CMB 45RS Out of the Box Squish band Clearance

[Shane Resiler]

I am wanting to know what the standard head clearance is for a CMB 45 RS?? Most importanly, what is the recommended % nitro to run for these engines...this info did not come with the engine and I would like to know so I can start tinckering!

Thanks!

 

[FloridaScaleBoater]

There is no "standard" that is one of thise things that needs to be checked & set before running the engine

.012" to .014" is a good conservative head clearance I am running 45% in mine

What are you going to be running it in, and with what pipe?

 

[steve wood]

i run 60% nitro,.010 head clearance,.003 to .004 rotor clearance. make sure the rotor is not sticking on the crank stub,it should fall off when clean(no oil)

 

[Rudi Arnesen]

i run 60% nitro,.010 head clearance,.003 to .004 rotor clearance. make sure the rotor is not sticking on the crank stub,it should fall off when clean(no oil)

What volume do you have in the dome?

 

[dwilfong]

Have done a lot of testing with my new 45RS in the last few months. The stock button set at .010 clearance will still frost over with 55% nitro. Had to dig out the button to .45 cc and it will stay shined. Did mine in the drill press wit a round 9/16 grinding stone came out real nice. Don't go any deeper than the original chamber just make it bigger.

This it what has worked for me.

David

 

[Shane Resiler]

I have 40% with the correct oil ratio here already, so I was going to run that first.

Sounds like I need some head shims. I'm new to the nitro engine world so I will jsut take it step by step.

I will check the rotor disk spacing first, also make sure it floats, and by the sounds I need to increase the head volume.

Increasing the head volume decreses the compression ratio??

 

[Shane Resiler]

There is no "standard" that is one of thise things that needs to be checked & set before running the engine

.012" to .014" is a good conservative head clearance I am running 45% in mine

What are you going to be running it in, and with what pipe?

Rick, I will be running a AB 45 Pipe and 40% nitro at first....I figured .012" head clearance would allow me to run this set up and the pipe at about 10.5"...

Then whne I want to get some mroe speed, up the nitro, drop the squish, cool the plug.....steadily.

What plugs are you guys using for what % nitro?

 

[NeilSharman]

Have done a lot of testing with my new 45RS in the last few months. The stock button set at .010 clearance will still frost over with 55% nitro. Had to dig out the button to .45 cc and it will stay shined. Did mine in the drill press wit a round 9/16 grinding stone came out real nice. Don't go any deeper than the original chamber just make it bigger.

This it what has worked for me.

David

David, how did you measure the Head Button Volume?

 

[dwilfong]

Have done a lot of testing with my new 45RS in the last few months. The stock button set at .010 clearance will still frost over with 55% nitro. Had to dig out the button to .45 cc and it will stay shined. Did mine in the drill press wit a round 9/16 grinding stone came out real nice. Don't go any deeper than the original chamber just make it bigger.

This it what has worked for me.

David

David, how did you measure the Head Button Volume?

Insulin syringe and a piece of Lexine with two Small holes in it. Use a piece of solder thew the plug hole to check clearance.

 

[steve wood]

i run 60% nitro,.010 head clearance,.003 to .004 rotor clearance. make sure the rotor is not sticking on the crank stub,it should fall off when clean(no oil)

What volume do you have in the dome?

.38 cc