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Chevy 350 pcv set up

down4thakrown

down4thakrown

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So I got some old mickey Thompson valve covers on my 350. And I got oil spewing from the baffled breather/oil filler and the pcv valve running to air cleaner. Only the one valve cover has both a opening for the pcv and oil filler. The other valve cover is sealed up. Would this cause the oil spewing from the breathers? since its not able to cycle the pressure evenly? It's only when I get on it. If im just cruiseing it doesn't leak.
 
Yes, improper cankcase ventilation could cause this problem, or a worn out engine. I once got a set of aftermarket valve covers, which only came with the small PCV grommet holes on both sides. The OEM covers had a small PCV grommet hole on one side, and a larger airbox grommet hole on the other side. So, I cured the problem by running dual PCV valves, and used a vacuum tee to run them both together on the large carb manifold vacuum port at the front of my Edelbrock Performer 750 CFM carb.
 
So you had a similair set up and just ran 2 pcv valves to a "t" and then to the base of carb? The engine doesnt have alot of miles. Doesn't smoke and runs great. It has world heads with true roller rockers so the rockers are pretty close to the openings and the valve covers have no baffles, but the breather does and pcv does. You know if cheap tall baffled valve covers from orielys would fit?
 
down4thakrown said:
So you had a similair set up and just ran 2 pcv valves to a "t" and then to the base of carb? The engine doesnt have alot of miles. Doesn't smoke and runs great. It has world heads with true roller rockers so the rockers are pretty close to the openings and the valve covers have no baffles, but the breather does and pcv does. You know if cheap tall baffled valve covers from orielys would fit?
Click to expand...
Forgot to add that before the pcv valve ran to the aire filter, I had it hooked to the large vacuum port and it didn't leak as bad ethier.
 
Your PCV should run to a vacuum port.

The unrestricted breather runs to the air cleaner.

Martin
 
The PCV NEEDS to be connected to a constant vacuum source, there is usually a small orifice in the PCV to keep it from being a big vacuum leak on the engine, but by providing the vacuum on the crankcase it keeps MOST pressure from blowing out gaskets and seals, and causing oil leaks. Under heavy engine load without enough vacuum on the crankcase you may experience additional pressure on the crankcase and the easiest route of pressure release is the breather on the valve cover. the factory setup was to have the PCV from the valve cover to the base of carb (3/8 port) and the vent breather to the air filter housing to suck in any vapors from the crankcase.
 
If your pcv isn't hooked to a vacuum source your blowby/oil vapor is just basically floating around instead of being directed into the engine to be reburned.
 
I think I'm going to try the dual pcv valves with "T" fitting to large vacuum port
 
Ok, sorry I didn't notice I had more then one response. But when I had the pcv hooked to vaccum sorce it still spewed oil from breather. But I'll try finding a breather that would allow me to connect hose to it and run it to filter. And run pcv back to the vacuum. I foresee a Ls swap in very near future
 
Teeing two PCV valves together probably wont work any better--each one will share half the "load" and not increase the flow much ...

The PCV valve has a spring loaded flapper,that shuts off most of the vacuum "leak" at idle,and the spring opens it when vacuum drops ,when you open the throttle--this lets it suck the fumes from the crankcase..

You might be able to come up with a PCV thats not the stock one that'll flow more off some other engine, or application..doing so may upset the air/fuel mixture by allowing a larger vacuum "leak" however..

You need a breather on one valve cover to let fresh air in the crankcase ,and the PCV valve on the opposite valve cover--otherwise the PVC valve will suck air in thru any other source like seals or gaskets that have leaks..or let pressure build up in the crankcase and oil spews out of those areas..

(GM hid the "mustache" breather filter in the air cleaner housing to avoid dust being inhaled,but an external one with the oiled mesh will work as well)..

I have just shoved the mustache filter in the stock valve covers on a few engines with bad blowby,to avoid soaking the air filter with oil..however,the fumes can and will soak nearby areas with oil and smoke if it hits the exhaust manifold...one motor I had way overdue for a rebuild,I routed the breather filter down under the inn fender using heater hose to connect it to the valve cover,so the fumes wouldn't gag me while driving !..
 
That's my problem I think, only one of my valve covers is opened up for pcv and breather. Other is sealed. Dam I don't want to get new valve covers. Maybe I'll pull the sealed one and take a hole saw to it?
 
http://s1229.photobucket.com/user/edostar/media/pcv_valve-scaled500-1.jpg.html

pcv_valve-scaled500-1.jpg
 
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You can use a vented oil filler cap for a breather,but if the oil filler is on the same valve cover as the PVC is,it wont work right--it has to be set up as indicated in the illustration above...

vented oil filler cap.jpg
 
You should get another set of valve covers, which come with some kind of breather holes on both sides. Summit or Jegs have some cheap in-house brands. I have had several sets of these cheap in-house brand chinese covers, and they worked just fine. Then hook them up like shown in the above diagram. Use vacuum adapters to adapt the lines to proper size needed.
 
That's what I'm thinking. I need it ready by this wknd. So I'm going to try dual pcv valves into "t" to vaccum. If it don't work in pulling the valve cover and taking hole saw to it. And if for whatever reason that don't work I'm getting naked and wearing gas mask and bringing plenty of oil..I'll post pics up when I get home
 
If you have that much blow by causing that much internal pressure you have other issues. Unless those valve covers don't have the proper baffle inside and even then. IMHO.
 
They have no baffles at all. Just what's in the breather, its only really bad when I get over 4k rpms (which is quite often). When I'm just cruiseing its hardly leaking if it even does at all
 
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down4thakrown said:
Anybody have any recommendations for tall high clearence covers with baffles?
Click to expand...

When you start talking about tall style valve covers, which are designed mainly to clear stud girdles, you are starting to talk much bigger money than a regular set...about 3-times more. Most tall style valve covers will come with grommet holes for baffles. Dragsters will usually run a vent line from the valve cover baffles to the header collector, in order to evacuate crankcase pressure.
 
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