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Kohler Heads

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WHX??

Found this and just thought I'd share.. might be something a guy knows already but I thought it was interesting read......

 

Kohler made five different cylinder heads for the 10hp, 12hp and 14hp K-series and Magnum engines through the years -

The First Generation Head -

cylhead1.jpgThis cylinder head was manufactured by Kohler from the early 1960s until 1971 and was available only on engine model K241 (10hp) before engine serial number 3184999. It has a heart-shaped and wedge-contoured combustion chamber and is now known as the high compression, "LP head." The spark plug is centered in the combustion chamber. This particular head was originally made for and came on the very early K241 (10hp) engines. It'll also work on the Magnum engine model M10 (10hp), K301/M12 (12hp) engines and the early K321/M14 (14hp) engines with a 1-1/8" exhaust valve. But being the later 14hp engines have a larger exhaust valve (1-3/8"), the exhaust area in the head would need to be machined out for use with the bigger exhaust valve. And because of its high compression ratios, if this head is used on a 12 or 14hp engine, Premium, race gas, E-85 or methanol fuels must be used, or the engine will overheat and wear out too soon. The compression ratio is 7:1 when used on a 10hp and 8.6:1 when used on a 12hp. If this head was used on a 14hp, it would yield a 9:1 compression ratio. And LP heads did not come on nor will they fit the 16hp (K341) engines. This head requires 2-1/2" long bolts. And due to early technology and design of the combustion chamber, the majority of the expanding gases or combustion pressure is placed over the valves instead of the piston, resulting in lower engine performance. The number embossed on this head is 235461. Cub Cadet part # is IH-385303-R1. It is no longer available from Kohler or new from any other source.

NOTE: This particular head was originally designed many years ago ONLY for the 10hp (K-241) engine because these engines have low compression due to their small bore and short stroke. The only reason anyone would put one of these heads on a bigger engine today is to attempt to get more power out of it. Also, people found that the LP head worked better than a newer low compression head on an engine burning liquefied petroleum (propane) gas. LP gas is a high octane fuel (about 110-115 octane). Therefore, it burns more thoroughly and produces more power in a high compression engine. That's why these heads are known today as the "LP head." Also, the LP head, when used on any size engine including the 10hp, have been known to cause detonation (pinging) nowadays even with 93 octane Premium gas. That's why Kohler stopped making them. They replaced them with the "dished" head. Ê However, high octane race gas, E-85 or methanol fuels can be safely used with the LP head.

If you want to use an LP head on your engine, the genuine OEM Kohler LP head is no longer available from Kohler or any other source. They haven't been made since the early 1960s. They were discontinued when the 12hp engine came into production, because this engine require a lower compression head. So if you need an LP head, remember, they came only on the very early 10hp engines equipped with the starter/generator and no indention on the side of the block for the upper mount gear starter. But if you can't find an LP head at all or for a reasonable price, what you could do is cast an aluminum head just like the LP head. An LP head can be CNC-machined from billet aluminum, but if you prefer a head that's close to the genuine product, first, you'll need a good LP head to use as a mold or pattern.

 


The Second Generation Head -

cylhead2.jpgThe second type of head manufactured by Kohler has a heart-shaped and a depression area in the combustion chamber. It has improved technology over the earlier LP head. Kohler engineers made the depression area for a special reason and it helps engines to produce more torque and horsepower than the LP head at any RPM. This head was installed on Kohler's 10hp and 12hp engines, before the 14hp engine went into production. It's a good head. It flows good and with increased compression. The "hump" directs the incoming air/fuel toward the piston at higher RPM.

Unlike the sought-after, but misunderstood LP head, the depression area places the majority of the expanding gases or combustion pressure over the piston instead over of the valves, which produces more engine power and torque. The spark plug is centered in the combustion chamber. It was lowered in compression and was made for both the 10hp and 12hp engines, but would not work on the 14hp engine because of its' larger exhaust valve (it was manufactured before the 14hp engine appeared) unless reduce the size of the exhaust valve on a 14hp to a 1.125" (same as a 10 & 12hp) This can be accomplished by installing a valve seat insert in the block for the smaller valve. By the way - this type of head is not officially a "high compression head" because it has a depression in the combustion chamber. It is however, 'slightly higher' in compression than the newer style heads, but it's not a "high compression" or even an "LP head," but the next best to it. The compression ratio is 5.4:1 when used on a 10hp and 6.6:1 when used on a 12hp. If this head was used on a14hp (the exhaust circumference area would need to be machined larger), it would yield a 7:1 compression ratio. By the way - Kohler no longer makes this type of head either.

These early heads require 2-1/2" long bolts (OEM Kohler part # 236546-S; number embossed on head is 235461, but not an LP head), and the later ones require 1-1/2" long bolts (OEM Kohler part # 236675-S). Also, the reason Kohler redesigned the head with the low bosses for shorter head bolts is so more air flow can past over the head bolts to better efficiently cool the other parts of the head.

Edited by WHX8
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Wishin4a416

Brian Miller is a wealth of Kohler info. I use his sight a lot. Thanks.

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WHX??

Got a link to his site you could share Jack?

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Wishin4a416
14 minutes ago, WHX8 said:

Got a link to his site you could share Jack?

Absolutely. I hope this is not against the rules. Scroll down to the yellow highlighted box and you can open different informational sections.

 

http://gardentractorpullingtips.com/index.htm

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WHX??

Might have figured the guy to be a puller! ...yes all kinds of good poop as well as shop tips!

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ztnoo

WOW, I had NO IDEA about anything regarding Kohler heads.  jawdrop.gif

Unreal info.  wavetowel2.gif

You only scratched the surface here in this thread however on Kohler heads.

Here's a link to what appears to me to be the Bible of Kohler Heads:

http://gardentractorpullingtips.com/cylhead.htm

 

Amazing info!  high five.gif

This is a knowledge base unto itself that I venture to imagine few know much about, even here at RS.  light bulb.gif

Thanks for the heads up.

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MalMac

His site is amazing in the knowledge that can be learned from it. I will say this though, read and re-read things carefully. There are one liners in there that are hid that can totally change the outcome of a rebuild. If I would have re-read some of the info I would have saved myself a lot of time and money. This site is full of good stuff. I just wasn't smart enough to absorb what I read the first time or just totally missed it. Take your time, there is a lot of good and tremendous information in there.

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Wheel-N-It

Thank you for starting this thread with some great information !

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WHX??

Your welcome Van..... funny thing is in my daily perusing of :techie-ebay:for horse stuff I came across that in a for sale of the LP head.  Kudos to @Wishin4a416 for pointing out the author.

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JC 1965

I've learned a lot from Brian Millers web site.    :thumbs2:

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