KH Piston Clearance

Production K Models

Re: KH Piston Clearance

Postby EKHKHK56 » Tue Jan 30, 2018 4:24 pm

Ok. Did some research with my few old guys that are left...45 pounds is enough for this application, with no gasket and surfaces flat. Thick high heat silver paint. While no official numbers have been set, this is the ballpark that works from what they used on Joe's #98. So more than that is not needed. I agree you don't want to distort the deck or heads, or overstress old cast threads. Now with a head gasket you may want to go 50 for good measure. In three sets. 30 40 50 Erik K
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Re: KH Piston Clearance

Postby Noot » Fri Feb 02, 2018 6:35 pm

I just read this entire post. Bottom line folks is - Erik knows, same advice I'd give(good advice Erik) Clearance is based on piston material / bore size ratios. K model cast, cam ground I give .002 and break it in nice. Sportster 900 cast, cam ground I give .0035-.004. All others piston materials(forged, etc) read the mfgs' suggestions. If you race it, give it more, a street bike give it a less. If it's a young, hot shot kid, give it more. A responsible person, give it less. I've taken apart engines with +.008 clearance, and asked the guy, didn't it smoke??? Rattle??? Burn Oil???? his answer is NOPE.
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Re: KH Piston Clearance

Postby GuS » Sat Feb 03, 2018 2:53 am

Erik.
Thank for the nice words, but I believe you mistake me for a different Gus.
Noot, good summary, but you could also add, ....and check with measuring.

Venolia forged pistons.
They reccomend 0.005-0.007 at skirt for racing.
I measured a growth of 0.005 @ at 100 deg C (212 F)
I set them up with 0.007. (next one one the bench right now Im giving 0.006) Do they rattle cold? Yes!! Do they smoke? No!! Have I raced them? Yes!

Dixie/Superior repop
Reccomendation ... I dont know.
Measured 0.0019-0.002.
I set them up with 0.002 at skirt. I know one has been given some beating/raced. No issues.

T&O stroker 45 pistons
They really gave some strange results when measured hot. Seemed like they kept growing moore cam shape instead of being moore round when hot. I wouldnt reccomend any less than 0.004. Actually I have one set left on my shelve. I will give them some reshaping, remove some material from the side. Measure how the grow, and even consider to give them moore than 0.004

I know I have had one pair of OEM pistons out of the army wrapping. Just cant find my notes on that one. But as far as I can remember they gave less than the repop piston. But if that was as little as 0.0015, I honestly dont remember.

wz507.
The Enfield pistons are beauties..
I would really appreciate if you took your time to measure the piston hot/cold. Front to rear top and bottom of skirt. Sideways also, but since the sides are shaved off, that would only make sense to measure on just below the oil ring.

And what is being said here about toquing and distortion is true!! Torqueing has a lot of influence. Maybe moore on the flimsy wl base , than the Ks. And more on large ODs than std bore. No matter what clearance you give, the clearance will be ruined/lost unless you torqe the cylinders up to a plate for boring/honing. (I use top and bottom) If not, the cylls wil only be round when run on the hone. Once torqued to the crankcases they take any other shape than round, and start eating your rings, skirt etc. I have had wl cylls passing my hands where you could see the bore grooves at each base nut corner because they were clamped/torqed differently for boring than for honing.

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Re: KH Piston Clearance

Postby EKHKHK56 » Sat Feb 03, 2018 3:28 am

Great! Well I know a few Good Guses now :D Excellent Information. Thank you everyone for contributing ideas and experience. Yeah with the Cyl Base Studs being limited by smaller size than head bolts to hold everything together it is a weaker point in a way, yet it all holds together fine generally. The base studs often get the finger tight, hand tight, hand tight with good hand and grunt sequence...haha. Would be about 32 to 40. Plenty. And not overtight. Erik
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Re: KH Piston Clearance

Postby EKHKHK56 » Sat Feb 03, 2018 3:34 am

Thank you Noot, I appreciate that. As from the start, just trying to help figure stuff out. Mainly got my own experiences, or picked up on the way, etc. ;)
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Re: KH Piston Clearance

Postby Geodoc » Sat Feb 03, 2018 5:52 pm

Think I asked before, but looks like lost in the shuffle. What is the purpose of the oiling port that's drilled through the cylinder wall on K Models? Big end lubrication? Can't see that it would be much help for the piston skirts.
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Re: KH Piston Clearance

Postby EKHKHK56 » Sun Feb 04, 2018 12:11 am

Use the bore oilers. Check for flow. Long stroke needs oil. Short stroke high rpm needs oil. Modern oil rings 3 part scrub more oil than old one part rings did. Ps .. 45" pistons with flat skirts are W or trimmed. Erik
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Re: KH Piston Clearance

Postby Geodoc » Sun Feb 04, 2018 4:23 am

So they are to enhance the lubrication of he big-ends?

EKHKHK56 wrote:Use the bore oilers. Check for flow. Long stroke needs oil. Short stroke high rpm needs oil. Modern oil rings 3 part scrub more oil than old one part rings did. Ps .. 45" pistons with flat skirts are W or trimmed. Erik
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Re: KH Piston Clearance

Postby wz507 » Sun Feb 04, 2018 10:58 am

Geodoc wrote:So they are to enhance the lubrication of he big-ends?

EKHKHK56 wrote:Use the bore oilers. Check for flow. Long stroke needs oil. Short stroke high rpm needs oil. Modern oil rings 3 part scrub more oil than old one part rings did. Ps .. 45" pistons with flat skirts are W or trimmed. Erik

NO. As Erik stated above, the holes you refer to are piston/bore lubricators. The big ends are lubricated by full oil pump pressure, so are already very well lubricated. The only full pressure oil pump output not going directly to the crankpin are the two 1 mm holes that lubricate the pistons.
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Re: KH Piston Clearance

Postby Geodoc » Sun Feb 04, 2018 2:30 pm

Got it .................
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