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Velocity Stack for Strombergs?
- Thread starter Stinky
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I think Pegasus Racing has them but you will have to dig deep.
Bill
Bill
SkinnedKnuckles
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I ended up making 3 of them from - are you ready - bicycle horns. The bell on the horns I found were very nicely parabolic. Just cut them off a bit "long", then grind the base to get the diameters to match. They have to be notched to accomodate the filter mounting bolts, then epoxy them onto the filter housing (K&N's here). I then used 1/8" teflon packing on both sides of the filter to widen the air passage. All that for about 2" water column higher pressure in the cylinders, by calculation. But hey - it was something to do.
Alan_Myers
Luke Skywalker
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Velocity stacks are effective on ZS, SU, Weber and many other types of carbs.
Yes, they look cool, but can also be useful to "fine tune" the carbs' performance on the particular engine.
Generally speaking, use shorties to gain power in the lower rpm range - call it "grunt" - medium length to help in the mid range and longer ones to help out at the high end. They will rob a little from the opposite end, though. So extra long will have a little negative effect on performance at low rpms, and vice versa.
I don't know the specs for SU & ZS horns, but on Webers the shorties are only about 10 to 20mm deep, medium length are around 30 to 40mm and the deep ones might be 50 or 60mm.
If used with air filters fitted over them (killing the "wow" factor, but saving the engine!), there should be roughly 40mm space between the outer end of the horn and the inside of the air filter housing, or air flow might be restricted.
In most cases, the best air horns are full radius design, which is usually either cast or turned from a solid billet. Stamped or spun type are a little less effective, but often are less expensive. The really nice, ultra high performance ones are very expensive. At the other end of the spectrum, I recall reading that Kas Kastner bargained with a waitress in a restaurant to buy 3 metal butter containers off them, that were modified into ram pipes for one of the Group 44 cars!
The real differences in length and type of air horn may be difficult to detect without a dyno or split timer on a race track.
By the way, velocity stacks show up fairly often on eBay. That's where I finally got a nice set of four for my DCOEs. You might want to also watch out for them in auctions or sales of early Datsun 240Z and Volvo parts, too, since both used SUs or SU-knockoffs and the same air horns may fit. Hint: eBay sellers call them all sorts of things; "pipes", "tubes", etc.
Have fun!
Alan
Yes, they look cool, but can also be useful to "fine tune" the carbs' performance on the particular engine.
Generally speaking, use shorties to gain power in the lower rpm range - call it "grunt" - medium length to help in the mid range and longer ones to help out at the high end. They will rob a little from the opposite end, though. So extra long will have a little negative effect on performance at low rpms, and vice versa.
I don't know the specs for SU & ZS horns, but on Webers the shorties are only about 10 to 20mm deep, medium length are around 30 to 40mm and the deep ones might be 50 or 60mm.
If used with air filters fitted over them (killing the "wow" factor, but saving the engine!), there should be roughly 40mm space between the outer end of the horn and the inside of the air filter housing, or air flow might be restricted.
In most cases, the best air horns are full radius design, which is usually either cast or turned from a solid billet. Stamped or spun type are a little less effective, but often are less expensive. The really nice, ultra high performance ones are very expensive. At the other end of the spectrum, I recall reading that Kas Kastner bargained with a waitress in a restaurant to buy 3 metal butter containers off them, that were modified into ram pipes for one of the Group 44 cars!
The real differences in length and type of air horn may be difficult to detect without a dyno or split timer on a race track.
By the way, velocity stacks show up fairly often on eBay. That's where I finally got a nice set of four for my DCOEs. You might want to also watch out for them in auctions or sales of early Datsun 240Z and Volvo parts, too, since both used SUs or SU-knockoffs and the same air horns may fit. Hint: eBay sellers call them all sorts of things; "pipes", "tubes", etc.
Have fun!
Alan
SkinnedKnuckles
Jedi Trainee
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Yeah - sometimes they're even called "ram pipes", which I can't figure out at all. The whole intent is to basically eliminate the sharp 90 degree entrance which causes boundary layer separation from the momentum of the air getting sucked in from the side, and the accompanying non-recoverable pressure drop.
The design of the Z-S carb doesn't seem like it would benefit terribly from stacks. After the inlet there is that piston with it's sharp edges to cause turbulence. And the "dam" leading up to the jet...
If you look closely at the Z-S carb inlet there is a small 45 degree bevel at the entrance that I guess is supposed to help. Too bad it wasn't radiused... I'm a bit leary of the claims from "full radius" horns, too.
The design of the Z-S carb doesn't seem like it would benefit terribly from stacks. After the inlet there is that piston with it's sharp edges to cause turbulence. And the "dam" leading up to the jet...
