1600DP valves not adjustable, but not stuck - weird geometry? shim'em up? strange dimensions?

I'm rebuilding my 1600DP engine. got some 'aftermarket' heads long ago,
which I'm trying to use. intro: these heads I wanna use differ from my
original german ones in at LEAST the following manners:

their gasket surfaces (at rocker arm cover to head juncture, *and* also
at intake manifold to head (and maybe exhaust system to head, too - I
forget) appear to be UNmachined. they look to me to be only "finely sand
cast"...but more alarmingly, the two "bosses" which the rocker arm
assemblies bolt to also look unmachined. for all I know, though, this
type may be "all that's available new" these days <? could someone
confirm ?>

these 'reproduction' heads I got here must differ, somehow,
dimensionally, from german heads - because on one of my heads, with the
engine long block all bolted together, it's =impossible= to back the
valve adjusters out far enough to get ANY clearance between the adjuster
tip and the valve stem. same applies even if I 'adjust' the valves SO
far that the 'unthreaded tip' of each adjuster, at the non-slot end, is
"backed up entirely into" the rocker arms themselves. matter of fact,
even if I remove the adjuster screws and locknuts =entirely= from the
rocker arms, there's still *zero* clearance between the rocker arm and
valve spring 'tophat'. sheesh. woe is me...<dread>

I'm using: original cam in good shape, new german lifters, original (and
straight) pushrods, original german rocker arm assemblies, these
"problematic" DP heads, and correct german pistons and cyl's.

I've rebuilt about 20 of these engines over the decades, always
successfully - never got THIS weird krap before. admittedly, I always
used orig german heads in the past, though....

anyone else ever run into this problem?

is it possible to "shim up" the base of the rocker arm assemblies (where
they bolt to the head)? what *material* should I use -for- the shims?
aluminum? steel? hardened steel shims? or? budget is tight these days....

looks as if i was to shim the rocker arm assemblies up, say, approx .125
to .1875 inch, they'd "be at about the right height" and be able to
offer me the right range of adjustability THEN. <dread> got the same
head, and situation, on the other side of my engine now, but the opp
side is "slightly better, though still far from ideal". jeesh. it's been
my experience in the past that the adjuster screw tip UNthreaded
portion, and -maybe- a half-turn of thread or so, are normally visible
below the rocker arm, where it touches the valve...

please advise: what to do next? remedies?

thanks much, guys :-)

The heads you are using appear to have flycut by an excessive amount.
Or your jugs have been shortened or the case has been excessively
decked and no shims have been fitted. Or you're using a set of 40-horse
lifters. Or all of the above.

Whatever the cause, either the centerline of the rocker shaft has been
moved closer to the centerline of the crankshaft, upsetting the valve
train geometry, or you're using a push-rod that is too long for the
existing valve-train geometry.

The easy fix is to make up a new set of push-rods, shortened as
required to match the geometry of the valve train. Of course, that
assumes the other engine components are compatible.

It might be a good idea to tear it down and start over. Blueprinting
the parts, cc'ing the chambers and checking your valve train geometry
during a preassembly can save you a lot of grief. You may even have a
set of Brazilian alky heads, some of which are set-up for CR's as high
as 12:1, which would lead to a very interesting but short-lived engine.

-Bob Hoover