Velocity stack help

[thebossdj]

Hello gear heads. A question for all of you. I am looking for a velocity stack for my Dellorto SS1 27A for my Diana. Does someone out there know the length for the correct one? Also where to find one? Also will a velocity stack off a SS29 fit a SS27? Any help on this subject would be great. Thank you.

Cheers & Bevel Gears.

B

[DewCatTea-Bob]

" I am looking for a velocity stack for my Dellorto SS1 27A for my Diana. "

____ The "Diana" used a 24mm carb, so I assume that you (like most others ignorant of such details), must actually mean the 'Mark-III' !? _ As the 'Diana Mark-III' was indeed stock with the carb.model you've mentioned.


" Also will a velocity stack off a SS29 fit a SS27? "

____ YES but, when fitted, the resulting intake-throat would then have a 1mm step-reduction (which would likely cause some [insignificant] flow-turbulence).

____ Haven't you looked on eBay ?
How about this ? - http://www.ebay.com/itm/130276520187?ss ... 1438.l2649
__ You may wish to expand your search (for whichever particular inlet-stack you actually seek), to include Harley-Sprints, as that model also used the 27mm carb.size .


Hopeful-Cheers,
-Bob

[Jordan]

All I know is that a short stack works better than a long one on Ducati singles, which is a shame because the longer ones look horny.

Jordan

[thebossdj]

Thanks for the help so far. My Diana has the factory race kit with Megaphone plus the SS27, upgraded from the 24mm. As for looking on ebay I have. Not knowing what length or size to go with is the problem. How short is the short stack?

Thank you.

[double diamond]

Guzzino has some SSI stacks on the website.

[Jordan]

Re: Velocity stack help

Post by thebossdj
How short is the short stack?


30mm, not including the threaded part.

Addit: I shouldn't have said all Ducati singles, as a longer one might be OK for a 250. My experience has been with 350 fitted with SSI 29, and 450 with VHB 29.
There's a picture in the Photo Gallery of a short one, under "Modified 350".

Jordan

[Bevel bob]

I have wondered about the blowback stains on my 250's toolbox ,perhaps a shorter stack will change the resonance and improve fuel economy too.Its a well known fact that the curved shape trumpets are most effective.

[wcorey]

The relative scavenging efficiency of a motor is effected by both total length of the intake tract and exhaust. So the desired stack length can be dependent on many factors, also including the intake manifold length, compression and cam profile. On the 900ss belt drive motors, a shorter intake length produced more top end power but took it away from lower rev torque. It all depends on what you're after...


Bill

[Jordan]

My bikes' engines were not hotted up - just standard specs, apart from different mufflers and jets, and removing valve springs from the desmo.
With the longer horn, I couldn't get it to run cleanly through the rev range, despite trying different jets, needles and slides. With the short stack it behaves better.
I couldn't say if performance was better with either one, not noticeably anyway.

Jordan

[thebossdj]

Thanks for all the suggestions and help. The pic of the wide case with the short stack was very helpful.. Yes the long ones look horny for sure. Do bikes with elocity stacks run better with silentiums or factory megaphones? Any feedback would be nice.

btw Domiracer was out of all stacks for SS1's 27 to 29's.