Supercharged Briggs

[karl]

I am doing this for the coolness factor and the motor and pump was free so why not. The motor is a cool bore so it will not be missed. The smog pump is from a 80s gm 350. I made up some manifolds, and mounted up a gy6 carb I got from bmi karts for $1. I modified it for blow through operation. I blocked off the choke and the bowl is pressurized. Gas will be fed from a pulse pump off a lawn mower. I need to fabricate a bracket to mount the pump as pictured below. Then a hose and two clamps and we are boosting! I will mount a gauge somewhere. If this makes boost I will invest in a billet rod. I dont expect it to last very long but it will be fun. The true test will be throwing it on a minibike and drag racing a rotaderp powered mini, and a naturally aspirated 5hp briggs. Anyway it gives maximum bragging rights.

 

[Flyinhillbilly]

Cool. Are you planning on doing anything with the timing? What kind of fuel will you be running in it?

 

[Rail rider]

Really bro.. We are trolling every post right now.... GOOD LUCK!!

 

[karl]

Cool. Are you planning on doing anything with the timing? What kind of fuel will you be running in it?

Have not thought of timing at all. 93 octane dinosaur squeezings.

Really bro.. We are trolling every post right now.... GOOD LUCK!!

Your more than welcome to get off the keyboard and try to remove a predator governor or something.

 

[thebroketeenager]

Good luck to you! Ill be following this thread for sure.

 

[Kleyny]

interesting concept.
I wonder if the pump use more power than it'll make

 

[Kartorbust]

It'll kind of be like a centrifugal supercharger mixed with twin screw. I too hope it'll give more power. Think it probably uses 3hp minimum to turn it, so hopefully it has double the output or more.

 

[karl]

Well this is all I got done tonight. I picked up a belt and determined the resting place of the pump.

 

[karl]

I am on the way to mad horsepowers.

 

[Bbqjoe]

I predict this will either rock and roll, or fall flat on it's face.
I don't think there'll be an in between.

 

[Kartorbust]

Well it's just an old GM smog air pump probably from a 350/5.7L, shouldn't use more than 2hp. But I can't find what the output of it is, at any given speed. Only thing I've found is it's mostly used for smog at cold starts usually.

 

[Flyinhillbilly]

They just pumped air right into the exhaust manifolds. The automakers claimed it was to help with catalytic converter efficiency, but I think they were just diluting the exhaust with air. I think the pulley ratios, timing, and jetting will be of critical importance. I've boosted lots of engines and the don't live well with a lean condition or too much timing. Other than that it's just the mechanical limits of the parts that says how far you can go.

 

[Kartorbust]

Yeah I don't think they were of any practical use. Most people anyway just ripped them out and bypassed everything. Though with a pulley needing to be on the engine to make it work, is there enough room on the PTO for a clutch or CVT?

 

[karl]

Yeah I don't think they were of any practical use. Most people anyway just ripped them out and bypassed everything. Though with a pulley needing to be on the engine to make it work, is there enough room on the PTO for a clutch or CVT?

I can mount a clutch outboard no prob. Its a ball bearing crank what's the worst that can happen lol.

I am thinking the motor pulley will need to be bigger but ill see how it goes. I am having trouble finding a hose to link this together.

 

[karl]

https://www.youtube.com/watch?v=FRxE4gsHtp0
Its alive. Carb is leaking but it works. Good 1st test. Used arc billet rod on the way. So I am $30 deep into the project now.

 

[thebroketeenager]

A mikuni carb and a different pulley ratio I think would do you some good. Stock carbs aren't that good at all. Also I'd shorten the intake track so you have a smaller area to pressurise. What's your pulley ratio now?

Sent from my KFOT using Tapatalk

 

[Kartorbust]

Yeah I'd have to agree, too much plumbing will cut overall airflow. 22mm Mikuni will also help.

 

[karl]

I do agree on the pulley ratio, I shall get a bigger motor pulley. I don't understand how a different slide valve carb will help. Mikuni carbs are not meant for this.

Also the plumbing is hard to improve from this.

 

[Kartorbust]

Larger carb and better throttle response.

 

[karl]

Larger carb and better throttle response.

I agree larger is better, in some cases, but if it cannot provide a good air fuel ratio under boost, how will I be better off? I keep flooding right now. I think I should find a pump with an inlet and go draw through.

And from what I have read going to a bigger carb size might make problems worse.
And since I am not relying on the piston to draw in air, a larger carb will not provide much benefit at all.