VAC Rod bearing condition after 13k miles

[Black Gold]

This is encouraging, thank you for posting

I think I would go vac over any other considering this information. Not to say others aren't good too, but this is a nice case study

[BPMSport]

Originally Posted by Helmsman

Title Mike - 13k miles. "First you go blind on are the eyes"...😊

Ah... Who reads titles nowadays? Thanks!

These bearings are at the top of my list now..

[Doc Oc]

Just plasti-gauged them. Surprisingly tight compared to other measurements I've seen. Looks like about .0017" of clearance by this, but I've seen them measured as loose as .002"

Edit: later found my torque wrench was set on 48 lbs instead of 45 which probably accounts for the tight measurement.

[SSJVegita]

sub for real issue of why the engine was making all that noise

[Doc Oc]

Originally Posted by Malek@MRF

The original coated VAC bearings did not however, and those bearings paired with the correct ARP hardware, also exhibited zero wear.

There is no question that the bearing clearances on these engines are far from where they should be and operating in a dangerous catastrophic range, but there are other factors involved too.

Do you think it's the bearing surface or the bolt clamping force that makes the difference? The vac's eccentricity is the same as oem 088/9 bearings if I'm not mistaken so it could only be one of the two right?

[Mvy]

I have the same VAC coated bearings, the ones before the clearance changed to open them up. I was worried it would be the same story as the last bearings but so far so good. Ive been running them 11k now. Ive had two oil changes and checked the filter each time. No flakes of coating were present in the filter after the oil changes. No unusual wear metals in my last oil test. Fingers crossed these hold up after I add a SC. Will probably still change them out in another 20k to see whats doing.

[Doc Oc]

Got the bed plate off. Main bearings are fine! A little worn but nothing spun or seized. Crank journals are fine. Gotta be in the vanos.

[doogee]

Originally Posted by Doc Oc

Got the bed plate off. Main bearings are fine! A little worn but nothing spun or seized. Crank journals are fine. Gotta be in the vanos.

Jesus, those don't look good at all.

[Doc Oc]

No, not really, especially the back two (top of picture) but they didn't fail so I'm stumped.

[CHE///MIST3]

Now get some VAC coated mains and this thing will spin like an air hockey puck! ....I wonder what the failure was?

GM

[Doc Oc]

A ringland failure has been suggested...or something went really wrong in the vanos. This whole thing started when I heard a noise at wot around 4k rpm that sounded a lot like detonation. Gotta find an easier way to check the pistons than pulling the heads.

[VictorH]

How fun!! Take it all apart and build a stroker! You've got the basis for everything you need, just add the parts (too bad they're a bit more than an LS3 for crank and rods). Add the high duration schrick cams and you can ditch the vanos too.

[Doc Oc]

Lol, everything I need except funds and ability! Probably going to sell it as is. Interested?

[whats77inaname]

Originally Posted by Doc Oc

Gotta find an easier way to check the pistons than pulling the heads.

Pull spark plugs and send in a scope?

[Gesler]

Thanks for the update. This is very encouraging for everyone else pondering this issue.

[pbonsalb]

Originally Posted by whats77inaname

Pull spark plugs and send in a scope?

You will see the tops but maybe not rings and ringlands. CR leakdown test.

[deansbimmer]

Mains look about average. Nothing alarming. The rear main looks more worn than usual though. It's usually the front main that's in the worst shape.

If a ring land failed you would usually see evidence in the cylinder wall. (Odd failure for a non boosted motor) A bore scope might work. I'd try that after a leak down test but before replacing a Vanos...

[pbonsalb]

HF has inspection camera for $79. I have a Milwaukee (all my 12/18V tools are Milwaukee) that should be comparable and dont think you would have the resolution to see the detail you want.

[Doc Oc]

Originally Posted by deansbimmer

Mains look about average. Nothing alarming. The rear main looks more worn than usual though. It's usually the front main that's in the worst shape.

If a ring land failed you would usually see evidence in the cylinder wall. (Odd failure for a non boosted motor) A bore scope might work. I'd try that after a leak down test but before replacing a Vanos...

I was surprised as well. The front bearing was actually the cleanest and they got progressively worse as you go back. The way that back bearing is beat up, might that indicate a ringland failure on one of the corresponding pistons. But could that type of failure cause a noise as loud as what I heard (wish I had it recorded)? I could see it causing the loud ticking that proceeded the failure but I don't see how a busted ringland could cause such a loud snapped rod type clank. Also didn't notice any cylinder wall damage. Obviously can't see a lot from the bottom but I put each piston at TDC and didn't see anything.

[admranger]

what's the mileage on the mains?

Vanos. One of Darth Vader's minions.

[Doc Oc]

Originally Posted by admranger

what's the mileage on the mains?

Vanos. One of Darth Vader's minions.

LOL. 73k.

[bluemonster]

Which rod bolts did you use with your VAC bearings?