High Performance Pontiac
Click here to find out more!

PCV question

  
High Performance Pontiac
1 |  2 |  Next   | Last 
Item Posts    Sort Order

PCV question

 
67firebird455 67firebird455
New User | Posts: 13 | Joined: 04/10
Posted: 04/05/10
09:55 PM

Hi all, this is my first post on this great site.I have a 73 455 in my 67 bird and the grommet from the valve cover pcv ripped apart and needs replacing.My question is can I put a breather in the hole instead? I know there is pcv in the intake to the carb but for some reason there is one from the valve cover to the air cleaner.Any help would be great. Thanks  

tuffnuff tuffnuff
Moderator | Posts: 2534 | Joined: 12/09
Posted: 04/05/10
10:10 PM

Yes, you can put a breather in the hole, I have a breather on both my Eddy covers and no PCV at all.
Wink  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

barneyformula barneyformula
Addict | Posts: 3298 | Joined: 01/07
Posted: 04/06/10
04:22 AM

I assume you mean the tube that goes in the valve cover? There shouldn't be a PCV valve there at all. The Pcv system is intended to be a closed system, the PCV valve in the valley pan draws oil vapors from the crankcase under vacuum from the intake manifold. The reason for the tube to the air cleaner is to provide clean filtered air back into the crankcase so a vacuum suction won't be created in the crankcase. The idea is: fumes out of crankcase thru the PCV and fresh air in thru the filter (that little foam wedge in the air cleaner). However, under low vacuum conditions, like wide open throttle, the pcv valve cannot function due to the lack of vacuum. When this happens you get oil vapors blowing back up the valve cover tube into the air cleaner, where they are sucked in through the carb. An air breather in the valve cover does the same job, but under WOT conditions you will get some oil vapor blowing out the breathers and that can make a mess. It is up to you, if you find it too oily, put the tube back to the air cleaner.
Steve  
A little help... 'cause we don't all have to learn the hard way!

idrivejunk idrivejunk
Addict | Posts: 4987 | Joined: 12/09
Posted: 04/06/10
05:06 AM

Yep, you can put a breather in the valve cover hole. And yep it makes a mess depending on use and condition. All thats supposed to be there stock is the one PCV in the lifter valley pan, an oil fill cap on one valve cover, and a pipe to the air cleaner from the other valve cover. Are you sure thats not just a plastic elbow in the valve cover, that kinda looks like a PCV valve? Either way, new grommet, yepper.  
idrivejunk

67firebird455 67firebird455
New User | Posts: 13 | Joined: 04/10
Posted: 04/06/10
06:40 AM

Thanks guys,I went and looked again and it is just an elbow but because I have an aftermarket air cleaner there is no filter in the cleaner,do I need one?When you say messy at wot is it just a case of wiping off the valve cover or is all over the place?I didnt build this engine but I am trying to fix the screw ups.  

barneyformula barneyformula
Addict | Posts: 3298 | Joined: 01/07
Posted: 04/06/10
07:29 AM

How messy depends on how fresh the engine is, the more wear, the more blowby and more mess. Usually aftermarket open element air cleaners have a knockout plug underneath and come with a hose nipple that can be connected to your valve cover tube. Because this knockout is inside the main filter element, there is no need for the little gauze filter since the air is already filtered coming into the carb. We don't run a PCV on the race car because it is at WOT 90% of the time and a PCV is pointless. We run a K&N filter on a 1 1/4" tube welded on the valve cover over the PCV hole. The stock oil baffle in the cover catches most of the oil and drains it back to the head but some still makes it out of the breather and mists onto the cover and surrounding area. A quick shot of degreaser and garden hose cleans it up, but it is hardly a show piece to begin with.
Steve  
A little help... 'cause we don't all have to learn the hard way!

tuffnuff tuffnuff
Moderator | Posts: 2534 | Joined: 12/09
Posted: 04/06/10
08:15 AM

