Don Terrill’s Speed-Talk

Has anyone used Half Coated and Half Non Coated bearings to set clearance??

I havent but i cant imagine why it would be an issue.

I have done it several times in rod and main bearings with no problems.

Yep

Thanks for the reply's. The Clevites are .005 thicker than the non coated and ACLs are a full.001 thicker than the Clevite.

The engine I built a few months ago has both. I had 3 sets of mains and rods to mix and match. I was being overly anal on with it but a lot of time and money invested and I wanted what I wanted

Kenny M wrote: ↑Sat Jan 11, 2020 12:31 pm Thanks for the reply's. The Clevites are .005 thicker than the non coated and ACLs are a full.001 thicker than the Clevite.

I believe you might be missing a 0 in your dimensions.

Coating on a typical Clevite plated bearing is .00035" per shell, therefore the total difference on vertical oil clearance on the coated shells is .0007" per journal. Therefore the coated shell may be used with an uncoated shell to juggle the oil clearance just the same as utilizing a shell from a .001" journal set. i.e. .00035" versus .0005 clearance difference.

I would put the coated shell on the bottom of the mains and top of the rods and at least put that coating to work.

The write up I read (I forget which bearing company) said the coating thickness should be ignored in measuring the clearance. In other words, if they coat a standard size pair of shells it's still considered a standard size set.

MadBill wrote: ↑Sun Jan 12, 2020 9:56 pm The write up I read (I forget which bearing company) said the coating thickness should be ignored in measuring the clearance. In other words, if they coat a standard size pair of shells it's still considered a standard size set.

No, you need to take the coating thickness into account when checking bearing oil clearances. For instance a Clevite STD COATED bearing will have approximately .0007" LESS oil clearance than the same bearing STD size. "Ignoring" the coating thickness will result in problems when calculating oil clearances.

I think my info was from Calico; I'll have to check my records. Here's their FAQ reference:

https://www.calicocoatings.com/company/coating-faqs/

"Will I have to change my clearances to use coatings?
Calico's CT-1 dry film lubricant used on engine bearings, valve springs, oil pump gears, timing and transmission gears is 0.0002" to 0.0004" thick and generally does not require extra clearances. A benefit of Calico coated bearings is the allowance for tighter clearances. Keeping in mind that bearing clearances of .002" to .003" are typical for high performance applications."

engineguyBill wrote: ↑Sat Jan 11, 2020 5:04 pm Coating on a typical Clevite plated bearing is .00035" per shell, therefore the total difference on vertical oil clearance on the coated shells is .0007" per journal. Therefore the coated shell may be used with an uncoated shell to juggle the oil clearance just the same as utilizing a shell from a .001" journal set. i.e. .00035" versus .0005 clearance difference.

Agree 100%
Clevite will not steer you wrong if you follow recommendations in the catalog.

Or, as a general guess I'd say far as target clearance, you -can- run .0005" less clearance with coated bearings, or in this case .00025 less with one coated shell.

IMO you can mix different brands of bearing shell, even different materials, and never have I heard a single problem from it.
Tho for whatever reason people rarely do that, so.... can't say we know for sure in every scenario.
Even some OE engines use tri-metal bearing for the top shell of the conrod, with an aluminum bottom shell. Seems pretty clever. I setup a few other oddball engines I rebuilt that same way and they all did fine.

IMO go for it.