Milling a slant six head

A friend has the head off his 225 to fix an oil leak. The only reason he has the truck is to abandon it at the airport terminal when he is flying. As such, he doesn't want to spend any unnecessary money on it.
It's a lean burn hydraulic motor. Compression was a nice even 135-139 psi on all 6.

Other than accounting for the difference in head gasket thickness how far can he cut the head without having problems with the hydraulic lifters?

It would be nice to get a bit more compression.

I never did a Hydraulic cam but I had a solid cam 71 That I think I milled about .080 but gave about .020 back going from a .017 steel shim to an .037 Fel-pro blue. Stock cam I just put in i think they were 1.88" (360 size ) intake valves, a Factory aluminum 2BBL a 6 into 1 JR Header and a single 2 1/2" exhaust with a walker super turbo muffler, this was back in 1988! Used a 2 barrel 318 carb but I wanted to try a progressive 2bbl Weber on it and try to get 30MPG.

It ran really good....for what it was but the compression (and my mid 20 yr old lead foot!) eventually wore out the tired old rings.

I always wanted to find an old 170 with the short stroke and the old aluminum case 833 O/D 4 speed and build an old 64 valiant coupe and turn it into some kind of MPG champ.

170 has much lighter internals, too.

In this case, I'm worried about bottoming hydraulic lifters with a milled head using stock pushrods and non-adjustable rockers.

That's the big question is how much room in the lifters?

The head can stand -.100" easy. If he has a valve job done it will sink the valves a little too.

Realistically, you need to take .060" at least to do much good. I'd bet the lifters will be bottomed out or very near.

What did it have in it for a head gasket, steel shim? If so a Fel Pro will add about .025" back.

I'm assuming a hydraulic slant doesn't have adjustable rockers?

Can earlier adjustables be swapped in?

Kevin

Yup
You need to mill at least the difference in original head gasket thickness vs replacement head gasket thickness just to stay status quo and not lose ground.

No. The hydraulic Slant oil the lifters from the top down through the pushrods.

The stock gasket on the layer /6 was composite, not a shim. Measuring the fire ring shows it to be close to thickness of the replacement.
Van he get away with .020 or .030 without crashing the lifters?

Again, the only reason he bough this old low mileage farm truck was to avoid leaving his Redeye at the airport terminal for days on end.

hi '
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if you mill the head you could shim up the rocker arm shaft to unload the lifter some , prob get away with .030" and still be fine .

Without knowing how much travel is left in the lifters the only correct answer is "maybe". In all honesty a .020 or .030 cut isn't going to gain anything. It's .0066" cut per CC of chamber, so .030 won't get 5 CC. You might get the compression up to 8:1.

IF my old brain remembers correctly, there SHOULD be about .090" of travel left in the lifters.

If you pulled a composite gasket out it has most likely been apart before.

Worst case tho, pushrods are cheap... and you only need 12 of them :-)

1981-1984 truck /6 used composite head gaskets.