So I'm hoping Mike at TA or someone with building tomahawks can answer my questions...Just came from my machine shop and was told these bearing clearances on my mains are wierd. So the block was line bored .001,but the crank (crower) is ground on the low side. Clevite standard hp bearings have .004 clearance. So they get 1 under bearings from King and there description says the surface is crowned. To get the clearances set they have to swap some halves so some have a standard shell and a .001 under. But the clearance is .0023 to .003. Checking in the vertical spot ,and if you check 1/2 inch from parting line its .004. I've been told its common to sway bearing halves. Never seen or had that before. Anyone ??
It's not an uncommon practice, but I've only seen it done for budgetary reasons- like a weekend rebuild to tighten the tolerances without machining the crank or block. For a high end build like yours I'd consider it kind of half-assed and a fix for sloppy machine work especially with all new parts. I can't say if it'll effect the longevity of the engine but I can say I'd be nervous about it.
I'm going to call King bearing company tomorrow to ask about their design. Its supposed to help crank flex.
Does King make .002 under bearings?, that would get you there. Ideally, bore gaging the mains then giving Crower a size to grind the crank mains to initially would be the ticket. JW uses King bearings and mixed bearing halves to tighten clearances. Maybe give him a call.
another option would be to send the clevites out and have them coated. mixing standards and .001 is normal but not between brands
I think rod bearing alot of time have extra room on the parting line areas. Its not where the load is and gives room for sine stretch and flex without having the bearing pinch onto the crank as it would if the measurements were the same
I bought a guys pile of parts so... The crower crank is .001 lower on the low side and today I find out the clevite bearing MS1039HX has .001 smaller for more clearance for better oil flow! I'm looking for a .001 under bearing now. Anyone know where I can find some?
For a stk 455 crankpin size????? Good luck. Might have to send the bearings out to be costed or the crank massaged
I’m building a T/a Tomahawk with a Crower crankshaft and I’ve had the same issues. The Crower crank is ground 1 1/2 thousands under the spec therefore I had to get bearings that are .001 tight King bearings generally run big compared to other bearings I have tried. If you go and research is on yellow bullet.com there’s a thread about king bearings and that they generally do run big. You also run into the problem that clevite does not make a tight bearing only to get looser clearance. I ended up using ACL bearings And having them coated to achieve .003 clearance. Also be aware of number one and number four fillet on the crankshaft rubbing on the bearing I had to purchase a fixture that holds the bearing so that you could put a extra large chamfer on those bearings. It’s easy to miss. I don’t know when you purchased your block but mine was not relieved on number four web and cap just like it would look on the thrust side of number three. On my Block the cap and the block had to be relieved to make room for the number four Crankshaft throw. I just had .020 thousands removed on the backside of number 4 cap And then did the block by hand. I did start a thread about some of these issues but didn’t get much feedback so was hoping to save someone else a potential failure because if you don’t catch these things for sure you would. Hope this information helps, Tom
What your seeing there Dan is pretty normal on these. No issue mixing and matching std and .001 King mains to dial in the clearance, but you have quite a variation there, don't usually see .0007 variation in the mains. .0023 is too tight on that for my tastes, if you run that, make sure you have the block plenty warm before taking a base, so you don't catch a main. I like those motors up around .0027-.0028 on the mains, maybe a touch more. All engine bearings are thinner at the parting line, this is so they can flow oik out of the bearing, in a low stress area. The term for it is bearing eccentricity Race bearings typically don't have quite as much as the standard passenger car stuff. Make sure you using King HP bearings, not the XP series. Nothing makes things uglier than any kind of failure, with a hard bearing. This is why I went away from the H series clevites, years ago, even after having a stock crank nitrided. King HP rods in the 808 series come in X, Std, and .001 so you can find tune your rod clearances. In a perfect world, the main and rod housings are done to a specific size, bearings installed and checked for size, and then the crank is ground to exact size. But the world we live in is not perfect, and the work around with the bearings is common practice. Have them study the dimensions and fits on the thrust bearing carefully. JW
Here’s some pictures of number one and number four with a heavy chamfer that was put on the bearings, also the cap clearance.These are the ACL bearings and Are the more forgiving material. Like I said if you are loose on your clearances the ACL were .0003 to .0004 tenths tighter than the kings. The king bearings would definitely help you out if you were on the tighter side.I don’t know if I would do it but I’ve seen it done already where two different brands used to get the size they wanted.
Hi Jim, left you a phone message on 10/9/2020 about engine bearings suggestion. I am getting old! Completely forgot about V8buick.com until this Am and looked up this thread. Do you by chance have the part numbers for King Bearings for a .020 under 455 crankshaft? Rods and Mains. I have called them twice and left messages but Ron does not call back, I do not see Buick 455 bearing in any of their catalogues. I have a .010 crankshaft that I have saved by tearing the engine down before the bearing wore out, clearances are to tight. Just checked rod clearances on 2 rods that the inserts just fell out of the rods and caps and there was only .0015 clearance. I cannot get the .001 extra clearance bearings for a ground crankshaft so I would like to buy the King bearing in .020 under and regrind the crank with the extra clearance.
Unfortunately, King does not make any Buick BB bearings... No direct replacement for the Clevite 908 series main, or the 762 series rod bearing. We only use them on on the 3" mains, which use a Ford 429/460 bearing, and on rod journals which share either small or big block Chev diameters. JW
Thanks Jim, I knew you would be able to confirm or deny the availability of the King bearings. I appreciate your wisdom on the BB engines and your willingness to share.
