head button 1.01

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dwilfong

Well-Known Member
Joined
Jul 1, 2008
Messages
5,968
DSCN2124.JPGDSCN2127.JPG

Here is a head button I am going to try on my CMB 1.01

It is .62cc set at .006 clearance and with a 188 ex it is 13.5 CR

I will start with 50% nitro and see what happens.

I tried this design about 4 years ago but there where to many other problems to over come with the piston holing and pin boss breaking.

I have decided to try aluminum as I don't thing keeping the chamber hot will be of any concern. LOL

If I get the time I will give it a spin this weekend.

Wish me luck I think I will need all I can get.
 
IT WORKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

No detonation and all the bottom end you will ever want.

Can crawl finger off the throttle for half a strait and pop a 2167/3 of so hard you need full left rudder to keep it strait.

Thank you Jim Allen for the insight!!!!!!!!!
 
David,

Any rpm loss ? Been on my mind to make a few of these for the 91 !
 
The Canto 6.9 1667 would not come up to RPM had to lean it down and took the plug on two tries.

Put my redone 2167/3 on and it lit right up.

It takes lots of load to make it work.

Way more than usual.

Will try it more here when I get time. Only got 4 runs in till the rain came.

It will change how you prop the boat big time.

For heat racing this will change every thing!!!!!!!!!!!!

Time for a new boat it is way over powered now for heat racing.

You pull the trigger and it walks side ways with all the power.

Do it Martin you will not regret it!

It is hard to wrap you mind around a 15 to 1 + CR on high nitro.

There is a point I am told that the RPM will go down then you back up a little.

There is no exact answer to how much is to much.

This is virgin territory.

shorter pipes and higher timing will be on the plate with this as the CR will take care of the bottom end.

This will be a great tuning tool.

Keep the MSV under 60 M/sec and the plug will live and make the squash as tight as you can with out hitting the piston at top RPMs,

45 to 50% squash area.

Start at 14 to 15 CR to see results.

DO NOT use brass! I tried this a few years ago with brass and it was a disaster.

That is why I shelved it till now.

toroidal head 3.jpg courtesy of Jim Allen.
 
Last edited by a moderator:
Im going to. Ive made em for 21 and 45s and didnt like them. 91 is a different animal. Never liked brass for any heads lol.

Any idea on speed comparison with a loaded prop?
 
I don't think as just a bolt on with no changes other wise it will increase top end on a already good setup.

But as a tool to launch larger props with raised timing and or shorter pipes it will shine.

You will have to think different to get the best out of it.

The 2167/3 did rev higher with this head on my set up as It was at the top of my eng load limit.

I think it will allow lower nitro content on the big eng with great results for heat racing boats.
 
I dont know about thinking different, I know what you mean :) 100 plus?!?
 
The Canto 6.9 1667 would not come up to RPM had to lean it down and took the plug on two tries.

Put my redone 2167/3 on and it lit right up.

It takes lots of load to make it work.

Way more than usual.

Will try it more here when I get time. Only got 4 runs in till the rain came.

It will change how you prop the boat big time.

For heat racing this will change every thing!!!!!!!!!!!!

Time for a new boat it is way over powered now for heat racing.

You pull the trigger and it walks side ways with all the power.

Do it Martin you will not regret it!

It is hard to wrap you mind around a 15 to 1 + CR on high nitro.

There is a point I am told that the RPM will go down then you back up a little.

There is no exact answer to how much is to much.

This is virgin territory.

shorter pipes and higher timing will be on the plate with this as the CR will take care of the bottom end.

This will be a great tuning tool.

Keep the MSV under 60 M/sec and the plug will live and make the squash as tight as you can with out hitting the piston at top RPMs,

45 to 50% squash area.

Start at 14 to 15 CR to see results.

DO NOT use brass! I tried this a few years ago with brass and it was a disaster.

That is why I shelved it till now.

attachicon.gif
toroidal head 3.jpg courtesy of Jim Allen.
David, why do U think? " It takes lots of load to make it work.

Way more than usual.

Moby
 
The Canto 6.9 1667 would not come up to RPM had to lean it down and took the plug on two tries.

Put my redone 2167/3 on and it lit right up.

It takes lots of load to make it work.

Way more than usual.

Will try it more here when I get time. Only got 4 runs in till the rain came.

It will change how you prop the boat big time.

For heat racing this will change every thing!!!!!!!!!!!!

Time for a new boat it is way over powered now for heat racing.

You pull the trigger and it walks side ways with all the power.

Do it Martin you will not regret it!

It is hard to wrap you mind around a 15 to 1 + CR on high nitro.

There is a point I am told that the RPM will go down then you back up a little.

There is no exact answer to how much is to much.

This is virgin territory.

shorter pipes and higher timing will be on the plate with this as the CR will take care of the bottom end.

This will be a great tuning tool.

Keep the MSV under 60 M/sec and the plug will live and make the squash as tight as you can with out hitting the piston at top RPMs,

45 to 50% squash area.

Start at 14 to 15 CR to see results.

DO NOT use brass! I tried this a few years ago with brass and it was a disaster.

That is why I shelved it till now.

attachicon.gif
toroidal head 3.jpg courtesy of Jim Allen.
David, why do U think? " It takes lots of load to make it work.

Way more than usual.

Moby
Still thinking about that.

I think to start it takes load to control the burn rate. you always told me to think about the burn rate.

If the load is to little the fuel dose not burn completely before the cyl pressure drops. the load hold the pressure higher for a longer time and let the fuel burn at the higher cyl pressure completely using the fuel supplied in the chamber.

also with the smaller chamber it has less distance for the flame front to travel?

The design of the chamber induces swirl and mixes the fuel better to control detonation to utilize the higher cyl pressure?
 
Thanks Dick now you are going to have me up all night thinking about this c$%p.

You know I have to go to work tomorrow.
 
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