Intake plenum

[Onthebar]

I'm building a 1978 gs1000 drag/street bike. The air box has been removed due to frame mods. I am aware that it acts as a plenum of sorts, but was wondering if putting an aluminum plenum behind the carbs (between carbs & intake runners) joining all 4 into 1 plenum is a realistic endeavor, or if there is any performance gains to be had ? Am I off my rocker ?

 

[tom203]

So you've removed stock airfilter/airbox, why not just go with individual pod liters with as little restriction as you desire?

 

[mvalenti]

Between carb and heads no, before carbs in place of an air box yes. Some guys who run pods make a 5 sided box to help with crosswind issues they have with pods. Good luck and post pix.

 

[Onthebar]

I do have pods. What I don't understand is, the difference between having a plenum before or after the slides (or butterflies) on this type of engine. A ton of torque can be had by using a plenum between the butterflies & intake runners on other motors & also bump the HP numbers as well. Just curious & am equipped well enough to build 1... you know...mad scientist stuff. Thanks

 

[tom203]

Mad scientist , ok. ditch the 4 puny carbs and get a 4 barrel Holley on an Edelbrock manifold

 

[tkent02]

Do you want low end torque or high end horsepower?

 

[Onthebar]

The bike has a car rear tire, so I'm looking for bottom end torque, not to get it off the line, but to get it to pull hard thru the gears

 

[gs11ezrydr]

I used the stock air plenum with the velocity stacks inside it, and completely removed the air filter case, and installed a K& N Ru-1810 in the place of the air box attached to the back of the plenum, with 36 mm carbs and a stage 3 jet kit witch I had to go up on the main jets a little .But throttle response is great and I think with Constant velocity carbs the velocity stacks help some also with low end and throttle response. The air filter is in a dead air space and I get no cross drafts like with pods. Carb bowl vents are also critical to get them into a dead air space also as not to draw no negative pressure at the bowl vents witch can cause a lean condition witch was hard to track down. I think a plenum after the carbs could possible cause negative effects. But you never know unless you try a plenum is a dead air space just attach a filter and go with it .