Technical 327 pushing (dumping) oil out of breather, real head scratcher

Hi guys, long time lurker first time poster. I've recently become stumped with my little 327 pushing oil out of the breather. And when I say pushin oil, I'm talkin blast the vent cap off and spray oil over the entire engine compartment!

A little background: small journal 327 bored .30 over, 331 ci., 11.5:1, afr street heads, solid roller .640 lift 308 dur. 106 lobe center, edelbrock tr1yx tunnel ram, 600 double pumpers, 4 speed, 12 bolt with 4:88's. This thing runs like a bat outta hell. Don't skip a beat and pulls like a freight train all the way through 8,000 rpm. The problem that I've been battling is that I can't even get on it without it dumping oil all over the engine compartment/engine. I'd say that it's happeneing above 6000 rpm which is bad news for me because that's when this thing really comes alive.

As far as engine ventilation goes: I used to have the breathers in the valve covers but, oil was pushing out of them at high rpm as well (used some of the wife's hair scruntchies which helped a ton). I assumed since the covers weren't baffled, it was causing the oil to push through. I switched to the early style no hole covers with a pcv in the rear of the block (hooked up to the rear carb pcv provision) coupled with the baffle in the lifter valley along with the original style fill spout breather. I assumed since there would be less windage this way it would solve my problem, WRONG. I feel like this has made it worse. When I get on it, it'll pop the breather cap off. I was able to secure the cap properly but, it still pukes oil out of the fill tube. I'm talkin an easy 1/8 of a quart on a hard pass.

I'm pulling 7-8hg of vacuum at idle. At this point I'm not sure how to remedy this. I've scoured the interenet searching for a similar situation and was unsuccessful.

I recently performed a leakdown test thinking that there may be extreme blow by. All cylinders are in acceptable range with 25% or less leakdown per cylinder. Not ideal, but "acceptable".

Any thoughts on this issue would be GREATLY appreciated. I'm about to pull this thing apart and have it rebuilt. It's a shame because it is running the best it ever has and I'd hate to dump a ton of money in it and still have the same issue.

Thanks y'all!!

 

25% leakage and 8000 rpms? can you make the filler/breather tube longer?

 

Your crankcase is pressurizing under power/RPM. An improved crankcase ventilating system might be in order. You could scavenge the pressure through an oil separator back into the intake via the carb base ports or you could do the same scavenging into your exhaust through an oil separator. The second way is primarily for track setup cars but it works too. I am using the first method on my post 65 engine setup.

 

Thinking that possibly the pcv or baffle in the lifter valley may get blocked with oil after 6 grand.
Are you running headers?
I run a similar setup on my 434 sbc using a Mr Gasket header crankcase e vac system.

 

unfortunately I don't think that would help as the pressure from the crankcase may be carrying the windage up and out.

Is there a setup that attaches at the filler tube for this? I really like the look of the no hole valve covers. The only one I've seen is the vette pcv style filler tube with the rear block vent routing back to the air cleaner (non option for me as I have velocity stacks).

I seen the moroso vac. pan kit. My pops swears by it. I'd hate to cut up my fenderwells. They're an old school set that are in great condition.

 

Are you using a high volume/high pressure oil pump!?!!
If so..........that could be it, pumping too much oil to the top end.
6sally6

 

I can't imagine the windage in there at 8k plus rpm. I recently had the heads off, that's when I istalled the baffle so I'm sure its clean and the PCV is new. I checked the hose on that end and there is no oil going in it.

I have a set of fenderwell headers installed. I'd hate to cut them up for the vac pan. And I would lose the no hole valve covers, which I like cause it screams 327.

 

Yes, I have a melling HV pump installed. I don't have the balls to glance down and look at the oil gauge at that RPM running through the gears. I'm assuming it's over 100 lbs as it's upwards of 80 lbs at idle. I'm no engine builder but, I assumed when I built this thing when I was a kid (some 14 years ago) the HV pump was a necessity and the way to go?

 

I see why you would like to adapt to the filler tube and I think it would work well, you would have to modify the filler tube to attach a 3/8" vacuum tube to it and run it to the vacuum source of your choice. As bad as yours is behaving I would definitely source it through an oil separator though. No matter where you are taking the residual from the crankcase you are not going to want the oil to be going there!

 

I think that I may still have an issue this way as the breather cap blows off under load. Do you think that the extra vacuum pull would be enough to overcome the excessive outward pressure?

 

Didn't see the pictures the first time around; using my phone to post. Slick setup you got there tickety!

