MGB MGB crankcase venting

[wkilleffer]

I sometimes read the MG mailing list from team.net, and they've had an interesting item over the past couple of days.

Someone on the list said that a good conversion for a chrome-bumpered or 74.5 car is to remove the smog pump and gulp valve, plug the holes, and also remove the crankcase vent that goes back into the inlet and plug it as well. Then use a long hose to vent the crankcase under the car.

Their reasoning was that anything like smog gear and breathers are a potential source of vacuum leaks, and that putting the crankcase vapors back through the inlet can take the fuel octane down.

Someone disputed this, but someone else said it was a credible conversion according to Lindsey Porter.

So, what are your thoughts on this? My car no longer has the smog pump nor the gulp valve, and the holes were well plugged. The crankcase still vents to the inlet. While I understand that it's an anti-pollution item, it also seems like it's sending dirty air back through the engine.

Any advice would be appreciated.

Thank you,
-Bill

 

[DrEntropy]

Depends a lot on what condition the engine is in. Usually higher crankcase pressure is from worn rings and/or guides and there will be some amount of particulate in the vapor too. Usually not enough to do any real 'dilution' of the combustion process. Crankcase vents on racing engines are usually ported to a 'spill bottle' someplace in the engine bay. I'd be reluctant to just stuff it out the bottom.

 

[eschneider]

removal of emissions components can be a very sensitive subject. here are some facts to consider as you contemplate removal.....

1) modern converters do not require smog pumps or gulp valves. The purpose of these devices was to provide early style converters with the extr oxygen molecules to convert HC and CO to H20 and CO2

2) crankcase venting via the intake helps reduce internal pressure on the engine, especially an older one. you may find that removing the vent will increase the tendency for oil leaks.

3) catalytic converters do reduce HC and CO, but at the expense of increased CO2 and water vapor. If you're into the whole global warming thing....... Catalytic converters also create sulfuric acid as a by-product. Further, catalytic converters are 90% ineffective of speeds over 65mph.

4) ditto the global warming thing for EGR valves; the trade-off for lower combustion temperatures was lover NOx at the expense of decreased thermal efficiency, reducing mileage, performance, and increased overall emissions, particularly CO2.

5) however remote the possibility of enforcement, federal law imposes stiff penalties for removing or tampering with any emissions device, especially if you are an automotive professional. Last I heard, the penalty for an automotive professional was 6 months imprisonment and a $10k fine - for a first-time offense. It is notable, however, that auto manufacturers have relieved of the burden of supplying these parts after 8 years of the vehicles manufacturing date, and made the sale of re-used (junkyard) components illegal.

It was my intent to provide objective information here. I hope I did not offend anyones' sensitivies.

 

[wkilleffer]

No offense taken to the above post. I'm not trying to find new ways to pollute the air or anything like that. Smog equipment has never been my favorite topic as some of it seems to recycle dirty combustion by-products back through the engine. But the tradeoff comes in somewhat cleaner air. It just seems that a car with almost all of its smog stuff already gone might benefit from taking it all off. Maybe, maybe not.

The smog pump and gulp valve had already been removed from my car when I got it. The removal looked kind of dodgy, and the engine was in bad shape due to abuse. I had it rebuilt, and the rebuilders finished the removal job. The only place where it's obvious something was removed was on the manifold where the gulp valve would have been.

I thought that after reading that exchange on the mailing list that making the crankcase vent open might be advantageous since the rest of the smog stuff except for the evap system was already gone. As far as the evap system goes, mine doesn't seem fully functional these days, but I'm not going to remove it. It seems that there could be an advantage to venting the crankcase, but maybe not.

I have an air rail and gulp valve, but never bought a smog pump. This was just in case my state decided to inspect all cars, but only Memphis, TN does that, and I'm not planning to move there. They do it on their own, it's not a state mandate. My county started smog tests on cars 1975 and later, but my 1974 MGB is too old and is therefore exempt from the test. I've thought about selling the rail and valve, but keep them just in case.

 

[xsteamer]

My 73B had all the smog equipment removed except for the air rail which was plugged. I removed air rail and plugged holes and changed out the vented valve cover for a chrome non-vented cover and was told it shouldn't affect crankcase pressure as long as the valve cover had a vented cap. Meanwhile I also changed SU's for weber downdraft. My crankcase pressure definitely increased as I noticed oil leaking out of dip stick. Got a proper boot for dipstick to stop oil leak.Now when I check air filter noticed quite a bit of oil laying in cover. Any suggestions?

 

[DrEntropy]

You should have a side cover on the engine's port side under the manifolds with a vent tube on it. I run the vent to a "spill bottle".

 

[Hap Waldrop]

If sucking crankcase pressure thru the carbs was a performance thing, every race car in the country would be doing it, crankcase pressure is just that pressure, it does not need to sucked out, believe me it will find it's own way out. A easy way to do it on a MGB is just get one of those small K&N breather filters the right sizes to slip over the tube coming off the front lifter cover, they are pretty popular, you can get them at most part stores like Autozone, Advanced, etc., works great. As for de-smogging a MGB in most states it is 100% legal and a smog pump was a big joke when it came to the enviroment anyway.

