When I ordered both my Comp and Lunati roller cams, both companies had me specify if I wanted the rear journal groove.
.
I bought both second hand so I can't say as to how or why, but you would think that any cam company would put the groove their standard (since that is how all 348/409 cams are) and that you'd have to special order a cam without one if you didn't want it for some reason. I can see why they don't do it on 396-454 cams as the only ones of those that need it are the 65 & 66.
With a grooved rear cam bearing, you could probably get away with no groove in the rear cam journal, however, I hate that word "probably". Call Comp and get their reasoning for sending out the cam without a groove. Personally, I would have the cam grooved at the local machine shop.
I guess I could call them Ronnie, but I trust everyone here's knowledge of the W a thousand times more than ANY of the parts manufacturers. There may be a couple guys at Comp (and at each company) that know 348/409's, but the chances of me getting one on the phone are zip I bet.
Instead of going with the CH5 cam bearings, I bought the CHP4's and had the oiling holes drilled to match the rear W bearing. Learned that one from ya'll since I will be running more spring pressure than is recommended on the stock replacement W cam bearings. I'm pretty sure that rear bearing in the CHP4 set is not grooved. Even if it is, I am with you on hating that word "probably". Better to do what we all know works than gamble.
I seem to recall another fix is to cut a groove in the journal in the block.
I saw that in an old post while researching this last night. I'm sure that would work, but it seems like it would be harder to do than to just groove the cam. Plus if the block gets grooved then a grooved cam was used in it later, it seems that would be an oiling nightmare.
Chevrolet put that groove in the rear cam journal for a reason,I'm wouldn't try to reinvent the wheel in something as important as the oiling system.
My thoughts too Don.
I am shocked that I've ran into this with BOTH cams yet didn't find where anyone else had received one that wasn't grooved. (Although did see several posts recommending to check and make sure it is.)
At least I got them both at prices that I can have them grooved and still come out very good. I've been swapping a lot of late model Trans Am parts to my machinist for fab work out of his shop at home. The machine shop he is half owner with and out of respect for his partner he doesn't swap out machine shop labor. Maybe he'll fix them with no more $$ on his mill at home.