KH vs KHRM Motor Differences?

Racing K Models

Re: KH vs KHRM Motor Differences?

Postby wz507 » Tue Mar 03, 2020 2:59 pm

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.
Last edited by wz507 on Tue Mar 03, 2020 3:35 pm, edited 1 time in total.
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Re: KH vs KHRM Motor Differences?

Postby EKHKHK56 » Tue Mar 03, 2020 3:20 pm

I think you are on the right track. I know Tom Sifton used one cam with less duration than front intake KHK, although the normal lift increase to .395. He also timed it one tooth advanced from stock. 12°. In Joe Leonard's 1954 Championship KR45. This was to tune the two cylinders as individuals like they are. It is a fact that with same cams, etc, the rear cyl in a V45 arrangement gets a longer intake drink than front. This must be due to different piston dwell times between cylinders at this event time. To increase lift to .395" takes a few minutes on a belt sander to take .020" off the base circle. EZ PZ.
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Re: KH vs KHRM Motor Differences?

Postby panic » Tue Mar 03, 2020 5:22 pm

The gears timing the individual cams each have 28 teeth, or 25.7° per tooth (the result of moving one cam w/r/t its neighbor).
Re-clocking the entire gear train (by changing the 36 tooth #2 cam's engagement with the 18 tooth pinion gear) moves them all 20°.
There is a method of obtaining finer adjustment to the entire train, read my comments here: http://victorylibrary.com/tech/degree.htm.
Branch corrected lobe positions by cutting the lobe free of the gear and welding it back.

By "longer drink" are you referring to the manifold volume?

Since both cylinders have the same stroke length and connecting rod length, how is piston dwell different?

W/r/t KHK vs. -53KR cams: even if the durations are identical, are the actual events identical (ICL, LSA)?
[url="http://victorylibrary.com/L-BK.htm"]The Linkert Book[/url]
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Re: KH vs KHRM Motor Differences?

Postby thefrenchowl » Tue Mar 03, 2020 5:39 pm

My set of 54 OEM KHK cams (same as KK cams) have the same duration except one cylinder timing is shifted 10 degrees away from the other.

Front cylinder:

Image

Rear cylinder:

Image

2 deg diff is machining tolerance, 10 deg sounds more like by design to compensate for the rear cylinder bias...

As for KK/KHK cam and KR cam lifts, one simple explanation for slightly different max lift is the operating rpm... KK/KHK = 6000/5500, KR = 7500...

Same cam in both engines would not fulfil all their different requirements.

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Re: KH vs KHRM Motor Differences?

Postby wz507 » Tue Mar 10, 2020 5:02 pm

Here is another piece of data to ponder on early KR cams. A friend recently provided a lender KR cam (KR2). The image below shows a KHK and the subject KR cam and it is clear from this image that this particular KR cam has significantly longer duration than the KHK cam as evidenced by the broader nose and same size base circle. Because this cam is considerably longer duration than a KHK cam, this suggests it is not a -53R cam since the -53R cam has the same opening/closing timing and duration as the KHK lobe.

Since this cam has no other identity aside from the KR stamping can we assume it is the next member in the chronological series of KR cam offerings, namely a -55R cam, which is considerably longer duration than a KHK cam? The next KR cam in chronological sequence following the -55R would be the -58R which is believed to be the 1st KR cam to be stamped with alphabetical cam ID and labeled A & I (IN & EX). Thereafter it is believed that alphabetical characters were used to identify factory cam offerings. The -58R IN lobe was also of considerably longer duration than the -55R and would therefore be inconsistent from an appearance standpoint with the subject KR2 lobe image, which is slightly longer duration than a KHK. Since the KR2 lobe appears to be too long in duration for a -53R lobe, and too short in duration for a -58R lobe is it in fact a -55R lobe?

The last bit of info to report here is the lift of the KR2 lobe. If it were a -55R or -58R the IN lift should be 0.395” or 0.420” respectively. The KHK and KR lobes picture above were measured with a dial caliper to determine the overall lobe height and base circle diameter so maximum lift could be determined. Quite surprisingly the KR2 lobe was 0.375” lift and the KHK lobe was 0.377” lift. The significance of this result is that no matter which KR lobe we have here it should have been at least 0.395” lift and it comes up ~ 0.20” short of that.

