CMB 67 HR Headspace

[Norm Doerr]

What are people setting the stoch headbutton at?

Thanks

Norm Doerr

 

[Duck899]

.014"

 

[acaptn]

.010 - .012

 

[Terry Keeley]

12

 

[Hydro Junkie]

I was told by several experienced racers that it should be at .016. That said, it could be the 50% nitro fuel I run that requires that setting

 

[Jeff whiddon]

.011

 

[SayMikey]

There you have it Norm many answers. My first question to you is What kind of boat? Hydros need less squish. A mono or scale boat more to pull that heavy boat off the corner. So id say Rigger .011 all the way to scale .016

 

[Hydro Junkie]

Thanks Mike. I had forgotten about the hull type and weight. When I was told .016, that's in a 14lb scale hydroplane so it would make sense that a 67 rigger could use a tighter squish without detonating, something that my engine did when I didn't add any shims to the button

 

[Steve White]

What are people setting the stoch headbutton at?

Thanks

Norm Doerr

I always vary based upon engine size as well. .008" for a .21, up to 0.012" for a .90. As well, consider some taper on the squish band - full taper or partial taper.

 

[Tom Foley]

.012" - .013" Seems to work well , 50 - 60 % .

 

[Mike Cathey]

I wonder why they come with so much headspace. I have purchased three in the last year and they were all .020. Perhaps they are set up for the European market who use different nitro percentages than commonly used here?

For 1/8th scale I always seem to end up at .015 but on a hot day with some altitude I may add to the clearance by a thousandth at a time if the acceleration or grunt out of the hole seems really sluggish.