PCV VALVE [or not!] 67 BJ8

[ttrotter]

I've been considering installing one for a while now and have done quite a bit of research here and other places. It seems there is no clear cut answer.
I've been to healey6's site (really great site) and reviewed his Technical write up (my BJ8 does have a brake servo unit).
If you have some experience with this modification, I would really appreciate your input as to the effectiveness of this modification. The primary issue I am trying to address is some oil leakage from the slinger (the Healey rust prevention system) and the timing chain cover gasket--both are relatively minor, just a bit irritating
Thanks in advance for the help.
Tom

 

[steveg]

Tom,
You'll want to review this thread:
https://www.britishcarforum.com/bcf...Jumping-in-With-Both-Feet&highlight=pcv valve
-or-
https://preview.tinyurl.com/plm3ahk

I'd add: why not do it - it's cheap and doesn't require any real mods to the car.

I did it several years ago (no booster) and can't see any bad side effects.

 

[Keoke]

I tried it several times never worked for me

 

[John Turney]

I installed one on my freshly-rebuilt 3000 engine with BJ8 intake manifold, HD8's and no brake booster. I am using a Denis Welch ITG air filter with no provision for attaching a crankcase vent hose. It made a noticeable difference in oil leakage, but I found the top side of my #5 and #6 intake valves had a lot of coke on them from carburized oil. The tops of #1 - #4 intake valves were clean.

Based on the tops of the intake valves, I removed the PCV valve and added a fitting to the ITG filter baseplate to vent the valve cover there.

 

[Bob_Spidell]

I've had one installed for, oh, probably 5 years or more and 30K+ miles. No ill effects, though i haven't inspected any intake valves. I pulled the PCV valve out a couple times to inspect and clean, and there was no sign of oil or any buildup on it. I gotta believe--since I usually use name-brand premium in my BJ8--that all the additives are doing a pretty good job of cleaning the backside of the intake valves. After all, that's what the additives are for and, ironically, some of the direct injection engines seem to be having some issues with carbon buildup in the intake manifolds and on the valves since the intake valves aren't getting a bath. In fact, one of the Japanese manufacturers--don't remember if it's Honda or Toyota--has 2 injectors per cylinder, one of which, I believe is for keeping the intake valve from gunking up.

After installing the valve, my oil consumption went from a quart every 800 (highway) miles or so to a quart every 1,200 miles or more.

 

[ttrotter]

I've had one installed for, oh, probably 5 years or more and 30K+ miles. No ill effects, though i haven't inspected any intake valves. I pulled the PCV valve out a couple times to inspect and clean, and there was no sign of oil or any buildup on it. I gotta believe--since I usually use name-brand premium in my BJ8--that all the additives are doing a pretty good job of cleaning the backside of the intake valves. After all, that's what the additives are for and, ironically, some of the direct injection engines seem to be having some issues with carbon buildup in the intake manifolds and on the valves since the intake valves aren't getting a bath. In fact, one of the Japanese manufacturers--don't remember if it's Honda or Toyota--has 2 injectors per cylinder, one of which, I believe is for keeping the intake valve from gunking up.After installing the valve, my oil consumption went from a quart every 800 (highway) miles or so to a quart every 1,200 miles or more.

Bob, is your installation as shown on healey6's site here?
https://www.healey6.com/Technical/PCV.pdf

I'm running Pure brand-non-ethanol, premium gas and occasionally a higher octane (106 racing fuel) , leaded, non ethanol. Am I risking coke buildup on the intake valves by doing so?


Thanks to all for the input.
Regards,
Tom

 

[Bob_Spidell]

Bob, is your installation as shown on healey6's site here?
https://www.healey6.com/Technical/PCV.pdf

I'm running Pure brand-non-ethanol, premium gas and occasionally a higher octane (106 racing fuel) , leaded, non ethanol. Am I risking coke buildup on the intake valves by doing so?


Thanks to all for the input.
Regards,
Tom

Nope ... I have a brake servo so ran the PCV line into the smaller hole near the rear of the manifold (I believe that's why at least one person has noted carbon buildup on the #5 and #6 intake valves). I think that port might have been intended for a vacuum gauge or some vacuum-powered accessory, but on BJ8s the hole was plugged. Otherwise, my installation is basically the same.