Here's a picture of my 67 with crankcase breather installed

 

[Rob_Edwards]

As for de-smogging a MGB in most states it is 100% legal and a smog pump was a big joke when it came to the enviroment anyway.

Forgive me for correcting you Hap, but it is legal in no state -- tempering with emissions control equipment violates federal law (and I think can carry a $25,000 fine). Enforcement, of course, is a different matter....

A positive crankcase ventilation system will not only be good for the environment (crankcase vapors are nasty stuff), it's also good for your engine -- as Hap says, pressure will find its own way out (if not vented properly) and that's often through or past a seal, in the form of an oil leak. Crankcase ventilation also makes your enigne last longer because it helps purge the oil more quickly of fuel and water that contaminate it, especially at cold start.

HTH!

 

[Hap Waldrop]

Nobody is being put in jail for and in alot of states if you don't have it on your car after a certain number of years, it is not enforced, so that's legal to me.

Rob, We always disagreed on smog pumps and vaccumm evacucated crank case pressure and we always will.

And if you want ot get truely technical about it, you tell me Rob, which is better, buring any oil mist you get from the crankcase through your intake stroke, or capturing it with a filter and not burning it into the atmosphere, think about it?

 

[Rob_Edwards]

Nobody is being put in jail for and in alot of states if you don't have it on your car after a certain number of years, it is not enforced, so that's legal to me.

Legal means it's ok. Illegal but unenforced means that you won't get in trouble -- until someone decides to start enforcing it! There was a recent series in the Raleigh paper about speeding in NC. It's illegal but not very much enforced, and the problem has gotten out of hand. So, enforcement is starting to step up. As air quality continues to deteriorate (especially here in NC where the pace of development is projected to increase our population 50% in the next 25 years), can you always count on the law to take a blind eye to flagrant violations?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Rob, We always disagreed on smog pumps and vaccumm evacucated crank case pressure and we always will.[/QUOTE]

Agreed! ;-)

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]And if you want ot get truely technical about it, you tell me Rob, which is better, buring any oil mist you get from the crankcase through your intake stroke, or capturing it with a filter and not burning it into the atmosphere, think about it?

[/QUOTE]

That's oversimplifying. It's more than just oil mist -- it's all kinds of unburned HCs. It's far better to burn it. It's well proven that PCV reduces smog: compare air quality in L.A. in quality before the mandate for PCV systems versus after. I read in one report that one time WWII, the air quality got so bad in L.A. that people mistook it for a chemical weapons attack from the Japanese. L.A. tried numerous measures to combat smog, but they made very little headway until they started demanding pollution control equipment on automobiles. As I'm sure you know, the PCV system was the first pollution control effort.

And are you denying that sucking water and fuel out of the crankcase faster does not enhance engine longevity? Fuel dilutes oil and water combines with combustion products to form acid (and that mayonaisey stuff if there's a sufficient quantity. That stuff can't help lubricate....)

Hap, I respect you as an engine builder and mechanic, but I guess we're gonna hafta disagree on this one.

 

[mark75b]

Hi,

This is what I did with my smog. I took all the old smog off and kind of made my own. The pump and rail are gone and plugged.

I made a canister up out of large PVC pipe with screw-on ends. I ran two hoses from the valve cover and the crankcase into the canister. Out of the canister, I ran one hose underneath the car and one hose to the air filter on my Webber. I also tied into the Webber line a hose from the gas tank vapor line.

I figured in this way the Webber only sucks in what it can take and excess solid waste is in the canister. Excess pressure and vapors go out under the car.

 

[Hap Waldrop]

Rob you can suck air pressure out of a inflated tire with a hose and a vaccum pump, or your can just remove the valve core and it will find it's own way out, after all it is pressure.

As for as a engine that has vaccum assisted crankcase vs, non vaccum assisted, I never seen anything to lead to believe it did anything to hurt the motor, if it did racers would use carb vaccum to evactuate crankcase pressure. Since the ignition portion of the engine and the bottom end are more or less isolated form each other in a well sealing engine there ot much mixture of gases and oil. The main reason you ventalate a bottom end is because with rotation of the crank and rods at rpm, pressure is created, it has nothing to do with the firing stroke of a engine, of course all bets are off when we talking about a worn engine with bad ring seal and lots of blow by.

 

[Rob_Edwards]

Rob you can suck air pressure out of a inflated tire with a hose and a vaccum pump, or your can just remove the valve core and it will find it's own way out, after all it is pressure.

Lets assume that there's moisture in that tire. Once the air in the tire and the atmosphere are at equilibrium, the moisture just sits there. If you start drawing a little bit of air through it though, pretty soon the moisture is gone.

