your clamping force. If you notice that the torque needed to rotate them is dropping off as you turn, they are done and won't get you an increase in clamping force. The increase in clamping force might decrease the clearance as the bearing shells get further compressed in the housing and the housing obtains its actual running dimension (the block is machined with the mains fully torqued).

This is all academic since with old bearings you would only be concerned with too much clearance, and its pretty much impossible to go the other way.

Short story, nice to see they held up so well after so many miles and they may even be better than your first set of numbers would indicate. You could have plastigage them using 65 ft lbs and then a small increase in rotation. 45° degrees might just be enough to simulate the correct preload or just get you a bit closer. Not as good as using a new set of bolts and then throwing them away, but a bit better than just using the TTY preload.

I'm sure there is a procedure in the manual that outlines how to measure without throwing away a set of bolts, but the only way to get an accurate measurement is to use the fastener preload the motor will be run with, fortunately yours is fine. Before taking the old bolts out you could mark them for location and rotation that would get you to very close to the original clamping force. Could be a cheap way to get the correct clamping load with used fasteners.

[EuroxS4]

To get an accurate measurement, you need to have the housing torqued to its final value. The upside is that it will only reduce the clearance slightly, so your good. The initial torque on a TTY bolt set the preload. In that range the fastener is supposed to deform elastically ( stretches and will return to its original length). The 90° turn is supposed to put the fastener into its inelastic range. The clamping force increases to a level where it permanently deforms.

Since you using old bolts, yours have obviously deformed once. The issue is they lose repeatability and will deform at a different clamping force. As a bolt deforms, its initial strength goes up as it work hardens. Past a certain point, the bolt starts to neck down and looses clamping force. The strength per square inch of material is still increasing, but not as fast as the bolt is losing diameter from deforming.

If your old bolts have not deformed past the steep fall off from necking down, you can still continue to tighten them to increase your clamping force. If you notice that the torque needed to rotate them is dropping off as you turn, they are done and won't get you an increase in clamping force. The increase in clamping force might decrease the clearance as the bearing shells get further compressed in the housing and the housing obtains its actual running dimension (the block is machined with the mains fully torqued).

This is all academic since with old bearings you would only be concerned with too much clearance, and its pretty much impossible to go the other way.

Short story, nice to see they held up so well after so many miles and they may even be better than your first set of numbers would indicate. You could have plastigage them using 65 ft lbs and then a small increase in rotation. 45° degrees might just be enough to simulate the correct preload or just get you a bit closer. Not as good as using a new set of bolts and then throwing them away, but a bit better than just using the TTY preload.

I'm sure there is a procedure in the manual that outlines how to measure without throwing away a set of bolts, but the only way to get an accurate measurement is to use the fastener preload the motor will be run with, fortunately yours is fine. Before taking the old bolts out you could mark them for location and rotation that would get you to very close to the original clamping force. Could be a cheap way to get the correct clamping load with used fasteners.

Well I just used the old bolts because I didnt have new ones.New ones have been ordered.I just wanted to check the clearance for myself to make sure I didnt have any issues.However new ACL Race bearings will be getting installed along with new oem bolts.I know alot of people swear by the billet mains and arp bolts but I have yet to see the oem main bolts fail on a engine build.Unless the engine is making well over 550whp thats a different story all together.

[Kevin C]

Well I just used the old bolts because I didnt have new ones.New ones have been ordered.I just wanted to check the clearance for myself to make sure I didnt have any issues.However new ACL Race bearings will be getting installed along with new oem bolts.I know alot of people swear by the billet mains and arp bolts but I have yet to see the oem main bolts fail on a engine build.Unless the engine is making well over 550whp thats a different story all together.

Just so you know, I would have done the same thing... Mostly I'm just beating a dead horse Seriously, I figured that an extra explanation might help some others that are building engines and or learning how to blueprint an engine.

[EuroxS4]

Just so you know, I would have done the same thing... Mostly I'm just beating a dead horse Seriously, I figured that an extra explanation might help some others that are building engines and or learning how to blueprint an engine.

Yeah I hear ya.It would be good to put together a thread or something like that.For those that want to build their own motors have a decent guide and accurate information.I personally Just dont have the time.The free time that I do have i devote to my family,honey to do list and of course building motor for my personal cars when im not building motors for clients.

[Kevin C]

Yeah I hear ya.It would be good to put together a thread or something like that.For those that want to build their own motors have a decent guide and accurate information.I personally Just dont have the time.The free time that I do have i devote to my family,honey to do list and of course building motor for my personal cars when im not building motors for clients.

This is my free time... An Hour of procrastination before I go out and finish / start whatever house project I'm involved with because its still too early to make noise. The working for living thing seems to get in the way. Most of my car projects are waiting for rainy weather when I can't work on outside home improvement projects.