PCV Question

[Stangman701]

Well after doing a lot of searching today I think my rear main seal leak may be due, at least in part, to excess crank case pressure. Anyone have any suggestions for a good PCV setup on a carb. application? I'd like to apply some kind of vacuum to it without getting too much unmetered air into the intake.

[somethingclever]

Moroso sells header evac kits. I was going to put one on my car but had read they don't pull a lot of vacuum. I was at PRP in the summer and noticed that setup on a guy's firebird. Asked him how he liked it and he said no complaints. Had excessive crankcase pressure before due to no PCV. He said he did not experience any more crankcase pressure problems after it was installed.

Doesn't your carb have a PCV provision port on it?

It would take a lot of pressure to push out a rear main seal. Do you currently have a PCV? If so, where is it hooked to? Is the dipstick tube blowing off? Are you getting oil out of any valve cover breathers?

[SonofaBish]

Did you get my return text message last night?

If not, i got my air/oil seperator for the ls1 at Walmart. Look in the air tools section... It was like $10. That along with a few brass barbs from Lowe's and some pcv hose, and you're money. Mine's no longer on the car, but i'll be putting it back on when the engine is done in May...
If you want to borrow mine to see if it fixes it rather than spending the money for nothing, you're welcome to!

[somethingclever]

Sonofbish brings up a good point too...i put an oil separator on my cobra like the one on his ls1 for $23 from autozone. You'd be surprised how much oil normally goes through the pcv and back into the engine.

[Stangman701]

Moroso sells header evac kits. I was going to put one on my car but had read they don't pull a lot of vacuum. I was at PRP in the summer and noticed that setup on a guy's firebird. Asked him how he liked it and he said no complaints. Had excessive crankcase pressure before due to no PCV. He said he did not experience any more crankcase pressure problems after it was installed.

Doesn't your carb have a PCV provision port on it?

It would take a lot of pressure to push out a rear main seal. Do you currently have a PCV? If so, where is it hooked to? Is the dipstick tube blowing off? Are you getting oil out of any valve cover breathers?

Edit: Also...the air is already metered once it goes through the carb...


Thanks for the reply :goodidea: . I didn't have a pcv system at all before. I had pcv valves in the valve covers, but I didn't have the vac lines hooked up to anything. I'm not 100% sure if my carb has a vacuum port that's meant for pcv of not. I've got a holley 650 dp and it has three vacuum ports on it, one on the side for the dist. and two on the base plate. A large one in the rear(I'm thinking this may be for PCV) and a smaller one on the front. What I did last night was just run a vac hose from the driver side pcv to the front of the carb and one from the passenger side to the larger port on the back. I'm afraid this is gonna make the car act like is has a vacuum leak though. I'm going to fire it up on Thursday, what do you think?

[somethingclever]

Thanks for the reply :goodidea: . I didn't have a pcv system at all before. I had pcv valves in the valve covers, but I didn't have the vac lines hooked up to anything. I'm not 100% sure if my carb has a vacuum port that's meant for pcv of not. I've got a holley 650 dp and it has three vacuum ports on it, one on the side for the dist. and two on the base plate. A large one in the rear(I'm thinking this may be for PCV) and a smaller one on the front. What I did last night was just run a vac hose from the driver side pcv to the front of the carb and one from the passenger side to the larger port on the back. I'm afraid this is gonna make the car act like is has a vacuum leak though. I'm going to fire it up on Thursday, what do you think?


You caught my post before I edited it again...the air through the PCV actually is supposed to be unmetered....i wasn't thinking clearly that early in the morning!

Setup of PCV should be a breather on one valve cover, and a PCV on the other connected to a vacuum port. In this case, it is the port on the back of your carb's baseplate (the larger port). (I'm also assuming those cars do not have vacuum assisted power brakes.) Just put a nipple on the other smaller one you will not be using.

The way you have the vacuum lines set up now will result in a "vacuum leak".

[Stangman701]

You caught my post before I edited it again...the air through the PCV actually is supposed to be unmetered....i wasn't thinking clearly that early in the morning!

Setup of PCV should be a breather on one valve cover, and a PCV on the other connected to a vacuum port. In this case, it is the port on the back of your carb's baseplate (the larger port). (I'm also assuming those cars do not have vacuum assisted power brakes.) Just put a nipple on the other smaller one you will not be using.

The way you have the vacuum lines set up now will result in a "vacuum leak".

I'll give this setup a try and see what happens. I'm pretty sure my car has vacuum assisted brakes though, will that make a difference? It's plugged into a large vacuum port on the back of intake manifold.

[somethingclever]

I'll give this setup a try and see what happens. I'm pretty sure my car has vacuum assisted brakes though, will that make a difference? It's plugged into a large vacuum port on the back of intake manifold.


well if your brakes are already connected to a vacuum source and they seem adequate, just use the carb port for your PCV. :awsome:

[Stangman701]

well if your brakes are already connected to a vacuum source and they seem adequate, just use the carb port for your PCV. :awsome:

Thanks for your help man, this almost completely cured my oil leak. It went from leaving a trail of oil to just a very small drop once I park the car :awsome:

[somethingclever]

Thanks for your help man, this almost completely cured my oil leak. It went from leaving a trail of oil to just a very small drop once I park the car :awsome:


Glad you got it all straightened out..:pinkthumb: