Earl Wrote:
========================================
>
... Getting a 480 (or a 490) to run perfectly square
> in forward and reverse would be a major under-
> taking starting at ground zero and going from
> there. In the recent past some valve gear parts
> were "put to the print" which made things worse
>
and {since} the rest of the engine was not "to
> print". The only thing to do in the interim is to
> make the engine run decently square in forward
> motion in the "company notch" (2-4 notches from
> center) and get a good 1/8" of lead in the valve.
Thanks, Earl -
What do you mean by "a good 1/8 inch of lead in the valve"? That the valve should "lead" the piston by opening 1/8 of an inch just before the piston stroke starts in the opposite direction, or that the valve has 1/8 inch to go before opening when the piston has reached its extreme position at one end or the other of the cylinder, just about to start its stroke in the opposite direction?
- Roosso
p.s. There is a fairly thorough discussion of the Walschearts valve gear at [
en.wikipedia.org], of which the following is a brief excerpt. Note that the contributor of this part of the article seems to be British, and the terms "Fly Crank" and "Fly Crank Rod" are used to identify of what we Yanks usually call the "Eccentric Crank"* and "Eccentric Rod". Note also a minor error in the last sentence above the diagram - EFFICIENCY, not POWER, is increased as the radius rod is moved closer to the pivot point of the expansion link.**
Many other illustrations of valve gear - including an animated but much smaller version of the above - can be found by Googling "Walschearts Valve Gear".
* Not to be confused with certain occasional contributors to this forum.
** In other words, 'closer to the "Company Notch"' - reducing the usage of steam, hence fuel & water, and thus reducing the company's expenses.