+1 Steve
The mist is no big deal and I use WD-40 before and after washing my engine bay,,,
The mess is minor and blows off easy at wash time.
A quick wipe with a rag does the same thing.
without the wash
Wink  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

67firebird455 67firebird455
New User | Posts: 13 | Joined: 04/10
Posted: 04/06/10
09:06 AM

Thanks alot guys, I was out at my local speed shop to buy a breather and he told me they are illeagal to run on the street in ontario canada so I got the grommet and put the hose back in.He said it was a $300+ fine, Mad  sounds like another dumb rule from the DOT.Well at least I wont have to worry about cleaning the oil up.Thanks again.  

barneyformula barneyformula
Addict | Posts: 3298 | Joined: 01/07
Posted: 04/06/10
03:19 PM

Where in Ontario are you? I'm in Brockville, about an hour south of Ottawa. We've been having problems the last three summers with joint spotchecks by the MTO/MOE/local cops. Basically if all the emissions equipment appears to be intact and functional, they leave you alone. That's why my 75 350 is dressed with all the Evaporative canister lines and air cleaner from the original 301 in my 79 Formula and it's getting dual cats before it cruises this year.
Steve  
A little help... 'cause we don't all have to learn the hard way!

idrivejunk idrivejunk
Addict | Posts: 4987 | Joined: 12/09
Posted: 04/06/10
04:27 PM

Every aftermarket open element air cleaner I've seen has a provision for running the pipe from the valve cover to the air cleaner base, so you can have the looks and retain PCV system function. Usually its a stamped circle that has to be knocked out, then you screw the supplied elbow over the hole, with a gasket. I figured this out first time I actually purchased a NEW air cleaner and it had all the stuff with it. Smile  
idrivejunk

67firebird455 67firebird455
New User | Posts: 13 | Joined: 04/10
Posted: 04/07/10
06:01 AM

Im in Stratford about an hour and a half west of toronto.The air cleaner I have does have the nipple but that rubber hose doesn't look as nice as a chrome breather.I guess I could dress it up a little.  

idrivejunk idrivejunk
Addict | Posts: 4987 | Joined: 12/09
Posted: 04/07/10
07:28 AM

The breathers work fine, but after you run it hard there may be a bit of valve cover wiping off to do. Real easy until it gets dirty. The Edelbrock one I got awhile back has good plastic mesh in it and keeps the M/Ts pretty clean.

Cool  
idrivejunk

thinman56 thinman56
User | Posts: 107 | Joined: 04/13
Posted: 12/03/13
01:05 PM

Quick question on this topic - my stock 2 bbl PCV valve was hosed to a tee and then to two fittings on the intake manifold, I assume both 'sides' of the dual plenum.  My replacement Edelbrock P4B (I know, vintage...) has a tap on both sides of the manifold as well.  Should I keep the tee setup so that the PCV valve gets vacuum from both sides of the manifold, or is one side adequate?  I can see if there's a little oil how it might impact 4 cylinders different in the long run.  Engine is street-driven.

Thanks.  

wayne712222 wayne712222
Moderator | Posts: 161 | Joined: 10/13
Posted: 12/03/13
01:47 PM

both sides..

as the PCV has significant flow... just having it on one side.. will effect idle air mixtures..  

it will have twice as much air leak on one side.. and none on the other..

go with both sides..  or.. if you have a PCV port on the aftermarket carb. you can hook to that..


the Pcv test is to pinch off the flow at idle.. the engine at idle should drop 50 to 70 RPMS if the pcv has the proper calibration for this engine..  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 279 | Joined: 11/13
Posted: 12/03/13
02:41 PM

ideally it should be hooked to the carb. in theory it will cause the cylinders it is connected closest to, to run leaner as wayne suggested

having it hooked up to a t takes some of the load off one cylinder but it is still closer to the rear cyls than the front ones so it is still not ideal.  

1 |  2 |  Next   | Last