New CMB 21 VAC

[BB Mods's]

Fellow RC boaters, welcome to the 2010 CMB VAC 21.

For guys with EAP the measurements are as follows.

Top of piston to top of liner = .093" (close to the normal .093~.095 of the mac's. )

Top of liner to top of exhaust = .466"

Top of liner to top of transfer = .606"

Top of liner to top of boost port = .601

Simplified Timing numbers (non-EAP)

Exhaust 183*

Transfer 130*

Boost 130*

PDF copy of parts sheet.

More to come, lots more pictures to be taken.

This post is a work in progress.

 

[Marty Davis]

Ill do high res internal shots tonight when I get home, aswell as measurements and timing numbers for those interested..

1 engine to replace an army.

EXCELLENT, will be anxious to see the new engine.

 

[julianconde]

are those all my engines in the background lol

 

[BB Mods's]

Iv got a spare p/s/r sitting here Marty, after I get things figured out, ill swap the p/s/r and bearing's and send it your way for testing, at that point I should have a few of them.

Yep, they are now Julian

 

[julianconde]

well i have a Piston and sleeve just need a connecting rod going to buy one from a RS7 Valvola

 

[Richard Dahlheimer]

well i have a Piston and sleeve just need a connecting rod going to buy one from a RS7 Valvola

 

[Richard Dahlheimer]

well i have a Piston and sleeve just need a connecting rod going to buy one from a RS7 Valvola

Very good thread. Have you ran the new motor? Richard D

 

[BB Mods's]

ZERO fuel through the motor at this point, I should be on the water testing by wednesday.

I had enough time monday to get it torn down and cleaned up, had a few areas Stu was pointing out to be bothersome, made a few passes with the micro rotary tool acros all the liner ports to knock the chrome flashing off (there was a bunch of it)

There will be ZERO modifications done to this engine, Every test from here forward will be limited to plug/carb bore changes. And ill test my other housing that's been cut to 215* total on the intake.

The case is a work of art internally, Stu was spot on when he said it looks like a micro 67/80 HR, the transfers have a wonderful swept back (slightly canted) angle, the boost port has a nice clean tract from the rotor housing to the port window. No info on the head vol, but ill get to that tomorrow!

One note, Mine came with 1 head shim, with the squish set at .010, I removed that shim and went to a .008 shim, with just a light lapping done to the top of the liner. got the squish down to .006

 

[BB Mods's]

Pics updated.

I put the stock carb guts back in for the first part of my testing, to be done in a speedmaster mono with a ABC prop prepped by Marty Davis...or 2... h34r:

Part 2 of the test will be in a new JAG III 21 hydro (production boat as they will all come, nothing special has/will be done to the boat)

 

[julianconde]

Nice i may have to buy a few of theses also lol

 

[BB Mods's]

Just let me build you a mac/vac hybrid, I can rework the case for the new p/s.

 

[julianconde]

too much money to getb that done

 

[steve wood]

ZERO fuel through the motor at this point, I should be on the water testing by wednesday.

I had enough time monday to get it torn down and cleaned up, had a few areas Stu was pointing out to be bothersome, made a few passes with the micro rotary tool acros all the liner ports to knock the chrome flashing off (there was a bunch of it)

There will be ZERO modifications done to this engine, Every test from here forward will be limited to plug/carb bore changes. And ill test my other housing that's been cut to 215* total on the intake.

The case is a work of art internally, Stu was spot on when he said it looks like a micro 67/80 HR, the transfers have a wonderful swept back (slightly canted) angle, the boost port has a nice clean tract from the rotor housing to the port window. No info on the head vol, but ill get to that tomorrow!

One note, Mine came with 1 head shim, with the squish set at .010, I removed that shim and went to a .008 shim, with just a light lapping done to the top of the liner. got the squish down to .006

head volume on mine was .22cc

 

[BB Mods's]

Mine came out to .19cc with a K&B HP plug seated fully.

 

[Marty Davis]

Mine came out to .19cc with a K&B HP plug seated fully.

Plus a dish in the piston of .06 ???

 

[BB Mods's]

yes, counting the dish.

 

[Richard Dahlheimer]

yes, counting the dish.

Thanks for the up dates Tommy. How is the piston/liner fit in your new motor? Richard D

 

[BB Mods's]

Both of the p/s set's I have come with a super fine finish, I cant even see any hone marks in the cylinder, and to my surprise, CMB gave us back the single exhaust port

Ill get leak-down % info after I get a gallon through it, so sometime friday?

 

[BB Mods's]

Just ran the last of 3 tanks through the engine, so that's ruffly 36oz through the engine thus far, after it cools all the way back down I will pull the intake and check the rod for visual wear and report back!

 

[Nigtmare]

Hey Tom did you run it on the bench, or the lake?