Rod Bolt and bearing questions??

[arthur39]

getting ready to install new rods and pistons. Got a few questions though. I'll be using the plastigauge for bearing measurements and stretch gauge for rod bolts. Question is to get an accurate  measurement of the bearings, will I have to torque and stretch the new rod bolts to see if the bearings are within spec. Am I going about this right? a bit concerned about torquing the rod bolts 2 to 3 times to make sure the bearings fit right. Is this what u guys do?

[Johnnnycheese]

I used to use plasticguage but you will never know what you really have with that stuff.
bore guage and a mic that goes 4 decimal places to the right

[speedduck]

Engine builders usually say not to use the same rod bolts for measuring with plastigauge and final assembly. I don`t know why, because bolts seem to return to original length when unfastening. I have used Carrillo rods with same bolts over and over again, maybe pushing my luck 

[Competition CNC]

I used to use  but you will never know what you really have with that stuff.
bore guage and a mic that goes 4 decimal places to the right

+1 use good quality measuring tools and get a set of gauge blocks.  Throw away the plastigauge, it cant tell you if a journal is out of round, or tapered.   And rods need to be checked in 3 clock positions so you know if there round.

you can reuse some bolts several times. You need to document them in your blueprint sheet.  oal,torque,stretch, each time there cycled.  If one doesn't return to within.001" of its natural oal then its junk.   Some times its 3 times some times its 10 times.   You never know.  This is why your builder needs to keep all his blueprint sheets on file for your engine so it can be referenced.

Your builder does have all the sheets right?

[speedduck]

Measurements are on some paper somewhere and hopefully found when needed.
So, let`s say if you got block main bearing code AAAAA and you are installing billet crankshaft, what colour it mostly has been ? Is it mostly on the thin or thick side ?

[arthur39]

ok thanks,  good to know, I have a brand new set of crower rods and wossner pistons going in, with spec sheet., The rest of the motor has been built for a turbo,  just didn't have the funds to go the extra mile last year. THis will be the first time crank and pistons will be touched with a motor with 6k. I will mic everything just to be sure. Good to know about the bolts. I will keep an accurate log.

[Competition CNC]

Forget about all the codes on the rods and cases.
Assemble the cases and rods with all the same color bearings in them without the crank in the motor.  Make sure everything is torqued and or stretched to spec.
Then use a bore gauge and measure each main and rod bearing in 3 clock positions and on both sides of the oil groves.
Measure the crank the same way and then do the math and select the proper bearings.
Put the selected bearings in and remeasure everything again.

[speedduck]

Ok, now i measured every bearing and it shows adequate clearance for mains, but when torqued crank got stuck, more measuring and crank is crooked .001". So, what would be acceptable tolerance, can i have perfectly straight crankshaft ?

[mike46]

Forget about all the codes on the rods and cases.
Assemble the cases and rods with all the same color bearings in them without the crank in the motor.  Make sure everything is torqued and or stretched to spec.
Then use a bore gauge and measure each main and rod bearing in 3 clock positions and on both sides of the oil groves.
Measure the crank the same way and then do the math and select the proper bearings.
Put the selected bearings in and remeasure everything again.

That sounds like a lot of work.

[arthur39]

I mic'd everything, and referred to the case numbers, since these have been matched from the factory, this gave me a chance to order the proper bearing first, since they are over 200 dollars for all of em, don't want to waste money on these, they were all black and one brown, when they come in I will check everything again and use plastigauge in 3 spots on the journals and see what I get. Black should get me to .002 on the rods and .0015 on the mains. that's what i'm shooting for. 

[entropy]

Forget about all the codes on the rods and cases.
Assemble the cases and rods with all the same color bearings in them without the crank in the motor.  Make sure everything is torqued and or stretched to spec.
Then use a bore gauge and measure each main and rod bearing in 3 clock positions and on both sides of the oil groves.
Measure the crank the same way and then do the math and select the proper bearings.
Put the selected bearings in and remeasure everything again.

That sounds like a lot of work.

re-building the motor is a lot of work... 

whatever Jim says, I take to the bank. 

[mike46]

Forget about all the codes on the rods and cases.
Assemble the cases and rods with all the same color bearings in them without the crank in the motor.  Make sure everything is torqued and or stretched to spec.
Then use a bore gauge and measure each main and rod bearing in 3 clock positions and on both sides of the oil groves.
Measure the crank the same way and then do the math and select the proper bearings.
Put the selected bearings in and remeasure everything again.

