neat

I'm putting together a 5.3 for a boosted application and and working on setting up the bottom end. I am looking for .002 or so on the rod and main bearing clearance. I am using the stock crank and rods.

I can't seem to find any bearings that give me more than about .0015 clearance. Those of you who are adjusting the bearing clearances on the bottom end, are you polishing / turning / machining the crank to achieve the larger than stock numbers? Or am I just too dumb to find the correct size bearings?

DietCoke

iTrader: (18)

Just use whatever over/under bearing you need. swap a half if you need an in between.

64post

iTrader: (5)

You can have your rods and main bores honed to "low limits" this gives the most clearance with standard bearings, should give you what you are looking for. You can use .001 +or- bearing shells to get what you want as well ^^^. Polishing the crank to get your clearance is not the way to set your clearances. Spend a little bit and have a machine shop get it right with inside dial bore gauge, not plastic gauge.

rpturbo

iTrader: (47)

I can say this:
Bearings from different manufactures, will all have different clearances. On my stock 6.0, that had good bearings in it, when I took it apart, I was shooting for the same thing. I started with Clevites I think, and they were standard bearings, and they were tight ( more like a stock application). My friend had some Federal Mogul bearings, and we checked those (also standard bearings) and they were much looser, so I bought those, and most everything was near .002 with having the crank polished. I wasn't going to not polish it, and it didn't need turned. Running a unpolished crank, unturned, is just asking for trouble IMO. But yeah, don't use the polish to make your clearances.

Those King bearings come just about as advertised from what I hear, and on those, you can mix and match .001 under or .0005 or whatever, but, you have to buy more bearings that way.

neat

Where are you buying the bearings though? This is what I've been able to find; unless I'm not understanding this stuff (which is likely) there are no bearings available to increase the clearance in the bottom end with stock bottom end parts. None of the available bearings are thinner than a stock bearing, none of them will increase bearing clearance - in fact they will all have the opposite effect - reducing bearing clearance.

Summit sells a .001 undersize, which means that the bearing is .001 thicker to take up for the material that was removed from the crank. On a stock crank, a bearing like that would reduce bearing clearance, that's the opposite of what I am trying to do.

They also sell a .001 oversize bearing. This bearing is thicker as well, trying to make up for a larger saddle being machined into the block via line hone. Installing that bearing, in a stock saddle, will result in less bearing clearance as well.

I can't seem to find a bearing that is designed to do what everyone here is describing, .001 and mix/match etc... None of that seems to work because all the bearings are thicker than a stock bearing, some are thicker on the back side -making the OD of the bearing larger to allow for material that was removed from the saddles- Others are thicker on the front side - making up for material that was removed from the crank -

regardless, any of those bearings, or combinations of those bearings reduces my bearing clearance.

I am shooting for .0025 or so on main bearing clearance, as measured with a micrometer and dial bore gauge. My loosest journal right now is about .0019.

I have considered taking a scotchbrite on a cylinder hone to the bearings in an effort to uniformly open them up slightly.

Or I am thinking of trying to find another engine, one with more miles on it or something, and try mocking everything up with those used bearings. If those bearings are worn a little, they might put me where I want to be.

Others that have achieved the .0025 clearances with a stock crank, how did you do it? What bearings, specifically, did you use? I can't find any bearing, from any supplier, that is thinner than a stock bearing.

KCS

iTrader: (20)

You're confused. The "oversized" bearings are for .001" larger bearing bores, not housing bores. The bearing shells are .0005" thinner so they should give you .001" more clearance than the standard bearings or .0005" more clearance when mixed with standard bearings.

Whatever part number bearing you're using should be available with an "x" at the end which would be the bearing to get for more clearance. For example, Clevite's MS2199H main bearing is available as a MS2199H-1 for .001" less clearance or MS2199HX for .001" more clearance. For example:

https://m.summitracing.com/parts/cle-ms2199hx

The problem is that you end up spending a lot of money on bearings. Once you check them you can't return them if the clearance is too tight/loose. On used cranks, I like to buy a .010" undersize bearing, measure the ID of the bearing, and have a local crank grinder grind the crank to get the clearance I want for only about $75. This keeps me from wasting money on different bearings sets and having the crank ground professionally ensures that the journals are straight, round, and indexed properly.

neat

Thanks!

I didn't realize that the X suffix denoted a smaller bearing for "Xtra" clearance. I thought it was a typical undersize bearing for a crank that had been machined to a smaller diameter.

I like the idea of putting the caps on without the crank installed, measuring, and then carrying those measurements to a machine shop to have them adjust the crank.

RonSSNova

iTrader: (3)

I was going to say what KCS said.
Requires you have an excellent crank shop to deal with.

My guy did the mix and match bearing approach. I'm not sure why.....
So now I have a mismatched set of spare Clevite bearings. :-)

Mine is the alum L33 and we aimed for .002" clearance. He got 2 and 4 slightly looser as this is a turbo setup.

It was hard to get definitive answers on the "correct" clearances for the alum block.

KCS

iTrader: (20)

You're right about that. Ask 10 engine builders what clearances to use and you might get 3-5 different answers. I think what you have should be good though. I like the saying, "too loose and only you know it; too tight and everyone will know it."

I like to use coated bearings. They're a little more money but worth it IMO. I'll use a bearing that might get me .003" clearance and have them coated by a local place here in Houston named Polymer Dynamics. With the coating, the clearance will end up around .002", but if something happens (low oil, overboost, crank flex, etc) the coating will wipe away without damaging the bearing or the engine. It will kind of wear into the perfect clearance.

RonSSNova

iTrader: (3)

Thanks.
I got answers that ranged from .0015 to .003".
And of course the clearance will grow with heat.
I drive to the track, so it should be warmed up good before I make passes.

One thing I failed to do was give him the block with the stock bearings and cap bolts torqued up so we could see where we started from. Had about 100 passes under boost. Got ahead of myself on that one!

Ron

pantera_efi

iTrader: (1)

When you have "standard" journals, the chance is EASY to buy many bearings that will fit.
Most performance bearings will have that +.001" size needed in their standard part.
The + .001" item can also be ordered though with that item you may have too much clearance.

My use of a King Performance Bearing has always provided the required rod clearance of .0025" -.0035".
My use of a King Bearing at the main position has most often provided a clearance of .002"-.0025".

Make sure you fit the Tri-Metal bearings, NOT the steel backed Aluminum part.

Lance

squarles67

I struggled getting the clearances on mine recently. As has been said the X bearings are extra clearance. I used Speed Pro race bearings.

One set I got from Summit was actually marked wrong on the box which really through me for a loop and confused things.