Technical Advice on Crankcase Evac System

I've been working on a Hilborn Injected BBC and have a blow by issue. There's no way I know of to setup a PCV so I have as much breathers as I can on the engine but it doesn't seem to be enough. Under load it'll still try and push the dip stick tube out and oil as well. It also oils around the distributor. So now I'm beginning to explore other options. I currently have a breather on both valve covers, one sorta on the valley & made a plate for the fuel pump boss up to another breather. Any other practical Ideas???????

 

Depending on your exhaust system, you could run a header evac setup, but it's not the best thing on the street by a long shot. You could run that valley breather fitting to either a belt mounted vac pump or an electric-even in the trunk if you really want it clean. But maybe it's best to start off with a leak down test to make sure the mill is tight.

-rick

 

why not? I used one on Plan II for ten years, 33k miles...didn't see any problems with it.

Pictures of what's inside the valve covers, and inside the breathers, might help us help you figure out why it's not working like it should. Perhaps they are really restrictive?

also, what prevents you from drilling some holes and adding PCV? although it won't handle lots of blowby, it can be effective most of the time, when the throttle is not open very far

 

I suspect your current breathers are restrictive, maybe open element breathers as shown below would help.

 

I would have no problems trying one on a street strip car with exhaust that breathes very well, but I was always told that a really quiet (restrictive) exhaust can cause it to have limited function and a free breathing exhaust can cause it to over scavenge oil- maybe that's wrong info, but I dont know what type of muffs he has.

-rick

 

Before you go and open a window in the oil pan (the Studebaker Avanti R4 had an oil pan breather, as did some Flat Heads !).

I'd be looking for the reason...WHY...the engine has so much crankcase pressure, NOT, how to hide it !!!

Normally a good running engine may have a small amount of pan pressure, but NOT as it seems as much as your engine does.
You don't mention how many miles / hours the engine has on it.
Were the rings installed correctly (file fit...correctly?) ?
What gaps do the rings have ?
Were the cylinder walls prepped correctly for the type of piston ring used ?
Have you done a cylinder "leakdown" test (all cylinders) ?
Or even a compression test ?

Again -
WHY...does the engine have so much crankcase pressure !!!

Mike

P.s. - I'll add, does the engine have chrome rings ? Did the cylinders get the proper surface finish for chrome rings ?

 

Electric vacuum pump? Hide it inside a bee hive oil filter.

 

X2 what Mike VV said.

 

The Hilborn ITB setup has no was of doing that that I'm aware of. I've really been looing into the Header Evac system.

 

This is worth a shot. Easy enough to test out.

 

I agree with your reasoning. This engine is brand new & hasn't really been broken in yet. It started life as a GM 572 but the owner opted to do some "upgrades" 11:1 forged pistons & a really big cam. The motor was done by a reputable builder but I'm not totally sure on some of the details like rings and stuff.

 

Because it has no CRANKCASE VENTILATION SYSTEM ...?

Just having the crankcase open will not ventilate it. Just wait until it starts blowing gaskets and the oil goes filthy/acidic with a healthy dose of water.

 

Unless you have a excessive amount of blowby just have the system open will prevent blowing gaskets etc. I need to hook mine to my headers but I am to lazy. So for now I have both sides going into a oil bottle , works fine for the last 3 years . Spin it to around 6500 every time I drive it. But my motor has no blowby at all.

 

X3 what Mike said.
I do circuit racing where you’re full throttle for long periods and a breather off each rocker cover to a catch can suffices. Either your breathers are too restrictive or you have another problem.

 

I stuck these breathers on that I had laying around to see if it made a difference. Seemed to have helped especially with the oil coming out of the dip stick tube but I'm still getting quite a but from around the distributor.

 

O-ring in good shape around distrib ?
6sally6

 

chevys use a gasket, is it there?

 

The Gasket is there. I'm going to investigate & see if it just isn't sealing well.

 

Intake not being in quite the right location fore aft or the distributor bottoming out on the oil pump can cause a leak.

 

If the intake has been milled to match a decked block / milled heads you usually need a spacer between the intake and dizzy. [it won't seat properly]

 

X4 what Mike VV posted.

Confirm good cylinder sealing by performing a leak down test. Never any issues with header evac systems on street or race and usually run them without the hose to intake vacuum. To me any system that reintroduces crank case vapors back into the intake is not good. It contaminates the fuel mixture and increases carbon deposits in the combustion chamber. Crank case vapors are toxic, corrosive, nasty $hit!