 

Thanks Gonzol717
67-68 sbc oil fill tubes have a threaded bung welded on but it is only pcv size.

 

Might even help to put a baffle under the oil fill tube.

 

A high volume oil pump will not produce crankcase pressure. 25% leakage is probably why your pushing oil. That said if you don't want to fix the cylinder leakage you could just run a hose from your crankcase vents ( all of them) into a can with tampons in it. Soak up the oil when gouging on the throttle.....we did this with a 331 with Buick ( dart made them) cylinder heads in a DIRT modified and won a bunch of races....

 

put some new rings in it?

 

You have way too much oil pressure. With the engine warm you should have 40 psi at idle. For racing we like to see 60 psi at 6000, 70 psi at 7000, and 80 psi at 8000 rpms as a "rule of thumb". Too much oil pressure is not a good thing. The first thing you should do is drop the oil pressure. Pull the pump and inspect the oil pressure relief valve because it may be stuck closed. Once you get the oil pressure into an acceptable range the problem will probably be less severe. Your leak down figure of 25% is way too high for an engine running at 8000 rpms. I am not surprised that you are pumping oil out of every orifice. Your suspicion that most of the leakage occurs above 6000 rpms is probably correct. I think that trying to take the oil system, as it is, and trying to take the excess oil and putting it into the intake manifold etc is a fools errand. Can you imagine that amount of oil being burned in the combustion chambers? Your exhaust would look like a Saturn Rocket at launch. Unfortunately, to really fix the problem involves rebuilding the engine.

 

Yeah, I was thinking of doing some sore of series of screens in the tube.

So, make some sort of top fitting to attach to the filler tube and route it to a catch can? Based upon my readings is that the filler "should" be providing the fresh air "inlet" and the pcv is the exit. In my case it's blowing out both ends LOL!
I obviously would like it fixed correctly as it's becoming somewhat of a safety concern as the oil may cause a fire. I'd hate to lose my car over a simple rebuild.

This was my first time performing a leakdown, on all cylinders the air blow by into the crankcase was immediately noticeable; even on the cylinders that had 10% or less. Is this normal?

I think I may be fighting the inevitable. The engine may need a tear down. I wanted to get everyone's opinion on it before I start ripping the car apart. At this point, it's driving me nuts. It's hard to enjoy the car when I can't mash on the throttle. I mean, that's the whole purpose of it, right? LOL

 

You have arrived at the decision that was inevitable from your OP. Excessive blowby cannot be band aided .

 

Yep, what sort of oil ring do you have? I’ve always liked the three piece, the cast ones can brake and I don’t think they work as well. Just an opinion , someone will be along shortly with a different one

 

Gonzo wrote -
A little background: small journal 327 bored .30 over, 331 ci., 11.5:1, afr street heads,

A heads-up, no small Chevy or many other automotive engines can be bored .30" over..! That's well over 1/4"..!
I believe you meant... .03".!?

Mike

 

I suspected that the oil pressure may be out of control but, I assumed that it was correct as it is an HV pump. When I built this engine, I did it on an 18 years olds budget. I think I paid something to the tune of 600 for machine work. Needless to say it wasn't the best you could buy but, got the job done. Now, back then I ran an isky z-70 flat tappet which wasn't spinning anywhere near the rpm with the roller. This engine has always spit "some" oil out of the breathers. I've always chalked it up to no baffles in the valve covers.

I suppose I'll drop in a standard flow pump and see how it does (can easily drop the pan in the car). Still doesn't help the "blowin the breather" off the fill spout issue which is due to the leakage.

Looks like a tear down may be in the near future. Anyone know of some reputable machine shops in the SoCal area?

 

Hard to recall now but, i believe they are the three piece rings (two small one "wafer" style ring).

Good catch Mike! Excuse my typos.. currently indulging in some distilled beverages.

 

I've done that with a breather bottle on a Kent Ford , but with a bilge pump to pump oil back into the crankcase
Racers try to reinvent the wheel by removing the factory breather [ which Ford strategically placed on the R/H side of the crankcase so the crankshaft fires oil directly up the tube]
When the factory breather was removed and a bottle added, under racing environment the engine would fill the bottle [approx. 3 pints] in one race.

The fix was an oil separator [eg the factory breather]

 

A question for the OP "Gonzol717"

A 327 engine breathes IN the breather on the filler tube, and OUT of the fitting on the rear of the block.

