CMB VAC91 tuned Pipe

[u60]

New to riggers, what pipe are you guys running on the VAC91? Thanks, Fred

 

[Elias Vazquez]

I've seen good results from the CMB67/80 muffled, and even better results

From the old 67/80 Rossi nitro.

Elias

 

[John Knight]

An AB 84 parabolic (currently available from Al Hobbs) works well on a 91HR. It is not a 91 VAC but essentially is the same engine. The MACS 15cc nitro pipe did not work as well as the parabolic.

 

[gil sonsino]

I second the AB .84 but it's recommended to open the baffle for this size of engine...mine is running well with it.

 

[ALLAN YUEN]

I like my CMB91 VAC use Brown 67 Parabolic( drill size 27/64" into stinger) also CMB header small diameter 22mm O.D than too big 25mm O.D Set up 12.75" center to pipe line B) Great running very well !

 

[u60]

Thanks for all your suggestions. Fred

 

[John Knight]

I second the AB .84 but it's recommended to open the baffle for this size of engine...mine is running well with it.

Gil,

Everyone of my parabolics has the baffle drillled regardless of size and I have them all.

 

[rick lindow]

John, please explain open the baffel, drillled the baffle maybe a pic of the pipe? thanks, Rick Lindow

 

[John Knight]

John, please explain open the baffel, drillled the baffle maybe a pic of the pipe? thanks, Rick Lindow

It is the standard Andy Brown 84 parabolic pipe. You drill out the internal baffle inside the stinger to decrease the back pressure and let the pipe breathe. Take a drill bit just a tiny amount smaller than the ID of the stinger and drill the baffle out through the stinger.. Do not drill out any of the stinger itself. Then flush out the pipe in running water heavily from both directions to get out all of shavings. I will usually fill the pipe up with water and shake it up hard and drain it out. It takes about 6+ times to flush it well. If you do not get them all out, your engine will eat them and it will be toast.

 

[rick lindow]

John, I have a new RR 2011 80/101 starting with a cmb 80/ 84 parabolic . pipe set @11.75. that i have not ran yet, maybe two weeks. ive looked through this pipe the stinger is the same size inside and out (iner stinger /outer stinger) i bought the pipe on iw sold as new,pertnear!!! you can look down the pipe and see through it correct? Rick L.

 

[John Knight]

John, I have a new RR 2011 80/101 starting with a cmb 80/ 84 parabolic . pipe set @11.75. that i have not ran yet, maybe two weeks. ive looked through this pipe the stinger is the same size inside and out (iner stinger /outer stinger) i bought the pipe on iw sold as new,pertnear!!! you can look down the pipe and see through it correct? Rick L.

If the original baffle is in place, you can look through the stinger end and easily see it inside the pipe. If it is fairly wide open, then it has been drilled. Just to test, do the drill bit test as I noted before. Pipe length is about right but not sure just what engine you have.

 

[rick lindow]

John , i bought it first of 2010 red head 80 rs-h may be an 2009 MOD through Stu B.RICK L.

 

[John Knight]

John , i bought it first of 2010 red head 80 rs-h may be an 2009 MOD through Stu B.RICK L.

You may be able to go in to 11 1/2" on the pipe. Try 11 3/4" first and if it runs well, try 11 1/2 and see then.

 

[rick lindow]

John, i was wrong in what i posted earlier,my pipe that i got off of i.w.has not been drilled! i was thinking of the wrong pipe, head up somewhere! you all where talking about 91s in the beginning , i think i should run the 80 first and then see what happens,i all so have a( CMB AB 67/80 MUFFLED),(13 CC MACS MUFFLED 1389 OPENED TO 1") any thoughts ,

 

[John Knight]

John, i was wrong in what i posted earlier,my pipe that i got off of i.w.has not been drilled! i was thinking of the wrong pipe, head up somewhere! you all where talking about 91s in the beginning , i think i should run the 80 first and then see what happens,i all so have a( CMB AB 67/80 MUFFLED),(13 CC MACS MUFFLED 1389 OPENED TO 1") any thoughts ,

Rick,

I have run big blocks, a 67, 84, 90 & 91HR with a parabolic and all pipes are drilled. My CMB 90 EVO likes a MACS 15CC nitro pipe better but all others run very well with the parabolic. The 80 will run very well with the CMB/AB 67/80 muffled pipe.

 

[Buckshot]

John, i was wrong in what i posted earlier,my pipe that i got off of i.w.has not been drilled! i was thinking of the wrong pipe, head up somewhere! you all where talking about 91s in the beginning , i think i should run the 80 first and then see what happens,i all so have a( CMB AB 67/80 MUFFLED),(13 CC MACS MUFFLED 1389 OPENED TO 1") any thoughts ,

Rick,

I run the Black AB/CMB .67 Muffled pipes on my .80 twin and they seem happy. I run them at 11.5".

This time of year down where you are you'll prolly need to pull it out to 11.75 or more.

Buck