CMB VAC 21 engine - Is it any good ??????

[Mike Larson]

It was an AJM test boat... and it tested great!... I'd just thrown a nova parts test engine in it for end of year performance grade..... I have 0 experience with the front/rear exhaust CMB's..... but just a pipe change bumped Butch's JAE right up there..... those that know, and the Grim's may.... throw out what youve done to these engines, please.... drum timing easily, some case/housing flowing/blending..... clearance and sleeve #'s possibly..... there are just too many variables from searching the best length with any prop/motor combination and beyond.... box stock or not, any engine, HOT or not...... WORKING ON THE TOTAL COMBINATION will justify the end sought result...... I've got fast ones and slow ones..... its the mid speed one, thats shows heat race reliability, and runs moderately well every time goes to the event with me....... well.... some days you take a knife to a gunfight...... test 'em up. Mike

 

[anthony_marquart]

Glad you like the boat,.. it's a real good little rigger design!!! I love mine.. turns so quick it's hard to keep your eyes on it!!

But I agree.. no amount of engine mods will ever be as good as having a good pipe / prop / fuel / engine combo..

 

[Butch Londrigan]

Thought that was your boat Rodney. I made a pipe change and it picked up a lot of rpm's was not the same as when you seen it. We'll see next year what it has.

 

[anthony_marquart]

from what pipe to what pipe,.. prop and fuel details also..

 

[Butch Londrigan]

Mac pipe to cmb 21 nito pipe 60% nitro 8". Will try shorten pipe next year. Only mod to this motor was drop liner down .010 and set clearence at .006.

 

[julianconde]

So all in All - what is the general view on the 21 VAC - I dont race, but still want the boat to be fast - I just dont like a boat with a 180deg header, otherwise Novarossi's would be fine. Has anyone used a CMB 21RS red head - is that any good - I own both of these CMB 21 engines plus a MAC 21, and are not sure what to use.

So all in All - what is the general view on the 21 VAC - I dont race, but still want the boat to be fast - I just dont like a boat with a 180deg header, otherwise Novarossi's would be fine. Has anyone used a CMB 21RS red head - is that any good - I own both of these CMB 21 engines plus a MAC 21, and are not sure what to use.

Mac 21's would be the best just like my Twin 21..

 

[RodneyPierce]

Thought that was your boat Rodney. I made a pipe change and it picked up a lot of rpm's was not the same as when you seen it. We'll see next year what it has.

no issues brother. Nope, its an AJM Rigger. Only thing I did was help Anthony with a few things. his design (mine had some changes to it from the "stock kit" boat but nothing crazy)

And cant wait to get it on the gun next year. Will be a fun year of once again trying to find that ever elusive speed.

 

[Bert Dygert]

Shane,

I run a converted CMB Valvola engine with the VAC carb and rotor housing and love the set-up. The boat is a 21 Black Jack made by Brad Christy. I race here in district two with Steve Ball, the Betkes (Mike and Robbie), Ron Jefferson, and Oilly Douglass. Probally some of the best 21 hydro racers out there who ever get lane one and the start usually wins. Motors are Nova Rossi's, CMB's, and Macs.

It's all about motor set-up , pipe and prop. I run the converted CMB with a CMB nitro pipe at 8.5" (a little long) H-4 or H-5 prop and 65% Wildcat fuel. Motor is stock except for VAC carb. and drum housing. Just make sure the head clearance is 0.006-0.008.

Bert Dygert

 

[julianconde]

another good pipe for the Mac 21's are the OPS 3280 pipes at 8 inches and 65 % nitro they will haul the mail.. My Twin 21 the pipes are right at 8 inches and im using the CMDI Fat belly pipes and they run very good.. i have 2 VAC intakes systems complete plus Zoom Carbs on the way, Bearings and P/L and i will refresh the motors and go at it again.. 8 thousands head clearance run very well

Julian

 

[Tom Foley]

Shane,

I run a converted CMB Valvola engine with the VAC carb and rotor housing and love the set-up. The boat is a 21 Black Jack made by Brad Christy. I race here in district two with Steve Ball, the Betkes (Mike and Robbie), Ron Jefferson, and Oilly Douglass. Probally some of the best 21 hydro racers out there who ever get lane one and the start usually wins. Motors are Nova Rossi's, CMB's, and Macs.

It's all about motor set-up , pipe and prop. I run the converted CMB with a CMB nitro pipe at 8.5" (a little long) H-4 or H-5 prop and 65% Wildcat fuel. Motor is stock except for VAC carb. and drum housing. Just make sure the head clearance is 0.006-0.008.

Bert Dygert

Good info Bert ,that's a fast group !!!!!

 

[dave roach]

Julian

I have found that the new CMB 21 pipe works real well on the Mac.

Set it 7 /78

Dave

 

[Shane Bastick]

thanks for all the info guys, I have got some local feedback here in Australia on the VAC 21 as well, with nothing but high regard for the engine and top recommendations, so i will be using the VAC 21's in my twin rigger