Hi guys Looking for some help on a main bearing choice. The engine is an old school small inch Big chevy . Its actually a 396 ran out to a 408 . The engine will have a 6-71 on top making somewhere in the neighborhood of 5-7 lbs of boost for a street application . Im running an Isky Z33 grind solid lift cam and to help prevent wiping the cam out , i went with the Isky "EDM" solid lifters . Now here is where im at and my question , i am running a gm factory forged steel " CROSS DRILLED " crank as was found n all the HP big chevys . I am not sure what Bearings to run . You see im worried that with the EDM lifters and a 3/4 groove bearing that there is going to be to much oil pressure bleed. And oil pressure is one thing i have to have with the cross drilled crank. Should i run a, Half groove or 3/4 ? and what are your recomendations . The target rating for the engine is a 600-650 streetable hp . Its not going to see sky high rpm's I am aiming for a dependable street monster that will see its share of track time , but i also want it to survive for awhile and do not want to run into an oiling problem . Any help would be greatly appreciated.
A standard "P" type or "A" series bearing will do what you want. The "P" series is a tri-metal 1/2 groove bearing that was hot setup in the sixties/seventies, still is for street/strip machines. The "A" series is an aluminum bearing. Similar design. A good heavy duty bearing but just a little more sensative to contaminants, dirt etc.
I talked to the guys at summit also . THey recomended and H Bearing , MS829h Its a half groove Clevite . Anybody ever have any issues with that one ?
Hi "Mac", years ago that cross-drilling deal was the way to go. Things have changed through the years. Having said that, stay with MS829P's, they are all you need! Been there and done it! (Add) We usually do modify all the upper main shells on any "blown" units, we are able to increase the load capacity up to 20%. We've proved this through much testing, with your HP numbers it isn't necessary though. At a minimum we do the front upper shell (I have photos of this mod if needed) due to the blower belt "loads". Thanks, Gary in N.Y. P.S. I'm sure Summit would recommend the "H's" over the "P's", the profit margin is much better. You actually lose some surface area with the chamfers, not alot, but some. The "H's" are required only on shafts with larger radii! Same with the rods, CB743P's!
I ran a cross drill BBC in a road-race corvette. With cross drilled cranks you only need a groove in the top half. Run H series bearings. [ the counter jockey's gave you good advice ] I did run standard "77's" and the engine was "exploding" the surface material. Under a microscope it looked like the surface of a dry lake. This was all checked out in the science lab at ACL [ it was an interesting learning curve for me ] I got all sorts of conflicting advice from engine experts, but I took ACL's advice When I switched to H series the problem was fixed. [ ACL is a engine component manufacturer down our way, now owned by Mahle ]
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