TECH: PCV for your SBC (or any other engine for that matter)

Hey!

Many times I've seen people ask how to install a PCV system without cutting up thier valve covers.

Well, here's how I did it.

The secret is the '65 Corvette PCV valve. Unlike most PCV valves which press into a grommet on the valve cover, the Corvette PCV valve has 1/4 NPT threads on one side.

Here's where we get tricky. Drill and tap a 1/4 NPT hole in the back of your intake manifold. Make sure your hole is over top of the valley and NOT in an intake runner. Thread the Corvette PCV valve into this hole (I used a street elbow to get it to lay flat).

Connect the other end of your PCV valve to the base of your carb or to an intake runner. Makes no matter which.

On the front of your intake, plug in an oil fill tube with a breather in the cap. If your intake doesn't have a hole for an oil fill tube, find a flat spot and make a hole with an appropriately sized hole saw.

At this point I'd like to thank Bryan Barts (aka Tokyo) for making the cuts on my intake.

Well, that's it.


Ed

 

Sometimes a simple PCV like that will suck oil, if so, a simple baffle can be fabbed up and it will work like factory stuff. They are so simple to make, all old engines should have them to promote long life.

 

Have you or are you currently using this set up?
Or is it an idea you came up with and assume will work?
I think you'll find that if you stick a vaccum in the intake over the valley without some form of fairly sophisticated baffle it will pull oil out of the valley as that area has the highest concentration of oil in the whole motor except for the pan and area between the main webs.
Even a valve cover has to be baffled pretty well.Just a cautionary thought.

 

I can verify that if not baffled they will suck a lot o oil. I've seen a valve in an unbaffled rocker cover suck half the pan over a 10 hour highway trip. Those covers got baffles pretty quick after that! No more oil usage.

 

...........Even a valve cover has to be baffled pretty well.Just a cautionary thought.

Good point. How do you provide "breathing" to an engine that is using the old-style filler tube?

Reason I'm asking is because I've got a sbc about to go into my Model A, and haven't figured out how to do it, aside from cutting holes in my original CalCustom valve covers.

Thank you.

 

You let it breathe through the filler tube with an extra set of baffles hung down it's throat on a loop of wire or flats wth holes in 'em spot welded in.
You can make a double walled cage stuffed with ss chore boy that is screwed to the bottom of the intake.
Hook your pcv hose to a well baffled riser tube where the draft tube used to be on early motors and a breather on the fill tube.
Like I said earlier,you might have to use your imagination.
But it is imperative that the suction side be baffled at least some if not alot and that the breather be as far from the pcv vale as possible.

 

i have a 59 283. it has the draft tube and i have breathers in both valve covers. should i still run a pvc?

 

'65-'67 hp 327's had a oil fill tube in the front of the manifold that had a screw on cap that sealed off the tube. On the side of the tube there was a threaded bung where the PCV valve screwed in. A vacuum hose was then connected to the valve and ran to the base of the carb which is either threaded for a fitting or has a press in tube for the hose. Done deal. If the oil fill tube is no longer available from Chevrolet I see them all the time on Ebay. I just picked one up from there for a retro looking small block that i intend for my '48 F1 1/2 ton.

Frank

 

I hear this PCV argument all the time and maybe I'm stupid but, why do they need them so bad now when old 283 and 327 motors back in the day ran forever without them? Some had the breather tubes off the back of the block and some had the breathers at the front on top of the oil fill tubes or both? Enlighten me? I have a 283 with old cal custom covers and an old 6 Deuce ontake on it. I think I am going to stay oldskool "no PCV" Will my motor make it? I don't want to screw upnice old vintage stuff!

 

Mr Gasket offers a Oil Fill Breather Cap for those engines with a little tube sticking out. You could put a PCV inline with one of those, too.

 

Where do you put the other end on a 6 Deuce setup?

 

This idea has been posted several times (at least twice by me) and was in Street Rodder. You need to make a baffle or cover over the inlet side under the manifold, this can be a simple aluminum plate pop riveted or screwed to the manifold.

 

Here is one You would still need a breather wouldnt you?

 

A pcv system is not a must have deal.But... if you are gonna have one it might as well work,Right?
I also suppose I should clarify about a baffled riser in the draft tube hole.A baffled riser in that hole is only necessary if the factory baffle in the valley is not used.
Oakland,I would go for somewhere in the plenum chamber that ties all the runners together.
I should also clarify that a breather is not a neccesity with a pcv system,as per Fabs and Scotts example of the closed fill tube with a pcv valve in it,but if you have one(a breather), it should be located as far from the pcv valve as possible because if it is near the pcv valve it pretty much makes the valve redundant because it connot create either a draft or vaccum because it just draws in fresh air from the breather.
With a breather in the system
I might also point out that the fill tube pcv was used in conjunction with a draft tube to help maintain a neutral pressure.
Crankcase ventilation frees up horsepower by allowing positive pressure in the crankcase to be relieved and a pcv system frees up horsepower by actually creating a negative pressure(closed system) or at least a neutral pressure in the crankcase(breather system) and both keep the buildup of positive crankcase pressure from forcing oil out of the motor through gaskets or seals and also makes it harder for negative cylinder pressure(the intake stroke)to pull oil by the oil control ring and into the combustion chamber.