That's way oversimplifying of course -- a running engine is a dynamic system. But the basic analogy holds: If you actively move air through the crankcase, you'll remove contaminants faster than if you just let them find their way out at their own pace.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]As for as a engine that has vaccum assisted crankcase vs, non vaccum assisted, I never seen anything to lead to believe it did anything to hurt the motor, if it did racers would use carb vaccum to evactuate crankcase pressure.[/QUOTE]

I'm sure you'll agree that race engines and street engines are different beasts. For instance, how much time at full throttle & high rpm does a race car spend versus a street car? While it may make sense to do as I've seen some racers do and pin the distributor advance mechanism (thereby disabling it), it makes absolutely no sense to do so on a street engine (unless you want something completely undrivable). And while it make make sense to build a race engine that pulls like a freight train above 5000 rpm (say), if that engine makes less power below 3000 rpm than the stock engine (a situation I've also seen), the the race setup is a poor choice for the street. So what racers do may or may not have any bearing on what's good in a street car.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Since the ignition portion of the engine and the bottom end are more or less isolated form each other in a well sealing engine there ot much mixture of gases and oil. The main reason you ventalate a bottom end is because with rotation of the crank and rods at rpm, pressure is created, it has nothing to do with the firing stroke of a engine, of course all bets are off when we talking about a worn engine with bad ring seal and lots of blow by. [/QUOTE]

I think that assuming a well-sealed engine with no blowby is an invalid assumption for the vast majority of the MGs on the street today. I'll bet every one you check would have non-trivial blowby. How often is a race engine rebuilt? The bottom end in my B has 150,000 miles on it. In fact, it has developed enough blowby and oil consumption that I have taken it off the road -- I blame a nice tight new head on a tired bottom end and a run to Columbia SC for its demise. I've stopped driving it and it'll sit in the yard until I can get my garage finished and get it inside where I can fix it -- I'm tired of pulling engines on the gravel driveway! ;-)

Cheers!

 

[Hap Waldrop]

We could go forever Rob /bcforum/images/%%GRAEMLIN_URL%%/smile.gif First off the only air being pulled thru a engine's bottom end would be whatever leakage is getting by the rings, in a decent motor this should be less than 5% leakage per cylinder, in the aerage motor less than 10% a cylinder, anything more than that and you're probably already smoking anyway, so you going to burn the oil one way or another. Most racers don't even used a stock based distributor, but a machanical fixed aftermarket distributor like a Mallory dual point or 1-2-3. A engine producing less rpms produce lesser crankcase pressures, so street engine driven in a street manner produce alot less crakcase pressure than a race car.

I think it comes down to this, if you feel omiting crankcase pressure, which may some oil vapor in it, some moisture in it, is better for engine if sucked thru the carbs and fired on a compression stroke, then do it that way, but if you think it's better to capture this stuff in a filter or catch tank and not burn it into the air is better for the engine and enviroment then do it that way, I choose the later and always will.

I think the key is too not sucked into to believing what a bunch of congressmen and automakers came up with in a rush 30 years ago to be the save-all, and is no longer used on any modern vehicle to be a valid attempt to save the air we breathe, then keep your smog pump, but Rob I think you already are in the minority on this one, but you do put up a good fight and I commend you for that /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

 

[Rob_Edwards]

We could go forever Rob /bcforum/images/%%GRAEMLIN_URL%%/smile.gif First off the only air being pulled thru a engine's bottom end would be whatever leakage is getting by the rings,...

I'm not sure we're talking about the same thing. As I'm sure you know, in a stock B setup, there's a measured amount of air being admitted into the crankcase either through an orifice in the rocker cover vent tube, or through the vented oil pressure cap. That air gets drawn through the crankcase, out the front tappet cover, and into the intake tract (either into the carbs or into the manifold via the PCV valve).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]...in a decent motor this should be less than 5% leakage per cylinder, in the aerage motor less than 10% a cylinder, anything more than that and you're probably already smoking anyway, so you going to burn the oil one way or another. Most racers don't even used a stock based distributor, but a machanical fixed aftermarket distributor like a Mallory dual point or 1-2-3. A engine producing less rpms produce lesser crankcase pressures, so street engine driven in a street manner produce alot less crakcase pressure than a race car.

I think it comes down to this, if you feel omiting crankcase pressure, which may some oil vapor in it, some moisture in it, is better for engine if sucked thru the carbs and fired on a compression stroke, then do it that way, but if you think it's better to capture this stuff in a filter or catch tank and not burn it into the air is better for the engine and enviroment then do it that way, I choose the later and always will. [/QUOTE]

So I guess we'll always differ. ;-) I look at the improvements in air quality such as I mentioned before -- especially L.A. -- and say, "This stuff has some merit."

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I think the key is too not sucked into to believing what a bunch of congressmen and automakers came up with in a rush 30 years ago to be the save-all, and is no longer used on any modern vehicle to be a valid attempt to save the air we breathe, [/QUOTE]

I just see it as evolution -- each step was incrementally better than the previous at doing it's job. And pcv is still being used -- my '91 Honda just got treated to a new pcv valve, and while I've not replaced one yet on the Mini, I know removing the oil filler cap screws with the idle, so some kind of crankcase scavenging is in play....

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]then keep your smog pump, but Rob I think you already are in the minority on this one, but you do put up a good fight and I commend you for that /bcforum/images/%%GRAEMLIN_URL%%/smile.gif [/QUOTE]

I'll take that as a compliment! Thanks!

It's been an interesting discussion.....