Ketchmi

If you groove the bearing by 25% of it's width, you are a mad man. We groove them about .15 wide and .050 deep. There shouldn't be any problem with the oil film. Dimensions are important.

Fastest928

Well said Erkka!

Fastest928

Dave, your recommended width is not sufficient for oiling for a DEVEK/Scat crank ... the width of the goove MUST be at least the width of the oil passage in the crank! The depth is also critical and controls the "volume" and pressure drop of oil flow. Yes, dimensions are important.

John Veninger

I grooved mine the same dimensions as the other Porsche grooved main bearings. This would be the width of the oil hole in the bearing (lines up nice with the crank oil hole) and .055 deep. I'll use one grooved half on the motor and exchange the other grooved half with someone else building a stroker.

Chris

Well it seems the Glyco main bearings have the same upper and lower half, guess that is why they are cheaper.

Chris

Black Sea RD

Hi John,

I don't know the answer but I do know Mark A. and Joe F. have been running their stroker motors in races with no problems. I would ask them or their engine builder about this. It would seem they or he know the answer.

Kind regards,
Constantine

atb

ketchmi wrote:

THIS is what THAT looks like:

heinrich

Hmmmm ... that groove looks to be exactly 20% of the total surface.

heinrich

Say .... how about 3 split grooves?

John Veninger

The reason for the groove is to supply oil to the oil hole in the crank. One groove and it seems like only one side, like the factory does on the rest.

Adam,

Find someone else building a stroker and trade him one half ofthe thrust bearing, I am.

heinrich

If the raison d'etre of the groove is supply to the hole, then why would one not groove all the way to the hole?

Vilhuer

I think bearings in Adam's picture are both upper halfs as they have those two oil feed holes on both of them. If one of them was meant to be lower half it would not need it's own feed holes as other half has it's holes right next to the ends. IIRR factory bearings have half circle holes on both sides making together full hole.

John Veninger

Nope, the top and bottom thrust bearing is the same.

Vilhuer

Thinking it for a minute those holes are from the factory.

Stock version is same on up and bottom but is one of these Adma's bearings meant to be used as bottom half? If yes, there is risk of lowering bottom halfs capasity to form oil film to carry the crank. Is groove really needed there? Do these drilled-like-Chevy cranks not have hole drilled straight through the crank to allow it pick up oil 360 degrees of rotation even though only upper half has the groove? If there is no straight through hole in crank, why? Sounds like Porsche way of doing things is better as it allows much larger bearing area where it matters. If stroker cranks do not have the through hole on center do they have it on four other main bearing areas? If not, isn't similar grooves needed for bottom half of those bearings also?

Fastest928

Adam,
Needs to be wider. Trading is good.

Marc