Thread: crankshaft bearing speed and other questions ( might be kinda long!!! )

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Where does the car run, track or street??? We run low tension oil rings on a drag engine, replace them after one season, usually about 100 to 150 passes. The big crank radius' and narrowed bearings work good.... Guess it'd be up to you and the engines' intended usage as to whether or not it's worth the extra expense and effort... Don't think I would bother on a street engine, hard to hook up and use the available horsepower without even going to all the trick stuff...... Some of these power gains will only show up on a dyno, not much "seat of the pants" improvement....

Originally Posted by Dave Severson

Where does the car run, track or street???

Right now it runs nowhere. This is just all in my head. If I had to pick it would be street.

These are just things floating in my head. Smaller diameter coated main and rod bearings, slightly thinner metric ring packs. I ask these questions because there is much to be learned from you guys. Thanks....


Robert

Robert, first off, let me applaud you for thinking outside the box.

Dave has pretty much nailed it as far as street or street/strip motors that most of us on this forum would build.

I was just reading the other day about the rod journal sizes on NASCAR motors. The builders have been running 'em as small as 1.880" and using Honda rod bearings. I think in that article was a reference to an even smaller journal and bearing, but I didn't pay that much attention to it, so don't remember it. But just as Dave said, this kind of "out in left field" stuff has little appeal to us hot rodders. A Cup builder may be able to dominate the field by having a motor with 5 additional horsepower over his competitors, whereas you would never feel 5 horsepower in the seat of your pants on a street motor.

The flip side is the money. I have no idea about NASCAR cranks or Formula 1 cranks or any of that high-buck stuff, but I would be willing to say that I could build a couple of street motors for the cost of a crank that would use the smaller journals. I further suspect that I could make up the difference in power between a production motor and a real good runnin' street/strip motor with a good 5-angle valve job on the seats and a couple of back cuts on the valves without having to go to a Cola or Callies or whatever crank with 1.880" rod journals. Those high-buck guys have already done the valve and fine-tuned every other piece on the motor several times, so the smaller journals may be getting toward the end of finding additional power.

I did notice with interest that the Gen I small block's days may be numbered. The new NASCAR "spec" motor is based on a warmed-over LS2.

I'll just end this with saying that if you have run the cam in needle bearings, are using roller tappets and roller rockers and have tweaked every other part in the motor as far as you can, then you may be looking to decrease the crank journals. Otherwise, it's just so much fluff, blowin' in the wind.