Excessive blow by

[gumby77]

Ok. Have been looking at other threads in peoples experiences and none seem to quite match mine. Here it is.

351 w mild cam build with Holley sniper. My issue is mostly on the driver side valve cover from the fill hole i am getting excessive blow by. Enough to smoke and get on the header as i come to a stop where people wave me down to tell me.
I have the same symptoms as most. Smoking lightly and oil/ moisture coming form the exhaust Until warmers up.
MY QUESTION is do i need to run a PCV valve to the sniper kit? The only vac i am running currently is to my brake booster. (Stock) Currently i have the breather on the driver side and a smaller k&n filter on the passenger side..which is saturated but not leaking like the driver side.

Sorry for the messy post and thank you for any advice you may have.

 

[gumby77]

Link is iCloud photo.. dont use this platform enough to know how to add photos any other way.
https://share.icloud.com/photos/09cukA7MG6Jh8JnppBpzdmABA

 

[jamesroney]

Ok. Have been looking at other threads in peoples experiences and none seem to quite match mine. Here it is.

351 w mild cam build with Holley sniper. My issue is mostly on the driver side valve cover from the fill hole i am getting excessive blow by. Enough to smoke and get on the header as i come to a stop where people wave me down to tell me.
I have the same symptoms as most. Smoking lightly and oil/ moisture coming form the exhaust Until warmers up.
MY QUESTION is do i need to run a PCV valve to the sniper kit? The only vac i am running currently is to my brake booster. (Stock) Currently i have the breather on the driver side and a smaller k&n filter on the passenger side..which is saturated but not leaking like the driver side.

Sorry for the messy post and thank you for any advice you may have.

1. Yes, you need a PCV valve.
2. Yes, it should connect to the manifold vacuum port in the Sniper base.
3. No, it should not be anywhere near your brake booster connection.
4. Yes, a PCV valve is basically a controlled vacuum leak. So anything that needs a “good” vacuum signal will get confused if it is near the PCV tap.
5. No, a brake booster does not use a lot of vacuum. In fact, it only uses vacuum when you let go of the brake pedal. So it uses very little volume. The PCV uses a ton of vacuum, all the time.
6. Yes, your K&N filter is OK, and you can put the PCV valve in the driver’s side fill hole without any problem. This WILL change the fuel mixture ratio in the sniper. It shouldn’t change it very much. The fuel map programmed into the Sniper should be expecting a PCV valve.

This will fix your crankcase vent problem.

 

[DirtDonk]

Changing induction type, does not change the need for a good, working PCV system.
Going from carb to EFI, or from one type of carb to another, or one type of EFI to another. Does not matter. Always keep the PCV system in the loop, so to speak.
Pun intended...

Paul

 

[gumby77]

Ok great. Thanks for the advice. I have had the motor in for a few years now and not too many miles on either the motor or the sniper kit since i did the swap on both at the same time and never had much if any residual from the fill hole side. seemed to be a newer problem but i have not ran a PCV the entire time. Will get one set up and see what happens. Thanks again!

 

[Broncobowsher]

As others stated, yes you need a working PCV system. For a carb style that you are running, fresh air in one valve cover, flushes through the engine and mixes with the blowby and is sucked out via the PCV valve. A thing to think about, the PCV is a continous flow. It is the only vacuum item that continously flows into the engine (except vacuum wipers). Everything else is either a signal (transmission modulator, vacuum advance, EGR, thermactor, etc.) or a quick gulp of air and back to no flow (brake booster). Since it is a continous flow of air, some raw air, some inert exhaust, some combustible gasses that is getting mixed into the engine it needs to be distributed evenly. That is not putting the PCV line into a single intake runner. That will lean out that cylinder and put all the blowby into that cylinder. The Sniper has a large vacuum port centered that distributes evenly to both sides of the intake.

Next thing I want you to take a look at is if there is a baffle on the driver's side (the one that is spewing oil). If you can look through that hole and see rocker arms, you don't have a baffle and there will be oil consumption issues no matter what. There needs to be a baffle to prevent splash off the rocker arms from being thrown right at that hole.

 

[DirtDonk]

And maybe the reason it wasn’t doing it before, was because everything was fresh.
With you driving it often enough without a PCV valve, over time things may have deteriorated inside to the point where you do have more blow-by than you should, given its relatively young age.
Hopefully that’s not the case, and is just a worst case horror story scenario. But it is at least something to be aware of.
An engine that is constantly run up to a good operating temperature is safer than one that is driven in short bursts and never really heats up.
What kind of driving have you been doing on it for the past couple of years?

 

[gumby77]

no baffle on the valve cover. I’ll be taking it off today to confirm whether there was one or not. I believe there was at some point but id some how it came off and I’ve been lucky enough to not have failures i would be impressed. However as far as the pvc goes ilol be installing one soon. My question is which vac port to use. if looking at the sniper unit from the rear as its mounted im using the left (3/16 manifold vac port) for the shift modulator and the center large for brake booster as it’s labeled. However the right side is current not being used and plugged. Which is labeled ported manifold vac for vac advance.. that im not using for my ignition set up.
My question is what one would be used for pcv?
I’ve been driving mostly on the road shorter distances but at operating temp. And off-road primarily in the Arizona desert. Noting fast. Just slow rolling. A few pictures to follow.

 

[DirtDonk]

Broncobowsher pretty much laid it out in post #6 above.
You will connect PCV vacuum to the 3/8” port on the throttle body, or suitable alternative.
Which is to say, a 3/8 barbed fitting in the common plenum area, at the base of, or under the throttle body.

 

[Broncobowsher]

Brake booster will work perfect going to a single runner vacuum port. I think it is cylinder #4 on most Fords.