Great. Your working within the air flow restrictions of three small carbs on what is now a very strong 206 cubic inch engine.
You can enlarge the venturis as much as the casting will take via 3m emery paper on a drill attachment. 31 mm each venturi, or 2 mm or 78 thou extra would be a safe maximum.
As long as the ventri has a similar profile (shape/taper) as stock, and you don't break into the zinc oxide casting, then you'll do fine. If you do break into the casing during your work on three valuble 200 dollar Weber 34's, just add a little JB Weld or Devcon filler, and then reprofile.
At the moment, your total carb venturi area is just 3.07 sq inches for about 200 cubes of engine. Compared to any other performance engine, that's a lot less than it should be.If your engine was a 400 cube V8 needing 400 to 450 hp, it would need a carb like a 3310 Holley 750 cfm or Quadrajet 4MA with about 6.216 sq inches of carb venturi area to get 1 hp per cube. Proportionally, you are close with what you have on your 200, but there is not quite enough carb area with the cam package and jetting you have. If there was enough carb venturi area, you'd get stable 12:1 fuel air ratios right off the dyno at WOT. Hence the condition and diagnosis is under carburation. The prognois is continued failure to get the right fuel air ratio and hp. The remedy is to just find a valid way of gaining air flow to match the demands of the rest of your pacakge.
If you can take your carb venturi area up to 3.5 sq in by taking the venturs out to 31 mm, you carb will still work, but will yield close to a 14% increase in air flow. Vizard found that the Holley Weber carbs were too small in the total venturi area in just a 2 liter Pinto engine. A 227 cfm carb suddenly became a 275 cfm carb with just a few gentle mods with a die grinder, and showed huge improvments in power. His carb was taken from the 26/27 mm stock size to 29 and 31 mm, and it still worked well, but made a 21% aiflow improvment still using a stock carb. Area for a Holley Weber 5200 carb was just 1.736 sq in for a 121 cube engine. After mods, it was 2.19 sq in, and power increase was proportional to the area increase. So on a 206 cube engine, 3.625 sq inches would not be too much.
If you've exhasted all your jetting options, and have done the best work on cam and ignition , then its quite okay to gently whittle away the venturi to gain hp. Its what all the pro stockers do with there carbs on race engines when they are allowed to..find the ideal air flow on a stock carb by trial and error venturi area changes. You do reach a point when the carb won't function if you go too big, but as long as you have a 10 to 15% restriction from the carb throttle to the venturi, it will still funtion okay. In side and down draft webers where there is port on port carburation, you cant use venturis less than 5 mm lower than the carbs throttle size. So a DCOE 40 floes less with a 34 mm venturi than a 45 DCOE with a 32 mm venturi. On engines with less than port on port carburation thoug, they are under a lot more restriction, so a 32/36 Weber can go from 26/27 venturis to an insane 29/31 without turning the carb in to a pile of crap.
Then you can go up on jet size to more than the 175/190 combo you have, and then get better fuel air ratios. 195 or whatever jets you can get would then deliver more fuel.
If you engine won't make a fat 12.5: fuel air ratio under wide open throttle, just do the mods to make it do so..whatever mods work that still give you a functioning, safe carburation system, that's what you can do.
That should give you the the 200 hp with ease.
You can enlarge the venturis as much as the casting will take via 3m emery paper on a drill attachment. 31 mm each venturi, or 2 mm or 78 thou extra would be a safe maximum.
As long as the ventri has a similar profile (shape/taper) as stock, and you don't break into the zinc oxide casting, then you'll do fine. If you do break into the casing during your work on three valuble 200 dollar Weber 34's, just add a little JB Weld or Devcon filler, and then reprofile.
At the moment, your total carb venturi area is just 3.07 sq inches for about 200 cubes of engine. Compared to any other performance engine, that's a lot less than it should be.If your engine was a 400 cube V8 needing 400 to 450 hp, it would need a carb like a 3310 Holley 750 cfm or Quadrajet 4MA with about 6.216 sq inches of carb venturi area to get 1 hp per cube. Proportionally, you are close with what you have on your 200, but there is not quite enough carb area with the cam package and jetting you have. If there was enough carb venturi area, you'd get stable 12:1 fuel air ratios right off the dyno at WOT. Hence the condition and diagnosis is under carburation. The prognois is continued failure to get the right fuel air ratio and hp. The remedy is to just find a valid way of gaining air flow to match the demands of the rest of your pacakge.
If you can take your carb venturi area up to 3.5 sq in by taking the venturs out to 31 mm, you carb will still work, but will yield close to a 14% increase in air flow. Vizard found that the Holley Weber carbs were too small in the total venturi area in just a 2 liter Pinto engine. A 227 cfm carb suddenly became a 275 cfm carb with just a few gentle mods with a die grinder, and showed huge improvments in power. His carb was taken from the 26/27 mm stock size to 29 and 31 mm, and it still worked well, but made a 21% aiflow improvment still using a stock carb. Area for a Holley Weber 5200 carb was just 1.736 sq in for a 121 cube engine. After mods, it was 2.19 sq in, and power increase was proportional to the area increase. So on a 206 cube engine, 3.625 sq inches would not be too much.
If you've exhasted all your jetting options, and have done the best work on cam and ignition , then its quite okay to gently whittle away the venturi to gain hp. Its what all the pro stockers do with there carbs on race engines when they are allowed to..find the ideal air flow on a stock carb by trial and error venturi area changes. You do reach a point when the carb won't function if you go too big, but as long as you have a 10 to 15% restriction from the carb throttle to the venturi, it will still funtion okay. In side and down draft webers where there is port on port carburation, you cant use venturis less than 5 mm lower than the carbs throttle size. So a DCOE 40 floes less with a 34 mm venturi than a 45 DCOE with a 32 mm venturi. On engines with less than port on port carburation thoug, they are under a lot more restriction, so a 32/36 Weber can go from 26/27 venturis to an insane 29/31 without turning the carb in to a pile of crap.
Then you can go up on jet size to more than the 175/190 combo you have, and then get better fuel air ratios. 195 or whatever jets you can get would then deliver more fuel.
If you engine won't make a fat 12.5: fuel air ratio under wide open throttle, just do the mods to make it do so..whatever mods work that still give you a functioning, safe carburation system, that's what you can do.
That should give you the the 200 hp with ease.
