GREGGPENN

Measuring this afternoon for correct bearing size. My builder likes to use (at least) 3/4 groove bearings. And, actually, he likes full groove's better.

However, he's says he's seen a lot of scat cranks need an adjustment (from std bearing size) to fit correctly (i.e., +.010"). And, that can mean full groove bearings aren't available (according to him). IOW, not all bearing sizes come in full-groove.

Is he limiting himself based on local availability? Is the use of 3/4 or full groove main bearings a good/bad idea for a street motor? Since that groove lets oil flow and lube the rods, why use anything OTHER than full groove bearings?

Also, what brands/kinds of bearings do you like? (Building for longevity and street use.) Anything to stay away from?

(Note: After he measures, I can go buy whatever kind I want.)

Edit: Oh yeah....how will the selection of 1/2, 3/4, or full groove affect oil pressure (if at all)?

Bad Karma

I've used OEM, Federal Mogal and Clevite with good success. We've used the Clevite's in most and the ones pumping out the most power.

But I can't recall spinning a bearing that was the fault of the bearing. Had one spin on a rebuilt engine we bought because they used the wrong bearing. Jeep bearing spun due to failure of the oil pump, caused some good carnage. Some other interesting failures due to bad tuning come to mind as well.

BLOCKMAN

We use a lot of the Clevite V-series bearings where we can fit them in other wise we use the ACL coated 3/4 groove bearings and have good luck with the Clevite H-series bearings.

Like I said we use the V-bearing where we can fi them in and they are 1/2 groove and these are in our blower engines we build and these egines are in pulling tractors run 9200 RPM for up to 45 seconds at a time.

We build a lot of circle track engines and the V bearings again work very well.

I can say in 38 yeares of building engines never have had a bearing issue with any of the engines we build.

Having the correct clearances is a must!!!!!!!!!!!!!!!

GREGGPENN

Crank measurement complete. Builder said the Scat crank was SLIGHTLY undersized. He's going to cut about .002" off the big ends and install a .001"' under bearings (or .001 over if you look at ACL's terminology).

Looks like the choices are FedMogul/SpeedPro competition series 3/4 groove bearings, ACL 3/4 groove bearings, or King HP series.

The builder has seen the King HP Series fail and doesn't like them. His first recommendation was the SpeedPro (though he thinks the ACL are just as good).

Because there's a restocking fee from the company where I'd buy the ACL's, I'll buy the FedMogul/SpeedPro 3/4 groove bearings tomorrow. (CNC-Motorsports hit me with a restocking fee -- even though I returned a balancer for an upgrade. It was only 1 day after I received it. The worst part was they didn't know of another option for our vette's until Will found it for me! They SUCK.)

Here's the bearings I plan on buying....
http://www.summitracing.com/parts/FEM-139M1/ - main bearings (SpeedPro)
http://www.summitracing.com/parts/FEM-8-7100CH1/ - rod bearing (Federal Mogul)

Unless someone has a better idea!

(BTW: Clevite doesn't sell a 3/4 or full groove bearing in the .001" under size)

Klondike

We used to cut bearings ourselves to 3/4 groove before the industry started offering them. We did it for our circle track car to keep the rod bearings oiled at high rpm with a stock engine parts rule. We left the bottom section in the mains un-cut for more crank support with stock type bearings. Worked...Never spun or even scuffed another rod bearing!

bjankuski

I have never used full groove main bearings on a SBC, and have never had any problems. I am not saying they will not work or may not work better but I have no experience with them. My only reason for not using them is years ago I read a book by Grumpy Jenkins and he did not recommend full grooved main bearings because he claimed they reduced the bearing load carrying capacity by 70% with the full groove.

I would be interested to know other peoples experiences with more current data. Are grooved bearing a benifit or problem?

JimiHendrix

I can't understand why your builder would'nt like King HP series bearings. They are considered the creme of de creme. If your builder said they fail because of the way they're made, it would make me wonder. Most bearings fail because of oil starvation, bad clearances, dirty oil etc. . . not because of the make and brand. King HPs are damn good bearing and they tolerate a lot of abuse.

This is the first time I heard a Scat crank was off in measurement. That is usually reserved for the "bird" brand.

I ran full groove King HPs with no problems whatsoever.

GREGGPENN

Well, I did see a batch of Eagle cranks that were undersize being let go for less than full price (at one of the merchants where I shopped). Between size issues and links to broken Eagle (cast) cranks, I stuck with the Scat hoping it really is better/harder.

Part of the issue on the bearing size may/may not have to do with how he sets up bearing fit. He said he was shootin' for a .001-.002" elongation of the bearing fit. IOW, he's going to shave a couple thou off the rods to get a slight elongation (in conjunction with the .001" oversized bearings). Says that helps at higher rpms with the caps are trying to pull away from the block.

I asked if that was SOP for a street motor being built for 5500ish rpms. He said yeah and that factory even does this. (FWIW, I'm building a 450ishhp/525ishTQ setup (at the crank). 383/SR-like build (see note) Maybe he's thinking torque is as big an issue as HP on the caps?

He didn't say he'd be removing anything from the crank thou.

Is elongation of the main bearings SOP?


Note: Build is pretty much like the 383 stealth TPI build found on the net.