Converting to roller crank bearings?

[BitterRoot]

I am building an engine for a car that is being built with throttlebodies, large cams, etc and will be a screamer.

The biggest problem with high revs on these engines seems to be the failure of the lower end bearings. I would like to be able to find a company that can convert my lower end from 'plain' bearings to roller bearings in both the crank and rod bearings.

Any thoughts or ideas??

 

[bobqzzi04]

I don't know what the exact problems you are having with bearings are, but, in general, roller bearings are less capable of high rpm.

 

[R1100S]

You don't want to do it.

What kind of car and what engine. How much horsepower at what rpm are you trying to make. Is the oil film breaking down, or are the bearing caps flexing? Is it a bearing problem or is the crank flexing?

 

[franzh]

There are plenty engines with insert type lower end bearings turning far in excess of 10,000 rpm at 600 bhp reliably (as reliable as you can get for an Indy car engine, or a NHRA Top Fuel engine at over 5000 bhp).
If you have an engine that is losing its lower end repeatedly, there is someting wrong with its design, construction, assembly, clearances, oil type, and the list goes on.
Roller bearings are no problem for high rpm, not not for high loading.
Franz

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[RRBD]

Agreed, dont waste your money. A properly designed insert bearing set up should last a very long time. A common problem in high rpm applications is the main caps will "pinch" the crank, which in turn will wipe the oil wedge away, which means crank to bearing contact and shortly after the engine will quit making noise...period.
Four bolt mains help this situation. In circumstances where two bolt mains are the only option, you can have a shop Dowel the main caps to the block. I have Doweled many blocks, one of which, a 736 hp, pump gas v-8. Good luck.

 

[lasse80]

My experience with motorcycle engines is that singles always have needle bearings in the lower end (I guess it´s because it´s possible due to having built crankshafts, contrary to forged), whereas multicylinder engines use plain bearings.

Any thoughts why this is the case? Surely the hydro static "lube" system is the more sophisticated one!

 

[patprimmer]

There has been much discussion on this in previous threads. Why not use the search feature and save us the work of repeating it.

Regards

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[richdubbya]

roller bearing cranks are usually made in pieces and pressed together and tend to twist in multi-cylinder engines. They are used sucessfully in Suzuki GS 1150+ 4 cylinders used in drag racing at 12k rpm and 300+ hp. I imagine the sections are welded and the crank isn't serviceable afterwards.

 

[R1100S]

You are correct richdubbya. Same with Harley drag motors.

 

[sacem1]

Original Porsche and VW aftermarket cranks were used in the 60's and 70's but they were discarded because they could not take much abuse specially in drag racing starts when the clutch is let go at high engine rpm's.

All off roaders who also used VW engines also have avoided roller cranks because of reliability problems and these units only had rollers in the rod journals not on the main bearings.

I would say forget the idea, besides I doubt that there will be enough "meat" to carve at the main bearing caps in order to fit the neadle bearings.

Cheers

SACEM1

 

[icrman]

Give us some dimensions and some photos of those bad bearings. And also of the saddles and crankshaft.
The whole system is most likly very weak. And after all that expense you would end up having the same problem with rollers as well. Is the crank case iron or aluminum?
What is the crank material?
Maybe your cheaper and more affordable route would be to transplant an engine capable of generating the kinda power you want. The Chevrolet small block comes to mind.
And the after market speed equipment parts availability is mind boggling. If a V8 is not the answer then consider a V-6 Chevrolet.