Hi guys,
I am tracking my r53 and just have a couple of questions for you guys, my car has not spin a rod bearing, so I'm looking to replace the rod bearings with new ones as preventative maintenance, as i have not done this before, am i correct that as long as the motor has not spun the bearing, i can just get a standard size bearing set and replace it, no plastigage or anything? And also do i need to replace the bolts?

Cheers

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Yes, as long as you haven't done any damage to the crank (not just spun a bearing) and are working with a non-machined build (ie factory build or back to OEM spec build) you should be fine with the Factory spec replacement bearing size, without gauging it. (But again, check the Crank well) King Bearings are the most popular choice, besides OEM.
And yes, you DO need to replace the Rod Bolts, and should use the ARP's

Speaking of the ARP rod bolts, they are really the biggest reason I'd change the Rod Bearings strictly as a PM measure, esp racing the car. Because more frequent Oil Changes are the most important PM you can do.
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Thanks for the reply, what's wrong with just ordering new OEM rod bolts? Arp bolts seem to be a lot more expensive by a lot actually

 

There's nothing wrong with the OEM's, it's just that the ARP's are stronger with less chance of unwanted stretch, esp for a racing application.
You'll just have to ultimately decide.

 

Cheers bro, any other things i should do if I'm tracking the car? I am doing frequent oil changes, new factory oil cooler on the car, and all new seals so no oil leaks. Supercharger also serviced by me. Car does have 17% pulley, 380 cc injectors, step colder plugs and a tune from adrian cl. Not looking to be competitive as went to my last event and was almost dead last😅. Just wanting it to be beaten on and be reliable ish.

Also how do i check the crank? Do i just take the pan off, take offall the rod bolts and all the bearings, and see if they have scoring marks? If they don't, pop the new bearings in and torque to spec?

 

Basically yes, without a full "pull and disassemble" of the motor, it's really all you can do.
Exactly as you stated, look for scoring, and reinstall the new bearings and bolts.

Seems like you've cover your other bases.

 

A couple of things that may cause you to hold off on replacing rod bearings until it's time for a complete motor rebuild. And I only say this from the experience of building big block and LS motors for various applications and nothing more - I can honestly say I haven't ever laid eyes on a mini cooper's connecting rod. haha.

1. If you replace the factory rod bolt with an ARP fastner, the rod will likely need resized. The clamping force is drastically different at the desired rod bolt stretch value (which is provided with the ARP fastner). And getting a stretch gauge on a connecting rod bold that is in a motor is not easy and difficult to measure accurately as we are talking ten and hundred thou values. We usually measure rod stretch with the connecting rod in a vise (with proper clamping jaws), take the torque reading required to get the desired stretch, and then verify that torque value on 3 seperate rods t o validate. Then when assembling the motor the ARP rod bolts are torqued to that value that gives the rod bolt the necessary stretch.

2. If you are going to race your R53, consider the motor a consumable that will need rebuilt soon. There is a theory in the LS motor world that says if you open the crank case for any reason, you simply let the magic out and something will go wrong. What I mean by that is don't fix something that isn't broken. Other stuff will definitely break along the way and you will see all the bearings during your next rebuild.

3. When you pull the rod caps and pull the bearings, you will need to at a minimum polish the crank journals by hand, which requires the use of abrasives. The finest of abrasive residue will absolutely destroy new bearings - and I am talking the residue left by the sand paper used to polish the crank, which will be almost impossible to clean out of the crank case with the motor assembled and in the car.

I am assuming you are doing this with the motor in the car, only becuase if it is out there would be a number of other things you would be doing as well. And if it is out, consider a re-ring / hone with a full disassembly and assembly with new bearings and surface prep on the head and deck. With that, you would want to measure cylinder eccentricity with a dial bore gauge and other "blueprinting" tasks to make sure no other maching work is needed.

Just some thoughts and by no means absolute on motor work. There are some FB groups that are "sloppy ls" people that take a junk yard LS motor, slap a bunch of used unmachined **** together, and boost it to 750hp with a season of success. But when they fail, they failr catastrophically. haha.

 

Platigauge is cheap, a new engine is not.
You'd be foolish not to check bearing clearances, even if the crank is pristine.

 

If oil pressure is good and motor is happy, damned if I wouldn't leave well enough alone. There will be plenty mechanic time in your future soon enough.

 

Thanks for the info, I will keep it in mind.

 

There's no such thing as preventative maintenance on rod or crank bearings; there's only excessive wear and wear that's within acceptable limits. Take a hot oil sample and send it to Blackstone Labs; the results will tell you if you are experiencing excessive bearing wear. Engine oil provides a hydrodynamic wedge between these moving parts; contact between parts doesn't happen unless you've got tribology issues or mechanical failure. I worked on fighter jets for 28 years in the USAF, and I'm sure glad we didn't pull engines for preventative engine bearing replacements. We used oil analysis.