That sounds like a lot of work.

re-building the motor is a lot of work... 

whatever Jim says, I take to the bank. 

No shit. I have 3 sitting in my shop and a cbx engine that has to come apart. I was just busting balls.

[Competition CNC]

Yep, blueprinting an engine is very time consuming.  Thats why very few shops do it. 

As for the crank not spinning. We measure the crank run out on every crank when its being spun up on the balancer.  As long its under .001" its ok.  If its over .001" we straighten it. The same goes for the cams.

If the crank run out is under .001" and you know the clearance on all journals is .0015" and its binding then the cases need line honing on the mains or the thrust clearance is too tight.

Line honing on these engines is very tricky.  There not like a SBC engine to do, you cant just cut the caps, you need to lap the cases.  Not an easy task to do correctly.  We have a very flat special lapping table that we use for hand lapping Porsche cases and bike cases as needed during the line honing process.

But once its all done, a straight crank riding on a new set of bearings with the correct clearances will spin very freely. Very freely.

[KZScott]

Jim, how much material is usually removed from the case halves when lapped? or is that custom for each build?

[Competition CNC]

Jim, how much material is usually removed from the case halves when lapped? or is that custom for each build?

Scott,  it depends on how large the main bores are and how out of align they are.  we have a procedure for mapping the concentricity and cylindricity and then calculate the aprox material needed to be removed from the main bearing bores.
Then we know how much to lap the cases before honeing the mains.

[entropy]

Jim, do you have to bore/hone the trans bearing mounts also after lapping?

[Competition CNC]

Jim, do you have to bore/hone the trans bearing mounts also after lapping?

Karl, thats an excellent question!!!  No, because of the way we lap the cases.
But, if you remove too much material from the tranny shaft bearing bore mating area then the cases are either junk or you need to use a special jig to bore the cases for the tranny bearing.

[Jbriggs]

Forget about all the codes on the rods and cases.
Assemble the cases and rods with all the same color bearings in them without the crank in the motor.  Make sure everything is torqued and or stretched to spec.
Then use a bore gauge and measure each main and rod bearing in 3 clock positions and on both sides of the oil groves.
Measure the crank the same way and then do the math and select the proper bearings.
Put the selected bearings in and remeasure everything again.

So how do you decide which color to begin with? By measuring the journals? Really don't want to buy "extra" bearings if I don't need to...

[Competition CNC]

You measure the case and rod bores with bearings in and torqued with a bore gauge.

Then measure all the journals on the crank and do the math.   You will need an assortment of bearings to get everything right on the money.

[nappinj12]

i know this is old but, what brand bore gauge do you guys use. mine marked bearings up  also why would you measure at 3 oclock with bearings installed to get oil clearence. 12 oclock would be better, i could see 3 oclock for checking roundness without bearings in

[Stainless1]

OK, reread the bore gauge part... 3 clock positions, not the 3 o'clock position
I use a Standard Gauge dial bore indicator, and yes, it might leave a mark on the bearing, but it is not scratching it.  Your indicator needs to read to .0001 (tenths) to measure accurately.  If you are using telescoping bore gauges and trying to measure those with a mike, you might be giving up some accuracy. 
Good luck with your project.

[nappinj12]

lol i had 3 o-clock stuck in my head  was wondering how that was done. i have a cheap bore gauge but, i was thinking on getting a sunnen

[Competition CNC]

Don't worry about the marks in the bearings, they are only visual and don't have any depth.  They will not cause any problem.

I do not recommend using snap or T gauges at all for this type of measuring.  You can not measure .0001" with a T gauge.  To even get .001" repeatability takes a lot of skill that very few people have.
You must use a bore gauge.  SPI makes affordable bore gauges that work fine.  Just make sure the dial reads .0001" not .0005" or .001"

[LVBUSA]

Old post. Terrific technical info. Thanks everyone !

A.

[knecum]

Wow, so complicated. I can count on 2 fingers how many engines I've seen with a main bearing problem and I build very few engines.  Lol. If your using the same crank that came out of the cases just put the same color back in especially if it looked good when you split the cases.  Geez😉

[knecum]

Carry on!!

[LVBUSA]

Steve,

 What kind of bore gauge are you using ?.  I need one that will reach the center main.

Thanks, Adam