Anybody know of a velocity stack for a Surpass 70? I notice the photos of the FL-70 seems to have one. I am looking for one for 70s. I know all the Saito's can be fitted with one.

Cheers,

Chip

The way the bottom of the carb is made with a round part protruding from the carb. A split end aluminum tube could be camped to this area.

Enjoy,

Jim

Chip:

Pictures are my first added stack, used to prove the throry. It's on a Magnum 25, it also has the conic shaped protrusion on the intake casting. I just swaged it, you can see the depression around the bottom end, it has not moved since I put it on.

Bill.

OT: What is a velocity stack and what does it do?

A velocity stack is like a tuned exhaust in a way except it relies more on having a long column of moving air that likes to keep on moving towards the inlet valve even after it's closed. This builds up some pressure to help force air past the valve next time it opens. In other words, it uses the inertia of a column of air to ram into the cylinder. Like the old Dodge Ramcharger engines or the Mercedes 300SL used. BTW, that's why the 300SL engine lays over at a 45 degree angle. It's to give room for the inlet manifold length. These engines were tuned for around the 6000 rev mark and used a manifold somewhere around 30" long but our engines run twice as fast so only need a velocity stack half as long which would be...errr...let's see....30 divided by 2 gives...ummm...I'm not sure but I think it's longer than in the photo

Sorry guys, I can't help myself sometimes

But what a stack like those in the photo will do is stop most of the fuel that sometimes spits out the carb. CL team race engines like the Oliver Tiger use a very long stack because they can't afford to waste any fuel.

Thanks. I did not want to make one but I guess that is the only solution. Among its advantages is that it tends to keep the firewall clean, that contains the carb spit back.

Cheers,

Chip

This has been discussed by William Robison before but you can put a "Bru Line air cleaner" on the carb and serve the purpose of keeping the fuel contained.

http://www2.towerhobbies.com/cgi-bin...?&I=LX9160&P=7

http://www2.towerhobbies.com/cgi-bin...p?&I=LX9158&P=

Chip:

Here are two pictures of the Bru-Line air filter installed. Both engines have sealed front bearings, both stay sterile except for the exhaust, and in the case of the Saito, out the case vent.

Bill.

Brian:

Because of the length needed for intake tuning you will not see me call this extension a "Velocity" stack, I refer to it as an "Intake" stack.

Interesting that the team race boys use the trick, I had never heard of it when I started thinking about having a cleaner and more economical engine.

Bill.

I have an OS 70 Surpass and am also looking to putting a Velocity Stack on it.
W8YE described the extension below the carburetor it measures .470 in diameter and is .175 tall.
Does any one have the inside diameter of the Saito velocity stack, or the carburetor extension OD of the Saito.
If the Saito is the same or just a little bigger like .475 the Saito will go on the OS 70 Surpass.
The picture of the Bru Line filter is attached to a Saito, so I'm wondering how much of a difference in diameter is there?
I looked at the Bru-Line site and I think the small end of the rubber filter housing was 3/8, thats .100 smaller than the OS extension.
The rubber may stretch that much, but I don't know.
If anyone can measure there Saito 72, or 82 carb extension and post it, that would be much appreciated.

The bolt holes on a Saito venturi are 12.75mm apart

The flanges on a Saito venturi are 14.5 mm apart

I measure the I.D. of the Saito venturi as 7.75mm

The venturi is 12mm long

The O.D. of the bell mouth inlet is 12mm

The Bru Line in Bill's picture is on a Saito 120 which is much bigger. I have one of those also if you need the measurements

anyone tached an engine with/without this bruline filter to see if there is much loss of power when using it?

W8YE Thank you for responding.
Just as I suspected the Saito Venturi small diameter is too small for the OS.
7.75mm = .305 inches and the OS extension that it would attach to is .470 inches or 11.938mm almost the size of the big end
of the venturi.

Looks like I will have to fabricate the stack and solder a screen to the inlet for the filter.

Yeah, but the Team Race crowd focuses on maximum mileage from their alloted fuel/number of pit stops (more is detrimental).


Ed Cregger

Yeah, but when you're only allowed 7cc of fuel including the fuel line (that's less than a 1/4 ounce) in FAI team race, you can't afford to waste even a drop .