K321A Curiosity

[JimT]

Today I was getting the engine I recently bought for Bee-atrice ready to install. Bee-atrice is a 109 Cadet. Well when I was checking for the fit of the muffler heat shield I notice it would not fit because of the spark plug placement in the head. The engine I bought has the plug closer to the side of the engine than the one that came out of a 147 that I bought. The flywheel cover shows both engines to be a K321A. The one I took out is a 1970 by the serial number and the one I am putting in is a 1972 by the serial number. In order to install the heat shield I will have to make a modification to it for clearance to go around the spark plug. I guess I will either modify the heat shield or just make a new bracket for the muffle to attach to.

My question is, is one style head any better that the other? Or is it just a difference due to the application the engine was used for?

Here are photos of the different heads. I'm still kinda new to the cub thing and am still learning all the different quirks with the engines.

Thanks for any replies. Just being curious.

[Jeff in Pa]

The top picture looks like the original head on my 1968 125 ( 12 hp K301 with high boss head ). The bottom picture looks like the replacement head that was on my 1966 122 ( 12 hp K301 with low boss head, studs and spacers for the gas tank & tin )

Jeff

( I'll put up pictures later )

[Jeff in Pa]

The top picture looks like the original head on my 1968 125 ( 12 hp K301 with high boss head ). The bottom picture looks like the replacement head that was on my 1966 122 ( 12 hp K301 with low boss head, studs and spacers for the gas tank & tin )

Jeff

( I'll put up pictures later )

Left head is high boss, right is low boss



Left head is high boss, right is low boss

[Paul B]

The spark plug location is also different, but either will work.

[BigBill]

Performance wise the location of the sparkplug inbetween both valves I think is better. It ignites the gas closer to the source. Now the location of the gap opening on the sparkplug matters too. The opening needs to face the intake valve in either head for the best performance.

[Merk]

I get best performace from a head that has the sparkplug over the exhaust valve.