Can I install a PCV system without changing valley pan?

Can I install a PCV system without changing valley pan?

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By oldcarmark - 17 Years Ago

I am going to be changing the intake manifold on my 292.While I have it off I would like to install a PCV and close off the road draft tube.Can I use the stock valley pan or do I need to find one with the hole and baffle in it?The holley carb has a large non-ported vacuum fitting which is for a PCV hose I assume.How can I install the PCV valve?I have looked at some of the previous threads on this topic and still am not clear on how to install this on mine.Thanks

By 46yblock - 17 Years Ago

To use your existing it will need to come off anyway, so it would be better to get a later pan.

By Ted - 17 Years Ago

Although the rear of the valley pan is the accepted spot for a PCV valve installation, it can be installed in a valve cover. But if the intake is going to be off, then pulling off the valley cover is only two bolts and a gasket away. The valley covers with the rear mounted road draft tube opening in them are already sized very closely to accepting the aftermarket PCV grommets so not much more is needed to using those particular covers in place of the covers that do not have a hole already in them.

By oldcarmark - 17 Years Ago

Thanks Ted,Does anyone have one of these that I can buy at a reasonable cost and is willing to Fedex it to me in Canada.It would be easier if That person had a Paypal account also.Thanks Mark

oldcarmark@hotmail.com

By bird55 - 17 Years Ago

Ted, I have usually experienced having to loosen or pull one head, to remove the valley cover because of the baffle. Is this not the norm? I know that some vc's have been trimmed to compensate for this. Or is it just me?

By speedpro56 - 17 Years Ago

You should'nt have to remove a head to pull the valley cover. By picking up the valley cover as far as you can and pulling to one side or the other> as far as it will go then you can usually tilt it and sometimes with the help of a screwdriver and sometimes without it should come right out. It's worked every time for me.

By charliemccraney - 17 Years Ago

I've not been able to pull one out without removing a head. I suppose it could be pried out but I don't like doing that. I modify mine during assembly so they can be easily removed.

By bird55 - 17 Years Ago

ok, so Mark, according to varied replies here if you pry it out be careful you don't bend or distort it as they don't like to reseal very well-again just my experience. make sure you get a good gasket seal when you go back on. I've seen guys trim the baffle so it will be an easier off and on, if there is a next go around.

By oldcarmark - 17 Years Ago

Thanks for your input.However the one I take off is not the one going back on-providing someone on this site will help me out and sell me the one I need.When I put it back on it will be trimmed a little.Thanks Mark

By DANIEL TINDER - 17 Years Ago

Mark,

Be advised that most valley pans have been distorted by over-tightening. Attempts to pound them true/straight seldom successful. OEM cork gasket only will usually leak (eventually).

A narrow bead of silicon (no gasket) works well, but won't hold paint, and rules out simple removal. Some people drill the block and pan for sheet metal screws (you can place them under the manifold where they can't be seen) if cork prefered. Thick neoprene gaskets are also available, which could be siliconed to the pan (to allow easy removal), which would at least cut the leak possibilities in half.

By oldcarmark - 17 Years Ago

Thanks Daniel,I will keep that in mind.I have found one from 55birdman who has had it for years off his own car.I am sure its better than many of the ones that have been passed around.So to make this PCV system work I add a PCV valve and grommet to fit the existing hole and then plug the hose into the vacuum fitting on carb.Remove and plug the road draft tube.Is there something else to check while the cover is off?A couple of previous threads mention something about 2 small holes to check and be sure they are open.Don't understand what is being discussed.Any other input appreciated.Mark

By Gerry - 17 Years Ago

Hit up the local VW speed shop and pick up a VW fuel pump block off plate, cost about $10.00 or so. Fits right over the road draft hole. Use the road draft hardware though. If you park in the garage you might notice after a while that the smell of the road draft tube is not there any more. Gerry

By DANIEL TINDER - 17 Years Ago

Mark,

You did not specify carb.#, but "Murphys' Law" usually proves most assumptions are wrong. If your new manifold has a vacuum port, why not use IT, and block the carb port if there is any doubt?

Also, be advised that an unrestricted PCV air source can sometimes act like a vacuum leak, and cause a lean-running condition. I had to install a 1/16" restrictor in the PCV hose on my 292 to keep it from plnging, even though the new valve came from a Y-Block-specific catalog source.

By kevink1955 - 17 Years Ago

Unless the mainfold vac port is in a location that feeds all cylinders equaly you will have better results using the pcv inlet provided on the carb. It's centraly located and will feed the extra flow ftom the pcv valve to all cylinders and not just cause a lean condition in a few cylinders.

The other poster who added the restriction to stop the pinging, could you have a few lean cylinders from an unbalanced pcv feed?? If not I would rather rejet the carb then restrict the pcv system, why have it if you are not going to let it flow as the valve wants it to. By restricting the line your pcv flow at low vac conditions will be low causing the crankcase pressure to vent out the breather cap pulling oil with it.

By oldcarmark - 17 Years Ago

Thanks for the input.The carb is a 390cfm Holley which has a vacuum fitting on it for PCV hookup.The other manifold vacuum fitting is the one on the backend where you would hookup the vacuum accessories.Should I plug the PCV into that rather than the carb?I was just going to plug that one.Good to know about the VW pump blockoff.Thanks all.Regards Mark

By Daniel Jessup - 17 Years Ago

Mark, just sent you an e-mail or private message through the system...

Dan

By kevink1955 - 17 Years Ago

oldcarmark (9/21/2008)

I also have the 390 carb and used the fitting on the carb, the fitting on the manifold is more direct to the rear cylinders and the added flow from the pcv system may cause a lean condition in the rear cylinders. My 390 is on a 312 engine and required no rejeting for the pvc.

