PCV breather question for a 406ci
11-05-2014, 01:54 AM
#1
Burning Brakes
Thread Starter
PCV breather question for a 406ci
So my head keeps spinning with all the little nuances that I find I need to know when building an engine. 
So I'm still looking around for 406 builds and what cams they use so I can feel comfortable about vacuum levels for my car accessories. Then I came across this from an eBay SkipWhite engine talking about PCV breathers:
Yes yes yes, I know, it's an eBay ad or maybe some say "who's Skip White?".
When I took my engine apart it seemed like a very simple system. Obviously there are little nuances all over that affect the engine.
I had planned on keeping my PCV connections on both valve covers to the qjet, but after reading this piece I'm thinking maybe that's a bad idea. Anyone willing to educate me on the topic? Is it a bad idea to reuse my existing vacuum lines for the gas vapor can and the 2 valve covers going to my qjet?
So I'm still looking around for 406 builds and what cams they use so I can feel comfortable about vacuum levels for my car accessories. Then I came across this from an eBay SkipWhite engine talking about PCV breathers:
Pictured below is our exhaust evacuation system. It will be your choice of the breather/pcv setup pictured above or the exhaust evac. system. If you have chose cam choice 1 or 2 then we highly recommend the exhaust evac. system. The vacuum created by the engine is somewhat insufficient when using these larger cams, heads, carb and intake to operate a pcv system at it's best, but the vacuum is also very erratic. It would be fair to say that the fuel to air ratio is somewhat erratic when using a pcv system on a street rod of this level. The evac system will pull the crankcase gases out of the engine at a very smooth and controlled rate. This allows the rings to seat in much faster and better, and can increase horse power to some degree by reducing crankcase pressure. Another benefit from the evac system is that your not contaminating the fuel and air mixture with semi burned by-products from the engine oil, and combustion process. Another downside to using the pcv system is that the vacuum levels are somewhat insufficient at medium to high rpm to handle the blow by gasses generated especially with a new high compression engine. This lower than normal level of vacuum is a result of the size of the heads, cam, carb and intake, and couple this with the higher than normal compression ratio, and you may have problems from an excess of blow by gasses building up in the crankcase. There are many factors to this, and it's not etched in stone that you can't run a conventional pcv system, but depending on your setup and driving habits, the evac system may serve you better. Oil leakage from engine seals and oil forcing out of any possible orifice are common with engines that are unable to rid them selves of excess crankcase pressure. On a stock low compression engine the pcv system operates much better, but not on a street rod or race engine. You will never see any race engine using one at the track for sure. We will let you decide what setup you want. After the engine is completely broke in the pcv setup is not as detrimental, but as mentioned depending on may factors, it may not be the best choice. The break in time is also likely to be much slower with the pcv setup.
Yes yes yes, I know, it's an eBay ad or maybe some say "who's Skip White?".
When I took my engine apart it seemed like a very simple system. Obviously there are little nuances all over that affect the engine.
I had planned on keeping my PCV connections on both valve covers to the qjet, but after reading this piece I'm thinking maybe that's a bad idea. Anyone willing to educate me on the topic? Is it a bad idea to reuse my existing vacuum lines for the gas vapor can and the 2 valve covers going to my qjet?
11-05-2014, 06:37 AM
#2
Burning Brakes
My 406 has a 243 degree solid roller and no PVC, just an old fashioned breather filter on the oil filler tube in the intake manifold. It makes plenty of vacuum to operate the headlights. The car has had the power brake booster removed. I installed Corvette finned valve covers and didn't want to put holes in them.
Normally the PVC valve is only on one valve cover because the system needs an inlet and an outlet.
Normally the PVC valve is only on one valve cover because the system needs an inlet and an outlet.
11-05-2014, 02:20 PM
#3
Burning Brakes
Thread Starter
I was trying to keep both and have the look of a base 350 as the standalone breathers are an easy giveaway that somethings changed.
