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

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...

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. 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