 

burger

I tried something similar once.. only I put the pvc down in the fuel pump block off plate..

even with a baffle it still sucked every once in awhile..

and I quickly abandoned the idea..

this idea is better but you wiill certainly need a baffle on the bottom..

 

Would it be a problem to run Moon style breathers in the valve covers and just seal up everything else?

 

It'd prolly be like an old Harley and just mark it's spot.LOL

 

im with muttley on this one

WOULD it be a problem

 

OK, most of you obviously don't have much of a mechanical background. So here's some reasons to run a PCV valve. Do you really think a big money making company like GM or Ford would put extra shit on an engine if it wasn't an improvement in some respects???? They don't like to spend lots of money of add on stuff to the cars. Reduces profit margins!
1. If you have no PCV, you have either a road draft tube, or open air breather, usually both (the road draft needs an opening to suck air in, as it evacuates air out). Oil vapor can escape out these openings, and deposit an oily film all over your nice clean engine.
2. Blowby (products of combustion, that escape past your rings) is pressure. If your breathing devices can't keep up with the amount of pressure produced, it will eventually blow out sealing surfaces/gaskets, and you'll have a bigger mess. PCV valves pull with vacuum to reduce this pressure, when needed (vacuum demand) More if you have your foot on the throttle a lot!
3. These gasses are very corrosive. They pollute your oil, and both make it corrosive, and add particles to contaminate it. PCV's pull out most of these corrosive gasses, and reburn them, instead of dumping them in your oil. It also has a job of removing moisture from the air inside your engine to prevent water in oil, and corrosion.
4. Pollution. It's marginally better to reburn those nasty vapors than to shoot them out into the air, raw. Also, you won't shoot oil vapor all over the front of the car that's riding behind you on the highway. The road draft in my 55 Olds did that to an embarassing degree....guys in my car club who rode behind me once, didn't like to ever do it again!
5. Older engines DID NOT last as long as the newer ones. PCV valves are one of the reasons! There are a host of other reasons (better oil control, better fuel control, better oil additives, etc.) but PCV is a big one.

 

Hey everyone, thanks for the replies. This setup is on the small block in my '54 truck. It seems to be working OK so far without any noticeable oil consumption. The baffle would be good insurance, but maybe not 100% necesary.

 

Anyone have an image of what the baffle ought to look like?

-Dave

 

So what am I looking forward to on this setup ? I have valve covers with dual breathers and the oil fill tube in the intake. I just couldn't pass up the valve covers, to me they look right on.

 

Here is the lifter valley baffle from a 283 ,it mounts to the rear of the valley by the road draft tube

 

Isn't that an oil-seperator canister? I have a 283 block with one, but I'd like to convert a post-oil-seperator engine to something without valvecover breathers and I don't know where to get another. Most of the old SBCs have disappeared from the local wrecking yards. In fact, it's easier to find a flathead.

-Dave

 

i'm actually pretty sure that a baffel isn't critical on a setup like this. There isn't any oil flow even close to this area. On a valve cover you absolutely need a baffel because the oil is comming up through the pushrods and being sprayed all over by the rockers. Plus on older motors or motors that have notorious drainback problems the rocker area can become flooded with oil under certain conditions. WHen this happens the pvc is definitely going to pick it up.

I've just drilled my new 3 duece intake with a similar setup so i'll let you all know how it works out.

PS. I got my car going last summer with an old edlebrock intake and 4 bareel as a temporary setup and skipped the PVC. I ran a filler tube type breather with hopes that this would work good enough to get me through. My motor is relatively fresh and blew out my front intake seal within the first few hundred miles. My oil also became dirty quite quickly and i found myself changing it pretty frequently to keep it decent. I ended up gutting my breather filter and removing the element to help it breath better. THis helped with the oil leaks but didn't help much in terms of keeping the oil clean. YOU NEED TO RUN A PVC, ESPECIALLY IF YOUR CAR WAS DESIGNED FOR ONE!!

 

ok quick question


these cool mooneye breathers like the small block in pic further up the thread

could you drill one of these and put a push in pcv in one of them with out any sort of baffle

im running early corvette covers and definatley dont wanna drill the tops of them and dont care much for the top of intake idea everyones speeaking of here

 

There is no restriction of any kind in the Moon breathers.A pcv may be redundant with them.
I know for sure that a set up like the one pictured above with the breathers on the outside of the valve covers will leak oil under thrash conditions,been there seen that,however not sure about cruise mode.
They work as well as can be expected on the inside edge only with no pcv.
I expect if you packed 'em with chore boy they would prolly be ok with a pcv in the closed type filler neck.

 

I used the PCV valve in the intake on my '32 because I didn't want to poke holes in my 6 rib valve covers. When I did it I called Ederbrock and asked them if it had been done...they said no but saw no reason why not. I fabs a cover for the hole on the bottom of the intake for a baffle and also cut a filler tube hole where it used to be before the intakes were redesigned with no tube. Two months later Streetrodder mag. came out with an article on how to do it. Mine has no indications of pressure buildup and no oil use. Works for me. I used JB Weld to attach the baffle.

 

Phil, why not run a pcv cap to the fill tube hooked to your carb, that way you have air into the engine, via the breathers on the valve covers and air out via the filler tube.