Done tons of research, and getting conflicting answers on this. Would really appreciate it if someone could give me advice.

Did a head job on my Disco2 about 10 years ago when I bought the car after it had overheating issues, and had them milled flat. It looked like to me the previous owner had had them reworked before as well, but it didn't look too significant so I just slapped the newly milled ones back on with the original lifters. Was lucky, and it ran great for 10 years. Then it developed another head gasket leak last year with some overheating so I completely restored the heads again, even lapping the valves down to nearly no bleed down pressure loss. I had the heads re-milled again because of some scarring from the gasket leak and a little warpage, about another .0020". Anyway, since it's probably had three mill jobs and the new valve lapping, I decided to put in new lifters as I wasn't confident the old gunky ones would be still capable of readjusting.

The new lifters came pre-filled with oil and are hard as a rock. My question is do I pre-bleed out some of the oil a bit before installing, or is the valve spring pressure in these engines strong enough to initially bleed them down for me and giving the crank a few turns and waiting for each set to adjust? I mean, pre-bleeding them down a bit won't hurt anything just to be safe would it? And yes, I plan to check pre-load gap as well once they are seated correctly as I may need shims if there's too much gap.

After that, I just put everything back together, then make sure to spin the engine for 5-10 minutes with the fuel relay pulled to get the oil pressure up enough to fill the lifters first, right? Then put the relay back in and should be able to start her up.

 

.020" is a very significant cut just for some head clean up. Why are you having them milled and not just surfaced? If they've already been cut that much and they need that much again, then you need to be looking at head saver shims or another set of heads. You're far outside the factory spec, and you're going to start running into detonation issues because of the significant increase in compression ratio.

As for lifters, I always just drop mine in a bucket of rotella to soak overnight before installing. Lifter manufacturers are almost universally against "pumping up" lifters if that's what you mean by bleeding, and as far as compressing the piston in the lifter - you do not measure lash with the lifter compressed.

Also, 5-10 minutes is a long time to crank a dry cam. I'd crank it for 30 seconds or so or you're going to wipe lobes.

 

Oh no man, not .02, .002. Oh and I might have misused the term "milling" I use it interchangeably with being resurfaced. I was concerned about going past spec as well but my machine shop guy said from his experience he could visually see they were fine after the last resurface. Other than taking his word for it (30 years experience doing this), I can't see any millage indicators on the head or any way to caliper check if he's right or not. I would love to know myself if they're cut too far before wasting time putting them on beforehand.

And yeah, I will be checking for pre-load gap when the valve is fully closed and the lifter isn't under load. I just want to make sure the damn lifter piston can move down and bleed out at initial set under the valve spring pressure alone.

 

Can't wait to get home to check em out

 

Oh man! That's way more reasonable, I misread. My mistake.

You've for +/-.025“ on the height with hydraulic lifters since they are somewhat self adjusting, so you should be fine to just slam it back together. .006" give or take does technically put you outside factory spec, but if it were mine I'd be perfectly comfortable with that.

 

UPDATE: Ok, if I would have just read a little further down in the RAVE manual (duh), it explains those numbers above are for a NEW head and you can mill down just another .5mm.

6. Cylinder head can be refaced to 0.50 mm (0.02 in) max. below head height.

Thus, the minimum dimensions for my resurfaced head would be: A: 22.44 B: 62.06

So, yeah, I'm a little past spec, but considering this is a cheap Harbor Freight Digital Caliper with a dubious accuracy anyway, I think I'm willing to risk it without a shim.

-- END UPDATE --

Ok, my numbers are as follows. Frankly I'm confused as the the spec listed above. Is that the minimum needed or what a NEW head should be? Am I significantly off spec here?

LEFT HEAD
L 22.37 62.17
R 22.39 62.00

RIGHT HEAD
L 22.00 62.13
R 22.17 62.53

 

Sounds like you’re right at the limit now, +/- the HF factor, assuming everything above is correct. Shaving it again will seem to surely put you below spec. You may be able to get an MLS headgasket(s) from Cometic that will give you some height back.

 

Oh, it's already been resurfaced/shaved, just wanna drop em in soon as I can. Those numbers are where it's at now after the last resurface. I was just concerned about the height because by now It been shaved within an inch of it's life! So, yeah if I can still use em, this will be the last time I rebuild em. Was considering using shims, but it just feels wrong putting something between the gasket and the block like that when I've spent so much time getting those finishes perfect.

So your idea about using MLS gaskets instead of the regular composite ones I've used before (STC4082) is a good one! MLS are typically thicker right? If they can give me another .02" (.5mm), that would be worth my while to use instead of my composites. Does the finish matter (RA) with MLS versus Composite? Right now the heads are at a mirror finish. I'm assuming it can't hurt, smoother is better right? Should work for both types?

Never shopped around for MLS gaskets. Do they come in different thicknesses? I checked out Cometic's website, but they don't have the Disco2 listed in their inventory

 

"I'm assuming it can't hurt, smoother is better right?"

I used to think the same, but some research lead me to the conclusion that a specified degree of roughness allows the surface to "bite" into the gasket better and form a stronger connection. Otherwise the surfaces would be mirror polished from the factory, and they aren't.

Maybe check compression after the heads are on, and re-jigger if pressure is really high, but these engines are pretty forgiving, not F1 or NASCAR.