12PAUL12, just so you might understand the tappet thing better.
When I rebuild a 258, my new tappets are in, and still "springy", since oil is only on them, NOT IN THEM.
Rockers are put on, One at a time, as this next step occurs
I rotate engine until each lobe on the cam, is down (as if valve, is in the closed position)
I install a "test" pushrod, and use a "dial Indicator" to measure, up and down pushrod travel, from CLOSED VALVE to BOTTOM of the "Springy Tappet"
I really push hard on the pushrod end, of the rocker
I want 100 thousanths of spring, to be gone, in the Dry Tappet, By using a longer or shorter push rod. Without bottoming out the center of the tappet.
This will spring back out, up to 100 thousandths, a little at a time, Every self-re-adjustment, the tappet makesas wear occurs on:
tappet bottom and center top
pushrod (both ends)
rocker arm ends and center
The valve seating in, actually reverses this process, sorta giving back to my "preset" tappet center depth.
I check all rockers and select a pushrod (length), that will somewhat closely achieve this goal, and install them permanently.
Now, when I am done, what I have is 12 dry, compressed tappets, when engine builds oil pressure, they will fill up, they will remain compressed, and start their self-adjusting operation, upward, from my preset depth.
Every time they move up and down, acting like a hydraulic jack.
Springing back out (ever so slowly, over time) WHEN METAL WEAR occurs, as the valve train wears in, then they will slowly adjust back out, over many miles of driving---hopefully never using up the 100 thousandths!
This is the advantage of tappets over solid lifters (no manual adjusting!)
If you replace a tappet or pushrod, as long as its not too long or short, the 1st time it moves up may not be right on the money, the second time up, it will have been self-re-adjusted and be correct new height.
Self responseYou are incredible, Turddog! Where do you get all of this? Its as if you study manuals, talk to machinists, auto parts fellers and have a Knack for repairing stuff, you will/ have make/make some girl really lucky to have you around! I wish I were your neighbor, so that I might get my Jeep fixed by an Expert!
Friday, April 23rd, 2010 AT 9:00 PM