PCV question

[mike93lx]

I have a Holley Systemax intake and it is suffering from what seems to be a pretty common problem with them - Oil gets sucked through the pcv valve into the throttle body, and a lot of it. I was wondering if there could be problems that could go along with putting on a bigger pcv valve. The way I'm looking at it is that if I use a bigger valve and hose, pressure will drop and flow will also decrease. As well as this, I have a small, clear in-line fuel filter i'll use to monitor the line and also slow down flow.

Any suggestions? What can I get a bigger pcv from? maybe for a 460?

 

[drgn5.0]

I'd like to know as well, i replaced the pcv valve when the holley was installed but i get oil dripping out the TB shaft for some reason.

 

[skeetmos]

yea! i always figured the lil bit of oil drippin from my TB was because it's a profess products 70mm, kinda cheap, so i thought it was the problem. can someone elaborate further on what the problem/fix is? i hate seein oil on my pretty valve covers. does this affect performance? my TB seems to get stuck shut alot. gotta flick the throttle to un stick it before moving from a stop, otherwise it'l chirp the tires.

 

[skeetmos]

i also have the holley systemax 2 intake manif.

 

[bmorrisj]

blowby from worn piston rings?

 

[Michael Yount]

Increasing the valve/line size won't decrease the flow. It'll reduce the velocity - which might help, but it won't change the flow. Flow is a function of how much vacuum you're pulling in part/small throttle conditions, and how much crankcase pressure/blow-by you have in open throttle conditions.

Most excessive oil into the intake or throttle body is caused either by 1) no lower intake baffle, 2) a clogged or missing separator screen below the pcv valve, 3) a malfunctioning pcv valve - which forces all flow through the valve cover/t-b line when the throttle is open large amounts or 4) excessive blow-by from tired/high mileage engines. If you can't address those issues directly, installing 'catch cans' in between the oil source (lower intake pcv valve/valve cover nipple) and where it shows up unwanted (upper intake/throttle body) seems to help.

 

[drgn5.0]

I didn't have a problem with oil from the tb shaft until the holley was installed. Does it matter or not if you have a genuine pcv valve?

 

[Michael Yount]

Not sure I know what a "genuine pcv valve" is - can you elaborate? The main difference I've found between a Motorcraft pcv, and the $1.99 part you get at AutoZone is that the Motorcraft fits more snugly in the grommet helping to eliminate potential vacuum leaks. You can replace the valve, hose, grommet and oil trap/screen for less than $20. If there's any doubt about the integrity of the system, or if it's original, I'd freshen it up, so you eliminate those as possible problems. Did your holley have the baffle on the bottom back-half of it?

 

[04sleeper]

A friend of mine just got done putting in a D&D HAWK Power 331 stroker with AFR 185's and Holley intake. It has 10.5 to 1 compression and he has the same problem with oil puddling in the intake. It goes all the way back to the mass air flow sensor. He has a breather to replace the fill cap and the tube to the throttle body blocked off. He was wondering what to do as well. A local shop told him to just unhook the PCV valve from the intake and run it to a catch can. Should it be doing this. It's a brand new engine.

 

[drgn5.0]

i meant to say genuine ford pcv valve, the baffle under the lower intake is installed and the pcv screen is on. i heard something about installing a crankcase evac system to get rid of the pcv and this problem.

 

[drgn5.0]

A friend helped me fix this problem on my car. what we did was where we were pulling vac. from we capped it off. we ran a 3/8th's tap onto the upper of the holley in the back, into the freeze plug of the holley and put a 3/8's fitting in it (instead of going underneath into the runners) and there is no oil at all in my tb/hose or any leaking now.

the original place is bad to draw from because of the shape of the opening and the intake will suck the oil up into the tb. it can't get back into the intake because it has a big hump it has to get over.

if you relocate it to a place where gravity will take place the problem will go away.

 

[Michael Yount]

89 sleeper - sometimes people forget the baffle on the bottom of the intake (under the screen) - and they seem to pick up more oil without it. If the screen or the pcv are clogged up, more venting will take place from the valve cover back to the throttle body, and that will likely deposit more oil in the throttle body - which can run down to the maf. Getting rid of the hose, and putting a breather on the valve cover will keep oil from getting to the throttle body via the hose, but it won't do anything to keep oil from getting into the intake via the pcv, and it also allows unmetered air to enter the manifold (via the breather - crankcase - pcv route) under high vacuum conditions. Also, if he's getting excessive blow-by, more oil will be picked up. I installed catch cans IN BETWEEN my pcv valve and manifold, and in between the valve cover filler nipple and throttle body - to try and knock oil out of the lines before it can reach the manifold or the throttle body. This keeps the oil-fumes out of the atmosphere (emissions legal in that regard) and helps keep oil out of the intake, and throttle body.