3.2 Carrera, spun #3 crank bearing shell
 

Hi Everyone

Recently tore down my 3.2 to find that #3 crank bearing was looking like kitchen aluminum foil. Took it to a recommended machinist and he mic'd the journal and estimates a grind is needed and may need +0.5mm oversized bearing. From some other threads here I found a +0.5mm bearing part which doesn't seem too expensive ($80 for both)

What worries me more is machinist says that mains will need to be ground as well and a oversized set of those seems to be very expensive

So all in all, with machining, magnaflux etc I would be approaching $1.5 to 2K and end up with a non-standard crank.

Anyone know of a good 3.2 crank or recommend a source? I think I'd rather go that way and stay with standard shells, which I'll need to get from our host anyway.

Thanks much for the advice

Mike

I sent you a PM
Bruce

Why not have Armando at CCR weld up and grind to standard the damaged journal? He is not far from Dallas.

Thank you Both for the advice. Will contact Armando today and discuss. Have told my machinist to hold off on the grind

Regards

Is welding a crank and different than welding a cam?

I see lots of threads where folks say you should never weld a cam, just grind it if needed. Yet, cranks get welded all the time...

I have pitting on 1 cam lobe due to a blocked spray bar. Would love to just fix that lobe rather than grind both cams, and redo all the rockers...

Thoughts?

Please keep us updated on what you end up doing on your crank.
I am thankfully not needing this, but was worried I would of ended up having the same issue with my crank and would have found a thread like this useful.

If it spun the bearing, wont the case be damaged as well? Finding a good Standard crank should not be too difficult. Getting the case right is likely easier said than done. Don't know why oversized bearings are always so expensive. There just curved metal.

Chris

Marine Crankshaft can repair your crank as well, with quick turn around times...

Thanks Everyone for your comments. Yes, I was thinking about calling Marine as well and see what they say. Will be sure to update the thread as to how I proceed. I'll take some pics of the journal before and after repair. The machine shop in Dallas (recommended by Zims) mic'd it and found about 6 thou wear on the journal. Not sure how much it affected the rod itself. Chris, you mentioned the case, not sure what you meant. Can you please clarify that. Yes, oversized bearings seem out of sight pricewise but guess it comes down to volume. Shame
I was told by the local machinist that he would need to grind the main shaft as well but not sure why.
Thanks to inputs from the forum experts though, I'm going to either work with CCR or Marine, so will let everyone know soon
What would we do without a forum like this. I know I would be totally lost. Nice to not feel alone

Crank Repair
 

Armando has done my crank work for years, single journal repairs are an easy way to fix the crank and remain STD, while your at it cross drill the #4 main journal and install a full groove #4 main bearing, Armando after the repair and heat treating finish grinds the journals and replaces the plugs.
Mike Bruns

The case where the bearing was spun will show wear on case journal from spinning the bearing.
I had this on the #7 journal and called about the fix, weld up and line bore to standard
Decision was to find another case and save a lot of time and lots of Monet.
Bruce

take material off the case half mating surfaces, then line bore main and layshaft back to standard so you can continue to use standard bearings. You will have an increase in compression, which may not be a bad thing depending on your performance goals.

The original post is confusing - it says #3 "crank" bearing is toast and journal needs repair, but then says the machinist says the main journals also need to be reground/repaired.

My supposition is the "crank" journal is the rod bearing journal? I don't think that damage to a rod bearing necessarily means the mains on the crank are going to be bad, much less that the case journals themselves are going to be out of round.

I'd get this straight before proceeding.

What you for sure will need is resizing of the #3 rod itself, as well as repair (whether welding to standard, or grinding to 1st undersize) to the crank #3 rod journal.

The "normal" rod bearings to go first are the #2 and #5, as those are at the center of the crank, the rod bearing surfaces are fed from the ends of the crank so these two are farthest from the source of oil, so a #3 is a bit unusual.

One might guess that from the sounds of all this that either the oil was run way too long, or there was some unusual contamination, or there was some oil starvation at some point. Has the mechanic discussed that?

# 3 rod bearing
 

I have fixed a number of motors with this failure.It is caused by the dreaded knuckle head owner who likes to get on the car before the oil is up to temp.# 3 has higher pressure when cooler than 2 or 5.The high pressure with thicker oil makes the failure.The oil cannot shed out the sides because it is thick and overheats the hardworking bearing from the knucklehead with the heavy foot.This is the same reason for most turbo charger units failing.Thick oil and spinning to 100,000 rpm cold smokes the bearings in a turbocharger because thick oil cannot provide proper lubrication.These failures occur on a lot of low miieage motors and the bearings on #2 & 5 look fine upon teardown.Fred

Fred - great point. Easy to forget (as I did) that in addition to providing the lubricating layer in the bearing, the flow of oil out of the bearing carries away the heat generated there.

Is a multi-grade synthetic going to be less susceptible to this cold oil problem?

different oil
 

Maybe a 0-20W synthetic would help but just waiting for oil temp to be 180 and then you can stand on it.Patience is a virtue with these beasts.