In a journal with an annular groove does the direction of the cam bearing oil hole matter? I've heard differing opinions.

Inline with the hole from the mains. (6 o'clock)
2 o'clock position
12 o'clock position

About in the 4-5 o'clock position is what I do. You want the strongest oil film to be directly at the bottom of the cam journal . If you put it in the 4-5 o'clock position the rotation of the cam will "sweep" the oil quickly down the 6 o'clock position where you need it most.

I would never recommend anything outside of the range of 3 o'clock to 6 o'clock position.

I put them at 12 o'clock one time before I knew better.
Wiped out the bearings in 20 min. cam lobes to. The machine shop
I go to says 6 to 8 o'clock, his reasoning is that oil pressure holds the cam up.
He also told me Dart is putting there oil hole in line with the fuel pump.

more opinions please?

My neighbor put mine in with the hole at 12:mad: . I was worried about it. I took it back to the machine shop with a new set of bearings for them to install and they said that they would be ok like they were. I have not finished my engine yet and I'm still a little nervous about it.

My machinist said I may notice a small drop in oil pressure at idle. I do plan on using a hv pump with a 7qt pan.

I have done either way. A long time engine builder I know ,goes 12 o'clock. He has never had an issue with any of the race engines he has built. My new blown 383 has not had issue and they are at 12. I am running 80 psi cold and 60 warm with a HV pump and 10/40 oil.

Let me explain why I put the hole down in the 4-5 o'clock position. Two things to consider:

1. The cam rotatates clockwise when the engine is running. It will try to sweep the oil in that direction.

2. The pressure the cam puts on the bearings is down. The lifters each push down on the cam at opposing 45* angles. The net resulting pressure on the cam ends up being basically straight down.

3. The tension side of the timing chain is pulling down on the cam to turn it.

All this leads me to believe that the bearing needs the oil most at the very bottom. Now you can add the oil in slightly before that point and it will get quickly swept down to the 6 o'clock position, but it's probably not very helpful to add it AFTER the 6 o'clock point since the oil will be swept UP, away from the point of max. load. And adding it in too far ahead will probably allow some of it to "squeeze" out of the bearing before it ever gets down to 6 o'clock.

Now, technically you can let oil in through the hole ANYWHERE since there is a full 360* groove full of pressurized oil around the entire cam bearing. So it's not unusual that you get conflicting answers on this subject since it's one of those "points of style" type of things. Different builders do different things.

I'm not saying anybody is "right" or anybody is "wrong." I am just explaining that I don't come by my personal opinion for no explainable reason or without consideration of the facts.