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Crankcase ventilation


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One outstanding bit of my Weber project is the crankcase breather. The old Stromberg system had pipes that connected the vent from the valve cover to the carbs and to the carbon canister. I no longer have the carb connections and I'm not sure where to connect the valve cover vent pipe. Right now I have a hose connected to it with the other end stuck into an empty brake fluild bottle (!).

 

How does the PI system vent the crankcase ?. Does it vent it into the air plenum or do you have something more sophisticated ?

 

Stan

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One outstanding bit of my Weber project is the crankcase breather. The old Stromberg system had pipes that connected the vent from the valve cover to the carbs and to the carbon canister. I no longer have the carb connections and I'm not sure where to connect the valve cover vent pipe. Right now I have a hose connected to it with the other end stuck into an empty brake fluild bottle (!).

 

How does the PI system vent the crankcase ?. Does it vent it into the air plenum or do you have something more sophisticated ?

 

Stan

 

Stan,

The Pi system vented the crankcase into the plenum, the second connection from the front.

Here's a pic, from the Haynes WSM on 2500Pi saloons, as my TR6 wsm just doesn't say anything about it!

 

John

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Forced, ie suction, ventilation is well worth doing imho.

You might be able to connect to the air filter(s).... ? I know some four-barrel filter housings have connectors for ccase ventilation.

 

Having said that, it looks to me from the pic he posted as if Wyn's Webered TR5 has no ccase ventilation on the carb side :unsure:

 

Ivor

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Should have said, Stan, why not go with the catch tank solution?

Racers etc, don't vent the crankcase into the air intake at all, as all it adds is dirty air, minus oxygen - no use for performance.

 

A properly made catch tank with an acessible drain plug and a breather filter on top is an acceptable way of doing it.

Instead of your empty pop-bottle, bright alloy has a certain bling to it!

 

Have a search here for "catch tank" (include quotes) - It's been discussed before.

 

John

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Should have said, Stan, why not go with the catch tank solution?

Racers etc, don't vent the crankcase into the air intake at all, as all it adds is dirty air, minus oxygen - no use for performance.

 

A properly made catch tank with an acessible drain plug and a breather filter on top is an acceptable way of doing it.

Instead of your empty pop-bottle, bright alloy has a certain bling to it!

 

Have a search here for "catch tank" (include quotes) - It's been discussed before.

 

John

 

Hi Stan

The above advise is the only way to go imho ;)

 

Neil

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Thanks everyone for the info. One solution I was considering is this setup from Richard Good. It has an option to feed separated oil back into the sump via the blanking plate used when the carbureted cars mechanical fuel pump is replaced with electric. It is just more stuff to have to accomodate in the engine bay however.

 

http://www.goodparts.com/shop/index.php?categoryID=8

 

Stan

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It seems others find the stench of the fumes, which permeate clothing, hair etc. in short order while tinkering under the bonnet with engine running, objectionable as I do :P

 

Both of my Webered '250s utilize the original PCV valve, as can be seen from the previously posted pic. I had a couple of brass adapters made to my sketches and made use of the banjo fitting and most of the original hoses too. Note this valve draws a slight amount of clean air from the filter to mix with the fumes, as per original. Feeding downstream of the carbs spares them unwanted gunk, and the method has proved totally reliable with 70,000+ miles of service. The slight vacuum produced will help control oil weepage from the rocker cover too. Oil consumption on my driver after 74,000 miles on the bottom end remains at 2000 miles/quart, as good or better than when installed, with no valve guide seals, btw. The PCV valve on my new engine is dry inside <_< .

 

This method may affect idle jet sizing; if anything it would kick it up one step richer. No change was needed on mine at the time.

 

Given the extreme lengths others have undertaken to address this issue I wonder if it would work on very high output or racing applications. For fast road spec I have full confidence, however, and if anyone wants the adapter sketches he should PM me.

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;) It seems others find the stench of the fumes, which permeate clothing, hair etc. in short order while tinkering under the bonnet with engine running, objectionable as I do

It depend's on where you pipe the outlet from the tank and if your engine is tired :P

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Forced, ie suction, ventilation is well worth doing imho.

You might be able to connect to the air filter(s).... ? I know some four-barrel filter housings have connectors for ccase ventilation.

 

Having said that, it looks to me from the pic he posted as if Wyn's Webered TR5 has no ccase ventilation on the carb side :unsure:

 

Ivor

 

Wyn seems to have something more elaborate set up on the other side, see the pic he posted a while back:

 

http://i265.photobucket.com/albums/ii237/W.../Picture144.jpg

 

Stan

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I have the Racetorations catch tank set-up as well, except mine has three pipes. One from the rocker cover to the tank, one from the blanking plate under the metering unit (PI) to the tank, and one from the tank to under the passenger side bulkhead so that any escaping fumes exit under the car. Works for me.

