[David Jones]

Ray Bohacz did an article about PCV's in the January Hemmings Muscle Machines and highlighted this piece.

http://mewagner.com/?page_id=456

[Tom Vaught]

The deal is, it is just one more think for someone to screw up in the engine calibration.

There is a very small range of cfm where the valve does its job. (From 1 to 4 cfm max) on 99% of the PCV valves designed by the automotive industry to meet emissions standards.

You want just enough flow to purge out the caustic Chemicals produced by the process of combustion in the crankcase. If you are trying to use the PCV valve to work like a vacuum pump at high rpm, then you have more study to do. Vacuum (flow) is very low at WOT.

Tom V.

[David Jones]

The setup instructions seem fairly straightforward vs not knowing if the PCV one is currently running is working.

[Tom Vaught]

What is the price, David?

If a person has a repop PCV, then I would agree that the M/E Wagner Adjustable PCV
unit might be a viable solution.

If a person does a little searching, (and others have) and you locate a factory PCV unit calibrated for your engine and model year application, then I would say, stay with what the Pontiac Engineers came up with.

Tom V.

[6t7goat]

$129.00 is the price.

[David Jones]

$129 is the price. Pretty spendy.
I suspect that if something works, possibly cures an issue, then up to a point cost isn't really an issue. Pop the hood on pretty much any car on this board and you'll find examples. Not many factory pistons out there, for example. Somebody developed something better and people spend the money.
How many people on this board run a Pontiac that is as it left the factory?
Most not even close.
So how does somebody that's not a trained PCV engineer know if the PCV they've selected works on their modified Pontiac. If it's not leaking oil, it's ok? Could the carb settings be crutching things? Timing?
$129 might be money well spent.
Or, you could guess.

[mgarblik]

There are a few basic tests for the PCV system that can be performed to get an idea if the system functions and has enough flow. First, the better your ring seal, the less need for crankcase ventilation. The PCV valve itself is a simple, yet very carefully engineered "shuttle type" flow control valve. The taper of the pintle inside, the spring wire size and spring rate, and the orifice size on both sides of the valve all contribute to the flow character of the valve. The valve shuttles in it's housing passing blowby gasses based on engine vacuum. If the engine makes 15" or more vacuum at idle, the correct stock PCV valve will work fine. If the engine has a hotter cam, gently raise the engine RPM to 1200 RPM. If you have 15" of vacuum at 1200, you will still be OK with stock system. If you have a really hot cam and are driving on the street, you really need a vacuum pump. Possibly, the adjustable valve mentioned in the thread would be a benefit on an engine making 10" of less vacuum at idle. Couple of other simple tests you can do. Pull out the pcv valve with the engine running and put your thumb over the end of the valve. You should get a 50-100 RPM drop as you do this. No drop, the PCV valve is not flowing much if at all at idle due to incorrect valve or very high vacuum. More than 100 RPM drop, the valve is passing too much at idle and can begin to use oil, smell like burning oil, smoke, idle rough or high. The single most common problem on restored or old muscle cars PCV systems is the hose from the valve to the engine. That hose from the factory is a molded or reinforced hose. When replaced, regular 3/8" fuel hose is often used. IT WILL SUCK SHUT easily and the system will no longer work. If a molded hose is not available, use power steering return line for the PCV hose and make sure it has no tight bends. Another test is to buy or find a heating and AC guy who had a water manometer, sometimes called a slack tube. It is a simple water low pressure gauge. Put the manometer hose tightly sealed to the dipstick tube. At idle, the engine should have a minimum of 1" of water. 1-5" of water is the range you want at idle. A final simple test that is much more fum is to take your Pontiac out and run the crap out of it. Make several runs wide open to the red line. Now open the hood and look at the dipstick. You have a PCV problem if the dipstick is pushed-up out of the tube, like a pencil tire gauge. If you don't see or smell any oil, the dipstick is firmly in the tube, the engine idles smooth, save your $129.00. Not saying the part described is stupid or overpriced, but only a very tiny % of street engines need or would benefit from it in my opinion.

