TOPIC:

Anyone want to pass on some experience running velocity stacks? Aside from the look (way cool!) I understand that they may have less turbulence at speed when compared to Emgo or K$N filters which suffer from air swirling/starvation. I don't drive in the rain or on non-asphalt roads, just around town when the traffic is light in the evening.
With my planned engine upgrade -810 kit-650 base, 750 cams and bigger carbs, I am just looking for maximum breathing on my little light-to-light sleeper. The velocity stacks were the way the go-fast guys and roadracers used to set up their bikes for max power.

Maybe the filter tech and design has surpassed the benefits of the old velocity stack's purpose.

Any help would be appreciated.

Cheers-Colin Firth-Ontario Canada

You will wipe out the valve seats in no time if you don't run filters. I never understood why guys would spend money to increase the power of their bikes and then run no filters and the motor is a leaker in no time and a lot of the new expensive performance is gone.

Jay

Moved the topic to the carb forum where it seems to be more on topic.

Jay, why would not running filters hurt valve seats? Can you explain your comment? I can understand sucking in dirt/insects/tree branches might not due valve seats any good... is this what hurts the valve seats?

there's an interesting blurb on velocity stacks/ram pipes here:

zparts.com/zptech/articles/mal_land/ml_s...4/SUcarb_111601d.htm

seems to be a mild form of turbocharging.

The following is my opinion, only, and is not set forth as any form of instruction or vast knowledge:

While it is well known that the lungs of residents of certain large cities are able to tolerate vast amounts of contaminates the internal combustion engine is not able to do so. Dirt and/or dust is the enemy. KEEP it CLEAN.
Over my many years of management and ownership of multi units of heavy construction equipment I have observed that the introduction of contaminates into an engine result in a number of problems. This is primarily due to the non use or use of damaged or substanard air filters.

1) It will tend to cause excessive wear on intake valve stems and guides.

2) Small particles may adhere to the valve face resulting in loss of sealing. This in turn will cause burning and deteriation of the valve.

3) Contaminates may very well wipe out the rings and dust out the pistons.

My final thought would be that the small increase in horse power would not be worth trashing an engine.

Personally, I think the rings would go before the valve seats, but it's a sure thing that you will decrease the life expectancy of your motor by a significant amount.
Rings, valves, bearings, all will suffer increased wear due to insufficient air filtering, silicon (dirt particles) is a really good abrasive.

Thanks guys for your input but I am still not quite sure on the risk/reward ratio but the velocity stacks certainly add a unique look to the intake side of the motor.

Here is the link to the ebay item that got me started on this inquiry.

cgi.ebay.com/ebaymotors/VELOCITY-STACK-K...QQrdZ1QQcmdZViewItem

I understand the ram air/supercharged or turbo effect of increasing the velocity and volume of air into the carb. My very first car was a 1970 Chevelle SS big block with the factory Cowl Induction hood. Under hard acceleration vacuum from a carb line opened a solenoid which activated a flap on the back or cowl side of the hood. There was a rubber, cold air gasket that sealed the air breather assembly to the underside of the hood.

The belief was that the cooler air from outside of the hood was better for making power than the hot air from under the engine compartment. If I/m not mistaken, the cowl inducted air bypassed the air filter thanks to the bulge in the hood which funneled the outside air down and over the carb intake area. My point in referring to this hood style that GM had designed this system knowing that some air was bypassing the filter. (This set-up wasn't ideal for hammering it down old dirt roads while following another car kicking up dust!)

Now, the velocity stacks I am considering have a mesh filter to avoid sucking in small cats or Kleenex tissue fragments from my sniffling Honda 750 Interceptor friends I plan on beating and while the primitive filtration of the velocity stacks are not up to snuff compared to the modern oiled media type filters, they will at least offer some degree of large particle protection.

My main concern is plugging up the carb circuits or jets with tiny dirt particles which would likely end up in the float bowl bases before making their way into the heads. Maybe I am wrong on this point.

As I mentioned in the initial posting, the bike is to be used for short adrenaline rushes, city roads only when there is not chance of rain.

Any other input or comments would be appreciated.

Cheers-Colin Firth

'77 Kz 650 with 700 Wiseco kit, ported heads, MAC Pipe, Pods, 14 tooth sprocket. 14K miles, totally rebuilt from frame up. Moving forward with 750 jugs, 750 cams and 810 Kit with 34Mikunis

my uncle had a 70 chevelle LS-6 4spd and all the goodies but i remember his aircleaner housing outside the filter being sealed to the hood with the rubber donut,no air bypassed the filter.chevy ducted the low pressure air from the base of the windshield like the nascar guys learned to do.back in the early days (mid 70s)when we started jacking with drag boats we would run velocity stacks on our big block chevys but we found out while they looked mean they didnt perform as well as an actual airfilter,and they were worthless for keeping the ducks out at a 100mph!in certain classes we would switch to a single 4 barrel and would run an aluminum scoop,but we found that turning it around backwards toward the back of the boat actually worked better.the ol man still runs his injector hat backwards on his blown flatbottem!

You're correct wireman about the air still passing through the air cleaner under the hood bulge. I dug up some old pics of my Chevelle with the hood up and the breather pan was there, however in some pics I had it removed, so that is where my confusion probably came from. Chalk it up to youth, but I did pull the top of the air filter every once in a while 'cause it gave a more throaty roaf when I had the big block running on full song.

I ran Emgo pods last year and didn't like their performance. A couple of times I pulled them off completely (for a quick spin around the block) and it seemed like the bike pulled better. Maybe it was just my wishful thinking.

I am still hoping for some more input on running velocity stacks for my limited use application if anyone can chime in.

Thanks in advance gang
Cheers-Colin Firth-Ontario Canada

maybe you could faction a retainer ring for each stack and cut up your stock filter if you really want to use them.

certain filters are suppose to actually straighten the airflow before it reaches the carb from what ive been told ,any engineering types on here that can explain this?i kind of understand,but i would have a hell of a time trying to make anyone else understand ,understand?now im baffled!haha

So, how often do you wish to rebuild your engine? F1 cars used to run open velocity stacks on their webbers, they also rebuilt their engines after every race. Any dirt ingested into the engine will wear it out, and there is always dirt in the air.
It isn't the filters that are causing the turbulance problem, it's the sharp edge at the carb throat. This causes a "burble" or air seperation at the edge of the throat due to the air trying to sharply change direction from say, perpendicular to the throat to into the throat, this in turn causes the turbulance in the throat. The Velocity stacks, If properly shaped, promotes the air to hug the wall of the stack and to smoothly change direction and flow straight into the carb throat, and does improve the air flow into the engine.
Depending on room available you can put a velocity stacks inside an air filter, my choice would be K&N (but that's just my opinion).
No matter what you choose, it should be fun.