some advice on tuning my scca l20b please!!

[albyneau]

500 or 600cfm by the looks... way too big for 2 liters not to mention it appears to be on a stock 2bbl manifold so that's 4 into two adapter? A 2bbl 300 cfm would have been big for this.

 

 

4bbl Holeys are for 5 liter V8s.

 

Mike's on track here~ let me expound on his wisdom....

My response is also to what no one else has addressed~ the SCCA in your thread title.

High performance holleys are great at what they do~ provide maximum fuel/air flow at high(er) rpm's. Street holleys are good at what they do~ provide a low-cost, easy to tune-n-tweak option for expensive factory carburetion. If the engine is the lungs, and the cam the brains of your power~ then the carb is the book that teaches them how to behave. My apologies to Grandpa~ he made the wrong call here. A rough guideline for street carb choice is a cfm number that's 150% of your cubic inches~ in this case 122~ so a good starting point would be about 200 cfm. The carb you've mounted is 3 times that! Carburetors function on the design principle of the venturis being the "bottleneck" of the system~ to provide a healthy strong vacuum signal to draw fuel into the system. By mounting this already hugemungous carb on the stock intake you've moved the point of maximum vacuum signal to significantly below the venutris~ grossly weakening the throttle response at all rpm's. A weak vacuum signal draws fuel poorly. This will require excessively rich calibrations to get back even meager performance.

 

If you simply must run a holley you'll need to do several things. First, get a 4 barrel manifold. A holley pattern mani's been made for just about every car ever sold in america~ but I'm guessing an L-series might be a bit of a quest. Second, get one of these~ http://www.holley.com/0-8007.asp It's the smallest you can get, has an electric choke for easy starts, and vacuum secondaries for great mid-rpm throttle response and tuneability. Next, and this is most important if you're serious about SCCA, is take off the float bowls and convert to center pivot bowls. The floats on all but the largest vacuum secondary carbs are side-hung~ which means in a right turn the fuel sloshes and you go rich, the left it leans out. Now imagine the problems that will arise with both a side pivot carb and that dinky intake~ You'll want to take a hammer to your induction system after your first race. And lastly for the ultimate in tuning you'd want to remove the metering plate from the secondaries (fixed jets) and replace with a metering block with idle screws and replacable jets for the ultimate in tuneability. Now you've spent a fair amount of money, and acquired more work than fixing/tuning the SU's. I've got my fair share of experience with holleys (as I'm sure you've now figured) and none with the SU's~ I've never even so much as adjusted the idle on them~ I would stick with them for all but the most all-out of racing efforts~ or go to sidedraft Weber$.

 

Scott

[ggzilla]

A 300 2-bbl flows about the same air as a 125 4-bbl. They rate 4-bbls different from 2-bbl carbs.

 

Weber 32/36 is 270 CFM (193 CFM equivalent to 4-bbl style rating). That's marginal for a hot-rodded 2-liter. Even the stock Hitachi DCH340 flows more air than a Weber 32/36.

 

In any case, a holley 390 can work well at full throttle. More horsepower would be found with twin weber 45 sidedrafts, which is why most racers fit L20Bs with twin webers (if racing class rules allow it).

[DAT510]

Buy The Damn Chilton... :lol: J/K man... Before Top Dead Center.

 

Damn it I neg repped you, I meant to pos rep you!!

[sam]

ok the 4 bbr arb was awesome on full throttle but driving normal it was a bit to rich so i went back to the su, i got a aem wideband and i wanted to know what should be my numbers looking at normal idle and then at wot .....

[DISLEXICDIME]

my l16 head was shaved that much the high comp maid the su's whistle like a super charger