Well, it looks like the '84 slant I picked up has a couple burnt valves; it failed a compression and leakdown test miserably. So... i figure I'll take it apart, and just do a little freshening before I swap it in. Provided that it's all in ok shape when I have it apart, I'm planning on just honing the cylinder bores, and reusing the pistons, cam, etc. The guy I bought it from claims it only had 60k on it, so we'll see...

Since I need to get the head redone, i was thinking, "why not shave the head a bit while it's at the machine shop?".

So my question is: How far can I get the head milled (if at all) w/o needing shorter pushrods on a hydraulic cam /6?

Not looking for a screamer, it's just a "while I have it apart..." sort of thought. Any power increase is a good thing.

Max

A hydraulic lifter SL6 engine (or any non-adjustable rocker arm - hydraulic lifter set-up) is "fussy" about having the correct preload on the hyd. lifters. Too much lifter preload and valves hang open, cylinder pressure drops, valves burn, etc. Too little lifter preload, lifters clatter, cam lobes get flattened, valve seats pound-out.

Here is a thought, recheck the compression and leak-down test with the rocker shaft removed to see if the readings change. If they do, you have to much lifter preload.

Anyway, back to the question, if you mill the head or do any valve work, the lifter preload has to be checked and reset. With non - adjustable rocker arms, the only adjustment is by sizing (grinding) the valve stem tips and / or using custom length pushrods.
DD

Clatter sounds like the noise I get when I really get on the gass in my truck. Might I have a preload issue?

_________________
The Old Goat '83 D150 225-2

AKA Ice Titan

Thanks for the tip about preload, didn't even think about that! I'll try removing the rocker shaft and redoing the leakdown next chance I get (weekend, maybe?)

The previous result was 2 cyl in the 'excellent' range (~25%), 2 hissing out the exhaust (~95%), one hissing out the intake(~95%), and one through the crankcase (rings most likely) (~70%). I gave them all healthly squirts of oil to help seal the rings. I expected readings to be low, since I'm doing it cold, but with 2 cylinders reading so nice, I figured the results were pretty conclusively bad.

Your answer sounds about like what I'd figured - custom length pushrods w/ the milled head. I'll have to think about whether it's worth the expense or not... I'm pretty much just going to be using this engine as an in-between while I build the '73 motor it replaces the way I want it.

The milling may be a bad combo, anyway... I don't want to change the carb and don't want to change the cam. I was thinking that just .5-1 point compression increase wouldn't really demand much more out of the setup, just get a little pick-me-up and possible a smidge of mileage, but mebbe I should think about it a little harder.

Could you maybe shim the rocker arm to make up the difference in the amount of material you removed from the head? Soft aluminum, cut, drilled and de-burred so the bolts will fit may work. May find some sheets in the thickness you need at an aerospace supply place, or get some free scrap, don't need much.

The shims offered for adjusting Mopar V8s with non-adjustable hyd. rocker arms work fine, they come in packs with .015, .030 and .060 shim thickness.
I file down the shim edges so they don't act as a wedge and split the rocker stands.
DD

The curiousity was killing me, so... off came the rocker shaft tonight, and I repeated the leakdown test to the same results. :/ Good thought, but this head is definately in need of a rebuild. I went ahead and yoinked the head to check it out and give a quick look down the cylinder bores. Things definately weren't burning right; a couple cylinders looked down right nasty, worse than I'd expected from looking at the plugs.

The good news is that the bottom end looks great at a cursory glance. I can't feel any ridge at the top of the bore, even with my fingernail, and the cylinder walls still have a crosshatch pattern in them! I'll measure the bores and all that later, but it looks encouraging.

So anyway, since I have a terminal case of the "While-I'm-at-it"'s, I figure I may as well have a little bit of fun with a rebuild. I'm thinking of milling the head a bit (.03 or so) and using spacers the shim up the rocker shaft, picking up a super 6 set up, new rings/bearings/etc, and possibly a slightly hotter cam. I was looking at Comp Cam's RV cam, grind # CR6 260H-10 as a possible step up, but I'm undecided on the cam part of the build right now, but if I do go that way, I'll be sure to check that the oil passages are drilled right! I know that the cast crank/hyd valvetrain aren't the best motors to build, but I'm not trying to make a race motor. If I came across solid lifter valvegear for cheap, I'd probably consider swapping it to the good ol' solid lifter setup.

I'm going to be using this motor in a daily driven Swinger, so good manners is important, and getting 15mpg city would sure be nice. I expect that what I listed above should do that, and probably run on the Cheap Stuff, but I wouldn't whine about using mid-grade. I'm just looking for /6 reliability, a little better than stock performance, better mileage than my v8 Dart, and to have a little fun while I'm at it.