And ya, always check distributor gear for proper tooth engagement/wear pattern with cam gear. This is often overlooked.

 

Had similar issues with the 327 in the avatar. Blowby wasn't terrible, but it had the habit of spitting out the dipstick on occasion. New motor, great compression.

I went the el-cheapo redneck option and fitted a small spring around the dipstick handle. Similar type of spring that you would use to keep a flyscreen door shut, but quite light. Ran the spring down to a header bolt, and it held the dipstick in really well. No more issues with it puking out the dipstick tube.

Fast forward three years, and unclipping that spring every time I wanted to check the oil was getting annoying. Fitted a Lokar locking dipstick to it. Got a free lesson in SBC internals too. Some of Lokar's wire-type dipsticks come with a warning that on a bad day they can wrap around the crank. They recommend using a "lower dipstick tube". I had no idea what that was, and it took a long time to find someone who did... longer still to find someone with a spare one.

Cheers,
Harv

 

I you confirm the engine itself is in good condition with no excessive crankcase pressure the Wagner PCV valve may be a good option. I installed one on the mild built Boss engine in my Comet and it has worked well.
https://mewagner.com/?p=444
Here is the valve in the RH valve cover, it is plumbed to a small oil separator then to the base of the rear carb.

 

If the engine crankcase has no ventilation system (road draft, PCV or header type), it will exhibit excessive crankcase pressure as there is no escape other than a couple of open breather caps. The pressure amount will vary with the build and condition of the engine. An open crankcase provides no ventilation. A catch can(s) will provide no ventilation, only prevents the vents (breather caps) from spitting on the engine/under carriage (if they don't blow off or melt).

You are not only fighting ring blow-by (another factor is the rings won't seal properly with excessive crankcase pressure), but also the rotating crankshaft/rods/pistons will also add to excessive crankcase pressure.

It is like having an engine that has a defective PCV SYSTEM, that pressure has to go somewhere. It starts with fouling the PCV system further and possible oil ingestion through the fuel supply and then goes to gaskets and seals. Once a gasket is damaged, it can then allow unfiltered outside air into the crankcase. No ventilation will also trap water vapor in the engine fouling the engine oil.

The only way a properly designed and functioning PCV SYSTEM will introduce oil into the cylinders is bad ring seal or bad guides/valve stem seals. It will also foul plugs and lower the octane rating of the fuel.

The WAGNER SYSTEM discussed above is adjustable. If you still have oil ingestion (plug reading), you would then add an air-oil separator or freshen the engine.

This gentleman has it correct, plus the oil filler cap is a closed type allowing no emissions into the air.

Put a vacuum/pressure gauge on the dipstick tube and report back what it reads. If the dipstick wants to blow-out, that is the first clue.

A remote mounted plastic bottle is not going to do it.

 

BEAUTIFUL BUILD!

Where does the PCV SYSTEM source fresh air, an open rocker cover breather or the air filter housing?

 

I noticed a lot of oil going into intake from PCV valve, not from blow by as blocking the other valve cover PCV intake would show crankcase vacuum. So I put separator in line. It did the job well but as bowl filled it would pass oil through. So to continuously empty bowl I added a scavenge oil pump. First pic [top to bottom] PCV valve to separator. Second pic from separator to intake vacuum source. Third pic is small gear oil pump mounted to dist tach drive. Forth pic oil line from bottom of separator bowl that goes to dist mounted pump. Fifth pic is another view of pump. Exit oil line goes to old dipstick tube hole and some oil is metered through the mount into the dist to lube the gears. Cut oil loss/use by about 80%. Been working for over 20 years.

 

Trick setup! How much air do you think the gear oil pump pulls into the crank case with the oil?


-rick

 

Why won't my plastic bottles do it ?

 

I added an O-ring to my dipstick in hopes that it'll help it seal. If not I might try the spring idea. I pulled the distributor & It wasn't sealing at all. My tuner guy said the slip collar style are hard to get sealed up. Should the distributor have some O-ring's or something to help it seal down in the block???

 

Stock Chevy distributors do not have O ring grooves down there, just wide lands. This is where it seals the oil that goes to the lifters, I think. Seems to me if the distributor is designed for O rings there, then maybe it should have them?

But that won't help the oil out the top of the distributor. Looks like they designed it to not be able to seal between the collar and the housing? One more reason I like to stick with more stockish parts, I guess.