Is there really no readily-available source for Tri-metal forged bearings?

[Capote]

Other than having them custom made? Best I could come up with was Mahle/Clevite bearings that are Bi-metal and have .001% more clearance for oil. Just happens most of the parts I've chosen for the '05 engine refurbishing that i'm using for the Turbo project, are Mahle/Clevite because I know they are a trusted brand for engine rebuilds.

 

[littleblazer]

What kind of clearance are we talking about here? I remember seeing a while back a chart for clearance vs film strength of oils and once you get to a certain gap you loose protection again. I'd imagine you want a little more to be safe with the turbo? If you math it the extra little bit you have is probably just fine. I know those brand bearings a pretty good in other applications so I would imagine they'll work here too. Just curious.

 

[Capote]

There's my second issue, not finding any oversized ones

 

[littleblazer]

You could use stock ones and if the crank is clean and round you could make your clearance by having the crank turned. Not the right way but if you have good clearance now and are just looking to add a little more it would work. Or is it that the crank is garbage and you need the over sized ones to make the gap good again?

 

[mrrsm]

The design of the stock nodular Crankshaft in the LL8 Engine took care of the problem of extreme vibration and risk of crank to bearing contact by making them 70mm in diameter. The stock Aluminum Silicate Crankshaft Bearings have a large surface area and should be able to attenuate the forces induced by Turbo Charging the Engine. If you have Forged Crankshaft Bearings installed in lieu of the more forgiving Aluminum Silacate metal... and you remain using a balanced, Stock Nodular Iron Crankshaft ... in the event of either a broken Con Rod or total loss of Oil Pressure... the softer Nodular Iron journals would be ground away instead of the Sacrificial Bearings and defeat the Engine rotating assembly in a catastrophic failure. You will not find better Bearings than those made by Mahle-Clevite... and their Bi-Metal flavor should give you peace of mind.

If you can find and use a Forged Steel Crankshaft.... then the stock Aluminum Silacate Bearings would work just as well. Please consider that in most of the tear downs we have seen of high mileage engines that suffer failure in the Top End... invariably... the Crank and Bearings look surprisingly good. The most significant thing you can do other than having your tolerance measurements leaning more towards being loose rather than being too snug... is to ensure that your entire rotating assembly components are as balanced as possible and the block Blue Printed before assembly.

 

[Capote]

You could use stock ones and if the crank is clean and round you could make your clearance by having the crank turned. Not the right way but if you have good clearance now and are just looking to add a little more it would work. Or is it that the crank is garbage and you need the over sized ones to make the gap good again?

We haven't tore down the '05 motor yet to see the condition of the crankshaft, so i'm trying to plan for both. It's not too too expensive to have it milled down a bit either if it is good.

 

[littleblazer]

We haven't tore down the '05 motor yet to see the condition of the crankshaft, so i'm trying to plan for both. It's not too too expensive to have it milled down a bit either if it is good.

This happen to be out of a certain former members ride?

 

[Capote]

This happen to be out of a certain former members ride?

Yeah, he was VERY hard on his truck.

 

[Sparky]

So.... plan on it being rather worn then I'd say

 

[Capote]

So.... plan on it being rather worn then I'd say

Quite likely

 

[littleblazer]

Yeah, he was VERY hard on his truck.

Bet mine would give his a run for its money as far as harshness. I won't even include the sierra in this as it just isn't fair. But seriously though, he kept up on maintenance. They run forever if you take care of them like that.