Simon wrote:Whilst Marsh is not wrong, they came with KH cams or KR/KHK grind as options, as the shop dope shows timing alternatives for both.
Since the comment was raised about early KR cams, I have a few questions about the KHK and -53R cams.
From other recent and related cam topics here on the forum it appears clear that the first KR cam, circa 1952, was the -52R flat tappet cam that was basically an angle ground version of the WR cam with flat-shoe lifter as discussed at the link below.
viewtopic.php?f=8&t=1169&hilit=starcain
The first KR roller cam was the -53R, that is often asserted to be the same grind as a KHK cam. I’ve never seen a -53R cam and understand that in the early KR years the factory was not diligent about clearly identifying the cams with stampings and that many lacked an identifying stamping. So with that brief background my simple question is “were the -53R and KHK cams one and the same or were they distinct offerings?”
In comparing notes with others here on the forum that have measured KHK cams, between 3 of us (Patrick and Starcain) the maximum IN and EX lift at 0 lash ranged from 0.375” to 0.382”. Although these lifts are slightly less than the -53R specification of 0.395”, the difference in airflow at these high lifts is minute and barely measureable, and in turn would have a negligible effect on HP produced, so IMHO seems an insignificant difference.
With respect to duration, within experimental error there appears to be no real difference between the factory quoted -53R specification (IN – 281 deg, EX 277 deg) and my measured values of KHK lobes (IN – 282, EX - 277).
Regarding opening/closing timing, given that timing is specified at such a low lift (0.010”), where significant crankshaft rotation results in very small changes in lift, we would expect to see some difference where one or the other cam might be slightly advanced or retarded relative to the specification, which was the case.
In light of the above I’m not suggesting that the -53R and KHK lobes are one and the same, but the measured results suggest that the subject lobes are so similar that resulting performance would be essentially the same with either lobe. So the question remains, has anyone seen or have a -53R lobe and is the lobe similar to the KHK lobe but with 0.395” lift? Or might this disparity in lift be nothing more than a printing error or difference from design to production?
Eager to hear people’s thoughts on any of the above. Thank you.