Looking through the federal mogul online catalog for main bearings I came across two options. O.E Replacement P.N 4663M and Competition Series P.N 139M I'm assuming the O.E replacement (Copper-lead material) are the ones I want, because it's a standard 383. The competition series are made from a differnt alloy and have a 3/4 groove. I assume thats for a high-volume oil pump? I hate to assume, so I'd thought I'd ask. Out of curiousity would a competition bearing be used more on circle track? Thanks

Maybe I scewed up, but I just went for 4663M's.

I suppose the 139M's are a little better.

The competition bearings have 3/4 oil grooves. This allows oil flowing to the rods at all times during rotation.

I like the 3/4 groove bearings better than the full groove Clevite 77's because there is more bearing surface.

i like anything better than clevites, they're junk and there's no control of their manufacturing process.

I guess thats kinda why I'm looking at the FM, too many people talk about Clevite's quality issues. So I got the right bearing manufacturer down. Next is choosing which ones.

Five7 - what kind of engine did you use the 4663's in? street/strip type motor? rpm range? power output?

One half of the bearings have a groove thats fits in the cap or block, I can't remember. So on the competition bearins, the 3/4 groove would extend into the other half? If they supply more oil to the rods wouldn't you need a high volume oil pump? My guess would be because of the higher rpm that they would need more oil. I'm not really sure. I plan on having my bearing clearances at stock spec. Maybe RB could shed some light on the subject...

I got them for the ZZ shortblock I'm putting together for street/strip in the Camaro.

The 4663m bearings are listed as a full groove in Summit.

Why can't I find any FM bearings that have the half groove? I don't need a high volume pump and full grooved bearings. I trust the very reliable SBC oiling system.

I went with the FM 139M bearings. They are 3/4 groove. I'm using a standard volume oil pump with a high pressure spring. Bearing clearances for the mains are .002-.0025 (I forget the exact numbers) and .0027 on #5. Rods are ~.002 (again forget exact numbers). Oil pressure is great, 60-70 psi cold start and about 40 psi hot idle with 10w-30, I might switch to 5w-30 and see how that goes. Couldn't tell ya cruising, because the car hasn't been outa the garage yet...

4663 are half groove, not full groove.

Summir lists the 4663m FM bearings as a full groove, upper and lower.

http://store.summitracing.com/partde...5&autoview=sku

And JEGS doesn't even list the 4663m's in their catalog....I would really like to stay away from Clevite for this build.

It doesn't matter what Summit calls them. Federal Mogul calls them half groove, and the sets I have laying around all agree.

I believe you and I don't want to start anything stupid but I would hate to order them and get full grooved bearings.

Is there a possiblilty FM changed the design or is there a difference between the 4663m's and the 4663's? I searched just for 4663 and didn't find anything.

They don't have a "4663", just the "4663M". The "M" indicates that it's a kit of different bearings. It comes with 4 3201CP and 1 3202CP for the rear main.