Reworking the 273 Adjustable Rockers

nm9stheham said
there are 3 places where the oil flow TO the rocker shafts is limited:
1. The 'oiling interrupter' holes in the cam: .049 sq inch flow area and about a 5-6% duty cycle per calculations and some estimating
2. The head bolt to oil passage clearance inside the head, approx .050-.060" sq inch flow area with standard head bolts; this will get restricted down further if the ARP head studs are used, since the studs are considerably thicker than the bolts.
3. The clearance between the rocker shaft hold down bolt and the hole in the rocker shaft through which it passes;

So the rockers will rise in level to some level due to this pulsating oil flow and the level will fall due to the outflow from the shaft. With some RPM's I think the shaft will fill fairly well, BUT for the pushrod oiling holes to be effective, the shaft has to fill higher since it is 'uphill'.

1. If you haven't read Guitar Jone's Sticky titled "Anyone interested in my oiling mods I did." page 7 or 8 I think talks about the restriction of the oil passage to the head by turning the cam bearing. Then drill a hole thru to the main oil galley to make the heads full time oiling.
They also make cams with groves around the #2 and #4 journals for full time oiling. This is fine for a street motor but not a racing motor.
2. Never used studs. Not aloud in NHRA stock as far as I know. So you know more about this than I do.
3. Unless you have drilled out the holes for bigger hold down bolts this should not be a problem. On the original 273 shafts that is I've never used after market so don"t know about them.

If your using a high volume pump the rocker shafts will always be full. The pressure will vary with the different rpm levels but they never will drain out all the oil.

The thread was started to show how to fix the rocker pushrod, valve tip gaulding problem.
Now it has gotten interesting with all the input from you guys. An Yellow Rose saved my engine by getting me to check my rocker shafts. I found where my engine assembler put them in upside down plus he did not remove the plugs in the end of the shafts and clean them out. My bad.

Now over on the right side of the post were it says 'edit" or "quote" is a "Thanks" button feel free to push it anytime you see it.