Inliners International Forums General Discussion Engines PCV mods

Ok, it's a 1964 Nova with a 194 0.030" over, high lift crane cam, clifford "heated", 390cfm holley, headers w/ 2.5" flowmaster. It loves to be over 2,500rpm. Now the question: What gain if any in perfomance/power is there by re-routing the PCV valve from the vacuum port to the exhaust via a venturi. No I don't have to deal with emmision testing. Also looking for tips on what size/rating power valve should be handling the secondaries on the Holley in this set-up?

It is probably best to leave the PCV as it is for a steet car. There is really just one size power valve used in all Holleys it is the power valve resrtiction channel(PVRC) that controls how much fuel flows through. Most 390's use a metering plate for the secondaries and do not have jets or a power valve. You can buy a kit to add a metering block (like on the primary side) if you want go that way. But the metering plate can't be tuned.

You will never get any gain in performance by re-routing the PCV. The valve meters the amount of air and its very small. The vacuum in the intake drops off as you apply throttle so it makes even less differance at full throttle than at idle. As long as you jet the carb with it hooked up it makes absolutely no differance.

look up the specs on a holley list # 6299. it is a 390cfm with a secondary jets. i can't remember if it uses a power valve in the rear. the specs will say. tom

Is the #6299 different from the #8007 390 CFM 4160 Holley? The #8007 has one power valve, since it's a 4160 there's only one metering block IIRC.

´68 OrangeSunshine,
My Holley is the #8007 390cfm 4160. It has one power valve in the primary metering block. What is the best method for determining the correct size or value power valve that should be installed for the mods that I have installed on my 194. Diesel Dan posted that there is just one size yet a mechanic in my town has given me a couple different sizes to try. One is a 2.5 and the other is a 6.5. My guess is that I need to install an accurate vacuum gauge, run it into the car so I can determine the vacuum value that it develops when I would want the secondaries to open. Am I on the right track.

A 1964 vehicle doesn't require a PCV system in California. Take it off, use a vent on the pan (Jeggs) & one in the valvecover (oil cap); Now there's one less factor in the equation.

If you want power, why have a variable vacuum leak??

Good luck.

John, could you please expand a bit on the Jeggs vent for the pan.

Sorry, It's in the MOON catalog, page 9, $38.00.

It's a venting device that vents the oil pan W/O leaking any oil. You put it on the R-side just behind the distributor.

You can vent the top (oil cap) if you want also.

Now; there's one less hose to clutter things up and less vacuum lost as well.

Good luck.

When I ran the Holley [I now have an Edelbrock 1404 -- but that's another story) I had a 7.5"Hg power valve in the 390 carb. Or was it 8.5"? My application is a pickup truck, daily driver, manual gears. I'm sorry I'm not up on the technical voodoo end of how to figure at what vacuum pressure [measured in inches of mercury (X"Hg)] you set up the secondaries to kick in at. But basically the later the secondaries kick, the more economical it is on just 2 barrels. I always bribed a more knowledgeable Holley Guru with a 12-pack and handed him wrenches. In the spirit of self-reliance I now have an Edelbrock. But my Holley ran 25 years before blowing up on me.
I have a Moon Eyes vacuum gauge. I got it back in the day, and it still works good.

Try a pan evacuator system, you can make your own with a smog pump check valve and a mopar style breather. There are kits available to do this. basically its what you mentioned in the head pipe or header collector you add a venturi with the check valve and run a hose to the crankcase vent. This creates a Vacuum in the crankcase, and expels any blowby out the exhaust. It will keep oil leaks in check, and at high RPM actually give you a couple of Horsepower. Drag racers have even gone to running smog pumps to suck the crankcase out, less pressure behind the pistons as they move = more horsepower, especially with a motor that has some blow by. A PCV system introduces this back into the combustion chamber, I'd rather it go into the exhaust, no need to contaminate the A/F mixture in the engine, and the exhaust is hot enough to burn off most of the blow by. Murf

Hello 68OrangeSunshine and 64Duce, sorry if one of my earlier posts was kind of confusing, but for the record there IS only one SIZE power valve,(they did make it in a '2 stage" for some smog carbs back when though). It seems there has been some confusion between Hg (vacuum) ratings and sizes. All power valves are much larger, and flow way more, than the restriction channel they feed into. Holley uses different size power valve restriction chanels (PVRC's) that are built into the metering block, but just one SIZE power valve.

Some times if tuning is to be done right you will find out you need a bigger PVRC and smaller jets. What this does is keep you from being rich at cruise, and lean at WOT. I would also be quick to say that you need to be sure of what you are doing if you are going to mess with your PVRC's, because once you drill, there is no turning back. As far as choosing a the right vacuum rating goes, a good place to start is with a valve that is rated a little less than half the vacumm you have at cruise.