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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › OS 91SZ-H and 91HZ head question
01-14-2010 07:46 PM  8 years agoPost 1
Chris Herzog

rrApprentice

Covington, La. USA

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Just wondering what is the different between the OS 91SZ-H and the new 91HZ other than the color and shape of the head. Also will the 91HZ head work on the 91SZ-H engine with no problems?

Thanks in advance,
C Herzog

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01-15-2010 04:02 AM  8 years agoPost 2
Dr.Ben

rrMaster

Richmond, VA, USA

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Chris,

The benefits of the HZ head are improved cooling and a smoother run. The design of the SZ head really wasn't optimized for helicopter cooling.

You can put the HZ head on an SZ, shimming it the same or maybe 0.004" less than the SZ head depending on your fuel choice. 16 thou is a conservative starting point.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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01-15-2010 01:05 PM  8 years agoPost 3
Chris Herzog

rrApprentice

Covington, La. USA

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Thank you for your reply. That is basically what I thought would be the case. I have a HZ and have a SZ on the way. I think I'll go ahead and order the black head (the HZ) today for the engine I have coming. Tower has them for 75.00.

Thanks again,
C Herzog

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01-15-2010 01:12 PM  8 years agoPost 4
cdrking

rrElite Veteran

Seattle

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You may want to consider the Dual plug Viper head for the SZ if have to buy a head. The Viper head smooths the engine(SZ)considerably.

Jeff

To hover is divine, the alternative is rather PLANE.

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01-15-2010 07:05 PM  8 years agoPost 5
Dr.Ben

rrMaster

Richmond, VA, USA

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Good idea.

I keep seeing used OS Viperheads coming up for sale for 50 cents on the dollar.

Ben

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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