The VW block off plate is a great idea, I was lucky and had a TBird block off plate, the bird (55-56-57) had a rear road draft tube (the valley cover you are looking for) but the block had a side opening for a road draft canister so the factory installed a block off plate.

By DANIEL TINDER - 17 Years Ago

Kevin,

PCV vac. source is ported spacer under the carb. Unless breather cap is restricted, oil won't pump out, even after hard/high rpm running.

Still plenty of vacuum pull through the filler tube at idle with PCV restrictor. Wouldn't main jet change be moot at low manifold vac.? Back in the day, jets were sized by reading the plugs after a full speed pull (throttle wide open=low vacuum).

By kevink1955 - 17 Years Ago

DANIEL TINDER (9/22/2008)

The PCV port on the holley is straight manifold vac, it's not ported. While you may have plenty of flow at idle (at high Vac) I feel that at wide open throtle when vac is low (and blow by would be higher) the restrictor will cause the crankcase vapors to back out the filler cap. The PCV valve is spring loaded and opens up under low vac conditions to keep the PCV flow reletivly constant under all vac conditons. A restrictor will flow a lower flow under low vac conditions.

I agree reading plugs is the way to go, they should also all be even. Using the manifold rear port will result in uneven fuel mixtures between front and rear cylinders as the PCV flow will dilute the mixture to the rear cylinders.

By oldcarmark - 17 Years Ago

Hello Kevink1955,Do you happen to know what part#PCV you used or the application for it?I see your discussion regarding restrictors etc but if you think about it there are many different PCV valves depending on application.Part of the differences would be spring pressure and I would think internal passage size depending on flow requirements for a particular engine.Does this not qualify as a restrictor?If someone is using one with too much airflow and a restrictor corrects the problem isnt it the same thing as using the correct PCV valve?Just my opinion.RegardsMark

By DANIEL TINDER - 17 Years Ago

KevinK,

This discussion has got me thinking about why my jerry-rigged PCV restrictor performs so well. I suspect it involves the original Loadomatic setup. Since the carb./distributor combo was designed for precise interaction, could it be the change in manifold vacuum conditions caused by the PCV valve confused the teapots' spark control valve, thus limiting the amount of retard upon acceleration? My worn timing chain allows running quite a bit of initial advance, and the unrestricted PCV pushed me over the edge.

Regardless, does it really matter where the blow-by goes when the throttle is wide open? Though the EPA may not agree, I would rather send it out the breather under load than into the manifold, thus diluting the mixture. The crankcase is well vacuumed 99% of the time, prolonging oil/engine life. Also, I have become (over the years), a devotee of the "if-it-ain't-broke".....philosophy, and am just grateful the restrictor fix was so successful!

By kevink1955 - 17 Years Ago

oldcarmark (9/23/2008)

I used a valve from an early 80's 302, it was made to snap into a gromet in the 302 valve cover. The end is about 3/4" and I found a gromet that would fit in the Y Block valley cover, manifold side is 3/8" hose same as the holley PCV port. I figure 302 is close to my 312 in cubic inches and works fine.

Think of the PCV valve as a variable restrictor, At high vac it is held against the spring in a part closed position. As the manifold vac drops off the spring overcomes the vac and the valve opens wider. The idea is to adjust the flow to the rate the engine produces blowby.

At idle the engine produces very little blowby and high manifold vac keeps the valve pulled back against spring restricting flow, at wide open throttle the engine produces more blowby and low manifold vac the spring overcomes vac and valve opens wider.

A fixed restrictor will work in reverse, at high vac it will flow plenty but at low vac the flow will slow down.

Daniel, I agree that the restrictor works and if you get the flow you need most of the time it is better than the road draft tube and will keep the engine cleaner. Just a thought, I do not know what valve you used but could it be connected backwards that would pull it wide open and certanly result in a lean condition.

By oldcarmark - 17 Years Ago

Hello Kevink,Thanks for the info.Thats what I was going to try and use for the same reason.When I put this question in looking for some suggestions about installing PCV system I never thought it would get as many "hits" as it has.Thanks for the input from everyone.Just waiting for my replacement pan to come by mail(by the way it is called a pushrod cover in the aftermarket parts catalogue) and I will be installing this system.Regards Mark

By Gerry - 17 Years Ago

I don't think any one mentioned to change the oil fil cap. Find one with a nipple on it so it can be fed into the air cleaner. That should really help to get rid of all the fumes... Gerry

By DANIEL TINDER - 17 Years Ago

oldcarmark (9/23/2008)

Does anyone know how to obtain specific specs. of available PCV valves? It appears to be a hard subject to research.

The valve supplied with my current kit (obtained from CASCO) was a FoMoCo part, which I assume was selected to suit the average T-Bird Y-block. The fact that it needed additional restriction in my case could be related to unusually high manifold vacuum (22-23", due to retarded valve timing/mild cam?) or Loadomatic complications.

It would be nice if the PCV valve for the new motor I'm building could be selected/dialed-in according to IT'S specs., with no additional restrictor used. But how?

By oldcarmark - 17 Years Ago

Just to update anybody who's interested.I took the top end apart today.The valley cover(sorry,pushrod cover)thats on now came off with no trouble.There are notches to clear the intake ports.Is this the way they come or did some smart guy 30 years ago cut those into it?I want to block the heat crossover when I reassemble.I have some aluminum sheet that I can use.Will this stand up to the heat or should I use tin?I should have the replacement valley cover tomorrow.Am I better to glue the gasket to the cover or the block?Any other tips appreciated.I am installing a "B" manifold and rebuilt 390 cfm Holley.Looking forward to the results of this swap.Regards,Mark