KH with KR heads

Production K Models

Re: KH with KR heads

Postby EKHKHK56 » Sat Feb 16, 2019 9:23 pm

Here are 4 Numbers Styles for some K Heads. 52KR, 52K, 54KH, 56KHK all have different chambers. These heads interestingly are all non polished. Almost all my weakly cast "54" heads I have are not polished or modified factory in combustion chambers like the "56" head. I call the weak raised casting heads 54 for reference, because obviously they are earlier castings. They were machined for the KHK from 54-56 of course. My 56 KHK head shown here must have been NOS and not polished yet. I wondered if 54 had heads polished on sides because some photos appear to not be. Most my early KH Heads are unpolished. However I have a magazine I ran across that stated all 54Ks will have polished heads and case covers. Polished inside, and out sounded like. Erik
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20190216_144153_resized.jpg
K Rear Head #s
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Last edited by EKHKHK56 on Sun Feb 17, 2019 3:43 am, edited 1 time in total.
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Re: KH with KR heads

Postby JerrryR » Sat Feb 16, 2019 9:39 pm

55 Features.JPG
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Re: KH with KR heads

Postby EKHKHK56 » Sat Feb 16, 2019 10:05 pm

Thanks Jerry, that sounds quite polished for KH! Perhaps early KH 54 had not been externally polished yet, as I have many that are old and run, but never polished. Of course they could have been replacement NOS years ago and just not polished before install. Going to look closer at 54 photos. I believe the magazine article was announcing 1954s with polish in and out, Im looking for it. All my newer "55-56" heads are fully except one. It must be a NOS I guess. Erik
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Re: KH with KR heads

Postby Coolbreeze » Sun Feb 17, 2019 2:16 am

I am learning more about K model heads here than I dreamed was available. I got my original '56 KHK when I was a teenage farm kid studying engineering at Univ. of Ill. Then, when my heads cracked, I just called Hank Reiman (Roger's dad) and had him ship me KR heads because that was all he had. The bike ran fine with those heads; so, I figured there was not much difference. Recently, I swapped out the heads on my current '56 KHK and found there was a clearance problem with long thread spark plugs. The bike seems to run fine with the shorter thread plugs, but it seemed strange that there would be a difference. Now, I see a possible explanation: The replacement heads give more compression but less flow. I am not racing the bike; so, if it is happy with these heads, I shall be happy.

If I ever swap heads again, I will take note of the casting numbers just to know what I am putting on the bike.
'56 KHK
'60 XLCH
'48 Chief
'42 Indian 841
'64 BMW R69S
'84 Moto Guzzi V65Sp
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Re: KH with KR heads

Postby EKHKHK56 » Sun Feb 17, 2019 4:27 am

My 52KR heads have about 3/4" long Brass Thread Inserts cast in. The 52K has about 7/16" long HeliCoils factory. There is a combustion pocket in the std head plug hole making up the rest of the 3/4". So you need different lengths for these reasons. Roger Reiman was one of the best racers ever. 3 Daytona Wins plus. It was a sad day when he went down in practice 97 Daytona and we lost him. Erik
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IMG_20190216_233407_resized(3).jpg
52KR 52K Spark Plug Holes
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Re: KH with KR heads

Postby EKHKHK56 » Sun Feb 17, 2019 4:46 am

Here are a few examples of 52K and 55-56KHK heads. Flat shelf around Spark Plug hole becomes deeper and completely round plus...other chamber mods. For larger Valves and Taller Cams, more clearance. To avoid contact, and to assist flow by unshrouding all, particularly the backside of the valve port.
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20190216_232020.jpg
55-56KHK & 52K
20190216_232020.jpg (80.5 KiB) Viewed 11512 times
20190216_225845_resized_1(10).jpg
52K
20190216_225845_resized_1(10).jpg (67.48 KiB) Viewed 11512 times
20190216_231212_resized(13).jpg
55-56KHK
20190216_231212_resized(13).jpg (63.31 KiB) Viewed 11512 times
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Re: KH with KR heads

Postby thefrenchowl » Sun Feb 17, 2019 5:47 am

Coolbreeze,

Yours spark plug clearance problem using KR heads on KH barrels is due to the fact that KR cylinders have the valve seats and channels sunk much deeper for flow purposes.

Next time you open her up, do your cylinders like KR cylinders, see race manuals.

It never ceased to amaze me that folks using KR heads on an otherwise std motor think it will reap huge benefits...

Dick O'Brien and others knew better and found that std K/KH heads were in general better flowers than KR heads at low rpms, but sadly lost the edge once the engine left the K/KH rpm and went into the KR rpm range. But then, what did they knew?????????????, they only worked every day of their life for 17 years on the damn motor!!!

Now, who wants to have a K or a KH at the limit of breaking rods and pistons????????????????????

KR performance is a whole package, heads yes, but most of the flow work is done on the cylinders...

Patrick
Flat Head Forever
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Re: KH with KR heads

Postby LDB » Sun Feb 17, 2019 12:52 pm

When a spark plug electrode is lower into the combustion chamber such as with the KR, it has the same effect as advancing the ignition timing as the flame front is initiated closer to the piston top. That makes sense, since the KR is a higher RPM engine.
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Re: KH with KR heads

Postby thefrenchowl » Sun Feb 17, 2019 2:10 pm

Could also be that nobody ever made a race plug with 1/2 reach....

And hidden tip in its own little chamber also prevents fouling, great in a street engine, useless on a race engine...

The KR usually needs 36 degs compared to K/KH 27/30/32 degs, so where's the faster flame front? :D

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: KH with KR heads

Postby LDB » Sun Feb 17, 2019 2:35 pm

Well let me say it this way. With the ignition point physically closer the combustion time is reduced.
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