Don Terrill’s Speed-Talk

In an another thread the mention came up of dial bore gauges leaving marks on bearings.

My machinist refuses to use even the Sunnen dial bore gauge on new bearings. He hates marking up bearings. His thirty years of experience has him getting his main bores and rod big ends dead nuts and then trusting the bearings will be what they're supposed to be. Works for him.

Just me, but I've not found the light marks from a dial bore gauge to do any harm to the bearings and sometimes it's just a comfort to know the torqued bearing ID is what it's supposed to be.

What are the experiences here? How often do you find name brand bearings to be off size?

I've asked this question before myself. Having recently stripped a couple of engines I personally built, and measured bearing ID with a bore gauge, I can tell you that those marks I left back then are still there now. I can't see any issues, & will be leaving them for another season. You can't feel them, just visible.
As far as bearing manufacturer tolerances go. Well, again I can say you need to check clearances and not just rely on std being standard and 10' under being 10' under. I'm in a situation now that I've measured a set of Glyco(FM), King & Clevite shells and they all vary. Glyco tightest, King loosest in my case. 0.02 mm is the difference. 0.02x2 shells= 0.04mm! That's 2/3 of my total clearance. I'm going to linish the crank a little and set clearance where I want. I actually prefer them tight so I can do this.
No experience with American v8 ' s unfortunately so can't be specific to the majority here.

Kings v clevites, yes i have found differences of up to .001". Personally i prefer an inside mic to measure brg clearance on every thing i screw together and record the measurements that way i am certain of what clearance it had when it left.
When there is a failure from whatever? and things turn nasty in a legal sense at least you have a record to back up you work to verify it was in spec when it left. The older i get the less i leave to chance. No she'll be right mate.

If the marks bother you ,you can use Plastiguage for installed clearance [this won't check for bore distortion ].
I have found a wipe of oil with the finger minimizes the marks.[bore gauge pins also need to be replaced at intervals] I have yet to see a bearing fail from being measured and confirmed ,with, a witness from being checked,, i have seen bearing faults from not being checked and presumed to be on spec.

I am with you Packard , i need to see a confirmation on everything ,gaps, clearances,side plays, interference's, everything. If checking is always a part of your routine the job takes no longer.

Cheers.

You can check the bearing thickness, amount of interference fit, housing size, then you can know what the ID should be without measuring it, but to make sure you did all THAT right......

Bearing manufacturers are all over the place. The farther a motor gets from current production the worse its gets. If you don't like the marks put them get in the solvent tank and scotch brite them. Heck you can take a piece of paper and and almost polish the bearing.
The marks from the gauge do nothing. The one with marks are the best because they were the ones you didn't have to work on. I can't tell you how many times I've had to sit in the solvent tank and scotch brite a .0005" out of main shells because we torqued it up and had barely over a .001" main clearance, with Clevite especially. Even if you sand them til a hint of copper shows. Ford made bearings for a few years that had no babbit , just metal and copper. People used to take those engines apart and think it was toast, but the crank looked and checked perfect.
Mixing different brands isn't totally uncommon if that it what it takes to get your clearance right.
My favorite was fairly recent, we had a custom crank made. We got it and it looked beautiful. We throw the mic on it and it .0005" under the low. We get the block back and the align hone is .0002" over the split, put he bearings in it and we have .0032"-.0035" main clearance. So we sit and ponder what were gonna do. We could sand the caps a .0005", we could send bearings out and have them coated etc. We go digging through the archives and fine a set of -.002" factory ford bearings. Okay well that will take us from .0035 to .0015" well we don't like that either. Solution we use -.002 shell in the block and Std. shells in the caps. Torque it up and we have a good average of .0025" and good fallout to the sides. That motor was runs like a top has perfect oil pressure.
When the clearance is right its right, but you won't know unless you put a gauge in it and check it.

I use feeler gage stock for the dial bore gage to ride on and then add that thickness to the reading.
reed

I call them shadow marks. Has no effect on anything. The oil wedge would leave them there. IF they disappear then it's been a bad day or the engine is high mileage.

I can take this obsession with shadow marks a step further.
I had a CAT mechanic fresh out of school and knew everything about everything.
He got absolutely apoplectic about seeing the dial bore gauge mark on honed cylinder bores.
Explaining that he was seeing something that was counter to the hone hatch didn't register.
Explaining that the mark would disappear by the time he backed the unit out of the bay did not register.
He was convinced his 3208 diesel was going to be a compression and oil leaker. He was dead serious about this.
Seeing a dead end street here I gave the cylinders one more swipe after final measurement.
All was right with the world again.

I check them with the bearings torqued in the block and a bore gauge. My machinist tells his employees when they are checking bearing clearance "If you do a good job those marks will still be there when it comes back to get freshened up next season". Another engine builder I interned for in 2010 checked them the same way. Both build tons of circle track engines. I have done it that way for a while and have never had any issues as the marks usually are there when they come back apart given that they haven't had some sort of failure. As far as bearings, I only have experience with king. Some are perfect and some aren't. I have never went into depth figuring out if its the bearing or block. I just do what I have to, to get it right and move on.

I'm not one to chase reasons much either. I just get the combination that gives me what i want. As for the marks, they are USUALLY there when disassembled. Being as gentle as possible helps (I believe anyway).

Over the last several years, I have seen a whole lot of variation in size from one box of bearings to the next. I use mostly Clevite bearings and there is no way i would assemble an engine without checking clearance with a dial bore gauge. Had a set of standard 350 main bearings just last week that only yielded .0008-.001 clearance on a crank that was on the low side. Grabbed another set off the shelf, and got .002-.0022. Same part number, different batch number. Ended up using X- bearings and got .0033-.0035.

If bore gauge markings are disconcerning, simply run a surface profilometer over the
affected area to determine their actual depth relative to the bearing or bore surface.

If the marks are deep enough, they will still be visible when the engine is disassembled.

modok wrote: ↑Wed Mar 13, 2019 4:03 am You can check the bearing thickness, amount of interference fit, housing size, then you can know what the ID should be without measuring it, but to make sure you did all THAT right......

Not every time!! A quick check is with the outside mic and the dial gauge.
If you have way too many #s you get confused.

Unless you have a #75 pound spring on the dial you are fine with the little mark they leave

af2 wrote: ↑Sat Mar 16, 2019 6:44 pm If you have way too many #s you get confused.

Nope. I use a calculator.
If you want to see what confused looks like, watch me try to use an adding machine.

modok wrote: ↑Sat Mar 16, 2019 11:53 pm

af2 wrote: ↑Sat Mar 16, 2019 6:44 pm If you have way too many #s you get confused.

Nope. I use a calculator.
If you want to see what confused looks like, watch me try to use an adding machine.

I hear you!