Using Plastigage on bottom end bearing roll

I’m about to roll in new big end and main bearings on my CAT 3408 at the 8,000 hour interval which is a little over from last time. Do you guys use Plastigage on a preventative maintenance install like this or just roll the new bearings in without checking? We didn’t check last time but this time I’m thinking about it.

Would you re-use the main bearing cap bolts and con rod nuts and bolts? The cylinder packs have done 15,500 hours, main bearing cap bolts original I think.

Also last time with the torque-turn method of tightening main bearing cap bolts, we used a 1” drive impact wrench for the final turn after first using a torque wrench as per the manual, but I’ve since found an impact wrench isn’t a good idea for that final turn. I was thinking of buying one of those 3/4” drive torque multipliers which some guys use on wheel nuts. Ideas on this? Thanks.

 

You will likely not find a spec for plasti-gauge. Say it is off or out of your comfort zone? What are you gonna do next? I say roll them it with a visual and feel inspection. It’s a lot more work to torque them all just to check and then do it all over again. I just send them with lubriplate. Bolts are Ok to reuse on bottom end.

Torque turn with impacts is fine. A stout 3/4 gun is most times enough but whatever gets it there.

 

Gravity will fight you to use plastigage. To use it, you would have to hold up crank to get accurate results. Measure and check old ones, inspect crank with fingernail and roll on. Countless engines put together everyday with impact to get final turn. Always good idea to use new main and rod fasteners. Make sure use proper lube on fasteners which is engine oil. Rods you easily check clearance with Plastigage (0.0028-0.0066") 0.071-0.168 mm.

 

I rarely use plastigauge on a bearing roll unless I’m hunting an oil pressure issue. Or something about the old ones really catches my eye. As far as the main bolts I reuse them and put new rod bolts and nuts every time.


Those torque multipliers are the only way to go in my opinion


I have used an impact I can’t count the times never had an issue.

 

I’ve always done rolls on my 34XX series engines right around the 250,000 mark and I’ve never had one come apart showing copper on any of the shells. The Brakesaver engines tend to beat on them a little more than the others but I never found anything that made me do any more than lube up the new shells and shove them in. There’s a couple of schools of thought on the impact thing. Marine and Aircraft engines have been a part of my world since I was a little kid. Use an impact gun on a torque to yield fastener in an aircraft engine you’ll probably get your fingers rapped over it. That said I see truck engine mechanics doing it all the time. Myself, I’ll disassemble them with a gun, but I put them together with the large bar with a torque multiplier and indicator gauge on it. Not my place to say what’s right or wrong, I just know what I do and I haven’t had one blow up yet.

 

Hi All
Thanks for the replies.
Just found out there is nil stock of main bearings in Australia, CAT are waiting on back order from USA.
There are aftermarket IPD bearings available here, what is your opinion on them? I would prefer genuine CAT, but the engine is over hours and the CAT delivery is some weeks away.

 

The shop I worked at I did a lot of in frames on Cat motors with many IPD and Interstate McBee kits . Never had any problems with them. They were local companies , so if there was a problem we would have heard about it really quick. These were Michigan trucks running well over 100,000 pounds , so the motors were working hard.

 

I build a 3406B a few yrs ago for a truck I built to sell. That engine is IPD from the head down. It’s still local to me and I know it just had a bearing roll so there’s at least an interval in the bearings. It’s a b-train tractor, and knowing him, more likely 300k plus before he got around to the roll. To be honest the only thing I didn’t like were the piston oilers they sent in the kit. Don’t know what it was about them, material, manufacture, I don’t know. I just didn’t like the look of them. I used the ones out of a Cat kit I had for another engine. Could have been a supplier problem, I was at the shop up the road recently and saw a kit he had, and the oilers in that kit were different. He uses IPD stuff, and most of what he builds are b-train tractors and logging trucks. Beyond that everything else was great. I got the calipers and micrometers out and went all Sherlock Holmes on the parts just because I’m like that. I measured flanges, walls, o-ring lands, bore. Same with the pistons, rings and rods. I mean I checked it all. I had brand new Cat stuff there to compare it to, so why wouldn’t I. Everything was spot on in dimension to the Cat stuff. I’d have no fear, shell ‘er up and get going.

 

I have used IPD kits also. Look equal to Cat platinum kits to me.
Kind of a roll them and go guy here also. It is also easy to mic the rod journals. If I did not like the finger nail test results plasti gauge the old bearings. If they were in spec I have hand polished many cranks in the block.
That is no ordinary engine you have. It is very expensive and I would spend some extra time on it. Check at least the front rear and center main bearing clearance. Core shift can happen. I would be more concerned about not enough clearance. One locked down when the new bearing shells were put in. You can just run them up with a 1/2 inch impact for this. No need to stretch the bolts again. Check the rod ends and or just have them remachined.

 

I have used PAI and IPD bearings. Not a thing to worry about in my opinion