Yes I know, if you look hard enough you'll be able to easily tell my 406 isn't the base 350 anymore, but I'm trying to disguise what I can. I like the retro look in the engine bay, while having more badass parts in it than expected.
11-05-2014, 05:14 PM
#4
Burning Brakes
My 406 is pretty old school stealth.
11-05-2014, 05:41 PM
#5
Drifting
For a street driven car, it's foolish not to run a PCV valve.
You can run open breathers only but that doesn't provide "positive" ventilation and in a street car, you want that constant circulation of clean air to keep combustion gases and moisture out of the motor.
Evac pumps are for track cars that never driven in street traffic IMO.
A 406 is no different than any other small block and the PCV configuration can be exactly the same as it was on the original motor.
You can run open breathers only but that doesn't provide "positive" ventilation and in a street car, you want that constant circulation of clean air to keep combustion gases and moisture out of the motor.
Evac pumps are for track cars that never driven in street traffic IMO.
A 406 is no different than any other small block and the PCV configuration can be exactly the same as it was on the original motor.
11-05-2014, 05:53 PM
#6
Melting Slicks
11-05-2014, 06:18 PM
#7
Burning Brakes
Thread Starter
11-05-2014, 07:22 PM
#8
Drifting
You have the PCV valve itself, which is a common replacement item.
A 'bad' PCV valve will either be stuck shut or stuck open. You can test them with your mouth.
Other than that, you have the vacuum source (usually from the baseplate on the carb), vacuum hose (not cracked, kinked or plugged) and the breather arrangement on the opposite bank that allows fresh air to be drawn in (filter elements can get clogged if not serviced).
That's really about all there is to it.
11-05-2014, 09:35 PM
#9
Burning Brakes
Thread Starter
There is not a whole lot to a PCV system-
You have the PCV valve itself, which is a common replacement item.
A 'bad' PCV valve will either be stuck shut or stuck open. You can test them with your mouth.
Other than that, you have the vacuum source (usually from the baseplate on the carb), vacuum hose (not cracked, kinked or plugged) and the breather arrangement on the opposite bank that allows fresh air to be drawn in (filter elements can get clogged if not serviced).
That's really about all there is to it.
You have the PCV valve itself, which is a common replacement item.
A 'bad' PCV valve will either be stuck shut or stuck open. You can test them with your mouth.
Other than that, you have the vacuum source (usually from the baseplate on the carb), vacuum hose (not cracked, kinked or plugged) and the breather arrangement on the opposite bank that allows fresh air to be drawn in (filter elements can get clogged if not serviced).
That's really about all there is to it.
I'm a little confused why the "inlet" side would be connected to the air cleaner other than it probably (obviously) requires fresh air which is filtered. I guess the vacuum inside of the air cleaner chamber isn't that great and would still allow air to be sucked out into the passenger side. I guess I had always assumed (there I go again) that the passenger side, since connected to the air cleaner base, was also an "outlet", so both I thought were "outlets".
It's beginning to make sense, and hence why I asked for clarification as I didn't know how this system worked.
11-10-2014, 02:36 PM
#10
Racer
So the passenger side is an "inlet" and the drivers side is an outlet (hence connected to my carb vacuum port)?
I'm a little confused why the "inlet" side would be connected to the air cleaner other than it probably (obviously) requires fresh air which is filtered. I guess the vacuum inside of the air cleaner chamber isn't that great and would still allow air to be sucked out into the passenger side. I guess I had always assumed (there I go again) that the passenger side, since connected to the air cleaner base, was also an "outlet", so both I thought were "outlets".
It's beginning to make sense, and hence why I asked for clarification as I didn't know how this system worked.
I'm a little confused why the "inlet" side would be connected to the air cleaner other than it probably (obviously) requires fresh air which is filtered. I guess the vacuum inside of the air cleaner chamber isn't that great and would still allow air to be sucked out into the passenger side. I guess I had always assumed (there I go again) that the passenger side, since connected to the air cleaner base, was also an "outlet", so both I thought were "outlets".
It's beginning to make sense, and hence why I asked for clarification as I didn't know how this system worked.