I can't answer the carbon buildup question until I pull the head and/or the whole engine. I believe all modern gasoline is required to have a minimum amount of detergent--e.g. 'Techron' 'V-Power,' or the like--which should at least mitigate the buildup on the intake valves (although, I believe, the detergents were first added to prevent fuel injector clogging). Also, I think of 'coke' as a hard, brownish combustion byproduct; what you usually see in manifolds on the backside of intake valves is a black, gooey substance that comes from the crankcase. Any car with a PCV valve--pretty much anything sold in the last 30-40 years--can experience this; my '96 Ranger would get a buildup around the throttle plate that caused a sticky pedal and had to be cleaned out every 10-20K miles.

Overall, I have been happy with the PCV setup. Oil consumption dropped, and the cloud of blue smoke I used to get when accelerating after a long downhill coast in gear is much smaller; almost gone, actually.

Unless you have seriously high compression 106 octane isn't necessary, but if you haven't installed a 'lead free' head--hardened valve seats and Stellite or similar valves--the lead probably doesn't hurt. I use to throw a gallon of 100 octane avgas in my car once in a while, and didn't notice any difference.

 

[RAC68]

Steve/Bob and All,

I have wanted to install a PCV setup for quite a while now and even built an oil separator to eliminate any oil contamination before it enters the intake manifold and/or fouls the operation of my vacuum brake servo. However, I have not been able to identify a suitable available PCV or any criteria to allow me to select a matching PCV for my engine .

As has been identified by many, there is quite a difference in engine compression, carburetion, and a number of other elements that allow our engines to perform differently. How did you select the PCV that performs well in your car? What selection criteria were used to match the device to your engine configuration?

Since my BJ8 is equipped with the original brake servo and the vacuum tap for the PCV is closely located, has anyone experienced any brake assist reduction or other affect that could be attributed to this co-location?

Many have found that installing a PCV has reduced engine oil usage and, therefore, consider it a successful installation. I would like to try using a PCV this spring and any help in identifying a reasonably proper PCV element would be appreciated.

Thanks and all the best,
Ray (64BJ8P1)

 

[ttrotter]

Bob, many thanks for all the help.

Ray, John Sims (healey6) suggest using a Y or T shaped fitting and connecting the brake booster and pcv to it using the single hole that the brake booster is installed to. So, I have the same question as it pertains to "any brake assist reduction". Additionally, the pcv valve he recommends is a Purolator PCV Valve PV770. Again, I also would like to hear other's answer to " How did you select the PCV that performs well in your car? What selection criteria were used to match the device to your engine configuration?"
Hopefully, I'm getting close to my decision to "go or no go"

Regards,
Tom

 

[Bob_Spidell]

I got the valve as part of a 'kit' from BCS. David Nock should be able to suggest an appropriate valve.

 

[steveg]

I bought one at the auto parts store that fit the Healey-size hose and was for a car with similar horsepower. In other words, I took a guess at which one. I'd guess that the spring in a valve for a large V8 would be too strong to be offset by the Healey vacuum, but that on a typical 100+ bhp 4-banger would work properly.

 

[RAC68]

Thanks Bob for the reference to Dave. Steve, can you post the number of the PCV you used?

Tom, I believe this is a good thing to do but only if reasonably matched to the engine and over the years things have changed. You bring up a good question about extracting vacuum for the brake servo and PCV from the same point on the intake manifold. Although I had intended to experiment once I had identified and installed the PCV, it would be nice to hear from someone experienced with running a PCV and brake servo (identifying the brand) as to any changes in operation.

I posted an article on the creation and installation of an oil catch in our prior PCV discussion and have referenced it here for convenience.

https://drive.google.com/file/d/0Bx4EjcJmfaScU29Fa0d0TWNXcm8/view?usp=sharing

The creation of this oil catch can is meant to address a number of oil smoking issues but was designed in simplicity at low expense to eliminate oil contamination and issues for this purpose.

As with scuttle shake, I hope we get to a real understanding of this seemingly simple issue.

Ray (64BJ8P1)

 

[steveg]

I used a Purolator PV770 which I bought at AutoZone (Now O'Reilly). It seems to work fine; car leaks very little. Can't say about valve burning, but with a DMD manifold with balance pipe, was able to feed into the center of that. Before doing this, on my O2 sensor, had noticed the rear cylinders ran a little leaner.

