KHK KR Cams

Production K Models

KHK KR Cams

Postby Mutt » Fri Jan 11, 2019 7:21 pm

Was wondering if I could get some opinions here. I'm fixing to bite the bullet and buy a set if those Enfield cam lobes for my 55" project.I assume that KHK cams are actually "streetable" ? .378"lift, 274º duration. But I was looking more at the J intake/K exhaust
.386" lift 312º duration, So I was wondering if this cam was also street able? Anyone care to chime in? This bike if for the highway
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Re: KHK KR Cams

Postby wz507 » Fri Jan 11, 2019 9:04 pm

You asked for opinions, and the following is my opinion on the subject, so take it for what it’s worth.

I think your cam decision would be impacted significantly by both your riding style and the exhaust system you choose to use (stock exhaust or R pipes) so you need to figure these factors into your decision process. I believe you could run just about any cam you want (large or small), with no bad manners if you use the small stock 2 into 1 exhaust system and would have no issues at all with reversion (stuttering/blubbering in the mid-range before the pipe comes into phase). I believe Dave Hennessey could confirm this suggestion as his ’54 KH that he just got fired has KR E or F cams in it that would be comparable to or slightly larger than the J and K lobes you inquired about. I believe Dave is riding it relatively gently (not buzzing it up yet) and has not mentioned anything about bad manners. However with a large cam and straight pipes, reversion could be a real issue that could deleteriously affect how the engine runs in the mid-range. But, if you plan to keep it “on the boil” perpetually it may not be an issue for you.

In some circles the KHK cam has the reputation of being a very hot cam, when in fact it is not that large a cam at all, having ~ 242 deg duration @ 0.050” lift, and with this relatively modest duration provides an engine having excellent manners no matter what exhaust system you choose that will pull from the bottom to the top. The KHK intake and exhaust lobes are identical.

The -69R J & K lobes you inquired about are one of the final KR lobe sets made for flat track racing and were used in the dome piston engines, but should work fine in flat top piston engines as well. The J intake lobe is a significantly larger lobe than the KHK, having ~ 272 deg duration @ 0.050” lift - ~ 30 deg more duration than the KHK lobe! Regarding the K exhaust lobe, this is a much shorter duration lobe, having ~ 245 deg duration at 0.050” lift, and in my opinion is an equivalent of the KHK exhaust lobe, with the exception that it has a pinch more lift and duration than the KHK exhaust lobe, and I suspect there would be little, if any, difference in engine output using either of these exhaust lobes since they are so similar.

With respect to opening/closing timing, turns out that the J and K lobes have essentially the same exhaust opening/closing and intake closing as the KHK lobes. The only difference in opening/closing events is that the J intake opens way earlier than the KHK lobe and consequently increases the overlap area dramatically, which in turn may lead to mid-range reversion/drivability issues with straight pipes.

The image below is an overlay plot of the valve motion provided by the KHK and J&K lobes and shows clearly that all the added duration of the J intake lobe occurs on the opening side of the equation. Also note that the J & K intake and exhaust closings are gentler than those of the KHK lobes due to the longer closing ramps employed on the J & K lobes.

Hope the above provides some food for thought.

PS - you can also get the lobes you seek from Jim Leineweber

KHK and JK cam comparison.jpg
KHK and JK cam comparison.jpg (94.75 KiB) Viewed 1080 times
Last edited by wz507 on Sat Jan 12, 2019 12:58 am, edited 1 time in total.
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Re: KHK KR Cams

Postby Mutt » Fri Jan 11, 2019 11:39 pm

awesome reply. Thanks. Lienweber did a set of KHK intakes for me last year, I still got to send him the exhausts to do. I check with Jim and see what kinda lobes he has available
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Re: KHK KR Cams

Postby Mutt » Fri Jan 11, 2019 11:43 pm

do ya have a chart for the KHK verses the F grind?
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Re: KHK KR Cams

Postby wz507 » Sat Jan 12, 2019 12:55 am

I don’t have the comparative data you seek for the F cam. I see in the factory lift specification that the F intake and exhaust is 0.420” lift vs the J & K at 0.395” lift. The installation timing spec suggests that the F intake lobe is 4 deg longer duration (@ 0.010" lift) than the J lobe and that the extra 4 degrees occurs on the opening side. The installation timing for the F exhaust is identical to the K, so possibly the same lobe as the K but with slightly higher lift. It’s dangerous to extrapolate regarding a lobe shape when you know nothing more than the cam installation timing, but that said, it is possible that the comparative plot you seek may be extremely similar to the existing comparison plot for the KHK and J/K lobes (with the exception of the difference in lift), where the F intake opening occurs 4 degrees earlier and all other opening/closing events and valve motion remain the same.
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Re: KHK KR Cams

Postby thefrenchowl » Sat Jan 12, 2019 7:35 am

A simpler answer!!! :D

KK/KHK cams are designed for 5500 rpm max power and

KR cams are designed for 7000 plus rpm max power....

Mutt, if you actually plan to completely trash your bike, there's only one way to go and that's the KR way...

By the way, ALL K, KK, KH, KHK and KR cams are pretty mild in degrees compared to other OHV/OHC 4 stroke racers (if you're curious, just go and check late CRTT cam timing... It'll be an eye opener!!!)

But because they are designed for side valve engines, a big advantage is the possibility of much steeper acceleration and deceleration ramps than OHV/OHC. Which give more full valve open degrees at the top since it spends less degrees to open and close.

Looked that way, yes, they are the wildest cams ever and any OHC/OHV engine fitted with them wouldn't last one minute before trashing valves, guides, pistons and cylinders....

Patrick
Flat Head Forever
https://web.archive.org/web/20071011184353/http://www.harleykrxlrtt.com/index.htm
I'm the one who has to die when it's time for me to die so let me live my life the way I want to...
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Re: KHK KR Cams

Postby hugoct » Sat Jan 12, 2019 9:04 am

The last factory KR racers used J/K, J/L, and J/M cam combinations for dirt track as well as road race events.
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Re: KHK KR Cams

Postby Mutt » Sat Jan 12, 2019 10:38 am

Couldn't find Lienwebers list of lobes he sells. I will call him. I think I have decided on the H grind if he has it.
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Re: KHK KR Cams

Postby Mutt » Sat Jan 12, 2019 10:40 am

So Dave, how are the E or F cams working out for ya?
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Re: KHK KR Cams

Postby EKHKHK56 » Sat Jan 12, 2019 8:37 pm

I run the high lift, .420" E cams in my 56KHKR. I couldn't be happier. Intakes open at 72° BTDC. Try that with an OHV. :lol: It idles fine and clean with Linkert. Surprisingly properly adjusted the emissions were only .90% front and 1.2% rear idling. That would pass most SMOG tests. Justin Jims son, is the man now at Leineweber. Great fellow. Jim's more in the back ground. Whatever you build, the carburetor is the most important component to bring it all together.
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