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lastchancegoat · 11-13-2005, 07:53 AM

New to the forum - first post!!! First, I have been reading the PCV posts and this problem, while related, is a bit different. Here goes. Building up a 400 - cam, aluminum heads, 750 cfm carb, etc. Have an excellent engine shop and am getting great assistance from experienced Pontiac folks in my area. However, I have one of the Butler valley pans (the newer ones with the small baffel in the PCV tube) and am concernbed about oil loss through the PCV. Am using this pan as this is a total engine build up and I had no pan to begin with. Another person has the same setup and was over yesterday and oil was being sucked out through the PCV at a pretty good rate. Some people I have talked to think the low location of the PCV in the Butler valley pan is the culprit as the stock pan has significantly more baffeling and is located higher away from the actual oil flow. Have talked to Jim Butler (he has been very nice to me - helpful) about this - he says not to worry, but when I saw this 400 yesterday sucking oil (engine setup was basically same as mine) I got concerned. My engine is not in the car yet - still plenty of time for mods - anyone with a Butler pan having same problems - have any solutions? Thanks. First post now under my belt.

David Jones · 11-13-2005, 10:19 AM

I have a Year One pan with a baffled PCV in the forward corner passenger side. On deceleration it sucked oil and smoked like it was on fire. I covered that with a rubber cover and put the PCV in a valve cover. Problem solved.

Skip Fix · 11-13-2005, 11:15 AM

My Butler pan did that very thing, suck oil on deceleration, last week when I took the car out for the first time. My KRE pan never did. Two differences the KRE pan only has three holes into the pan and only a small slit in their grommet. The Butler pan must have 20 holes under the baffled rubber grommet. Also the Butler provided grommet the PCV valve bottoms out into the baffels as it is shallower than the KRE one. I just tried adding some of the breather filter mesh under it, see how that goes.

What kind of PCV valve goes in the valve cover , one that is a 90 degree? Go pictures?

form406 · 11-13-2005, 11:55 AM

why cant you use a stock valley pan?...gotta have breathers too..

DiamondJim · 11-13-2005, 12:45 PM

A lot of people have had success with an aluminum valley pan and a Chrysler style breather/pcv in 1 valvecover and a breather in the other, that is what I am running. I have excess crankcase pressure but my motor is new. I was thinking last night, I bet I don't have 100 miles on this motor. Maybe it will get better after some more break-in miles. BTW, Pontiac Dude sells the aluminum valley pan. -Jim

DiamondJim · 11-13-2005, 12:48 PM

One more thing, I have no problems with oil thru the pcv and no problems with normal street driving. I used ultraviolet leak detector dye and with normal driving everything is perfect. HOWEVER, 6000 rpm thrashings at the strip are another story, I am getting oil from several places. FWIW -Jim

Skip Fix · 11-13-2005, 01:43 PM

I did not notice anything on the street with mine. Mild smoke on acceleration at the track, ALOT of smoke on decel at the top end.

Tom Vaught · 11-13-2005, 01:50 PM

Two things are happening under decels, oil trapped in the valley might be "slugging" the pcv and you have a very high engine vacuum sucking on the pcv.

A better baffle system might fix both issues but most likely will only fix the "slugging" issue.

Skip, if the baffle is touching the bottom of the pcv valve there basically is no baffling.

The best baffle design is a labyrinth design _/-\_/-\_/-\_/- where the air from the crankcase has to make several sharp turns.

Tom V.

Skip Fix · 11-13-2005, 06:59 PM

Did it today on some decel on the highway also. I'll have to engineer some better baffling , I like the fairly stock look of the valve cover to the air cleaner and PCV in the valley. Or use one of those PCV catch can devices.

alterator · 11-13-2005, 09:02 PM

If you are running a pvc in one valve cover and a breather in the other valve cover what is the difference from just running 2 breathers with road draft tubes?I guess I'm just not understanding something about the use of a pvc in a valve cover.

shaker455 · 11-13-2005, 09:31 PM

In this case it's hard to beat the engineering of the stock Pontiac valleypan.

