[67Chevelleguy]

Hi guys. Im rebuilding a '98 350 and have a question about the camshaft bearing installation. There is a groove aroung each bearing surface in the block with a feed hole in the bottom from the crank and a relief hole in the top. The rear is different with a feed hole in the top middle and two other holes that are <30*> offset to feed the lifter valleys. I talked to a machine shop and they say to line the bearing holes approximatly 45* offset with the feed hole in the block to keep oil pressure up. How is the rear bearing installed?
Thanks! :beers:
-wes

 

[Tom Mobley]

>> "feed hole in the bottom from the crank and a relief hole in the top"

Oops, actually, oil feeds down from the galley that runs along the top of the cam, to the groove in the block, around the cam bearings and down that hole to the crank.

with the block upside down on a table or engine stand I install the rear 4 bearings with the feed hole straight up, which will be straight down with the engine right side up. the front bearing is the one with 2 holes, I put those so they will be at 4 and 8 o'clock with the engine rightside up. Be careful with the bearings, they're not all the same. there's a paper in the box that gives the positions.

 

[BillK]

Wes,
The oil holes should be at about 2-3 oclock looking from the front with the engine sitting the way it is in the car. The front one will have the holes at about 10 and 2 oclock. Sorry Tom, the holes should never be straight down towards the mains. The pressure of the valve train pushing down on the cam can close off the oil holes and restrict lubrication.

This is different from a Rat because the Big Block does not ahve a groove behind the bearings.

 

[BillK]

From the DuraBond cam bearing site:

 

[racecar100]

Please give me the DuraBond cam bearing web address Thank you

 

[CNC BLOCKS N/E]

Remember that is your using big springs and high lift cams you may want to get into a et of performance cam bearings.

We use the ACL's as they are an aluminum bearing and are much stronger the Durabonds CHP-8 that are Babbit as we have tested both in circle track engines and after a season of running the ACL show very little wear compared to the Durabonds.

 

[BillK]

Please give me the DuraBond cam bearing web address Thank you

Looks like DuraBond's site has now merged with Mellings. I had that diagram on my hard drive from quite a while ago. They used to have other interesting info on cam bearings.

 

[gregpbass]

Hi guys, I'm knew to the site and just wanted to say hello! I'm very interested in your comments as I am installing new cam bearings in my 98 vortec motor also. I'm going to have to double check the hole alignment on the rear four after reading your thread. I read some interesting info on the clevite website that you might find interesting. My problem is that the front bearing fits snugly but will fall thru the hole with a slight push. I've bought two other sets with the same results and I'm sure it's the right bearing. I'm considering putting some locktite on the outside of the bearing to hold it in place. What da ya think?! The original bearing was a clevis type (not machined) and I can't find another to replace it with. Any advice would be appreciated. Also, do all 98(or vortec motors) 350's have a groove machined in the cam journals on the block? I don't remember seeing this, but I wasn't looking for a groove either. The front journal does.

 

[CNC BLOCKS N/E]

Hi guys, I'm knew to the site and just wanted to say hello! I'm very interested in your comments as I am installing new cam bearings in my 98 vortec motor also. I'm going to have to double check the hole alignment on the rear four after reading your thread. I read some interesting info on the clevite website that you might find interesting. My problem is that the front bearing fits snugly but will fall thru the hole with a slight push. I've bought two other sets with the same results and I'm sure it's the right bearing. I'm considering putting some locktite on the outside of the bearing to hold it in place. What da ya think?! The original bearing was a clevis type (not machined) and I can't find another to replace it with. Any advice would be appreciated. Also, do all 98(or vortec motors) 350's have a groove machined in the cam journals on the block? I don't remember seeing this, but I wasn't looking for a groove either. The front journal does.

There should be an annular groove in back of the cam bearing in the block, Sounds like the cam journal is over size on that block and may need to be line borred to a .010 over or bigger as you can go .040 over.

 

[BillK]

My problem is that the front bearing fits snugly but will fall thru the hole with a slight push. I'm considering putting some locktite on the outside of the bearing to hold it in place. .

Wont work Might have had an oversize od bearing in it from the factory. You might be able to find someone to machine just the front journal for a .010" os bearing, but usually you do all 5 of them.

Also, what do mean by a "clevis" type bearing that you say the original one was ??

 

[Tom Mobley]

Clevite bearing?