STRONGER PCV!!!!

[MPGmustang]

I need a stronger PCV, positive crank vacuum valve, as mine is 'stock' and best for stock engines, I'm pulling less vacuum and so I don't need it open as easily cause it's acting like a HUGE vacuum leak, not like a controled vacuum leak. I can unplug the hose from the TBI and NO change, but if I plug the PCV the idle fixes itself to 900rpm.

I want to get somehting stronger, not to plug it but to mainly pull fumes when I have great vacuum that way it 'kinda' works but only under 12+ vacuum conditions. right now it works ALL the time and tune is being affected.

 

[292fan]

gpmustang, while I don't know of a particular application or part number for your pcv, you could try restricting the hose diameter. I have used zip ties to progressively squeeze the hose down to a diameter that is workable. Or you could try to step down to a smaller diameter that will get the desires results. I have had friends use a wooden dowel in line with the hose with a hole drilled through to be a restrictor. The end result is to restrict the vacuum to a workable amount.
Just a couple of ideas.

292fan

 

[Soldmy66]

To determine and control the amount of vacuum necessary, you could insert any type of adjustable air control valve in the hose to restrict flow. This would allow you to determine the sweet spot.

 

[xctasy]

Ak Millar and Impco used to have problems with Ford Fuel control valves flowing to much air, upsetting the the converter and propane gas air valve, so they used to raid a Champion spark plugs screw off tip in the days that they were threaded on to the spark plug. Grab an 80's Brigss and Stratton lawnmowers Champion plug scew on item, and restrict the air flow from them PCV valve to the line. A brass ferule will probably do the trick.

 

[MPGmustang]

thanks guys, that's a great idea, I'm going to go to a fish tank store and pick up an air valve for bubble systems to make it 'adjustable'. that should do the trick for me. you guy's helped alot...

I guess I meant the title to be 'Stronger spring in PCV' to suck less, but I think the air throttle will be the trick for me.

 

[wsa111]

You could install a draft tube from an engine before pcv's.
Then you will not have any vacuum leak at all.
Another idea is install belt driven vacuum pump & create negitive crankcase pressure which will improve ring seal.
Another idea is use a header collector valve & hook it to the crankcase. Bill

 

[MustangSix]

PCV's have different ratings, but I can't seem to find the chart. You could just put in a plastic or metal restrictor of some kind in the hose. Drill a 1/8" hole and make it larger if need be.

 

[MPGmustang]

which car had about 5-6 vacuum at idle from factory? I heard I can use any that fit and just go for one that's stock to an engine with low vacuum from factory

 

[thesameguy]

I'm thinking here you are not going to be able to find such an animal. Any car made with s PCV system is going to be relatively modern, and pull high vacuum. You're only going to find "things" made for low-vacuum engines for very old stuff, or modified stuff, or diesel... none of which will probably use PCV. PCV is certainly good for the engine, but why not just run a breather like an older engine? Or, use a catch can with a valve/restrictor between it and the manifold. One of those $15 Home Depot air compressor driers and a fish tank valve would do ya.

http://www.redlineforums.com/forums/how ... h-can.html
http://www.dsmtuners.com/forums/bolt-te ... n-how.html

etc.

 

[MustangSix]

I thought you had a PCV that was overreacting to high vacuum. If you are only pulling 5-6 inches, you need a different approach.

On some race cars, you'll find a vacuum pump and an oil separator feeding back into a dry sump system. On others, you find crank evacuation systems using one way valves plumbed to take advantage of the exhaust flow.

But I don't think you'll find a PCV that's effective at low vacuums like that.

 

[thesameguy]

I think he was saying that his engine isn't creating enough vacuum for the PCV valve to seal itself off at idle. To the PCV, it always looks like the engine is at low vacuum, so the valve is open and flowing. He wants a valve that takes even less vacuum than "normal" to close.

Assuming that's true, finding a valve that will close at ~6in and open again at ~3in is probably not possible. A breather, catch can, pump, draft tube, or exhaust siphon would be possible solutions there I think.

If you want to get complicated, you could use a purge valve from most any modern car's evap system. Wire it up to your brake light switch, so when you're on the brakes it closes, blocking the PCV. When you're off the brakes, it opens back up & allows flow. If you're switching to TBI, you might be able to connect it to your throttle position sensor, so when the throttle is at rest it's closed. You'd need a DPST (I think) relay for that - wire the "at rest" output to the purge valve, and use continuity provided by the TPS "at idle" to pull the relay down and disable/close the purge valve. I think that would work. It would depend on whether the voltage from the TPS is enough to pull the relay or not. Meh - it's good in principal!

 

[MustangSix]

PCV's don't seal off completely at idle. They are always sucking up crankcase gasses but the flow rate varies with vacuum. At high vacuum (like at idle) there is a tapered pintle that is pulled into the internal valve opening to reduce the flow rate. As the vacuum decreases, the pintle moves back and flow increases. The result is a constant metered flow.

Try one for a much smaller engine. They should meter less air. Or as mentioned earlier, try restricting the flow on the one you have.

 

[MPGmustang]

after driving it around without the PCV hooked up, I think I'll keep it unplugged and runn a draft tube. vapors are coming out and I do want them to stop swirling around the engine bay and coming through the firwall (have a few holes).

so to run a draft tube, what do I need? just a hose running down low? is there a way to help the crank case 'breath' like direct the air from the fan into the 'oi filler' and the draft tube be the exit?

if this is a bad Idea go ahead and shoot me down.

I do remember by-passing the PCV with my carb setup gave me lower mpg's, and re-connecting gave me an insta boost in accel and power with more mpg's... I'm thinking it won't matter much with the TBI constantly adjusting.

 

[Soldmy66]

In some hi-po/racing applications, a fitting is welded into one of the header collectors and a hose connected to the valve cover -- to extract crankcase pressure along with exhaust. If you are not running headers, I assume you could do the same thing in the head pipe aftet the manifold. Kits are available, and I assume Summit (and others) carry them.

Here is an example (for a V8; thus there are two of everything): http://www.summitracing.com/parts/AAF-ALL34145/

 

[MPGmustang]

well I don't think it's my PCV valve that's the issue, use the link in my sig to see my TBI thread...