So now coming full circle back to my original query in a previous post in this topic about the KHK and -53R lobes being one and the same, with the exception of lift (KR specified at 0.395" and KHK actual averaging ~ 0.375-0.380"), the above finding suggests that at least one early KR cam has lower lift than the specified lift of 0.395”. Perhaps this is another piece of the puzzle pointing to the KHK and -53R lobe being one and the same and that in fact the -53R lobe may also come up a bit short on lift, which makes it the same as a KHK?

LR KHK & KR2 lobes.jpg
LR KHK & KR2 lobes.jpg (134.42 KiB) Viewed 3626 times
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Re: KH vs KHRM Motor Differences?

Postby EKHKHK56 » Tue Mar 10, 2020 5:31 pm

Very interesting. True that first KK had WR cams with axles not bearings. I had a set. On Siftons Cams for 54 he advanced front intake, I apologize my memory is getting worse. Too many days washing parts with hands in gas and sucking copious amounts of CO especially in this CO bowl I live in, plus tons of flooding carbs in shops in the 60s 70s 80s 90s etc. Heavy Metal has got me down. I can taste CO the instant I walk outside. So 1 tooth is what I remember, but it may have been 12° on cam lobe relocated... Have to find my paperwork.
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Re: KH vs KHRM Motor Differences?

Postby thefrenchowl » Tue Mar 10, 2020 6:56 pm

Hi,

You can't derive a cam timing and analysis from its shape on a photo....

For 2 cams with the same timing, one could be judged to have more degrees cause the top is broader, but it could just be that the ramps are just steeper...

Sifton proved in 54 that 53 R cams had too much degrees to compensate for the poor geometry and derivative valve bounce.

His experiments with the double Triumph spring set up and his stobe light set up ended up with a better cam with less degrees, less bounce, more ramp and more power.

Please, do like some of us do, stick a dial gauge on your valves and record actual timing, acceleration and lift.

Then we can compare profiles.

To anyone that looks at a WR and a KR cam would think the KR is way better, being broad rather than sharp, but it's just an illusion due to the different tappets being used, roller on KR and shoe on WR...

Patrick
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Re: KH vs KHRM Motor Differences?

Postby EKHKHK56 » Tue Mar 10, 2020 8:37 pm

Haha yes Patrick! That Cowboy Boot Lifter which lifts across the soul will make you think...
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Re: KH vs KHRM Motor Differences?

Postby panic » Wed Mar 11, 2020 10:09 am

The WR asymmetrical "foot" extension is to cover the entire path of lobe motion (which is offset from the tappet CL, as are all H-D cams). This is for safety only, the length of a flat tappet does not affect duration or lift.
If the WR tappet were rotated 180° (be careful, this does happen) the "short" corner of the tappet will chew the lobe to pieces. A reversed 45 or K roller tappet (actually rotated 90° by using the wrong tappet block) will plow a furrow down the center of the lobe.
Aside from this difference, the tappet motion and lobe function match common automotive practice: the tappet's flat contact surface always follows the highest point of lobe contact. A roller (or radiused tappet: Triumph etc.) always follows the closest point of lobe contact (tangency).
Despite the very large visual differences, WR and KR lobes may produce the same duration and lift (but not the same opening/closing rates).
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Re: KH vs KHRM Motor Differences?

Postby thefrenchowl » Wed Mar 11, 2020 12:20 pm

The "shoe" bit on the WR tappet is always on the closing side while the shorter "heel" is on the opening side.

I still wonder from time to time why the cam is offset from the tappet on Harleys...To start with it was probably just to get the valves in the right position in the cylinders despite the pitch of the gear train, but is there a physical need for it?

This is the only example I know of for offset cams.

Obviously, the offsetting of cylinders relative to the crank has been much used on old 4 stroke engines, Moto Guzzi, MAG, Koehler-Escoffier, some 2 strokes as well, but there, there's a gain for the straighter rod and the timing when the piston travels down ("working" strokes of combustion and intake strokes) as it covers more than 180 deg while moving less than 180 deg on the way up ("useless" stokes of compression and exhaust)

Patrick
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