Quote:
Originally Posted by Bored&Stroked
Another thing to think about is that flatheads don't have rocker arms - so when you have a higher lift cam like a .425 Potvin, this would be .637 lift on a simple 1.5 rocker. So, to get higher lifts on a flathead, the profile has to be pretty aggressive . . .which also leads to more wear.
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You have to remember that I'm reverse engineering on this forum. This is my first FH build, since 1959-60 era and it was my best friends car.
In the case of the SBC (1.5 rocker) that .637 lift, would put a load of 450 lb on the lifter (300 lb spring) and the SB lifter, is only .843 in diameter and not able to take the same lift rate as a 1" FH lifter. Not to mention (I love that term) that springs for that lift, would normally be North of 380 lb. The FE's use a ratio form 1.72-1.75 but, a slightly larger, .875 lifter. With a .600 lift cam and 380 lb springs, that's 675 lb on the lifter and cam.
I only ask this, because , I've read, more than once, that you have to be careful of what seems to me, fairly low spring pressure or the cam will wear. I just got some hollow Hi Lift Johnson adjustable lifters and I want to make sure I won't have any issues. I'm hoping to have Howard's grind a Schneider 250F cam for this, unless that cam is available, off the shelf somewhere.
Most flat tappet OHV engines, use cast cams, are the early Ford cams, so soft that they can't be hardened to modern spec's and that is the reason they wear?
Frank