[Tom Vaught]

The main question would be what does the Valve buy you for $129.00 at the end of the day. Attached is a typical PCV valve cut-away showing different modes of operation.

1) At High Idle Vacuum most of the valve is restricting flow to the intake manifold (call it 1 cfm of flow)

2) At Cruise - Moderate Vacuum most of the valve is not restricting flow to the intake manifold (call it 4 cfm of flow)

3) At Acceleration - Low Vacuum the valve is restricting flow to the intake manifold (call it 2-3 cfm of flow)

4) Under Boost or a Back-fire Condition in the intake - PRESSURE against the valve is sealing flow from the intake to the crankcase. (0 cfm Flow)

So we are playing with on average 2-3 cfm out of say 800 cfm of total carb flow. And at idle air flow 1 to 4 cfm of PCV flow.

The valve better be very impressive for me to spend $129.00 for me to play with 1 to 3 cfm of air flow adjustment capability.
Idle air flow is typically no more that 19 cfm even on large engines.

So you really know now what the PCV and Carb Engineer knows about the conditions. You might not have a PCV Flow Bench or the ability to make a make a PCV valve. GM already did that for you if you do some searching. The PCV Valves for the L-88 Engines are out there and they had idle behavior as wild as any street car a Pontiac guy would built. A GM Engineer designed the valve for that application and he would have been fired if the management thought he spent $129 for a PCV valve.

Tom V.

Post up the Instructions for the valve David and we can see what the valve is actually doing for $129.00

[mgarblik]

Agree, Tom, in a nutshell, an expensive solution to a problem that doesn't exist on 99.9% of the cars out there. So that often begs the question, why did anyone make this to begin with? I guess the answer is "if you build it, someone will buy it".

[David Jones]

I did post the instructions in the opening post.
And I got a lot of great information by doing it once I got past the 1st reply or few.

[Tom Vaught]

Unless the PCV valve is Stuck with contaminants, the Factory GM Chevrolet "L-88" valve (which I can buy for less that $3.00) will do everything in the Wagner Sheet. The L-88 Engine was a radical Idling Engine. I have a friend who ran a RA-IV camshaft in a 428 and the factory PCV valve worked fine in that application.

Tom v.

[bignate]

Originally Posted by Tom Vaught

Unless the PCV valve is Stuck with contaminants, the Factory GM Chevrolet "L-88" valve (which I can buy for less that $3.00) will do everything in the Wagner Sheet. The L-88 Engine was a radical Idling Engine. I have a friend who ran a RA-IV camshaft in a 428 and the factory PCV valve worked fine in that application.

Tom v.

Where would I get a correctly calibrated L-88 pcv valve? I may be interested as I'm running a valve from Inline Tube on my IV motor now, but I suspect that they just take whatever the cheapest available valve they can get and spray it with an olive green rattle can.

Nate

[Tom Vaught]

Rock Auto has both the L-88 PCV Valve and the 427-435 HP Tri-power carb Engine PCV Valve showing on their website.

Years ago HO Racing used some of the same part # Distributor Vacuum Cans as the Hi-Perf Chebby Engine 427-454 Engines so those
work well with Modded Pontiac Engines with some cam in them also.

Tom V.

[Old Goat Racer]

I came up with an old # 6484525 CV746C for 68-69 corvette 427 HD, but it's discontinued

[straycat]

Also a CV736C which I think is a 69-L88. Also Fram FV181 or FV178. Unfortunatly today all are being condensed to 1 size fits all.

[David Jones]

Condensed and deleted to the point that I question the accuracy of the ones that remain.....if they happen to fit your engines needs.

[Tom Vaught]

There are still valves on the parts shelves if you look a bit. Lots of Delco/GM stock still out there. I bought several of the L-88 & 396/427/ "H O Racing" distributor vacuum diaphragms (not to long ago). I can do a bit of looking to save $100 difference in price on a part.

Tom V.

[coonhunter70]

I was just looking on ebay at the L-88 valves mentioned above they appear to be valve cover applications. What # was the original Ram Air IV valve?

[Tom Vaught]

I will have to look into that as I do not have that info in front of me.

Tom V.

[i82much]

for thirty bucks i would buy one.