The two wall construction makes for good baffling as it's able to draw over the entire length of the engine as opposed to the single port of the Butler.

I have the 389 non-EGR valleypan on my car as it clears my taller rolller lifters.

Tom Vaught · 11-14-2005, 12:10 AM

Quote:

"If you are running a pvc in one valve cover and a breather in the other valve cover what is the difference from just running 2 breathers with road draft tubes?I guess I'm just not understanding something about the use of a pvc in a valve cover."

If the PCV in the valve cover is hooked up to manifold vacuum and the other valve cover has a breather you will have crankcase ventilation at all time except on wot.

The acids in the oil and the moisture will be burned off by the system.

With the road draft deal you need a properly designed tube in the airstream under the car to remove the bad stuff. Think about it this way, you and a buddy both suck on opposite ends of the same 3 foot long tube with the same suction, Is there any flow? NO! Your road draft deal will not pull fumes from the crankcase without a source to let fresh air into the system.

If you were not running a mechanical fuel pump and put a source for filtered air at that location to let the air into the crankcase and then used your two road draft tubes the system would work.

Tom V.

DiamondJim · 11-14-2005, 08:29 AM

So Tom, if a PCV is hooked to manifold vacume and vacume drops at WOT runs, pressure builds in the crankcase and THAT is my problem. I am beginning to understand. Other than messy draft tubes, what other options do I have? This has got to be a very common problem. -Jim

Skip Fix · 11-14-2005, 12:46 PM

My old 409 Impala had a road draft tube that went to an opening in the back of the intake from a baffle in the valley area on the intake underside, about 1" diameter.

rolling money pits · 11-14-2005, 12:56 PM

if some of you folks, with different pans, could post pix of the underside that would be GREAT.

thanks

lastchancegoat · 11-14-2005, 02:09 PM

Thanks for all the info everyone. To David Jones - your Year One pan is, I believe, a Butler pan. Do I understand that you just totally plugged the PCV hole in the pan and put a PCV breather in the Valve cover? Do you have stock valve covers?

From all the posts, it seems that it does not matter where the PCV valve is, so long as there is one in the system somewhere. Is this correct?

I understand about the 389 valley pan working - but what is the source for one (not looking for a used, gnarley one that can't be cleaned) is there a source for new ones?

Thanks again, guys.

Tom Vaught · 11-14-2005, 04:50 PM

Quote:

"So Tom, if a PCV is hooked to manifold vacume and vacume drops at WOT runs, pressure builds in the crankcase and THAT is my problem. I am beginning to understand. Other than messy draft tubes, what other options do I have? This has got to be a very common problem. -Jim

Actually Jim, EVERYONE SAYS that the pressure builds up in the crankcase (which is true but the pressure increase in reality is Very Small. Like blowing up a balloon, the actual PSI changes hardly any but the volume changed.

A typical crankcase might have a very large volume with a negative
pressure in the crankcase of 16" HG. Two inches of Mercury (2"HG)
is roughly 1 Pound per Square Inch (1 PSI). so your 16" Hg is about 8 PSI of negative pressure in the crankcase.

Some of this pressure is offset by a POSITIVE pressure of say 6 psi
from the ring blow-by. Actual pressure in the crankcase is 2 psi.

Now you punch the throttle and the vacuum in the engine drops to say 2" HG or 1 psi.

You now have 5 psi in the crankcase (vs the 2 psi before) or a 3 psi increase. A 3 psi increase doesn't seem like much but the additional CFM of air trapped in the crankcase loaded with oil vapors is a lot!

The oil laden air can't go out the pcv valve as it is almost closed so it goes out the open breather(s) or into the air filter housing. Some goes into the engine and some backflows out the air filter.

Either way you have a oily situation.

The longer you stay at wot the more oil is "pushed" out of the crankcase vs "pulled" into the engine past the pcv system.

Why the system is called a Push/Pull PCV strategy.

Hope this helps.

Tom V.

JSAauto · 11-14-2005, 10:11 PM

The road draft tube theory....

