CMB V5 45

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Terry Keeley

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Got to take a look at one finally, it's close to the VAC 45 except for a few changes:

The exhaust port is split into three with a main port and eyebrows.

The transfers are split into two making the whole thing an 8 port vs 4 for the VAC.

The piston is flat vs dished for the VAC.

The head volume has been increased to 0.35cc vs 0.29 + 0.02 piston dish for the VAC.  Trapped C/R is down from 13.7 to 12.1:1.

The squish band has half it's width tapered at 3* vs completely flat for the VAC.

The drum valve has some balancing cutouts.

Timing numbers are essentially the same.

Oh, and the cooling jacket is gold instead of blue.   :p

The motor I looked at had quite a bit of chrome globs around the ports, be sure to go around them with a small diamond file before running one of these!

CMB 45.jpg

Here's the complete story:  View attachment 2017 CMB V5 45.xls
 
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mtruex

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The Blue head 4 port VAC 45 had .35-.36 head and flat top piston for a long time!    I think only the first run had what you had, early versions also had less crankshaft counter weight.     The only changes to the V-5 were a slightly different head button config, sleeve ports that you mention and a drum with different timing and no ramp. And yes the cooling head!   
 

Terry Keeley

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The Blue head 4 port VAC 45 had .35-.36 head and flat top piston for a long time!    I think only the first run had what you had, early versions also had less crankshaft counter weight.     The only changes to the V-5 were a slightly different head button config, sleeve ports that you mention and a drum with different timing and no ramp. And yes the cooling head!   
Have you run the V5?  How's it compare to the VAC?  :rolleyes:
 

mtruex

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I think V5 is better but I will say this, I like the v5 sleeve with old head and ramped drum :)           Opinions will vary !
 

mtruex

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Yes a ramped drum.  I’m not sure how much the ramp actually does but The newer one opens a little earlier than I like.   Again opinions vary ! 
 

Mike Hughes

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Feb 23, 2003
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WOW, you can see the chrome in the pic. That looks bad from here.

Mike
 

Stuart Barr

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Terry,

That looks really bad.  I am sorry.  Most do not look that way.

Martin,

One time I flattened the ramp using a Dremel.  Picked up 3 MPH.

Stu 
 

gilbert galli

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Apr 27, 2013
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question, is it possible to replace the drum housing of the cmb v5 with the drum housing carb angle of cmb 45 hr with  use drum valve of the v5 ?
 

Terry Keeley

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I think V5 is better but I will say this, I like the v5 sleeve with old head and ramped drum :)           Opinions will vary !
Lol!  C/R is king, especially for what your doing!  :p
 

Terry Keeley

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Terry,

That looks really bad.  I am sorry.  Most do not look that way.

Martin,

One time I flattened the ramp using a Dremel.  Picked up 3 MPH.

Stu 
Ya, I've never seen one that bad either and I'm sure it's an anomaly.

I posted the picture not as a slam against CMB but just to be sure guys check before they run them.  That would have made a mess the first time the motor was fired.  :unsure:
 

Terry Keeley

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It's too bad the manufacturer's couldn't add a groove like this to the exhaust stub so we could get away from those goofy headers with their leaky o-rings, springs etc.

Stu?  Ron?

exhaust groove.jpg

exh goove.jpg
 
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David Bryant

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what is a good, or best, type of dremel bit to remove excess flashing (clean-up ports) ? 
 

Terry Keeley

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Jim Allen

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Got to take a look at one finally, it's close to the VAC 45 except for a few changes:

The exhaust port is split into three with a main port and eyebrows.

The transfers are split into two making the whole thing an 8 port vs 4 for the VAC.

The piston is flat vs dished for the VAC.

The head volume has been increased to 0.35cc vs 0.29 + 0.02 piston dish for the VAC.  Trapped C/R is down from 13.7 to 12.1:1.

The squish band has half it's width tapered at 3* vs completely flat for the VAC.

The drum valve has some balancing cutouts.

Timing numbers are essentially the same.

Oh, and the cooling jacket is gold instead of blue.   :p

The motor I looked at had quite a bit of chrome globs around the ports, be sure to go around them with a small diamond file before running one of these!

View attachment 100128

Here's the complete story:  View attachment 100129
Any sharp edge on the ID of a cylinder bore will cause the chrome to buildup on that edge. Careful removal, before chroming, of those sharp edges with an Exacto knife & brush hone eliminates this problem. 

Jim Allen

P8290016.JPG

P8290017.JPG

P5020003.JPG

P5020004.JPG

P6200009.JPG

P9080022.JPG
 

Andy Brown

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Feb 8, 2003
Messages
2,657
Any sharp edge on the ID of a cylinder bore will cause the chrome to buildup on that edge. Careful removal, before chroming, of those sharp edges with an Exacto knife & brush hone eliminates this problem. 

Jim Allen

View attachment 100151

View attachment 100152

View attachment 100153

View attachment 100154

View attachment 100155

View attachment 100156

Jim,  I see Nelson engines are still using double hemi heads. The Super Tigre X-40 Pylon engine (1973) used the double hemi.  Worked great in boats too. It was a popular after market part available for many engine brands through out the 70s and 80s.
 

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