Hey folks,

I am waiting for my heads to return from machining and then I'll be reassembling the top end of the motor in my 2004 Disco II.

QUESTION: Is this the correct way to check preload: Roll the first cylinder to top dead center where the valves are both closed. Check the gap between the bottom of the push rod and the top of the hydraulic lifter cylinder. Somewhere between 0.02 and 0.06 is acceptable.


thanks

ed

 

I don't know what you could use to measure between the pushrod and lifter, or between the pushrod and rocker.
A feeler guage isn't going between either.
Both ends of the pushrods are round, and where it meets the rocker and lifter is cup shaped so it fits.
The rocker shaft mounts can be shimmed.
You can search the Rave manual.
I'm almost done with a total engine rebuild now.
I just torqued everything to spec.
A hydraulic lifter can compensate for a small amount of wear.
To each there own, but I'm not concerned with a hydraulic lifter V8 that redlines around 5k rpm, and will rarely see over 4k.

 

I never figured it out, and my heads were not shaved, it ran well before, so I didn't sweat it.

That said, they make pencil leads of various thicknesses. You may use those, or I believe rpi engineering suggests filing welding rods to various thicknesses to check.

 

Quick and dirty: keep turning the engine over and monitor one bank at a time, look at one lifter on each rotation and ensure it never becomes fully un-compressed, i.e. the lifter cup is always pressed in ever so slightly at TDC

Best: look for anything around the house like a paperclip, nail, etc and find two with the correct thickness, 0.02 and 0.06. bend the tip slightly so you can stick it into the lifter cup
repeat process of turning engine over and making sure the gap between the lifter cup and the cage falls within 0.02-0.06

Shim the rocker pedestal accordingly

Pretty simple to do and definitely worth doing. Otherwise you could end up with ticking

 

You can feel .02-.06 of slack by just grabbing and trying to move each rocker when it's valve is closed.
Not precise, but works. Once the lifters pump up with oil, they will apply more pressure.
I work in QC, and measure everything, but this measurement is a real pain to get accurately.
For reference, .020 is roughly 2.5-3 beer cans thick(can wall thickness). So, if it's out of spec, just grabbing and trying to shake the rocker will tell you. Tight with no rattle or movement, cold engine, and it's good.
Also consider, too much shim under any bolt, and you can flex the rocker shaft.
The odds of too tight a clearance is also unlikely, as parts wear to larger openings, and rockers are rarely replaced, or need it. New pushrods and lifters are unlikely to be made oversized, but can be measured and checked before assembly.
I measured everything in my engine as I assembled it.
It just needs the valve covers on and put back in the truck. I have yet to measure rocker clearance, and came to the point to where I am comfortable with how they are.

 

Im with Sixpack on this, hydraulic lifters eliminate the need for adjusting/or adjustable pushrods. You really need something to be out of whack for the needing to try and make any adjustments with your rocker arm shaft or pushrods. As long as the push rod is near the mid stroke of a hydraulic lifter, your good. To do this correctly, you need the lifters to NOT be pumped up with oil. You cant really compress a lifter by hand that is full of oil.