Need quick help..

[Superdave]

Here is the situation:

My 3500's crank was re-ground due to a bearing failure, the shop is having a hard time getting bearings for it now though.. They ground it 10 under on the mains and 20 under on the rods.

I need to find main bearings at .010 over (these should be the same as a 3400 would use).. and rod bearings that are .020 oversized.

Anyone have any ideas?

Thanks,
Dave

[IsaacHayes]

Hmmmm. Any place make custom? Probably cost a lot. So rod bearings are the only problem huh? Offset grind time and stroke it? LOL

[ForcedFirebird]

Your machine shop should have access to more resources than here


The tangs will be the problem, bearing size should be available.

[Joseph Upson]

It's apparent they didn't realize what they were dealing with, as I've indicated before, when you go to the machine shop regarding the 60 degree V6 be prepared to give a history lesson because not much is known by many of them beyond the 2.8L.

I can't find the link at the moment but I recall one of the LS1 rods having a pin diameter just shy of the 3500 crank pins, the next closest I've found is the Ford 4.6L rod bearing for their 2.239" crank pins and in Summit, Chevy Manley rods # MAN-14030-8 and 14034-8 are for a crank pin diameter of 2.225" but that doesn't say much for the outer diameter.

Hate to add salt to the situation but I'd expect these guys to be resourceful enough to come up with something, especially since some for-thought of where they were going to get bearings should have been considered before the operation.

I listed the above options because they're common enough to have over sizes that may work.

[Superdave]

I found Clevite bearings for the mains at Napa for $104 that are the propper size but Napa can't get the rod bearings.. looks like the machine shop will be my only option @ 12.50 each.


I'm going to look more into other options.. i have untill tomorrow to get them ordered. I wanted to hit the track before it closes and i'm running out of time.

[Superdave]

Ok, after some research...

first off, all the main bearings from a 3500 fit in a 3400 just fine. ( i have both in the garage)

GM Part number 12591252 is the #3 main bearing, it crosses with all the 60v6's 2.8, 3.1, 3100, 3400 and 3500

12480252 is the 1 and 4 bearing for a 3400 and older
89017856 is the 1 and 4 bearing for the 3500
12480253 is #2 for the 3400 and older
12586083 is #2 for the 3500.

anyone know if they made material changes to the bearings?


a main bearing set for a 3400 is less than half the price the machine shop wants for the 3500, it looks like they'll work and i could probably get a premium set instead of the low grade they want to sell me.


rod bearings i'm still hosed on...

[ForcedFirebird]

I'm not sure what kind of bill you will paying at the machine shop, but it might have been wiser to grab another complete 3500 from the wrecker.

[Superdave]

$200 for the machine work to the crank plus whatever i can get bearings for. I looked for another 3500 around here and the prices went up quite a bit..

[asylummotorsports]

Prices have actually gone down up here on 3500's.

I can find relatively low mileage examples for under $600. www.car-parts.com

Good luck with the bearing search Dave. That might get expensive.

[Superdave]

i took a set of maincaps from a 3400 and the ones off my 3500 to them today, they agreed that the bearing place was full of shit. After another call and a bunch of confusion i have a set of 10 over mains coming for a 3400. just waiting on a final word for the rod bearings since the ones they quoted me on were for a 3.5 Olds...


Waiting on more details but the shop said that the grinding company offset ground my crank + .006 which will bring my pistons just a tad closer to the exhaust valves... a little more SCR is OK w/me but crap i wish they hadn't done that.

October 11th is coming way too fast

[Monzsta]

i took a set of maincaps from a 3400 and the ones off my 3500 to them today, they agreed that the bearing place was full of shit. After another call and a bunch of confusion i have a set of 10 over mains coming for a 3400. just waiting on a final word for the rod bearings since the ones they quoted me on were for a 3.5 Olds...


Waiting on more details but the shop said that the grinding company offset ground my crank + .006 which will bring my pistons just a tad closer to the exhaust valves... a little more SCR is OK w/me but crap i wish they hadn't done that.

October 11th is coming way too fast

They had to to get it to clean at .010 under. When a bearing fails, material is removed from the thrust side of the rod journal. (the quadrant of journal nearest to the main bearing) This, coincidentally is also where you grind to stroke a crank. But remember, your stroke increase is +.006", but your piston only goes up +.003" and then down an extra +.003". A human hair is .002" so I think you'll be fine.

[TurboGTU]

late 4.3l bearings? Paw (performance automotive wherehouse) has some odd ball stuff for this like bearing spacers. I know a company makes them but I don't know who.