CMB 67HR Green head

[Tim_Duggan]

Looking for reccomendations on bowl volume and squish clearance for a Green Head in a turbine style1/8 scale boat? Last time I played with 67's it was 0.59cc in the bowl, 50% squish area, at 0.012" clearance - that was with a K67 that had a flat top piston.

Also could use a starting pipe length for the black AB muffled pipe on the same boat / engine.

Thanks in advance!

Tim.

 

[FloridaScaleBoater]

Looking for reccomendations on bowl volume and squish clearance for a Green Head in a turbine style1/8 scale boat? Last time I played with 67's it was 0.59cc in the bowl, 50% squish area, at 0.012" clearance - that was with a K67 that had a flat top piston.

Also could use a starting pipe length for the black AB muffled pipe on the same boat / engine.

Thanks in advance!

Tim.

My opinion.

Run the bowl volume as CMB has designed in the engine.

Head clearance .016-.018" pipe length for the CMB/AB muffled pipe 11-3/4" Center of cylinder to seam bead on pipe.

 

[Ray Sametz]

Looking for reccomendations on bowl volume and squish clearance for a Green Head in a turbine style1/8 scale boat? Last time I played with 67's it was 0.59cc in the bowl, 50% squish area, at 0.012" clearance - that was with a K67 that had a flat top piston.

Also could use a starting pipe length for the black AB muffled pipe on the same boat / engine.

Thanks in advance!

Tim.

My opinion.

Run the bowl volume as CMB has designed in the engine.

Head clearance .016-.018" pipe length for the CMB/AB muffled pipe 11-3/4" Center of cylinder to seam bead on pipe.

Reduce the stinger to .411 with KS brass tubing.........==={}

 

[FloridaScaleBoater]

Looking for reccomendations on bowl volume and squish clearance for a Green Head in a turbine style1/8 scale boat? Last time I played with 67's it was 0.59cc in the bowl, 50% squish area, at 0.012" clearance - that was with a K67 that had a flat top piston.

Also could use a starting pipe length for the black AB muffled pipe on the same boat / engine.

Thanks in advance!

Tim.

My opinion.

Run the bowl volume as CMB has designed in the engine.

Head clearance .016-.018" pipe length for the CMB/AB muffled pipe 11-3/4" Center of cylinder to seam bead on pipe.

Reduce the stinger to .411 with KS brass tubing.........==={}

RRRay;

What is the reasoning for this??

 

[steve wood]

stock stinger,57 bowl volume,.012 clearance

 

[Hydro Junkie]

The smaller stinger gives multiple "theoretical" benefits:

1) Increased exhaust pressure to the fuel tank for increased fuel flow

2) A stronger return wave that forces more fuel back into the cylinder for more power

I'm sure the engine guru's, of which I'm NOT one, will have other things to add to the list or correct me if I've stated something improperly

 

[Greg Hahn]

Stock bowl, .014 head clearance, .411 stinger, 11 1/2 to 11 5/8 pipe,

gh

 

[glenng]

How is the K&S tubing held in the stinger?

 

[Greg Hahn]

How is the K&S tubing held in the stinger?

JB weld or a bolt through both sides..........I like JB

 

[Tim_Duggan]

Thanks everyone!

 

[dwilfong]

Tim pull all the shims out and slam the pipe in as far as you can.

Drill the spray bar out as much as you can.

Then slap the 60% to it.

 

[Tim_Duggan]

Tim be sure to check the stock volume I know there has been at least 3 different stock volumes that I know about

Yep, thats why I asked the question about the bowl volume. Shame we can't trust CMB's consistency with parts enough to just assume the stock bowl volume is OK, as that would be too easy.

This motor isn't mine by the way - it's for a friend, and I don't want it detonating the piston to bits but need it to drag a heavyish 1/8 scale boat reasonably well, so it's about finding that balance......

 

[Terry Keeley]

The original "bathtub" heads were About 0.60cc, newer ones I checked were 0.53cc:

https://www.intlwaters.com/gallery/displayimage.php?album=70&pos=65

 

[Marty Davis]

The smaller stinger gives multiple "theoretical" benefits:

1) Increased exhaust pressure to the fuel tank for increased fuel flow

2) A stronger return wave that forces more fuel back into the cylinder for more power

I'm sure the engine guru's, of which I'm NOT one, will have other things to add to the list or correct me if I've not stated something improperly

Yes, on a Scale boat it is important to have as much tank pressure as practical as the tank situation is not ideal and this will help the flow come to the carb without much change when the tanks transition from one to the other. If you are only using 1 tank, this is not necessary.

 

[Norm Doerr]

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

 

[Will Gallagher]

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

Nice idea!

 

[Norm Doerr]

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

Nice idea!

Thank Davis.. I did think of a way to make it tighter only did it once but it worked., put a dowel long enough to go into the pipe and the stinger reducer, (put a point on it).. stand the dowel in your vice put the pipe and reducer on the dowel and then solder the collar on. Also saves you from burns, and other fun things.

 

[Ray Sametz]

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

Nice idea!

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

Nice idea!

Thank Davis.. I did think of a way to make it tighter only did it once but it worked., put a dowel long enough to go into the pipe and the stinger reducer, (put a point on it).. stand the dowel in your vice put the pipe and reducer on the dowel and then solder the collar on. Also saves you from burns, and other fun things.

Nice idea but, on a muffled pipe you can't get to the last stinger from the inside if you flare it. ............==={}

 

[Norm Doerr]

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

Nice idea!

How is the K&S tubing held in the stinger?

Get one of them hard line flaring tools used for brake lines, fuel lines.. etc. flair the side towards the engine drop it in through the big hole.. hold it in place and solder a sleeve on the outside of the small end to hold it.

Nice idea!

Thank Davis.. I did think of a way to make it tighter only did it once but it worked., put a dowel long enough to go into the pipe and the stinger reducer, (put a point on it).. stand the dowel in your vice put the pipe and reducer on the dowel and then solder the collar on. Also saves you from burns, and other fun things.

Nice idea but, on a muffled pipe you can't get to the last stinger from the inside if you flare it. ............==={}

Very true.. never even thought of doing a muffled pipe.

 

[SayMikey]

Looking for reccomendations on bowl volume and squish clearance for a Green Head in a turbine style1/8 scale boat? Last time I played with 67's it was 0.59cc in the bowl, 50% squish area, at 0.012" clearance - that was with a K67 that had a flat top piston.

Also could use a starting pipe length for the black AB muffled pipe on the same boat / engine.

Thanks in advance!

Tim.

The latest button CMB makes is spot on,I run .014 squish ab pipe at 11 1/2. What boat is it going on? I Have a turbine style I run a 1457x3 no toungue and a 8255 boat runs a x460x3 again no toungue. My AB pipe has no stinger. I have found in heat it hurts performance so just tune without one in it