Inliners International Forums General Discussion Engines Cam Journal Diameter Question

I think I found the correct cam journal diameter which is 1.8682 - 1.8692. (I don't have the Santucci book with me.) Am I correct in calculating potential cam base circle where the lobe lift is subtracted from journal diameter? The cam's base circle cannot be any larger than this. That would be the maximum base circle allowed correct?

Journal minus twice the lift is max base circle.

Thanks. So 1.868 minus .700 nets me 1.168. Lobe lift is actually .343 for exhaust, I just used .350. Is that a little too large for base circle diameter? How much room do I need as that would be maximum amount of base circle?

I think you just need to be able to assemble into the block. I'm not aware of any other limitations. There may be some issues with lifter position relative to oiling passage and lifter bores but I don't know about that.

Okay thanks. I know that a larger base circle will be better in general as it helps the lobe profile with ability for ramp rates, area under the curve etc. I'll have to talk to the engine builder to see what would be do able. I know the numbers work in theory. I just don't know how much room would be ideal to help in assembly.

Now I'm second guessing myself on the cam journal size. Can someone confirm that 1.868 is the correct cam journal size for the 250-292 Chevy engine family? Thanks!

1.8687" is what my 62 book shows.
Along with a .1914" lobe lift for a smoooooooth idle.

Thanks! That's right in the middle of the range of tolerances I found on the web.