Early 265's and 283's had a "draft tube" out of the rear,
But 327's ran an Open PCV to the back of the carb. [see below] If you run this system you must use the "Tomato Can" underneath the manifold



Here's the Tomato can


If you have blocked off the rear vent, you will get oil blowby from the oil fill breather and a pressurised crankcase.
If you have removed the Tomato can you will get oil blowby out of the rear breather /or draft tube.

If the engine has a PCV breathing off the oil fill tube, the oil fill cap will be the sealed variety. [below]


That type usually has a hose off the rear to the air cleaner [closed loop]

 

Maybe walk us through how you did the leak down test, just to make sure your finding is accurate


Sent from my iPhone using H.A.M.B.

 

Three pints in one race! Holy cow!!

My block is a 65 block. I used the "tomato" can under the manifold. Installed a grommet at the back of the block, placed a pcv valve in it and routed it up to the rear carb.

Do you think that the fix may be removing the rear pcv setup and installing a draft tube? From my readings, somewhere in 62 corvettes went to the setup that I currently have.

I used a brand new snap on leakdown tester. I hooked it up to my air supply (115 psi) and adjusted the secondary gauge (percentage gauge) to exactly 0%. I believe that the psi reading on the first gauge was somewhere between 80-90 psi. I ensured that the piston(s) were at tdc (removed valve cover) and manually rotated the piston into position. Looking into the cylinder bore and ensuring the piston was at Tdc. I installed the fitting for the cylinder and hooked up the gauge. I waited about 5 minutes on each cylinder and noted the percentage.

The only direction from snap on that I did not follow was have the engine at normal operating temperature prior to testing.

Do you think that this would significantly impact the readings?

 

It's not the oil pump. Oil pumps do not create pressure. They create flow. Only resistance to the oil flow causes pressure. All modern oil pumps (including the one on the OP's Chevy) have a relief valve that limits the pressure. So again...it's not the oil pump. I have never once, in 30 years of building motors, seen an oil pump exhibit the phenomenon that the OP is experiencing. I can almost guarantee that the problem here is blow-by.

The alarm bell here is the OP's induction setup. He installed not one, but two double pumpers on this little engine. Double pumpers are basically toilet bowls for fuel. There is no on demand secondary. You're basically hitting a flush handle every time you step on the go pedal. With each throttle up, there is always unburned fuel washing down the cylinder walls, wearing the rings and diluting the oil. It's even worse in this case, with the OP's setup. With 1200 CFM of DP carb feeding 327 cubic inches, im really surprised that the piston rings lasted 14 years.

If I were the OP and wanted to continue running this engine, i'd jettison the fill tube/breather setup and get valve covers with twist-tight caps. Install a high flow PCV AND.....this is really important...install a decent capacity PCV pullover catch can. I install one of these on all of my rides to keep PCV pullover oil from being fed back to the motor thru the carb. You can even rig one up that has a drain valve in it, so you can empty it after each of those 8,000 RPM runs.

Any motor you build up and put under those twin DP's will have worn out piston rings in very short order, though.

 

Two 1" (one each) hoses at the top front of each valve cover. Baffles below to reduce splash and going to a high mounted puke tank. Venting at the rear of the block (or valve covers for that matter) under acceleration is not a good idea, and should be larger and allow flow between banks, not having a single small rear vent. Kind of the exact opposite of what you have now.

 

When I originally built this engine, I installed two holley 1850's (600 vacuum secondaries). The car felt "good" but by no means a "screamer". It was slow to rev and just did t have the "throw you in the seat" feel.

A "tech" from a local carb shop came in my pops' shop and informed me that there's no way I was pulling enormous th vacuum to operate the 1850's. He suggested 600 double pumpers. I went ahead and took heed to his advice and installed the DP's. It was like night and day. It really woke the car up.

However, I do agree with you re: fuel in the oil. The engine oil almost always smells heavily of "emissions". Over the years I've pretty kiched just summed it up as blow by.

A quick google search for PCV pullover catch can turns up a cylindrical can with a breather on top and two ports for fittings. Is this what you are referencing? Do you have a brand in particular that you use?

If I am understanding gyou correctly, route the hose from the rear of the block with a high flow pcv valve to the can and back to the carb port?

Is this sufficient ventilation with "no hole" valve covers? I don't mind pulling a cover off to do an oil change. I can't imagine twist cap covers providing any form of ventilation?

Thanks for the idea! Right now I want to try and stick to the no hole valve cover look. I will definitely consider this if there is no way around the oily mess. I do have a set of moroso gold covers to throw on to test out.

 

If and when you rebuild, restrict the flow to the top end. Putting a vacuum pump on the crank case will also help. Just my 2 cents worth.........