John, I simply asked you to quote the description of your PCV valves from your reference pages.  You refused to do that because the words would prove you wrong.  I don't care who is right or wrong.  What I care about is preventing personal injury from an exploding engine.

Two references I cited above are not year specific.  PCV valves haven't changed, either.  They vary in size and configuration (straight or ell, threaded or not), but they all work exactly the same way.

Retrofitting a new PCV to an old engine block is easy, but must be done properly.  If you had a good understanding of the operation of any generic PCV, you would not have made your false and dangerous statements.  Do your homework and never criticize correct safety information.  I only pray nobody gets hurt.

To my fellow Y-Block restorers and enthusiasts:
PCV's rarely get changed because they last so long under normal wear.  Some books ask you to rattle as an indication that it is still good.  That is NOT a good indication because the spring can be broken (and it will still rattle).  Also, make sure your PCV blocks in the backflow direction to prevent explosive gasses from entering your block.

Dave Dare
Ford Motor Co., Dearborn

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Dave, you haven't heard from me because I'm dealing with a pre-64 Y block and late '60s era pcv systems, not emission controlled '93 model cars.  Crucify me if you want because I don't have the equipment to copy and send stuff electronically.  I offered to snail mail the pages to you, but never received any hint you wanted them not any address to send them to.  My last statement on my previous post says what I mean to say about it.

John - "The Hoosier Hurricane"

Ted, the pictures don't exceed 600 pixels wide, have a hard return before and after, and my host server is Comcast.  Comcast is known for fast speed, but on occassion, they are slow or they go down, during maintenance.  Dial-up users will never see color pictures very fast, especially if their baud rate is lower than 56K/sec.  Does anyone NOT see any of my pictures?  If so, let me know. Thanks for the 'heads-up' Ted.  I'm surprised I haven't heard from Hoosier John, yet. -  Dave

Hey, BTW- http://www.y-blocksforever.com/forums/FindPost26072.aspx this thread has several color pictures at 800pix wide.  Both Ted and Hoosier are moderators there too, but I didn't see a complaint about dial-up.

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Dave.  Here are the picture posting instructions in case you missed them in the past threads.

Generalized picture posting instructions

For those of us on dial up, your particular picture hosting site inhibits the threads in which you insert picture links from coming up in a speedy manner.  Thanks.

Lorena, Texas (South of Waco)

You cited reference to two service manuals but are unable to share the wording about PCV valves from them, and you are absolutely SURE you didn't misread about the operation of PCV valves.  I guarantee NONE of them indicate the PCV valve allows fuel mixture into the block area.

John, this is a VERY serious safety issue (at Ford Motor, we classify it as 'double-inverted delta'), the highest, most lawsuit-prone concern.  We ALL need a full understanding of how a PCV works and how explosive 14.7:1 Air/Fuel ratio is.  The possibility of mixing fuel mixture into a block cannot happen.

Whether naturally aspirated or not, the bottom end of a crankcase can be like a flame-throwing  blowtorch, especially in old engines.  All of our Y-Blocks are old, now.  I tore mine down and measured ring end-gaps of .200".  By design, piston rings rotate.  At some point they all align for a time, sucking oil up and shooting flames down.

Since backfire alone can be dangerous, PCV valves close completely in one direction (like a check valve) preventing air/fuel mixture from entering the crankcase.  ALL of your manuals will explicitly indicate this.  According to your statement, you need a better understanding of how a PCV valve operates:

  Absolutely NOT TRUE.  Nobody can predict a backfire.  John, you need to retract this and rethink how things really work.