If you look closely at the Z-S carb inlet there is a small 45 degree bevel at the entrance that I guess is supposed to help. Too bad it wasn't radiused... I'm a bit leary of the claims from "full radius" horns, too.
trboost
Jedi Trainee
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Try calling Joe Curto in Queens N.Y. 718-762-SUSU
https://www.joecurto.com/
Although they are effective at high rpm's on the track, they are truly not intended for street use , especialy with out foam filter socks over them. That side of the motor sucks up LOTS of debris from the road. A coulple of thousand miles without filters would surely do damage.
Keep a helmet on those soldiers /ubbthreads/images/graemlins/crazy.gif
https://www.joecurto.com/
Although they are effective at high rpm's on the track, they are truly not intended for street use , especialy with out foam filter socks over them. That side of the motor sucks up LOTS of debris from the road. A coulple of thousand miles without filters would surely do damage.
Keep a helmet on those soldiers /ubbthreads/images/graemlins/crazy.gif
Alan_Myers
Luke Skywalker
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CORRECTION Re: Velocity Stack for Strombergs?
Hi again,
I need to correct something in my earlier response.
Shorter horns are most effective at *higher* rpms, longer horns are most effective at *lower* rpms... Just the opposite of what I wrote in my earlier post.
D'oh!
Alan
Hi again,
I need to correct something in my earlier response.
Shorter horns are most effective at *higher* rpms, longer horns are most effective at *lower* rpms... Just the opposite of what I wrote in my earlier post.
D'oh!
Alan
Alan_Myers
Luke Skywalker
Offline
Hi again,
I'm back to weigh in favoring air horns on ZS, SU or Webers... IMHO, they can help even a street engine breathe better. However, besides the "wow" factor, the greatest benefit would come in conjunction with other modifications such as porting, increased compression, a hotter cam, headers and anything else that helps the motor inhale and exhale well.
I agree that some sort of air filtration is essential. Running a motor without it is just asking for trouble. Race motors striving for every last little bit of power may be run with horns only, but are typically rebuilt every few hundred hours of use, or less, anyway.
There are filter options besides socks. I've got two 3-1/2" deep oval K&Ns covering the four 40mm air horns fitted to the DCOE 40s on my TR4. These give ample depth to allow the air horns to do their job. The only caveat is that some modification of the inner wheel well is usually needed to fit this deep a filter.
I'm fairly certain K&N makes air filters to fit SU/ZS carbs, too. Just get a deeper version that allows 1-1/2 inch or more of air space, between the very tip of the air horn and the inside of the filter end plate. Probably ITG and some of the other performance filter makers offer something that will work, too.
Other filtration options can be elaborate or simple. At the elaborate end of the spectrum, fabricate a sheet metal airbox serving all the carbs and fit a single, ample filter to the front of it, which would also serve to gather cooler air from the front of the engine compartment.
A simple solution might be a separate, clamp-on filter at each carb. These are made by various filter manufacturers. Some are even customizable, with a metal framework you can bend and shape to fit your particular needs.
So long as filters are used, I don't see much harm in experimenting with air horns on any passive induction fuel/air system (i.e., not turbo or supercharged). It's possible the carbs might need to be re-jetted or otherwise adjusted after air horns are installed. However, both ZS and SUs are pretty good at self-adjusting for changes in air flow, up to a point (Webers are not, would probably require re-jetting).
Cheers!
Alan
I'm back to weigh in favoring air horns on ZS, SU or Webers... IMHO, they can help even a street engine breathe better. However, besides the "wow" factor, the greatest benefit would come in conjunction with other modifications such as porting, increased compression, a hotter cam, headers and anything else that helps the motor inhale and exhale well.
I agree that some sort of air filtration is essential. Running a motor without it is just asking for trouble. Race motors striving for every last little bit of power may be run with horns only, but are typically rebuilt every few hundred hours of use, or less, anyway.
There are filter options besides socks. I've got two 3-1/2" deep oval K&Ns covering the four 40mm air horns fitted to the DCOE 40s on my TR4. These give ample depth to allow the air horns to do their job. The only caveat is that some modification of the inner wheel well is usually needed to fit this deep a filter.
I'm fairly certain K&N makes air filters to fit SU/ZS carbs, too. Just get a deeper version that allows 1-1/2 inch or more of air space, between the very tip of the air horn and the inside of the filter end plate. Probably ITG and some of the other performance filter makers offer something that will work, too.
Other filtration options can be elaborate or simple. At the elaborate end of the spectrum, fabricate a sheet metal airbox serving all the carbs and fit a single, ample filter to the front of it, which would also serve to gather cooler air from the front of the engine compartment.
A simple solution might be a separate, clamp-on filter at each carb. These are made by various filter manufacturers. Some are even customizable, with a metal framework you can bend and shape to fit your particular needs.
So long as filters are used, I don't see much harm in experimenting with air horns on any passive induction fuel/air system (i.e., not turbo or supercharged). It's possible the carbs might need to be re-jetted or otherwise adjusted after air horns are installed. However, both ZS and SUs are pretty good at self-adjusting for changes in air flow, up to a point (Webers are not, would probably require re-jetting).
Cheers!
Alan