Can anyone school me up on the differences with big block cam bearings, especially the roller bearing conversions. What's the story on cams for these bearings? Same? Different? Any info appreciated.

You would be pretty limited on off-the-shelf cams. (Probably none.) And the cams will be a lot more money. Roller cam bearings look sexy to me, but Sonny Leonard (and others) have told me that there's not a single horsepower to be gained. He said the only good thing about them is the engine is easier to turn over to adjust the valves.

Afaik the bearings used are needle (diameter is 10% or less of the length), a roller would greatly restrict cam journal and block dims. Typically, 1/16" (also used as Torringtons).
Needle, roller, and ball bearings have far less load capacity than plain bearings, although they will function with less oil volume.

In our super stock stuff cams were the same. Cam tunnel was machined for larger dia.roller bearing

I think you’re going to find there are only a few sizes of roller cam bearings available.
Usually something like 50, 55, 60mm.

Obviously the cam bores need to be bored to fit, and plan on needing a cam with the cam journals sized to go with the bearing diameter used.
Check with your favorite cam supplier for availability.

If you’re currently oiling the top end with the factory style “thru-the-cam” oiling, you’ll need to sort that out, since that option will go away.

The low deck 512 in my Duster had roller cam bearings. It was a factory 230 block that had been machined for roller cam bearings and cross bolted mains. We used an off the shelf roller cam bearing kit from Ford SVO. Cam was a custom hyd roller. Came with a funky dowel pin setup that required a custom gear set. At some point in the future a guy will pull that engine out for a rebuild and the shop he takes it to is going to go [censored]?

rebel-
It is not so much the utilization of needle bearings. The reason this is done is for large base circle camshafts which have bigger journals requiring specific bearings (both roller and conventional bearings are utilized for the big base circle cams). The proper application of the large base circle cams requires more than a simple lesson in camshaft profiles. The large base circle cams are utilized by many class racers, such as Super Stock and Competition eliminator plus, many Top Dragster, Top Sportsman and all the professional categories. There are many who will say there's no advantage and for some I'm sure that was true. However, when you check with the top qualifiers in those performance oriented categories you'll find most if not all use the big base circle cams. Like so many other things in Class racing you just can't bolt one in and have an immediate improvement. I was on my 3rd different grind before I saw meaningful improvement and those cams are much more expensive than a conventional roller cam. For those who are not Class racing there is a lot of lower hanging fruit to grab for getting more performance out of your motor. I hope this helps, good luck!
Bill

That's a Torrington full-complement (crowded needles, no cage separators), which has a suitable outer race (as shown) but uses the original cam journal as the inner race.
The advantage compared to a caged bearing: more rollers of the same size.
This is not always safe, the journal surface hardness may not survive.
The needles don't like being turned very fast (even with the cam at half-speed), since each needle is rotating opposite to it's neighbor on both sides.

So, if you were to go hunting for a cam to suit a roller cam bearing block, who do you go to?

There are many. The ones I dealt with were LSM, Bullet and Comp Cams. These are all custom so I doubt you would see much in any listing or catalog other than something mentioning that they provide them and to contact the factory for help. Last time I ordered a new one was ~15 years ago and it was just under $700 so with what has happened with prices over the last few years it wouldn't surprise me if the cost was close to $1000 possibly higher. Maybe I'm wrong, hope I'm wrong for your sake.
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I know several heads up no money worries racers that tried them and switch back to conventional cambearing for several different reasons, I wouldn't run them

Seems like they are trying to solve a problem that doesn’t exist. Cam bearings are relatively lightly loaded. Hell, a lot of engines have been rebuilt without even new bearings.

The problem exists when you get over 1000 lbs spring load

As stated the reason for going to abigger bearing is to be able have a larger base circle allowing for more lobe. You can only so much lobe on a stock cam core before it physically wont fit in the cam bearings. I have engines with roller bearing and babbits, all large cores. And yes the one HUGE difference is the effort required toto turn it over to adjust valves or start it. They say with oil pressure there is little if any loss of power but that is hard to believe knowing how much more difficult turning a babbit bearing large cam over VS a roller. My last predator was a 60MM Babbit bearing and you with a 3ft snap on ratchet on the crank bolt took a LOT of force to turn it over. Yes that is also a consequence of spring pressure but if you go to a larger core cam your likely gonna have a fair amount of spring pressure. It also puts a lot more stress on the battery. Bullet and LSM have cores Wedge cores are always a bit more difficult than Hemi cores. Currently Bullet is making me a new cam for my current predator start ot finihs should be 30 days or less.

There is no "lite load" on a cam that has 500 pounds and 1300+ open. Many reasons to go to larger base circle camshafts but to over simplify it, you do it to go faster. Whether you choose babbit or roller is your choice. But trust me two similar cams with similar springs it aint hard to tell which one has babbit bearings in it. While many say there is no power in that its hard to wrap your head around. FWIW we are changing the vette to a clamshell roller bearing. The reason we cannot get enough lobe on a 60MM core. The reason for most going to the larger base circle is two fold. Yes the larger core for more lift, but that also allows for a more forgiving "backside" to the lobe. Where cams of this nature tend to have issues controlling the lifters and keeping them on the lobe. There is a LOT more to it for sure.