Cat Crank - chamfered or not chamfered bearings

[Eticket]

So, we're working on a stock stroke all forged build up this week in my garage.

We have Cb1228p and Cb1398h bearings. It appears that either bearings will work, but I've read alot about cat cranks needing chamfered bearings. The 28p seems to definitely work at least because they are narrower by a decent margin, but I'd like to use the 98h's between the two.

Please tell /us me your experiences (not supposed experience - no offense) on whether some of these cat cranks didn't need additional chamfering on the bearings to work? it seems as though there was one thread that said the newer cat cranks didn't require chamfered bearings. I have no idea where and when this crank came from.

It seems as though when we started this months ago (stopped due to other machining issues), tried the cb1398h wider bearings and that they were just fine. It doesn't see like the crank has much radius on it at all (although I hadn't seen enough to know what big radii is).

This is a cat crank with stock stroke with the knurling in the end (which indicates it at least isn't the earliest of cranks).

Thanks much in advance.

 

[Nick Micale]

We have never built an engine with a China crank without chamfering the rod bearings, and never will.

The radius on the rod journals are larger than a BMS or billet crank.

I do know of a couple blocks that were assembled w/o the chamfer, and they had to be torn down to make them fit properly.

Maybe others have not done this chamfer, but I prefer to NOT take the chance of a possible issue after we send the engine out.

 

[ek02]

I tried the wide bearings on an early Cat crank and they hit the chamfer. I had to use stock width bearings, or I would have had to chamfer the wide bearings.

 

[Scott Atk]

Nothing new to add that hasn't been said. Yes, to the chamfer and I personally think a little additional chamfer is needed.

 

[Eticket]

Thanks guys; So, in that respect, the stock sized CB1228p will work or did they even need to be chamfered?

it may be that we just put it together but the bearings will be replaced before the pan is actually buttoned up with chamfered wider bearings.

 

[mikestertwo]

Make sure you check the radius on the flywheel flange. Some of those cranks have a large radius and the flywheel/flexplate will not seat up against the crank.

 

[ek02]

X2 for the flange. It should be put in a lathe and the chamfer squared, or you can do it the lazy way and take a dye grinder to the flywheel and taper the crank opening. Also, the crank key may need some .001 shim stock on either side of the key to make it tight enough. Other than these issues, these are not bad cranks for the price. The bearing surfaces are super hard.

 

[J-B Racing]

I ran a CAT Crank in my 109 for 3 full years and the CB1228P Rod and MS960P Mains. I shifted this poor Engine close to 7000 RPM and the Crank still looks as good as new. Then sold the engine to buy a S2.
You decide.

Joe

 

[Rodney87GN]

Thanks guys; So, in that respect, the stock sized CB1228p will work or did they even need to be chamfered?

Weber Racing used those same CB1228P bearings on my motor with a Cat crank without additional chamfering.

I confirmed that myself when I pulled my motor apart last year for a popped head gasket...I put in a new set of the same bearings and compared them with the old ones and they were not chamfered.

X2 on checking the radius on the flywheel flange...Weber had to machine mine so the flexplate will sit flat on the crank.

 

[Eticket]

Mucho gracias, thanks guys, john.
Ill let the owner decide