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Tech Question

Frank Capobianco, New Hyde Park, NY, ’74 Plymouth Cuda 410 sb

Rick, I’m building a stroked 340, long valve W2, rollerrocker, roller lifter engine. The right side lifter galley has been sleeved,it will see limited street use. The aluminum blocks that relocate the rockershaft all have a 3/8″ clearance hole top & bottom to mount the shaft. Do youthink this is enough space for proper oiling or should I modify the lowerhole on the oil fed pier? Also, is the pushrod length on shaft mounted adj.rockers only to prevent pushrod cup to rocker interference if the pushrodswere too long & have nothing to do with proper valve tip contact as it wouldon a ball stud arrangment? Thanks.

Frank-

Ideally, you will run the oil pump with a drill and slowly rotate the engineby hand and actually SEE the valve gear oiling! The holes in the stands areclearance holes for 3/8″ bolts – probably enought extra space for the oil.But, offhand, I’d say a rat-tail filing a small groove or notch in the standcouldn’t hurt. If it were mine, I’d do it.

The pushrod length does not change the valve tip contact pattern. Too long,as you noted, can cause obvious interference. Having ’em too short has twoeffects:

1. It actually changes the rocker arm ratio – especially with the valve on,or near, the seat. (all rockers are really variable ratio, this makes theratio vary more during a full sweep). This has almost the same effect asfast-ramp cams – not a bad thing. But it can slam the valves closed prettyviolently, better have good 1-pc. valves. (With a roller cam, I assumeyou’re there already.)

2. However, too-short pushrods causes lots more stress on the adjuster screw.

Therefore, I concur with the conventional view: have no more than 2 or 3screw threads visible below the rocker arm.

Rick

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