PDA

View Full Version : PCV Valve Suitable for Performance Camshaft with Lower Vacuum Signal



98Dak408
08-12-2012, 07:27 PM
I have tested various PCV valves to determine which perform better with the lower vacuum signal of a performance engine, using a camshaft with more duration and overlap. PCV valves are not all calibrated the same, and perform differently depending upon the amount of vacuum an engine produces. A performance camshaft will typically produce a lower vacuum signal than the stock engine/camshaft, and the stock PCV valve may not close enough at idle, which can cause an irregular and/or high idle, or otherwise not function efficiently throughout the operating range of the engine. An improperly functioning PCV valve can also cause the premature break-down of engine oil, sludge build-up, leaking gaskets and seals, water vapor build-up, as well as allow excessive oil to enter the intake manifold. A PCV valve that closes too easily and completely, can stay closed too long above idle, and can also interfere with the proper evacuation of blow-by gases.

The following two PCV valves function better at a lower vacuum signal, but still open once the engine vacuum changes during all-around operation. They both begin to close at a lower vacuum signal of ~1-2” hg. One is standard flow and the other is high flow. The high flow unit increases flow by 40% over the standard flow unit. It works well with a stroker motor, or shorter stroke, high rpm race applications.

1. Standard Flow: http://stores.hi-potek.com/pcv-valve-performance-camshaft-with-lower-vacuum-signal/ Grommet end is universal as well as hose end at 3/8” OD; it fits the stock plumbing. You can use either rubber automotive hose (3/8 ID) rated for vacuum and hose clamps, or 6AN stainless steel braided hose with AN fittings, depending upon how you wish to plumb it.

http://i850.photobucket.com/albums/ab68/98Dak408/P81200652.jpg
Standard Flow Unit

2. High Flow: http://stores.hi-potek.com/high-flow-pcv-valve-performance-camshaft-with-lower-vacuum-signal/ Grommet end is universal size although hose end is larger at 1/2" OD. You can use either rubber automotive hose (1/2” ID) rated for vacuum and hose clamps, or 8AN stainless steel braided hose with AN fittings, depending upon how you wish to plumb it.

http://i850.photobucket.com/albums/ab68/98Dak408/P81200642.jpg
High Flow Unit

A comparison of the standard flow PCV valve and the high flow PCV valve:

http://i850.photobucket.com/albums/ab68/98Dak408/P8120066.jpg
http://i850.photobucket.com/albums/ab68/98Dak408/P8120002.jpg
High Flow on Left


Note; PCV Valve Flutter:The PCV valve may flutter at idle, and is not a problem. It is caused by the repeated cycle of increased vacuum closing the pintle, and the opposing force of the spring opening it. This back-and-forth oscillating motion causes the flutter. It does not usually close completely, and when functioning properly, is a metered and controlled vacuum leak. However, it should close completely upon an engine backfire. Under normal operating conditions, the PCV pintle allows for greater or less flow, depending upon vacuum levels, according to throttle position and engine load.

mikset
08-12-2012, 10:51 PM
Hey Richard. Cool that you've done some research on this. I've noticed some oil in my intake, not sure if it's excessive or not. Would you recommend a standard or high flow for my 408?

98Dak408
08-13-2012, 12:39 AM
Hey Richard. Cool that you've done some research on this. I've noticed some oil in my intake, not sure if it's excessive or not. Would you recommend a standard or high flow for my 408?
Hey Mike, it’s very difficult to completely eliminate oil from the intake with a performance engine, even with a catch can, since at high rpm, more blow-by gases accumulate, and some amount of oil vapor does make it through to the intake. However, a properly functioning PCV valve will help regulate what gets through at idle, which is typically a higher vacuum situation. If you are also concerned with the removal of the harmful blow-by gases from the engine at high rpm with your larger displacement 408, I would go with the high flow pcv valve, since it is capable of flowing a higher volume of blow-by gases, which is certainly good for your engine. However, if you don’t want to re-plumb your PCV line for a larger hose, then the standard flow PCV valve would still be an improvement over stock.

Hugh Jassole
04-24-2013, 01:02 PM
Richard, I'm a stock displacement 360, but I have big valve heads(EQ) and a fairly sizeable cam. .544/.544, 235*/240* @ .050, 114LSA. Sucking oil is an issue, even with baffles etc. Which valve do you think ? Does the big cam push me towards the bigger PCV ?

98Dak408
04-24-2013, 02:09 PM
Richard, I'm a stock displacement 360, but I have big valve heads(EQ) and a fairly sizeable cam. .544/.544, 235*/240* @ .050, 114LSA. Sucking oil is an issue, even with baffles etc. Which valve do you think ? Does the big cam push me towards the bigger PCV ?
It’s really a matter of how much blow-by you are trying to evacuate. That can vary depending upon the amount of displacement and modifications. I would lean toward the higher flow PCV valve since there is less resistance to flow with the larger hose size. However, the standard flow valve is easier to plumb. These PCV valves will close at a lower vacuum signal. However, once open, vaporized oil is still going to end up in the intake, even with an oil seperator. These PCV valves are intended to prevent excessive oil passage at idle when closed or partly closed, while allowing the evacuation of blow-by gases at higher rpm.

Hugh Jassole
04-24-2013, 04:35 PM
Thanks Richard, just sent you an order

98Dak408
04-24-2013, 06:32 PM
Thanks Richard, just sent you an order Thanks Don! I'll get this out today for you.

Hugh Jassole
04-24-2013, 07:19 PM
no rush, it's still locked away in the storage locker until the end of the month.

stevenz1inoc
04-24-2013, 11:18 PM
So what's your suggestion to use for the closer to stock/bolt on guys. I hate that with the stock PCV valve I see oil in the intake. I'd like to reduce some of the oil consuption I know I am having through the PCV valve.

98Dak408
04-25-2013, 12:16 AM
So what's your suggestion to use for the closer to stock/bolt on guys. I hate that with the stock PCV valve I see oil in the intake. I'd like to reduce some of the oil consuption I know I am having through the PCV valve.
These PCV valves still function with higher levels of vacuum such as a stock engine. However, I was most concerned with finding a PCV vlave that functioned properly with the lower vacuum signals as a result of using a performance camshaft. A properly functioning PCV valve will help prevent excessive oil from passing through at idle and low rpm. However, when it is fully open, vaporized oil can still pass through. A baffled PCV valve canister or an oil separator will help with the amount of oil that gets through to the intake manifold when the PCV valve is open. The main objective of the PCV valve is to remove blow-by gasses, which can reduce or eliminate those gasses from blowing oil through gaskets and seals.

DakotaNash
04-26-2013, 11:44 PM
Very informative.

Broo42
02-12-2014, 11:18 AM
Order sent for high flow w/ grommet. :biggthumpup:

Broo42
02-15-2014, 06:40 PM
Already got it today! Thanks for the insanely fast shipping! :hail:

98Dak408
02-15-2014, 08:08 PM
I appreciate the order Dustin! Thanks!