SBC Cam Bearings: Which One not Used?

[ghrarhg]

I've tried searching and found very little info, and what I did find was conflicting between here and v6z24. Which bearing gets tossed out of the 5 in an SBC set?

I have 3 different bearings that pair up as: 1, 2 & 5, 3 & 4. #1 bearing is the largest of the 5, 2/5 being next largest and 3/4 being smallest. # 1 is the only one with 2 oil holes. None of them have a groove for timing set oiling.

I've read #1 gets thrown away, but then what do I do as far as having 2 oil holes in the bearing behind the timing set?

[ForcedFirebird]

IIRC, there is a 660 stock bearing with 2 holes...front maybe? been a while since I installed them. Might have a pic floating around

[ghrarhg]

The front bearing in the 660 has 2 holes. I figured this was to help support the load from the timing set and I wanted to make sure whatever bearing went in matched.

I have pics of the stock bearing with 2 holes, 1 at 3:00 and 1 at 6:00 as you face the timing cover, that i'll post later.

[geoffinbc]

The one odd one gets tossed. The 660 has 2 sizes the front and rear are about .010 larger on the OD that the 2 center ones. Why does it matter anyway? Just buy a box and install the ones that fit and toss the last one.

[ghrarhg]

The one odd one gets tossed. The 660 has 2 sizes the front and rear are about .010 larger on the OD that the 2 center ones. Why does it matter anyway? Just buy a box and install the ones that fit and toss the last one.

I have measured these numbers:

#1 2.025" (this is the one with 2 holes in it)
#2 2.015"
#3 2.005"
#4 2.005"
#5 2.015"

It matters to me because the front bearing from the factory had 2 oil supply holes in it. I figured this was to help support the weight and torque applied by the timing set. By running a bearing with only 1 hole, am I going to wipe it out? Do I have to drill the #2 bearing to have a second hole?

[geoffinbc]

No you don't need the extra hole. I really don't know why it is there. The Chevy power manual says to align all bearings with the holes at 4 o clock. I am running them and they work great. The SBC bearings are wider so there is more area for support anyway.

[ghrarhg]

I know you said that the extra hole isn't needed, but it seems like quite a few engines have it that way.

I can easily punch another hole in it with a drill press. Is there any reason why I shouldn't?

[geoffinbc]

I don't see why not. Just make sure you chamfer the edges and make it the correct size.

[ghrarhg]

Ok, punched the second hole at lunch time, but where is the oil groove supposed to go? I checked my #1 bearing when it came out, and I didn't see it. I have to add it to this one, but where?

1) Is it on the ID or OD?

2) Where is it relative to the other holes?

3) Dimensions of the groove, I found someone posted it is 0.080 wide and 0.015 deep, can anyone confirm this?

Thanks Jon

[geoffinbc]

If your talking about one to feed the thrust surface of the timing sprocket then I am not sure. But I don't believe it is necessary. Factory bearings never had it. As long as the thrust surface of the gear meets the block correctly there is no need for concern there will be plenty of oil to lubricate it and excess is not necessary. Do you see any excessive wear on the block now without the groove?

[ghrarhg]

Yeah, that's what I'm talking about. There was a previous thread that said to make sure to cut the groove in it:

http://60degreev6.com/forum/f97/replacing-cam-bearings-t42820

See Post 6.

The block doesn't seem to have excessive wear. Even though I didn't see the groove in my bearing, I thought maybe it was an improvement over the years since mine is in an 88.

[geoffinbc]

My bearings don't have the groove, I don't think any do. If I was really keen to supply oil to the thrust surface I would drill a .030" hole right into the main oil galley that runs from the cam bearing to the main bearing. This would supply pressurized oil right to the thrust surface. But honestly why try and fix a problem that does not exist?