Hi,
I'm new to the forum and new the V8 engine so go easy on me. I have a Porsche 924 with a TVR derived 3.5 V8. I believe the engine would originally be EFi but now has Edelbrok 4 barrel CFM500. My question is about the oil breather setup. Looking at engine from the front, the left cover has cone type breather, the right has a small pipe with like a round table top with just a pin prick of a hole. I'm sure something is missing or should be connect back to the air intake maybe. Any advice or suggestions?
I'd post some pics but dont seem to have the option to do so.
Rocker Cover Breather Setup
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Rocker Cover Breather Setup
Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten
Porsche 944 2.5 Lux gone but not forgotten
Thanks. That's helpful. Just so that I am clear and order the correct parts...
In your pic back right the chrome tube is a flame trap and or PCV valve which would connect via a tube to the PCV port on the front of the Edelbrok carb. This is effectively the ventilation port for the crankcase gasses.
The mushroom with plastic cap and filter is a fresh air intake and can be replaced with a pipe to the underside of the carb air filter (possibly if I can get the mushroom off and replace with a pipe).
In your pic back right the chrome tube is a flame trap and or PCV valve which would connect via a tube to the PCV port on the front of the Edelbrok carb. This is effectively the ventilation port for the crankcase gasses.
The mushroom with plastic cap and filter is a fresh air intake and can be replaced with a pipe to the underside of the carb air filter (possibly if I can get the mushroom off and replace with a pipe).
Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten
Porsche 944 2.5 Lux gone but not forgotten
Prophead wrote:