Need an electrically switched vacuum control valve

[milner351]

Hey guys -

A friend of mine has an idea for his car he wants to try out.

He has a vac sec carb - he wants to be able to control from the driver seat when the secondaries can open - via a switch.

I was wondering if anyone knew of an electrically controlled vacuum switch?

purge control and similar devices on cars I know of are frequency controlled - not a simple on / off.

Any suggestions?

[CTX-SLPR]

Re: Need an electrically switched vacuum control valve

Evap canister purge valve comes to mind, I'm pretty sure thats on a vacuum line to the engine.

[dieselgeek]

Re: Need an electrically switched vacuum control valve

there are TONS of these valves in the junkyard. I use them for fast idle solenoids on some EFI projects. Evap purge solenoids, fast idle solenoids, etc. They're cheap at a parts store too...


you can ID them easily enough, they'll have two vacuum nipples (or, one nipple and a tiny filter), and a connector with two wires.

Make sure he sets it up so that he doesn't create a vacuum leak when it's enabled though,

-scott

[Falcon67]

Re: Need an electrically switched vacuum control valve

He'll have to butcher the carb or at least the vacuum chamber to make it work at all. I say "not a smart idea" - think massive bog.

[CTX-SLPR]

Re: Need an electrically switched vacuum control valve

Not so sure on that one, aren't the vacuum pots plumbed in with an external line on holleys? If so you'd just jump this into the line. I'm not as much of a carb guy and I've always liked Q-jets over holleys anyway.

[dieselgeek]

Re: Need an electrically switched vacuum control valve

Not so sure on that one, aren't the vacuum pots plumbed in with an external line on holleys? If so you'd just jump this into the line. I'm not as much of a carb guy and I've always liked Q-jets over holleys anyway.

agree, I am carb stupid but I'll gladly help them figure out how/where to find the valve just to see how it works ;D

[TheSilverBuick]

Re: Need an electrically switched vacuum control valve

I never thought about using the fast idle or purge valves! I've needed one for a couple months now since my T-birds headlight door's vacuum switch failed (it's separate from the head light switch) and I've been operating it manually. This might work for a temporay solution.

[dieselgeek]

Re: Need an electrically switched vacuum control valve

I never thought about using the fast idle or purge valves! I've needed one for a couple months now since my T-birds headlight door's vacuum switch failed (it's separate from the head light switch) and I've been operating it manually. This might work for a temporay solution.

that's what I'd suggest you use if you ditched the MS2 IAC controls, just run one of these to a vacuum line and let it "fast idle" during warmup. Works like a champ and that's what's been used on a ton of EFI cars before IACs were popular.

[squirrel]

Re: Need an electrically switched vacuum control valve

I can control when the vac secondaries open from the driver seat...but I use my foot instead of a wire.

[dieselgeek]

Re: Need an electrically switched vacuum control valve

I can control when the vac secondaries open from the driver seat...but I use my foot instead of a wire.

that's so 1980s Jim.

[milner351]

Re: Need an electrically switched vacuum control valve

OK - more background.

Say you are bracket racing and your car is .6 faster than the dial in with the secondaries hooked up.

To keep it consistant to it's dial in - you remove the secondary linkage and run on the front venturi's only.


Say you leave the line and spin the tires - or some other event happens that makes you know you're a bit slow on this run --- to "make up time" you flip a switch to allow the secondaries to open to give you more power to get back down to your dial in time - instead of loosing the race.

That's the concept anyhow - so - the search for an electrically controlled vacuum switch / solenoid continues.

[dieselgeek]

Re: Need an electrically switched vacuum control valve

OK - more background.

Say you are bracket racing and your car is .6 faster than the dial in with the secondaries hooked up.

To keep it consistant to it's dial in - you remove the secondary linkage and run on the front venturi's only.


Say you leave the line and spin the tires - or some other event happens that makes you know you're a bit slow on this run --- to "make up time" you flip a switch to allow the secondaries to open to give you more power to get back down to your dial in time - instead of loosing the race.

That's the concept anyhow - so - the search for an electrically controlled vacuum switch / solenoid continues.

If you want to slow the car down below dial and have "extra headroom" I would think there would be a few better ways of doing it more consistently than with shutting down half the throttle bodies. Even on a carb'd car. I.e., timing advance. Maybe use your check valve to block off a certain amount of advance or something instead.

-scott

[TheSilverBuick]

Re: Need an electrically switched vacuum control valve

I think he is looking for a way to gain "back" some speed/time in the event of a bad launch half way down the track rather than just slowing the car down. I'm sure he knows how to do that ;)

[smallblockjay]

Re: Need an electrically switched vacuum control valve

Interesting idea. With a mechanical secondary carb, your right foot still determines if or when the secondaries open. 8)

[yellomalibu]

Re: Need an electrically switched vacuum control valve

There's a racer around here that uses an ac clutch and a gas strut to slowly open the throttle... he never spins a tire. It looks like his mechanic is Jed Clampit, but I guess it works.

Vacuum operated stuff is bad for bracket racing. Modulator, secondaries, timing advance... can all change slightly round to round, adding up to inconsistency. (fan clutches, too)

Most of the racers I know just sandbag a few hundreths and drive the finish line. If you spin a little, you're still safe.