Ok, silly question, but I'm TBI ignorant.

I just put on some chrome valve covers. In the new covers I put on a couple of edelbrock breathers. I capped off the opening in the front of the TBI.

The original driver's side valve cover had a thing coming out of the top of it that ran over to the front of the TBI. The passenger side vc also had a fitting on it that was just hanging out- the previous owner left it that way with nothing connected to it.

I ran it in the driveway and everything appeared just fine- but now I am sitting here wondering if that hose running to the TBI was important- maybe for crankcase pressure regulation or something? Any thoughts?

If it matters: It is a '90 firebird w/ an L98 & Hooker headers are going on it this weekend. There will be no more catalytic so I have been removing whatever possible and trying to make more room under the hood.

 

it ain't important as far as i know it just recycles the oil vapor in the crank case to stop it being purged into the air.

 

The line in the passenger side valve cover should have run to the PCV filter in the air cleaner. The fitting in the driver side is the PCV valve.

The PCV system works by drawing crankcase blowby gasses into the throttle body through the PCV valve to be burned, and replaces them with clean air drawn in through the PCV filter.

By replacing it all with a couple of breathers, you'll probably be wiping oil off your valvecovers all the time.

 

Ok, another silly question - Why are you asking on the Carb forum?

 

Its a common misconception but it in fact is important. the pcv system draws out blow by gasses witch contain burnt fuel and moisture. if left in the crank case they from 2 very bad things... one is sludge wich isnt a big problem if you change your oil often the other is acid. if left sitting long enough it will mess your whole world up...

 

Yeah but you don't have to run them through the engine again. A filter on both breathers will be fine wont it? coz that is all i got.

 

Actually, you do want to run them through the engine again.

Breathers on both sides will vent the crankcase pressure, along with some oil mist that will end up on your valve covers. It won't do a lot for keeping the sludge and acids out of the oil, though.

 

Even before PCV, the "road draft" tube was placed in a "zone" that was at a different pressure than the top of the engine (typically the oil fill tube). This would draw the vapors out of the crankcase, which is what you really need to do.

 

Yeah but my rings are a bit worn out the motor dose not smoke but it breaths heaps, so it forces the vapor in the crank case out.
The engine only has to last till i get a house with a garage then the car is getting a ground up rebuild.
So you are saying to hook up the PCV system? I will do that when i rebuild the engine then thx.

What exactly will hapen if it is not vented properly?

EDIT: SRY to hi-jack the thread im just information hungry i got to learn to stop doing it.

 

The breathers allow some of the excess vapours to lazily make their way out, while still leaving a healthy amount circulating about inside the crankcase waiting to contaminate your oil. A properly working PCV system continuously flushes the crankcase with clean air so that there's no nastiness lingering inside.

 

Well i have bad rings and put just breathers in for a littlewile. It would blow oil around the breather gromits and after awile the breathers stoped up and it blew them out of the valvecovers.

 

ok i got 1 thing that is cofusing me The R/H Hole has a filter in it the L/H hole has the PCV valve with a hose but is not connected to anything, The valve side has nothing coming out of it BUT the RHS one with the filter blows out so damn mutch vapor it looks like it is smoking out the RHS hood vent.

 

Ok how about this..Leave the PVC hooked up, and on the other side run a breather??????? I have been curious about this for awhile now...Thanks guys...This is a good thread even tho it seems newbie....I knew the PVC would cut down on sludge, wans'nt sure what the other reasons for it were tho...Tom

 

that is basicly what i got but the PCV valve hose use to go to my Q-Jet base plate , now my Holley don't have a spot for it so the hose is just sitting there doing nuffin.

 

That works fine.

 

Thanks Apeiron, plus that will look good...i like the way the breathers look....

 

Thanks guys, I’ve decided to do a breather on the passenger side and the PCV on the driver’s side for now and see how that goes.

And thanks for answering my first post. I’m an active forum member on various (electronics) sites and know the routine.. I’ve been reading this one for a while. I didn’t bother signing up yet due to my lack of a project car, but I finally grabbed my latest FBody, a ‘90 Firebird w/ T-tops. I once had a sweet ‘84; I was younger and put in a 375hp 350, then, the rest of the car couldn’t handle it so I eventually replaced just about everything.. This time I am doing it backwards- all mods first, then the motor. So, I’ll be dropping by with some simple questions here and there- I may also be able to contribute a little as I’ve had had 7 total Camaros/Firebirds, several exhaust setups and 700R4s- or at least an opinion here & there.. Ok, that is the end of my intro, haha..

 

Welcome aboard Shadow.Im doing the same thing this time.I think we all have done the big motor, stock car thing............

 

Hello, I know this thread is pretty much dead but this thread had the closest info I was looking for, the new VCs I got made me change the pcv to the passenger side (tube going to the front of the tbi) and the drivers side now has a breather. The reverse sides of what it was originally. Does this really matter much or would it run better the factory way? Thanks

-Russ