Helping with a cam install on a Chevy small block. Fresh machine work etc. New cam bearings etc etc. Tried to put cam in and no go. Then tied a stock cam--no problem. Friend took back to machine shop. He tried the same--stock cam ok, after market NG. Lobes higher than bearing surface by .005 to .010 larger!! Never seen this before--returned cam and waiting for another. Anyone seen this before?
Yep Jim me too-I checked it too. Friends Uncle is doing most of ***embly and he could not believe it either. He is an engine guru in his late 70's and has built Offys etc etc and still builds high end sprint car motors as well. Has done this for 50 +years. Summit is sending a new cam. It is a 70 350 that has been bored, decked, line honed etc etc by a high end machine shop.All was good til cam install.
What does that have to do with anything....thyy all have the exact same size cam bearing bores in them. Every stock SBC block ever made has the same size cam bearing bores. The only difference in the very early 265 is that there is no oil annulus groove behind the bearings so it requires a cam with a groove cut in the rear bearing journal on the cam for proper oiling. Sounds like the cam grinder screwed up, lobe should never be higher than bearing journal diameter.
No custom grind Crane 266/440 have installed many--installed two last year in 327's mild cam--used to be the same specs from Cam Dynamics in the 80's
More than enough lift. Sounds like a bad set-up on the cam grinder. I spent 15 years with an aftermarket cam mfg who supplied OEM and the HP marketplace. Can't remember ever running across that particular problem.
I have put together quite a lot of SBCs.......never saw lobes that were bigger than the cam bearings......
me either but it was that way. Talked to a custom cam grinder a bit ago and he said it is very rare but does happen. He has seen it before.
I wonder how the cam could be installed with lobes outside the journal diameter.......some kind of voodoo? Two-piece bearings? Sounds like a data input mistake on the machine........right cam, wrong lobe profiles.....
We bought a cam once where the bearing journals were larger diameter then the bearing inside diameter. Sent it back and they replaced the cam with one of the same part number, the second cam was good. Stuff happens and sometimes slips by the inspection point. Happens with everything from time to time. Get the replacement and move on. Gene
I've read about a vintage engine that had a notch in the journal for a tall lobe to fit through. Can't remember where I saw it or the engine type though. Was probably really old and just a splasher system that didn't have pressured oil to a bearing. Some old engines ran the cam directly on the iron bore in the block.
***mins B series engines (the engines in OT Dodge pickups as well as a million other applications) have no cam bearings, the cam rides directly in the bore of the iron block. Bearing inserts are available for rebuilding engines, but they do not come with them originally (same thing with cylinder liners).
Not to mention virtually every overhead cam application runs without bearing inserts Sent from my iPhone using H.A.M.B.
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