Any tube you take and cut a 45 degree on it end will develop a "venturi vacuum" in the tube if air is rushed by that tube at a 90 degree angle. Look at your carburators for instance..... there are 3/8 or 5/16 tubes sticking out the tops that are right in the airstream of the engine/carb. This is to pull a slight venturi vacuum on the carb bowls and help ventilate them. How many of you guys have seen someone use a piece of 3/8 hose connecting the two bowl vents and cut a slit at the top? That's because after a certain amount of airflow, you'll actually start to feed the engine with fuel right from the bowl vents via venturi vacuum.

So... from my experience, the best "street" systems seem to be one PCV valve in one baffled valve cover (important it has a good baffle so you don't suck oil), and then use large a breather hose (3/4-1") coming from the other baffled valve cover to a 3/4-1" nipple in the base of the air cleaner. Nothing smaller than 3/4" for most V8 engines.

The best case scenario would be if you had a 3/4-1" tube shoved thru the bottom of your air cleaner base into the airstream of the carb with a 45 degree cut so as to pull a "venturi vaccum" on the large breather hose at Wide open throttle. The lower side of the cut should be facing the oncoming airstream.

Last chance... the goal of any PCV (positive crankcase ventilation) system is to clear out as much oil/combustion-blowby vapor out of the crankcase. So it would make sense to have your PCV valve and PCV breather at the farthest opposite ends of the engine. Understanding gravitational forces to play a role in oil scavenging, I would probably want to place the PCV valve which is under constant engine vacuum as far away from liquid oil. So therefore I'd opt for somewhere in the front of the engine, like in the forward position of a valve cover. Same with the breather tube. If the back of your cylinder heads have problems with oil return, you could theoretically push/pull (thanks Tom

) a substantial amount of oil up the breather tube helped by the venturi vacuum in the hose developed by the air rushing into the carb.

Crankcase ventilation is a problem in all forms of racing. You'll see the circle track or road raceers with 1 1/2in" crossover tubes connecting the valve covers with dual breathers on the tube because of the large amount of oil that shoots out of their breathers. Plus.... if its basically a "left-hander" turning car, they'll place the baffles on the opposite side of the gravitational forces of which way the normally turn. The idea of pulse check valves in the exhaust also uses the same "venturi vacuum" effect to "pull" crankcase pressures out of the crankcase. Only problem with these is then you've got oil vapors entering the exhaust system and it only works when you have a substantial amount of exhaust flow. You won't have any PCV scavenging during idle operation.

I have a 389 valley pan on my 455 with a Victor manifold. I don't have any problems with oil suckage. But then again, running std hyd lifters. Make sure you have someone hottank that thing because it can store alot of bad stuff that will get into your oiling system and ultimatly your bearing and such.

Hope this helps.

John

JSAauto · 11-14-2005, 10:57 PM

Take a look at this PCV example. Look at the green tube. This is your PCV valve which is under constant intake manifold vacuum via the intake plenum. Note that it is AFTER the throttle body and not before, so it is on the vacuum side of things. Look at the blue tube. This is your breather hose. Note that the breather tube is plumbed right into the duct between the air cleaner and the throttle body at a 90 degree angle. If you were to see the the other side of this tube pultruding into the duct, it would have a nipple with a 45 degree cut on it. Notice where they have the breather hose and PCV valve hose going to on the valve cover? It's at it's highest point. Nice and far away from liquid oil with a good baffle in the valve cover.

Everything you want to know about PCV systems.
http://www.autoshop101.com/forms/h63.pdf

Geoff · 11-15-2005, 08:14 AM

The curved valley shape reduces the available air volume in the Pontiac block, compared to many other engines. The volume of air in the engine cushions the blowby gases. If there is less volume, then there is less to cushion the blowby. At higher rpm's, there is less time for the blowby to dissipate out of the crankcase area & into the PCV and/or external breather[s]. So pressure builds up & it finds it's own way of exiting, past a gasket or seal....
It seems to me this seems to be more of a problem on Pontiacs, especially 455's, than other brands. I believe part of the problem is the lowered "reserve" volume created by the curved valley & also possibly unseating of the rings, due to the severe rod angle of the 455.

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