Mikester

Below is a quote from a builder/fabricator named Rutger in the Netherlands whose skill, knowledge and expertise I have immense respect for. Not trying to sway anyone either way... but I am a firm believer in gathering as much info as I can before making parts choices so I thought I would share this with everyone:

"I've noticed people tend to think ACL bearings are some sort of gift to your engine and add to the spec list. I've so far found out the exact opposite. When I had a vg30dett rebuild few years back the shop supplied with me with stock fit ACL bearings. Plastigaged them, way to loose (like 1,5 times the stock maximum clearance). When I rebuild my brother's sr20det, I received ACL race bearings as the normal type had run out. Their clearance was 0.08mm vs 0.02mm max according to the FSM. That crank had the 'thickest' Nissan indexing and was not worn or ground down. When the 'normal' ACL type showed up, they were 0.055mm, again way to much. I eventually ordered the bearings from another manufacturer and they cleared correctly.

Now this may all seem like a coincidence to me till I ripped my old ca18det apart last week. That engine ran for 18.000km after a rebuild (with ACL main bearings) but was eventually removed cause I started on the vg30 project. The only thing wrong with that engine was oil consumption (replacing the piston rings wasn't enough at the rebuild), about 1 liter per 1000km and a slight lifter tap but it ran fine and was always filled up with full synthetic oil.
When I took the crank out, all bearings were worn to the metal on several spots. If the main ends are too loose the big ends get less oil pressure as well. I did not check the clearance on these bearings upon assembly and trusted the advice of the shop who told me these were the right bearings for an unmodified crank. None of the other oil-lubricated parts on that engine showed any wear. Pretty odd how just the crank and big end bearings were badly worn huh?

I don't believe in race bearings, and have never heard an expert say they exist. The bearing is just a part of the assembly. It's the oil that gets in between that does the work.I know true racing rods are often 'oval' shaped at the big end to allow the rod to pull the sides of the big ends together at extreme rpm's. By using more clearance at the sides, the bearings won't touch the crank. Has dick to do with the bearing in between.
The bearings are the stock fitment according to the word on the ACL box. Nissan works with thousands of mm's for it's grades, but the difference between the smallest and largest is often just 0.02mm. Therefore, most aftermarket bearing manufacturers use just 1 replacement size that's an average of the Nissan clearances (apart from undersized bearings for ground cranks). Tell me how it's possible that 2 sets of ACL bearings have abnormal clearance when another set from a different manufacturer clears like it should.
A bearing with 4 times the FSM maximum clearance kills an engine faster than an old bearing that's just worn over the minimum thickness. Be smart, always check the clearances on your engine when rebuilding. And don't believe that 'race' logo on that bearing's box. I will NEVER EVER buy ACL crank bearings again. Total waste of money"


Rutger

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Food for thought...

--Mike

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