Quote:
Originally Posted by BimmerMan33
Agree with Solo M Tech's post above, changing rod bearings is probably a band aid but with increased clearance bearings the band aid might last to 175-200K miles, at which point this platform would be quite old and most people might move on to other cars/newer M3s.
For those who still hang on to their cars, might then consider an engine out rebuild and refresh/upgrade a bunch of other engine components as well, including main bearings, maybe make it a stroker motor or other etc...
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Unfortunately there isn't any evidence that the increased clearance really extends service life, since like I said before, each engine is different. I've pulled bearings at 22k miles and they were wiped, and I've pulled bearings out of a 113k mile 1 owner that were in almost new condition with minimal wear. I've pulled bearings with minimal wear but the parting lines were down to the copper, indicating the rod bore is out of round due to improper torque. While the extra clearance may be beneficial for the first candidate, it may not be for the latter. Same can be said for changing OE bolts for ARP, it might be the perfect solution for one engine and cause an out of round condition for the next. Ideally you should look at the wear on your OE bearings, take clearance measurements, install new bearings and repeat. Adjust until you obtain the proper clearance. Also anytime you replace the rod bolts you should check the rod end for an out of round condition with the bolts torqued. This requires an engine out experience. While we can all agree that changing your bearings out for any of the available kits ( BE, VAC, WPC, ACL, KING etc) is a very smart idea, it's not a cure all for every engine. Just the majority.