Interested to hear about destroyed plain cam bearings. Also not sure why rolling element bearings in a cam would be a big deal, like previously mentioned rolling element bearings are at use in the two stroke world all over with 10k+ rpm service being the norm.

I suspect anyone what can't find the right bearing hasn't called Timken.

For the past several years I have set up and maintained an assortment of fans/ blowers that run 24 7, if properly balanced and clearanced they run for years, if not , maybe weeks. Granted these are not needle bearings but I have to think the same principles apply.

Plenty of high rpm high HP engines running babbitt bearings. I've built a few myself and personally never used a roller cam bearing. If you're wiping out babbitt cam bearings there's something else fundamentally wrong.

I had a Sonny's 565 and a reher/morrison big chief 565 top sportsman engines a few years back, one dynoed @ 955, the other @1025 neither used roller cam bearings. The only reason they came about was to remove internal friction to pick up that last couple of HP in prostock engines where 5 hp might keep you from qualifying. That whole deal got totally out of hand when they started turning 500 inch motors way north of 11,000, and some changed valve springs after every pass..

That 5 extra hp may make the difference in having 996 hp and 1001 hp.

Can't say you make over 1000hp at 996hp. :lolhit:

Hows the new block?

After getting the block in my hands and thoroughly examining it. I have to say I don't think I will ever use a Big M block (in a boat) again. It's a totally different casting (very nice casting). Looks like it has more nickel in the material. Everything in the block is beefier all the way down to the main caps. Pan rails, bores and cam tunnel are already clearanced. For big stroke. At the end of the day the price of the block isn't that bad considering no clearance work needs done and you end up with a much better block. The only thing I'm not to sure on at this point is running roller bearings in the block. The cam tunnel is different then the big m. It's completely closed on top and has a minimal opening on the crank side so I'm not sure how the bearings will see any splash oiling. What did I get myself into?...

lifters get oil,so they'll leak into the tunnel.plus the crank will throw oil up there.and if you really concerned,drill holes up from the crank journals of bring oil from the front or back lifter journals,plumb it from the lifter valley.
your running a dry sump on this I assume.

Absolutely no experience here, just round table thinking out loud talk.

The lifters and cam lobes are getting oiled right ? Of course...so, this could be plenty of oil getting to the cam bearing.

Back to 2 strokes and roller bearing connecting rod and cranks, remember, they are using 60:1 - 70:1 fuel:oil ratios now. This means the roller bearings are seeing 60 to 70 parts fuel to 1 part oil, and surviving. Also remember, this is all in crankcase 'windage mist' - no splash and no direct oiling. Fuel is a cleaner, not to mention the stergents in pump fuel and the dtergents in the oil itself. Yes, some of us older blowhards are modifying our oil systems to get back to old school 50:1 ratios with our 2 strokes, but this is more for piston protection. These are spinning 8000-10,000 crank rpm vs camshafts which in a 4 stroke the cam spins 1/2 crank speed.

The only roller crank bearing failures in 2 trokes are usually because they are not large enough for the forces they see. In these applications, when larger bearings are used, problems go away. Anyone tell that I'm a Polaris guy ? Hah !

Ending my out loud thinking, I would call Dart. Your worry may become a non worry....Hopefully. LOL.

Great point! Don't no where my head was. Yes it is dry sump and will see vacuum. They closed lifter valley on the block does have oil crossovers built into it. I was thinking of tapping into the crossover and doing some sort of sprayers on the bearings. But you are correct the lifters should dump plenty of oil on there own...

the cam bearings are not pressure lubed?

No hole in the outer shell

No.

Think about the atmosphere inside a running engine's crank case with all the oil being thrown off the crank and rods. The bottom of the cam tunnel is open to the crank case and as you said, there is a lot of oil coming off the lifters as well. There is plenty of oil for the roller cam bearings. They don't function on a pressurized wedge of oil like a babbitt bearing.

We have been using the roller cam bearings for years. No issues but not likely worth but a few HP.

would there be any harm in drilling a very small hole in it?

that cage is hardened,,more like edm or grind a hole.

yeah,I wouldn't go out of my way to put them in.built a whole lot of 1000-1200hp whipple motors that use the convention cam bearing set up.

Probably ruin the bearing. Besides, there's no need.

so is the blocks oiling changed for this then ? I know std block does lube cam/lifters/rockers...

the way i understand it the oil hole is blocked by the bearing cage,correct me if that is wrong.i just can,t see any reason anything other than pro stock would need roller cam bearings,and really doubt they need it but if one does it they all do it.i built quite a few bbc that went 8700+ rpm and never had a cam or cam bearing failure.

most all of the prostock setups do not run any oil to the heads, they pour enough for the next pass, knowing the valve covers are coming off right after, and the don't drive to lanes or back anymore...so not much lube needed for 3-4 mins. as well as being dry sumps to.

i guess they get away with that .they change valve springs every pass.

thats true most due now, at least check pressure on them at a min...but when you turn all that heavy stuff north of 11k...