CMB Blue Head 67

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timothy johnson

timothy johnson

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Jul 9, 2011
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Foe those interested in the latest #s for the 8 port Blue head 67 here they are from Mauro Braghieri at CMB.

Drum:   Open @ 30 Deg. After BDC       Close @ 60 Deg After TDC

Liner:  Ports @ 128 Deg,   Exhaust @ 184 Deg

If your into cleaning and checking what should be the correct numbers for the stock motor this should help.
 
they should move the closing to 65 degrees ATDC.. This really wakes a motor up. . could also move the opening to 25 ABDC. This does however consume more fuel cause the port is open for a  longer duration.  USA engine could easily be Serial numbered. to identify the High Nitro engine  & higher timing.
 
Joe Warren said:
they should move the closing to 65 degrees ATDC.. This really wakes a motor up. . could also move the opening to 25 ABDC. This does however consume more fuel cause the port is open for a  longer duration.  USA engine could easily be Serial numbered. to identify the High Nitro engine  & higher timing.
Click to expand...
Are you changing the window's timing in the case, the valve or both? What is the stock case total opening? What is the stock valve total opening?

JA
 
Thanks Joe for the input. Any ID of the drum would be great. The new 45 V5s drum has been changed, so if you don't check stuff you have no idea what your running. i will try the 65" closing, I 've tried 15' opening ABDC and it works well. This is only drum changes not case changes.
 
Mark Bullard & I both have been running 65ATDC for years then we back the opening up as much as possible to get a 226-230 total.
 
Last edited by a moderator:
Good info Joe, so with your  closing @ 65 degrees ATDC and an opening of  17-20 degrees ABDC would give the duration you like of 226-230 VS CMB stock duration of 210 degrees.
 
Last edited by a moderator:
I just heard the sound of Dremel tools firing up.   :lol:
 
Last edited by a moderator:
Dont go pass 65 ATDC. then you can begin to back up the opening. Mark likes 224 I run 226-230 most of the time.
 
Anything passed 65ATDC the Piston is beginning to make Postive crankcase pressure by traveling downward.  You need to get the rotor closed or you begin to reverse the flow on the intake by blowing pressure back out the intake.
 
these are great number on 45 67 90 & 101 engines. Smaller bore engine the 65 ATDC is good But be careful changing the opening it efffects them more due to a smaller bore
 

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