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Need to tighten main bearing clearance

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jakelandry

10+ Year Contributor
976
157
Oct 13, 2009
Minden, Louisiana
Does anyone know of any bearing manufacturers that sell thicker bearings? I had my crank polished and mains line honed and my main clearances are coming out to .0032 - .0035 with standard bearings measured with a bore gauge.

I am really not sure how this is happening cause my crank is coming in at 2.2435, main bores at 2.4025 and bearing thickness, unchecked, should be .0783 which should yield .0024. My mic is calibrated from a gsg standard and bore gauge is new and appears to work correctly when changing the mic to known deltas.
 
Send the bearings off to be coated. I got mine done at Calico Coatings in NC. They'll put special shells over the bearing surface that'll get it to where you need it. It worked for my car and my brother's car.
 
Interesting idea that hadn’t crossed my mind. I wonder how that would hold up in an 800 hp setup. I’ll spend the day researching to determine if higher torque can “compress” the coating or something to that nature. Thanks for the suggestion.
 
If you are building an 800hp setup, don't skimp on thicker bearings, get a crank. I don't mean to sound brash, it is just a fact. Don't skimp in the beginning of a big build or you will regret it later.
Best of luck on that beast!!!
Feel free to look at the build sheet on the 92 6 bolt that I am currently breaking in and tuning.
I am sure some will want to criticize some of the numbers (maybe) but they are true and accurate numbers, not made up to look good. This motor should be good into the 600's on HP, as I have already seen high 500's and BIG torque numbers.That build sheet is here in that cars profile....
https://www.dsmtuners.com/dsm-profiles/1992-talon-tsi-6-4-auto.13170/ picture #17, I think. :)
Marty
 
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If it’s a big power engine it’ll be fine.

I put together a block with .004” main and rod clearance. It has over 100 passes on it with a 3000gt record best pass of 8.29@168. The record pass was probably number 99 of those 100 passes.

To be clear it’s a 6-bolt 4g63 block.
 
Thanks for sharing Marty. I will absolutely check it out. I feel like the coating could be considered “skimping” in ways, primarily due to my ignorance, but I don’t know that I would consider manufactured thicker bearings as a negative. Do you have any particular reason you feel this way? I’m all about not cutting corners so I’m open to all opinions.

As for my original statement, I have determined that both ACL and King make standard bore, .0005” thicker bearings. They’re labeled as .025 oversize which is misleading. I’ve always seen bearings labeled .001” over but for some reason they use metric measurements for our bearings.

I considered getting a new oem crank or even a billet crank. In this particular scenario, I can’t see where I would benefit to a new crank though. Mine is in spec and a “brand new” isn’t large enough to reduce my clearances by the .001ish I need.

How I see it is my options are:

1: Cut the crank and risk messing it all up again.

2: Hone the mains a second time which will bring the crank further up

3: Buy thicker bearings

4: Buy new block

Right now my preference of the above options would be 3, 4, 1, 2.

6 bolt blocks in my area are rare enough that I would just pursue a billet block before spending the amount of time and money I have in my current setup again.
 
Donnie is spot on if you really plan to make the numbers you are talking about. It isn't much of a tolerance difference. I build SBC with .003 on the mains if that's the way it comes out. I would be worried at .004 but with thick oil it would hold decent pressure and would have the clearances to spin fast and hard, just doesn't last the long miles I want my motor, in this instance, to last. When I build SBC's, I even give the rods additional side clearance so they will rev, and have had one Corvette block that I ran for A LONG time with .011 cylinder wall clearance and stock 11:1's in it. She revved to the moon.
Race motor, hell, build it and send it. But in my 92, I want to enjoy her for as many miles as I can so I was strict on tolerances and had they been looser, I would have went with a different crank. But that's for a motor I want to run for years, hopefully.
They classifieds had a Eagle crank in them a few days ago, but I don't remember if it was a 7 bolt or 6 bolt but was a good deal when I saw it. Might browse over there and see.
Thanks Donnie, for your input. Much appreciated.
 
Sometimes the genuine Mitsubishi bearings can be had in different sizes to make sure that the manufacturer was able to use most of the blocks even if they were off a bit during manufacturing, you might look in that direction.
 
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