 

Cheers

 

 

Dave

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  • 2 weeks later...
Thanks everyone for the info. One solution I was considering is this setup from Richard Good. It has an option to feed separated oil back into the sump via the blanking plate used when the carbureted cars mechanical fuel pump is replaced with electric. It is just more stuff to have to accomodate in the engine bay however.

 

http://www.goodparts.com/shop/index.php?categoryID=8

 

Stan

 

Stan,

That still uses the intake manifold suction. If it was sealed, what would happen to blow-by?

If you had so much oil being blown out of the crankcase that a re-circulator was needed, you have other problems!

John

Edited by john.r.davies
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Stan,

That still uses the intake manifold suction. If it was sealed, what would happen to blow-by?

If you had so much oil being blown out of the crankcase that a re-circulator was needed, you have other problems!

John

 

 

Good point John. I didnt think it could be used as-is but I have an email into Richard to ask if we could adapt it for my application. BTW its not that I have a lot of blow by, I had a little when the engine was first started but now that the rings have bedded in that has stopped and now I'm just dealing with the smell of the crankcase fumes. What I have rigged up at the moment was borrowed from another TR6 owner in the same predicament and it takes the rocker cover vent into the middle of a plastic bottle and then a pipe from the top of that bottle into the carbon canister. A third pipe from the carbon canister acts as a draught tube. So far it is holding up as a temporary solution. The original design used a pipe coming back to the carbs and included three vertical pipes with a slot in the side that were installed adjacent to each filter. Lots of design ideas here though.

 

Stan

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  • 3 months later...
Good point John. I didnt think it could be used as-is but I have an email into Richard to ask if we could adapt it for my application. BTW its not that I have a lot of blow by, I had a little when the engine was first started but now that the rings have bedded in that has stopped and now I'm just dealing with the smell of the crankcase fumes. What I have rigged up at the moment was borrowed from another TR6 owner in the same predicament and it takes the rocker cover vent into the middle of a plastic bottle and then a pipe from the top of that bottle into the carbon canister. A third pipe from the carbon canister acts as a draught tube. So far it is holding up as a temporary solution. The original design used a pipe coming back to the carbs and included three vertical pipes with a slot in the side that were installed adjacent to each filter. Lots of design ideas here though.

 

Stan

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Is the petrol pump blanking plate the 'other' exit for engine gases, ie an addition to the rocker cover breather and does its use as well make a noticable difference >?

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Is the petrol pump blanking plate the 'other' exit for engine gases, ie an addition to the rocker cover breather and does its use as well make a noticable difference >?

 

I dont think the petrol pump blanking plate is an exit point for fumes but it is used in some systems as an entry point for engine oil captured in a separator.

 

I ended up just putting a PCV valve between the valve cover and the servo hose via a T connector and that has worked out great for a very low cost.

 

Stan

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I dont think the petrol pump blanking plate is an exit point for fumes but it is used in some systems as an entry point for engine oil captured in a separator.

 

I ended up just putting a PCV valve between the valve cover and the servo hose via a T connector and that has worked out great for a very low cost.

 

Stan

 

Sorry Stan disagree it should be used as an additional form of crankcase ventilation

 

Neil

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Sorry Stan disagree it should be used as an additional form of crankcase ventilation

 

Neil

 

I'm sure you are correct Neil, as evidenced by my starting this thread, my experience in this area is quite limited and there seems to be numerous options for crankcase ventilation and oil capture including using the blanking plate as an output port, not an input.

 

In the parallel thread to this one there was a comment that crankcase ventilation was only about emissions and making the world a better smelling place but I have to think that Positive Crankcase Ventilation (vs venting to atmosphere) is a Good Thing and if nothing else might make the motor leak less.

 

Stan

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I'm sure you are correct Neil, as evidenced by my starting this thread, my experience in this area is quite limited and there seems to be numerous options for crankcase ventilation and oil capture including using the blanking plate as an output port, not an input.

 

In the parallel thread to this one there was a comment that crankcase ventilation was only about emissions and making the world a better smelling place but I have to think that Positive Crankcase Ventilation (vs venting to atmosphere) is a Good Thing and if nothing else might make the motor leak less.

 

Stan

 

Hi Stan

Still thinking on this one if you look at the ford kent engine breathing system the oil filler cap is only used as a vent the crankcase pressure is released by a pcv valve in the block it makes some sense ie: the rocker gear stays clean and most of the blow by is after combustion past the piston rings. This is why I always use the blanking plate as an output.

Neil

Edited by ntc
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Richard Good's oil separator is now on my engine, the blanking plate is used to feed any liquid oil back into the sump.