 

[Bob_Spidell]

Note that a typical PCV valve installation circulates fresh air sucked in through either a filter on one (or both) valve covers, or from a port inside the air cleaner on the carburettor. The Nock kit came with a rubber washer to seal the dipstick hole, and the instructions said to solder the little hole in the oil filler cap shut (I put a small sheet metal screw in the hole). Instead of circulating air, this setup pulls a vacuum on the crankcase, valve cover, etc.; if you put you hand over the oil filler hole with the engine running at idle you can feel the vacuum (probably a few inches' worth). Any air that is getting in is coming from around the rear main 'seal,' I suspect, as well as the timing cover seal or any small leaks around the block. I think--can't prove it--that this vacuum is a) preventing as much oil from leaking out into the bellhousing and b) keeping excess oil from seeping down the valve seals and guides (hence less blue smoke on acceleration).

My understanding of a PCV valve is that it's not supposed to draw air at low vacuum--i.e. at idle--but the small poppet valve in the PCV doesn't seal all that well, and probably isn't meant to. I enrichened the rear carb a bit to compensate for any air pulled into the manifold. Engine runs good; time will tell if I get buildup on the rear intake valves.

 

[RAC68]

Thanks Steve.

Bob, I think you partially resolved (for me at least) the issue of how to size the PCV for our Healeys. After reading your post, it finally hit me that we are not trying to size a PCV but install a variable self closing vacuum valve. This makes sizing a matter of how you intend to install the PCV (i.e. size of the hose) and the reasonable amount of vacuum needed to be pulled on the leaking seals when the valve is active. Since a modern 4 cylinder expects an open air flow through the bowels of the engine that we will not be satisfying, I would suggest that a PCV from a mid to small size 4 cylinder (i.e. 1.6 Honda Civic or smaller) could be sufficient. By removing most air passages into the engine, air intrusions will be concentrating air flow around the limited seal openings we are concerned with and should diminish or eliminate any potentially serious limits to the access of vacuum by the brake servo when called for and required. A one-way vacuum valve can be installed on the servos, however, I believe the Girling servo is already equipped.

What are the thoughts?

Ray (64BJ8P1)

 

[ttrotter]

"By removing most air passages into the engine, air intrusions will be concentrating air flow around the limited seal openings we are concerned with and should diminish or eliminate any potentially serious limits to the access of vacuum by the brake servo when called for and required."

Ray, fwiw, this makes sense to me, but I'm sure not an engineer or mechanic for that matter.

Since the hose from the T fitting on my valve cover over to the rear carb remains free of oil residue, the pcv valve should function as intended, at least when new.
I'm going to try the PCV installation and I really appreciate the help from all.
Regards,
Tom

 

[DerekJ]

As we know, PCV stands for Positive Crankcase Ventilation. Our cars already have this. The excess crankcase pressure is vented back to the air intake as a pollution control mechanism. Previously it was vented to atmosphere in the car's slipstream. My question is, what is the purpose of adding the PCV Valve? I understand that its main purpose is to prevent blow back, what other function does it perform? I also read that constant depression carburettors such as SUs already prevent blowback occurring.

 

[Bob_Spidell]

As we know, PCV stands for Positive Crankcase Ventilation. Our cars already have this. The excess crankcase pressure is vented back to the air intake as a pollution control mechanism. Previously it was vented to atmosphere in the car's slipstream. My question is, what is the purpose of adding the PCV Valve? I understand that its main purpose is to prevent blow back, what other function does it perform? I also read that constant depression carburettors such as SUs already prevent blowback occurring.

A good question, and good explanations here: https://auto.howstuffworks.com/positive-crankcase-ventilation-system.htm

and here: https://en.wikipedia.org/wiki/Crankcase_ventilation_system

What the 6-cyl Healeys have--the 4-cyls have draft tubes--cannot be considered 'positive' crankcase ventilation (I've always thought 'positive' was a bit of a misnomer since a vacuum; i.e. 'negative' air pressure is used, but never mind). I believe--though neither of these articles state it outright--is that the term 'positive' is used because air is circulated through the crankcase and into the intake manifold in a controlled, regulated fashion. To me, a better term would be 'active crankcase ventilation' instead of PCV, whereas the draft tube and vent to the carburettor could be considered 'passive crankcase ventilation' but, again, never mind.

