Snip of look before you buy lamentation. We've no doubt all been there, done
that. I have anyway. :-(
> So, I measured the lobes on both the new and old cams to see if they
> were the same (Hey, it's SOMETHING!). Well, unless I measured wrong
> (Possible, I'm going to go take the measurements on the old cam again
> tomorrow with a more familiar micrometer) I got a lobe height of about 1.38"
> on all the lobes of the old cam, and 1.32" on the new cam. Unfortunately
> the stats in the manuals don't give me lobe heights. The closest thing I
> could find was valve lift. Does anybody ever actually measure cam lobe
> height? Do any of these numbers sound familiar? Does Anybody know how to go
> from valve lift to cam lobe height, or is it not that simple?
You need to measure the height of the lobe and compare it to the "base circle"
which is the measurment perpendicular to the tallest direction. So subtract
the measurment of the base circle from the lobe O/A height and you have the
lift at the cam. The lift at the valve is then that number times the ratio of
the rocker. Measure from the center of the ball that the pushrod engages to
the center of the rocker shaft (perpendicular to the pushrod travel) and then
from the center of the rocker shaft to the centerline of the valve stem (again
perpendicular to valve travel). These two lever lengths give the rocker ratio.
I hope this is reasonably clear. ?
> Anybody have any great suggestions on what I can work on while I
> can't work on anything? And don't anybody in the know say my Spit's engine,
> because I'm currently denying that the crankshaft is bad. Hey, ~2 PSI oil
> pressure at 60 MPH isn't so bad, right? (And it only rattles when hit the
> gas :-) Besides, nobody on the MG list would tell me to work on a Tri***h
> now would they?
>
> ----
> Jeremy DuBois jer@thlogic.com
> Manager, Info Systems http://www.thlogic.com/~jer/
> Thermalogic Corporation '60 TR3A, '74 MGB, '76 Spit
>
Work on the Triwhateverumph! :-)
Ken
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