Thread: Anyone running holleys on their superchargers?

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I have a 350 holley on a small roots blower on my pushrod inline four. (Not a hotrod as such, but here in New Zealand thats the best I can afford)
I've externally referenced the power valve, and have an ample fuel supply. (Holley blue) I currently have size 82 jets in it. I'm running a low vacuum powervalve, because my manifold comes on boost so responsively I don't want it too rich under part throttle load. BUT, it seems to lean out at WOT at around 6000. It just hits the wall. With my old carb it pulled effortlessly up 7500-8000.

What HG powervalves are you guys running on your (drawthrough) supercharged holleys?

At 6,000 rpm you should have a positive boost and the power valve should be on fully? In any case Holley does make high flow power valves and/or you can enlarge the PV fuel passages as well as play with the main jets.

Kitz

Thats what I was thinking. I'm making 7psi from the instant the pedal touches the floor, so I've chosen a low vacuum power valve so It's not opening under light loads. It's very difficult to accelerate without making any boost at all. If I'm very gentle with the pedal, the best I can manage is zero vacuum/boost on the gauge.

Originally Posted by valvebounce

Thats what I was thinking. I'm making 7psi from the instant the pedal touches the floor, so I've chosen a low vacuum power valve so It's not opening under light loads. It's very difficult to accelerate without making any boost at all. If I'm very gentle with the pedal, the best I can manage is zero vacuum/boost on the gauge.

I don't see how a power valve could even be used in your situation, it would always be open.

hi bounce have you checked the float level that is the most important circuit in the in the carb it changes the fuel mixture in all 7 circuit or maybe its beacuse at the bottom of the world your carb is upside down LoL TED ------------------------------------------------------------- I KNOW ALL THE RULES AND I KMOW HOW TO BREAK EM

Yes. With the telltale hole screw out, theres a wee dribble of gas. I've had the carb apart a number of times, an have switched to a centre hung float chamber.

TyphoonZR, At idle and cruise throttle, there is enough vacuum to hold the valve closed.

Do you have a photo of your 350 carb? It must be a little old. Like said above you can adjust PV and jet sizes. In addition, I have owned Holleys since the mid 70's, all sorts, rebuilt and new, and sometimes they just will just not work right. That's when I go buy a new one.

Are you maintaining fuel pressure?

Kitz

ha bounce I was thinking about the problem I have had with holly 4 barrels in past that had been apart alot of times the 4 screws that hold the float bowel and jet plat on get over tightened and bend the main body out this this will cause the gasket to not compress in yhe center causing an internal vacuum leakin the center where the power valve is you can pull off the float bowel an jet and check it with a strait edge and flashlight if you see light dont beat it with a bfh cut a peice of glass about one and a half by six inch wrap sone fine wet and dry around it using plenty of solvent work it down untill you have full contact and check float bowel and jet too but I have never had a problem with those parts reassemble with new gasket do not over tighren screws you will be suprised at at what little torque the instrctions call for hope thi helps it has worked for me ted ------------------------------------------------------ I KNOW ALL THE RULES AND I KNOW HOW TO BREAK EM TED

Originally Posted by kitz

Do you have a photo of your 350 carb?Kitz

Here are some pics, Datsun 1200 Club
Datsun 1200 Club
(You can see the nitrous nozzle in the plate between the carb and the blower. And yes, the nozzle had blank jets blocking the holes up)

I'm not sure about the fuel pressure. But my old carb (a two stage weber 32/36, same as the holley used on the 2 litre pinto motor) didn't have this problem. And the holley has a larger bowl.(Can hold more fuel) My old carb used to lean out when I first got this engione running. Thats why I upgraded the tank pickup and fuel lines to 3/8, as well as fitting the holley blue and a mallory reg. Thats a BIG fuel supply for a 93CI motor. (Even a supercharged one)

That all looks good to me. The tapered spacer helps keep the carb level when under power; that's what I was looking for. If the fuel pressure is right (6-6.5 psi) then sounds like the carb needs to be tuned a tad richer with combos of main jet and PV.

It sure is helpfull to have an O2 meter when doing these things. Not including welding the parts for this are ~$100 from Summit, and you can make it permanent or temporary.

Good Luck, Kitz

Thanks.
A friend had loaned me his wideband A/F meter, but the O2 sensor was faulty. I'm hoping to get a good one off him in the next couple of days. Then, (weather permitting) I can see for sure what the A/F ratio is.


I think it's always going to be a work in progress. Maybe I should just sell it and buy a honda civic. No bloody way!!! lol

Sometimes the PV just doesn't work right on a blown motor. One of the local gys ran into that last year. He finally used the Holley PV blocker plugs and some richer secondary jets and it runs great now.

Manifold reference is the way to go but it is possible you have a vac leak as noted.

I got it all dialed sweet on saturday. Ran the wideband A/F meter, and fiddled with the idle, and the mains. I also had a problem with the accelerator pump check needle. the shaking of the motor was unseating it, and I was getting accelerator discharge nozzle dribble. bought a fangled kit from Mclendon carburator to remedy this. took quite a bit of fiddling around to get this spot on. (had to keep the needle seated, but also had to have little enough spring pressure on the needle to allow the pump actuator arm spring to overcome it so the pump could discharge.
Ended up with an Idle mixture around 12.7:1, and it runs about 12:1 at wide open throttle. At cruise throttle when doing the speed limit the mixture hovers around stoich too.
The larger carb has really made a difference to the available power up top too. The power curve used to begin tapering off about 6000, but know it pulls like crazy all the way to the red line. It was well worth the perseverence.

That's great. Thanks for letting us know how it turned out!

Kitz

Now I can finish fitting the rest of the nitrous kit