The difference between PCV and the draft tube/carb vent approaches is that in a PCV system fresh air is mixed with the blow-by gasses to aid in combustion of the gasses. As I wrote earlier, a true PCV system has a filtered fresh air intake, either on the valve cover(s) or behind the air filter atop the carburettor. The PCV valve minimizes the air/blow-by flow at idle, when it basically acts as an intake leak, but the valve opens up under more open throttle conditions, when blow-by is greater and the additional mixture (mostly air) is inconsequential. Also as I wrote earlier, installing a PCV valve on a Big Healey does not a PCV system make (unless you add a source for filtered air). We are using the PCV valve to pull a vacuum on the crankcase, which for my car created a) lower oil consumption/loss and b) less blue smoke on acceleration after extended high-vacuum conditions (long downhill coasts in gear).

I can't think of any reason why constant depression--aka 'variable venturi'--carburettors would prevent 'blowback' any more than a fixed venturi carb. A variable venturi carb, like an SU, is just a different--IMO superior, and certainly more elegant and simple--method of mixing fuel and air. Both types of carburettors produce a vacuum--'depression' to non-American speakers--in the intake manifold, and downstream of the throttle plates there is no significant difference. BTW, I'm old enough to remember when PCV systems were first required on American cars, and there was a huge controversy. As with catalytic converters, the car companies and 'car guys' complained furiously but--except for early cats which were defective--both have had largely, ahem, positive outcomes. As an aside, don't some Brit cars--like later MGBs--have an 'air pump?' I don't know the theory, but it sounds like the idea is to force air through the crankcase, in which case 'positive' crankcase ventilation would be the appropriate term.

Learned some interesting trivia: "During World War II a different type of crankcase ventilation had to be invented to allow tank engines to operate during deep fording operations, where the normal draft tube ventilator would have allowed water to enter the crankcase and destroy the engine.[SUP][4][/SUP] The PCV system and its control valve were invented to meet this need, but no need for it on automobiles was recognized." - Wikipedia article

 

[DerekJ]

Bob

I think any system which vents the crankcase can be called a Positive Crankcase Ventilation system. There is a pressure build up in the crank case during engine operation. This becomes a 'positive' or higher pressure area. There is no negative pressure or vacumn, there is just an area of lower pressure in the air intake, or indeed, simply outside of the crankcase. Air will always flow from a high pressure to low pressure area.

Getting back to the question posted by the original poster, I'm unclear how a PCV valve can help reduce oil loss from the areas he mentions. I would have thought that the installation of any valve will restrict rather than increase the venting of the system. I believe that the purpose of the valve is to limit the amount of gasses and vapours returned to the intake during certain phases of the engine operations when it is deemed to be detrimental to performance efficiency.

It can be argued that returning any of this 'waste' to the engine will have a negative impact on the engine's operation however small. I vent my crankcase into a catch tank fitted with a filter on its outlet, which avoids this re-circulation issue.

 

[Bob_Spidell]

Bob

I think any system which vents the crankcase can be called a Positive Crankcase Ventilation system. ...

It's terminology, may be a linguistics issue, and I disagree but will let it go at that.

I did some more thorough reading and did find, I think, the source of your statement that (some) SUs did not need a PCV valve (source: https://en.wikipedia.org/wiki/Crankcase_ventilation_system):

"Should the intake manifold's pressure be higher than that of the crankcase (which can happen in a turbocharged engine, or under certain conditions, such as an intake backfire), the PCV valve closes to prevent reversal of the exhausted air back into the crankcase again. In many cases PCV valves were only used for a few years, the function being taken over by a port on constant depression carburetors such as the SU. This has no moving parts or diaphragm to jam, block or rip like many PCV valves. It also does not have a 'one-way' function but the lack of it was never a problem in intake backfire."

Once again, the simplicity and elegance of the SU design triumphs.

Note that in a turbo'd engine, a 'PCV' valve may still be employed although the manifold pressure may be greater than the crankcase pressure. Also, I haven't seen a late model American car which did not have a PCV valve--my 2008 Mustang has one--but, of course, that doesn't mean there aren't any. Japanese engineers often seem to find clever and inventive ways to accomplish similar purposes with better solutions.