#CARB VELOCITY STACKS TRIAL#
There is no absolutes here, you run what works best for your rider and machine.Īnd the new exhaust will need tuning along with carb and intake.Ī lot of trial and error.My recent ignition fiasco really sucks because it's still winter here and dyno operators are begging for business. This is the reason for the vast differences in intakes and exhaust on very similar engines on LSR bikes. Longer length appears to move peak HP to a higher rpm and moves the torque lower and flatter at the same time.įor my racing I need both torque and HP at higher rpm. There appears to be two things happening at once from intake and or velocity stack length. Obviously a formula is only a quess and time spent on a dyno and at the track is the only way to know for sure. Simplified Formula 3 - Intake Length is 12.83 inches
Simplified Formula 2 - Intake Length is 13.60 inches Simplified Formula - Intake Length is 11.00 inches Simplified Chrysler Formula (with bigger cam) - Intake Length is 11.15 inches Simplified Chrysler Formula - Intake Length is 11.67 inches Gordon Blair Formula - Intake Length is 10.69 inches
#CARB VELOCITY STACKS PRO#
The stacks' inlets did come close, at their bell mouth entrances to the rear panel of the ham can but that did not seem to affect their performance at least as far as I could tell, with nothing to test it by.Using available formulas and plugging in my engine specification comes up with different results.Įngine Pro - Intake Port Length is 14.02 inches The rubbers for the velocity stacks were on the inside of the ham can's front plate. The velocity stacks, with their two rubbers were run through the two holes in the front plate of the ham can and then they were epoxied to the two carbs. I ran that set of carbs with epoxied bell mouths into the stock him can air cleaner assembly. I have a set of worn out 932s where I epoxied those velocity stacks on to the carburetor bodies and filled in the joint at the junction where the carb bell mouth meets the velocity stack. That said the design of the those velocity stacks is very good because they present a constant inside diameter to and at the point of the carburetor bellmouth and then that inside diameter continues out to the new bellmouth of the velocity stack. Yes, the grub screws ruin the threads on the carburetors and they loosen and fall out they might even loosen fall out and somehow get into the engine. If the weather is going better i will try needle one step down and air screw out. Plugs are deer-brown on the ground strap. I didnt drive under 3000rpm a lot, because of vibration issues, but i think that is normal. ways to fat but it is working.Īccelerating up to 5000rpm AF is moving between 12 an 13.5 and the bike runs really fine (it is my first norton so i can not compare with others). Stock default carb settings, only float hight is 1mm under chamber surface.Īir Fuel Ratio (AF) in idle is 10.5. stones to be sucked in or fire comming out.Īlso a wideband lambda sonde was fittet on the pipes near the footrests. I also fitted a chinese tea eggs over the stack to prevent eg. i made a test with a piece of aluminium and sealent in petrol with 10% ethanol for half a year. this gave a equal surface with no steps in the inlet. I glued the stacks to the carb with with a polyurethan sealent called "sika flex pro II". I try to report how things working yet, for anybody who is interested. Some time ago i asked about carb setting with the amal racing velocity stack. It might look less 'hot rod' but these FCRs were expensive! However, to prevent excess carb wear I put the stacks inside Ramair foam filters. I experimented with long and short stacks on the dyno and again favoured the short stacks. However, these long stacks tended to cause a stutter just off of idle that was very difficult, sometimes impossible, to tune out. On a road bike, I never felt any performance gain.
Short fat ones (not commonly available for Amals) give slightly less top end, but a broader spread of power, and were generally what I used on racers. Long ones (like theses RGM ones) give a small BHP increase at max RPM. In my personal experience, on a race tuned motor they do make a small BHP difference. Personally, I never detected excess engine wear from using them, but I definitely saw increased carb wear of the slide, body, needle and needle jets. I had 3 on a Trident that looked proper 'hot rod'! I have run these on several bike road and race, I think they look great, especially on a cafe racer.
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