I am quite tempted to fit transparent breather hoses as a temporary measure, as there is no drain plug no sight glass and no way to see what's going on, although I do know that it's ventilating the crankcase no less than the original setup did, and hopefully with less oil getting back into the engine.

So far I have done little mileage since fitting, hence 'hopefully' but after the trip to Silverstone for the Birkett on Saturday I'll check the inside of the plenum, it will give me a better indication.

 

Ivor

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Richard Good's oil separator is now on my engine, the blanking plate is used to feed any liquid oil back into the sump.

I am quite tempted to fit transparent breather hoses as a temporary measure, as there is no drain plug no sight glass and no way to see what's going on, although I do know that it's ventilating the crankcase no less than the original setup did, and hopefully with less oil getting back into the engine.

So far I have done little mileage since fitting, hence 'hopefully' but after the trip to Silverstone for the Birkett on Saturday I'll check the inside of the plenum, it will give me a better indication.

 

Ivor

 

Thanks for the update Ivor. One thing I dont think I mentioned yet is that when I did my dyno visit I noticed that I was getting oil running down the block apparently coming out of the dipstick hole as well as from the head to block interface. I had not seen that happen before or since despite many hour at highway speeds but it was doing it on the day and the only difference was that I was reving the motor up to 5500rpm in 4th and then just taking my foot of the gas pedal to let the dyno do the breaking.

 

I am suspecting that my simple PCV valve crankcase ventilation solution is perhaps not fully up to the task and I may have to look at something more sphisticated like Richards full system.

 

Stan

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Thanks for the update Ivor. One thing I dont think I mentioned yet is that when I did my dyno visit I noticed that I was getting oil running down the block apparently coming out of the dipstick hole as well as from the head to block interface. I had not seen that happen before or since despite many hour at highway speeds but it was doing it on the day and the only difference was that I was reving the motor up to 5500rpm in 4th and then just taking my foot of the gas pedal to let the dyno do the breaking.

 

I am suspecting that my simple PCV valve crankcase ventilation solution is perhaps not fully up to the task and I may have to look at something more sphisticated like Richards full system.

Stan

Ummm. That's the trouble with a shiny engine, you see all the oil leaks. Next time, paint it matt black :P

I'm taking the vacuum off the air plenum, so although I bought Richard's PCV valve I haven't fitted it, as the vacuum take-off is upstream of the butterflies and so is automatically damped by the reduced mass-flow when the butterflies are shut.

I hope :lol:

 

Ivor

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  • 2 weeks later...

I would like to add a general comment to the "crankcase ventilation".

Whatever you do regarding ventilation, MAKE SURE THAT THERE IS NO POSITIVE PRESSURE IN THE CRANKCASE! I have made this experience on several (british) cars of different manufacture (Jaguar, MG, Triumph): as soon as you have the slightest positive pressure in the crankcase, you will get of oil leaks on the crankshaft "seals".

The opposite is also true: if you can create a slight "vacuum" of e.g. 20mm H2O column whenever the engine is running, then you will stop all the common leaks on our Brits!! No need to replace the primitive srewtype seal on the rear crankshaft.

As there is no good permanent sucking device on the engine (the collector depressure is only good at idle), I have installed a little electric pump (or rather blower) which creates a negative pressure in the crankcase as soon as I switch on the ignition.

Wilfried

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I would like to add a general comment to the "crankcase ventilation".

Whatever you do regarding ventilation, MAKE SURE THAT THERE IS NO POSITIVE PRESSURE IN THE CRANKCASE! I have made this experience on several (british) cars of different manufacture (Jaguar, MG, Triumph): as soon as you have the slightest positive pressure in the crankcase, you will get of oil leaks on the crankshaft "seals".

The opposite is also true: if you can create a slight "vacuum" of e.g. 20mm H2O column whenever the engine is running, then you will stop all the common leaks on our Brits!! No need to replace the primitive srewtype seal on the rear crankshaft.

As there is no good permanent sucking device on the engine (the collector depressure is only good at idle), I have installed a little electric pump (or rather blower) which creates a negative pressure in the crankcase as soon as I switch on the ignition.

That's interesting. With my oil separator, and with the standard setup, there is positive pressure when one revs the engine, less positive pressure on idle, and negative pressure on the overrun. I know this because I wanted to check that the oil separator sucks, so I removed the oil filler cap and put some cling film over the hole.

 

I don't really see how there can be other than positive pressure with the engine under load, after all one is trying to compete with the blow-by from 6 cylinders at 220psi or thereabouts, there's no way that the piddling intake vacuum is going to compete with that. I always assumed that so long as one has a reasonable rate of crankcase evacuation, that should be OK ?

 

Ivor

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