C J Murray wrote: ↑Tue Nov 12, 2019 9:24 pm
Dan Epperly wrote: ↑Tue Nov 12, 2019 7:47 pm
Cam has R200.5 stamped on it.
Well, well, well! That is the dopey cam that was popular in the 1980s I think called Tricom or some such name. The lobe separation is 104* vs 108* for the stock cams and 11* more duration. Why this matters is because the cam takes up more room in the chamber, the valves are closer to the piston by virtue of both of those changes. Guess what cam put those marks in the pistons in my picture?
Dan, I commend you for posting all this! You are doing a great service to those who would go down a similar path of thinking that everything will work out fine if I just bolt it together. Just bolt it together ONLY works by luck or if you are dealing with 100% stock virgin parts. This is why many knowledgable people advise to keep your engine stock. The point is not that all rebuilds should be done to stock specs. The point is that if you don't check everything very carefully your machined parts and aftermarket crappy parts are going to bite you in the ass!
If I can help in any way please email or call. There are others that can help here. You have already helped many people here and I hope the do-over yields a fine result. Throw that cam in the trash.
+1
I had one of those RO200.5 cams, in a set of parts I'd bought, and sent it as a core, to be reground. I concur with C.J., on the extra duration, and lobe centers, hence, Ray's likely reason, to deepen the EX. valve relief.
At least, we've ruled out the AA or any other big bore sets, as culprits. Even those Industrials, are original German big bores, just initially set up as low C/R.
Now the question, can the heads be saved?
I helped a friend with a "crankshaftectomy, in a Ray Litz '58 N, which he converted to a S, in 1975, per the invoice, using factory stock 616-12 cast iron cylinders, and the 8.5:1 cast pistons, Mahle brand, that RO200.5 cam, but... the heads, looked nothing like these pictured. The compensating cut, to the inner fin surface, was conventional, like in Ron's photo...
I do have a set of core 912 heads, from a vintage racer, which have that same circular cut, as in Dan's pic...,