twin vac 91 pipe change

[Rick Pirrone]

hi all

i picked up a couple of cmb 67 quiet pipes here i would like to try them on my twin

at the moment im using the fat belly cmbs with vac 91s @11.5 and was wondering has any one played around with theses quiet pipes on a twin vac setup if so what was your likes and dislikes also what length was best for this combo

i have seen them run well on a 67/80 twin but interested in the performance on a 91 setup

cheers rick

 

[brett english]

i ran this set up on a twin roadrunner, these pipes worked very well, what i noticed is midrange torque...i could be cruising around 50mph and them give

full throttle and almost lift the front sponsons out of the water...pipe length was around 11 3/4 with 60% nitro...Foley and some other guys are running the

Rossi 80 pipes and seem to be getting some serious top end, the problem is to find these pipes..But these cmb muffled pipes are awesome, almost every boat

i run has them, and for good reason other than performance, if i loose a pipe at a race i can swap them out from boat to boat...good luck and keep us posted

 

[Tim Kish]

I have a brand new pair of the Rossi pipes that I'll try after I break in the newVACs with the 67/80 quiet pipes .

I'll post when I do , just waiting for the water to warm up a little first .

Tim

 

[Rick Pirrone]

hi brett

thanks for the reply

just waiting on some bearings from jon for the 91 s then i will give the pipes a go, a few guys here are running the macs 13cc on

there twins they seem to like the 1 inch band, i think there is one guy running the rossi pipes here

julian said he likes the fat belly which we have on the boat like i said they are friendly to use and with good results

i seen that your 80 twin runs awsome with these pipes so i hoping they will be good on my 91s

cheers rick

ps good luck this weekend

 

[Rick Pirrone]

I have a brand new pair of the Rossi pipes that I'll try after I break in the newVACs with the 67/80 quiet pipes .

I'll post when I do , just waiting for the water to warm up a little first .

Tim

hi tim

thanks for the reply

look forward to hearing you results

cheers rick

 

[Tom Foley]

They run great with the VACS. I ran mine at 11-3/4 - 12 " and had good results like Brett stated he had .

 

[Tim Kish]

They run great with the VACS. I ran mine at 11-3/4 - 12 " and had good results like Brett stated he had .

what are you using for mufflers Tom?

Tim

 

[Rick Pirrone]

They run great with the VACS. I ran mine at 11-3/4 - 12 " and had good results like Brett stated he had .

hi tom

thanks for the reply

ill start @12 and go from there

cheers rick

 

[Tom Foley]

They run great with the VACS. I ran mine at 11-3/4 - 12 " and had good results like Brett stated he had .

what are you using for mufflers Tom?

Tim

Some Harry Gerhardt mufflers I got from Joe Warren . The Rum Racing or Prather type look like they would work fine as well.

 

[dwilfong]

Try the MACS 13cc muffled pipe with the stinger drilled to .470 set at 11".

It is a pain to drill the inner stinger but you might be surprised how it will REV and throttle.

Also try the smaller.80 header it will increase the ex velocity.

David

 

[Rick Pirrone]

Try the MACS 13cc muffled pipe with the stinger drilled to .470 set at 11".

It is a pain to drill the inner stinger but you might be surprised how it will REV and throttle.

Also try the smaller.80 header it will increase the ex velocity.

David

hi david

im going to be useing the cmb 22 mm header for the vac 91s i think its about 3/4 internal size

which is the same size as the pipe

to get the desired length shoiuld i cut both pipe and header or just header leaving the pipe uncut ?????

cheers rick

 

[dwilfong]

Try the MACS 13cc muffled pipe with the stinger drilled to .470 set at 11".

It is a pain to drill the inner stinger but you might be surprised how it will REV and throttle.

Also try the smaller.80 header it will increase the ex velocity.

David

hi david

im going to be useing the cmb 22 mm header for the vac 91s i think its about 3/4 internal size

which is the same size as the pipe

to get the desired length shoiuld i cut both pipe and header or just header leaving the pipe uncut ?????

cheers rick

Dose not really mater what you cut just leave enough flat section on the pipe for the coupler to get a good hold.

The 80 header is .100 smaller on the inside and OD will also fit inside the pipe.

You will have to open up the header flange to fit and use different orings to seal it if you go this way.

I's a little bit of a pain to make work but it dose work good.