If you need further references here they are.  Click on the wording for each link:
"Operation: Should the intake manifold's pressure be higher than that of the crankcase (which can happen in a turbo charged engine or under certain conditions, such as an intake backfire), the PCV valve closes to prevent reversal of the exhausted air back into the crankcase again."  - http://en.wikipedia.org/wiki/PCV_valve

"One really comforting feature of the PCV valve is its behavior in the event of a backfire. If your car backfires in the manifold, the pressure makes the spring close the valve completely. With the valve closed, there is no chance that the flame can move into the crankcase and cause an explosion."  http://www.innerauto.com/Automotive_Systems/Exhaust_System/Pcv_Valve/

"The PCV valve controls the amount of vapors pulled into the intake manifold fromt the crankcase.  It also acts as a CHECK VALVE by preventing the flow of air from entering the crankcase in the opposite direction." - Pg.24 Chilton's Repair Manual (Part No. 8314) Thunderbird/Cougar 1983-92

This is straight out of one of my Chilton's manuals.  I've asked you to share with us, your reference manuals.  The invitation is always open.

Dave Dare

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Dave:

I have 3 Paxton blown '57 Fords.  Of course the intake is separated from the crankcase. There weren't pcv valves in '57.  All three of my cars are equipped with road draft tubes.

As for the manuals, I didn't mis read them.  Sorry, I can't scan, but I'll mail you copies if you need to see them.  Do you have access to any Ford manuals of that era?  Remember, except for Corvairs and Olds F-85s, there weren't turbocharged cars then.  Corvairs had draft tubes, I don't know about F85s.  My GM manual is Buick, no turbos in '65.  No turbo '68 Fords either.  That's why there wasn't a section in the manuals about pcvs and turbos.  I stand by my statement.  Thanks for your input.

John - "The Hoosier Hurricane"

  Oh John, be very careful and don't blow up the poor guy's engine.  Should the intake manifold's pressure be higher than that of the crankcase (which can happen in a turbo charged engine or under certain conditions, such as an intake backfire), the PCV valve closes to prevent reversal of the fuel mixture into the crankcase.

I didn't stutter when giving that advice.   Ford had Paxtons back in Y-Block days, but they separated intake from crankcase gasses.  If intake pressures EVER get higher than crankcase, that valve is not supposed to inject even the smallest amount of blended air/gas mixture into the crankcase.  In fact, if the PCV doesn't stop like a check valve, DON'T USE IT!

You may have missread your manuals, John.  Could you scan those sentences to share with us?  I think you are confused about when the PCV operates at idle speed (most vacuum) and 'most restricted' flow.  I'm sure the manuals are calling this condition a controlled orfice.  As the vacuum goes down under normal driving speed, the valve lets more crankcase air in.  At Wide Open Throttle (zero vacuum), the PCV is about useless.

Dave Dare

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Those corvettes would have 327 engines, so the valve should be OK on a Y Block.  Same valve probably fits other 327s of that era, not just corvettes.  I forgot to mention in my last post, the Chiltons manual has info for test proceedures of carb calibrations.  You put a plug in the pcv hose with a drilled hole to replicate the restriction of the valve.  The largest engines only used a 1/8" hole. 

John - "The Hoosier Hurricane"

I saw that number on CorvetteCentral.com. while searching for a cross reference to CV726C. Fits a 62-64 Corvette. Didn't say what engine. And thanks for that last post. That NAPA part #29255 and Standard #V100 does cross from CV726C

Dan      Kingman Az.      86409

Simplyconnected posted above that a pcv valve is a check valve to prevent a backfire from entering the crankcase.  This is simply incorrect information.  A pcv is an ORIFICED check valve, which means it has full flow in one direction and restricted flow in the other.  (Ref: '65 GM factory shop manual, '68 Ford/Merc factory shop manual, '68 Chilton repair manual).

The valve is installed so that under high vacuum conditions, ie idle, the pintle moves away from the full flow position to allow a small amount of air to flow.  At low vacuum conditions, ie cruise, the pintle moves to the full flow position for maximum scavenging.  At idle, if the valve were full open, it would be a huge vacuum leak.  A backfire would be the opposite of high vacuum, since it is pressure.  The pintle would move to full flow and would not restrict the backfire pressure from entering the crankcase.  If the system is workinig properly, there shouldn't be any explosive gases in the crankcase anyway.

I found an old pcv in my box of "stuff" this morning that works properly when threaded into the crankcase, ala Dutchy's installation.  It is an AC #CV590C.  Unfortunately I can't reference what size engine it came from.  Anyione have an AC catalog?

John - "The Hoosier Hurricane"