Jasam, my plan is to restore this car to original with the exception of invisible performance updates.
Chad, thanks for the post! I know you know a lot about 2,0 engines and have done a few.
Here are the broken studs.
length 50.7mm
length of long thread 19.5mm
length of short thread 16.5mm
Now, the PET claims these are BM 8x35, the original Parts Manual lists these studs as
BM 8x35 SN 1115 DIN 835-8G phr. That means a metric stud, nominal diameter 8mm, 35mm protruding length. . . hold it a minute.
DIN studs are described NOT by the overall length but by the length of the stud that would ordinarily protrude from the surface into which it's inserted. Wow what a sentence, try translating THAT into German.
Anyway, there are really three parts to the stud:
the short threaded portion or "tap end" (
e in diagram)
the unthreaded portion
and the long threaded portion or "nut end" (
b in diagram.)
The "length" measurement of 35mm in this example refers to the length of the nut end and the unthreaded portion, shown in the diagram as "
l."
A few more rules of thumb for DIN studs. Generally, the length of the tap end
e, is, for a DIN 835 stud, 2.0x the nominal diameter of the stud. So for an M8 stud, the
e is about 16mm, pretty close to my measurement. For DIN 939 the multiplier is 1.25x, 938 1.0, 940 2.5.
A guideline for calculating the nut end
b is, for studs whose
l is equal to 2x their nominal diameter but less than 125mm, then 2.0x the nominal diameter plus 6mm. So in my case M8x2 = 16mm +6mm is 22mm. I measured 19.5mm, not exactly right, but a little more length we can live with (as Bruce Anderson would say.)
So I'm looking for a DIN 835 stud with an
l of 35mm. This would imply that the tap end is 16mm, the nut end is 22mm, and the overall length around 51mm. Let me see what I can come up with.