Crankcase evac ?

So what's everyone's opinion on crankcase evac kits on a pretty stought street/strip 440 or just run breathers on valve covers?

If you run muffs dont bother with evacs...reason
why.. a evac will pull about 5"hg max so if you
have muffs on the car every inch of back pressure
the muffs have is 1" less that the evacs will pull
and if your muffs are greater than 5"hg you will
pressurize the crank case with exhaust

Makes sense, breathers it is. Thanks for the info 👍

Mister P, how/where do I measure the muffs (vac difference in/out?)

Tap in anywhere forward of the muffs... use
a "HG gauge.. can use a psi gauge also

what if you were to tap in at the end of the exhaust pipe after the muffs. would there be any vacuum there?

No.. but your trying to measure the pressure
before the muff.. that pressure is back pressure
on the engine

What are the merits of a PCV system at this application?

They are great for cruise rpm.. no help at
WOT

Pictured below is my preferred setup. Just -10 lines from each valve cover to a breather tank like you'd use for a vacuum pump setup. Works great.

I have a vacuum pump on my hemi and don't really care for it. Saw no change in performance. Wish I'd just used the same type of setup I have on my wedge motor.

an8sec70Cuda...what type of oil rings are you running?? If low tension do you remember what the tension was rated at in lbs?? Thanks

Had both in the hemi and saw no real difference. The current rings are low tension (18 lb).

I have a electric vac pump sitting on my bench
that I was gonna put on the Rampage.. but I dont
like vac pumps on a street car.. I run 2 breathers
on it and no oil comes out of it.. but they are
baffled

What would be better, just run breathers or the an line to a catch can like an8sec70cuda showed? Or about the same either way? My valve covers have no holes so I will have to drill them and have no baffles.

Does anyone make a catch can that can be used with header evacs?

The evacs could draw from the top of the can and the breather lines could enter somewhere midway up the can. This way it could still create vacuum but any oil would be left in the bottom of the can to be drained later?


Make sense?

I like the lines and can b/c there's no leaks like you get w/ breathers on the valve covers. They'll drip oil everywhere.

This is similar to what I was asking except you would need 2 tubes top and 2 tubes bottom. Or you could T them I guess. I have never tried it but seems like it would work and any oil drawn through the breather would end up in the bottom of the tank.

Correct me if I am wrong.

I use to make my own separator cans at work
(I used them on fuel) but its simple... I put
both lines in the top with different lengths
of tube inside the can with the short one being
the exit(to the engine in your case)

Moroso make oil/air separators.

Tex

I run a PCV and pan evacs. Before I bought my muffs I spent some time on the phone with them. They said as long as the pan evac is after the muff it will work. That's how I did it. The engine is sealed, the PCV pulls at idle and cruise, the PCV and pan evac at cruise and wide open.

Yes you can put the evac in AFTER the muffs so you
dont have the back pressure.. most dont like to run
that much heater hose to the back.. but some do

True. My muffs are short, so the hoses ar not extraordinarily long.

I put my muffs at the back bumper to control
the DB level so I wouldnt run that much 3/4
hose.. I just run breathers with good baffles
so I dont have any oil coming out of them

Well, Here's my input, for what it's worth..I have a street/strip car. I race, maybe 6-7 times a year. I also run a PCV valve and Evac system. The Evac system will pull 5 hg at higher rpm and of course the PCV will pull at idle and just above. The secret is the mufflers. You have to run straight threw type muffler like, MagnaFlow, Dynomax, etc. Flowmasters don't work........You need a muffler that doesn't have or create back pressure. Any "mousetrap" type muffler creates too much back pressure. The down side is that most straight threw mufflers are a little louder...

I had oil leaks after WOT pulls on my 499" low deck. After adding a crankcase evac system, the leaks are gone. This is with a 3 1/2" x-pipe system with Magnaflow race mufflers. It was well worth $50.

My car is mostly a street car as I have only been able to race about once a year the last 4 or 5 years. I run a PCV valve setup and on the drivers breather I just run the hose down under the car and put it in a hole on the unibody frame in case it spit any oil. But it lets it pull a vacum through so the PCV valve works fine and even when I race it does not spit out or get any oil at the end of the hose. I figured what I can do when I go racing is just pull the PCV valve and plug the hose and run a breather on the pass side like I use on the drivers side since at wide open throttle the PCV valve wont work and is closed at WOT. So I just run two breathers to race and hook the PCV valve back up when done before I drive out of the track. Them breathers with the nipple have a baffle in them and work nice as not to spit oil on the valve covers when racing like open bottom breathers do. And these valve covers I use have a baffle under the breather/PCV hole in the valve covers. Ron

Why not just plug the drivers side completely off and let the PCV pull some crankcase vacuum? It will only do it at idle and cruise but that's better than nothing.

The way it's plumbed now, you are pulling air from the drivers side through the engine and into the carb. May as well use all that work for some crank case vacuum.

The way it's plumbed now, you are pulling air from the drivers side through the engine and into the carb.

I pull off both valve covers into a T then into the center carb base on my stealth racer where on paper with the ring pack im using requires most to use a vac pump, but it works.

I dont now how much I might be loosing without a real vac pump but I dont see to have any issues as it is.

Of course I am pulling air/blowby through the crankcase into the carb. Thats what a normal PCV system does. Its basically a controlled vacum leak and its just what I want on my street car. I surely dont want to seal it off and pull a vacum in the crankcase I cant control. I would be looking into vacum pumps if I was that serious about it but I am not. I just want a standard PCV system on my street car. If it was sealed and not controlled then I would be worried about oil leaks from gaskets pulled in some. For my mild street car this works great keeping the crankcase vented. I dont need a vacum pump type setup for this mild combo I run on my driver. I might look at it different if I only raced it but this works good for me. About the only thing I could change is to run an air cleaner housing with the nipple to put the hose from the drivers valve cover to so I pulled filtered air through it but the breather does have a type of screen mesh filter in it. Ron