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Discussion Starter #1
Is there any reason to run a PVC valve ... as opposed to replacing it with a simple breather.

We are talking about a car that is exempt from any "Emmissions" laws.

Seems to me ... Just cap the vacuum port and go to the breather on the valve cover.

What'cha think??
 

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it will spray more oil out with just a breather.
 

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If you're venting to the aircleaner, you may as well leave the PCV setup on, no?
 

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Something I learned while working with the rear main leak on my 408W was that PCV systems were developed by or for the military to extend bearing life in all types of engines!! The vacuum system "sweeps" light contaminants from oil (ie: gasoline, water, low boiling combustion by products, etc.). This helps keep oil "cleaner", extending oil and bearing life considerably!!

I would keep the system if you plan to use the engine for anything other than all out racing and /or occasional operation where longevity is not an issue?? If set up right it doesn't cost any power and most modern carburetors are calibrated for this "controlled" vacuum leak.

Good Luck,
Cobrajack
 

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some all out raceing engines even seal the crankcase and use and external vacum pump to evacuate it, this creates better seal of the rings and as metioned before keeps some contaminates out of the oil

if your carb is set up right you really aren't looseing power

I have also seen people hook up the PCV to the smog pump but I am guessing you don't have one
 

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Discussion Starter #8
OK ... Here is the real basis of the question:

The PCV valve is a mechanical device. It seems to me that (aside for it's function as a crank case evacuation device) it is little more than a "controlled vacuum leak" (as it pretains to the intake process).

On the engine in question ... When I pull the PCV and plug the vacuum port ... The engine responds positively ... Runs smoother and with improved power.

In my mind, assuming you can effectively evacuate the crank case by venting to the air cleaner inside the filter (or some other way) and eliminate a mechanical device that has possibility of failure or improper function, then couple that with the fact that the engine does seem to respond well to the capping of that vacuum port ... you may have a good thing going


What do you think ... Am I all screwed up?
 

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It depends on where the pcv valve is plumbed into the manifold.It should really be connected under the base of the carb so it is exposed evenly to all cylinders.
What i am getting at is ,some engines have a port connected to only one runner and if the pcv is connected there it is exposing the controlled air leak you refer to only one cylinder which is then possibly lean.Some cleveland manifolds have a port on the #4 runner .
 

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Larry,

The reason you have improved idle when you plug the PCV vacuum port is probably due to a lean condition and you should be able to tune the carb to get the same results with the PCV system operational. You really don't have any vacuum in the air cleaner and "sweeping" of the crank case will not happen!!

Just hook it up the way you want to and run it!! Successful engineering has never meant anything to those of us who constantly want to "Re-engineer" everything......And I'm one of the worst, but I'm learning....SLOWLY!!!

Good Luck,
Cobrajack
 

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Discussion Starter #11
Actually the "running better" isn't just at idle ... the engine runs with more authority through out the entire "useable" power spectrum.

The way I have it set up it has two very free flowing vent tubes which vent to the air cleaner (one inside the filter and one outside the filter) so whatever minimal vacuum is there ... will be assisting the process.

I'll run it today and check the plugs for "lean / rich" running condition.

_________________

Larry Madsen
Las Vegas Nevada



<font size=-1>[ This Message was edited by: monstermach on 1/27/02 11:40pm ]</font>
 
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