Slide valves

[cowtown]

Does anyone have a link to a good explanation or picture of how slide valve heads work?

[dwightp]

Slide valve heads -or- slide valve throttle bodies?

[HawgRyder]

I think you might be thinking of the old "sleeve valve" engines like the Graham or Knight.
Imagine 2 liners in the bore with the piston in the centre....both liners move up and down exposing ports in the sides....very quiet...very smooth...very low RPM's.....lots of torque.
Try a search for Knight or sleeve valve.
Bob

[cowtown]

I guess I'm not sure what I mean...I saw in the "Mid-engine 911" thread that the referenced racecar has "slide valves."

Maybe they are referring to the throttle bodies and not the intake/exhaust valves. I'm just trying to figure out what the heck they are and how they work.

Thanks
Colin

[Paul Thomas]

Imagine a plate that has throttle bore size holes in it, sliding back and forth, in a housing with a return spring so it snaps closed like the butterfly intake when you let off of the throttle. As the throttle is depressed the opening kind of looks like a cresent moon until it is open all of the way, then it is a stright shot into the head with no interference.

Tha obvious benefit is that there is no air restriction when it is wide open. The down side is that they are tough to tune at anything but wide open, so they are largely impractical for street use. Kurt Zimmerman runs them on his 3.5, so he must have had some good reults. I talked to Jerry Woods about it for my car one time but they are VERY expensive.

Paul

[Randy Webb]

also they tend to stick

you don't want them

[Steve@Rennsport]

Hi Paul:

FWIW,...I've used slide valves in Porsche race cars since 1974 and they work VERY well with excellent drivability at any throttle opening. They are VERY smooth and work well in street applications with the only caveat below.

They are very prone to sticking if the engine has no aircleaners but thats about it. Fact is, they have much superior drivability over the tall-butterfly stacks used on previously Porsche race cars. Not cheap, but you get what you pay for.

LOL,...Just one more advantage of having built & raced these cars for a very long time.

[dwightp]

Colin:

If were talking slide valve induction,
Steve may have some pic's on his site. I know ANDIAL offers a set and may have pics. Here's another with 2 variants: http://www.protechnik.com/custom.htm

Steve:
Hmmmmm. U got me thinking again. Dangerous. Oh well, I guess I'm commited to make my butterflies work in the interest of $'s.

[beepbeep]

Hmm...i think he's asking about real slide valves, like Napier Sabre etc.

[cowtown]

Originally posted by beepbeep
Hmm...i think he's asking about real slide valves, like Napier Sabre etc.

Thanks for all the replies guys. Since my question was really vague, I'll try to be more specific.

I had heard about throttle body slide valves on high-end racers, and seeing the description and pictures is great. Holy cow are they expensive!

What I was really wondering, is if slide valves were ever used for intake/exhaust in the heads. I can't see this being possible, but was just curious.

Or- are there are other ways of getting the charge into the cylinders besides traditional valves or direct injection.

I'm just curious here, not trying to build anything.

Thanks
Colin

[Randy Webb]

I think I'd start looking thru some books on the history of the int. combustion engine. All sorts of things were tried early on, so maybe so. You'll also have to define exactly what you mean -- e.g. the Mazda's rotary could fit what you say as the trochoic (sp?) rotor slides past the ports as it rotates...

[cstreit]

These are very common on motorcycle carbs and injection and actually seem to work quite well for them and are very little maintenance.

Had Mikuni slide valves on my Ducati's and never had an issue with them.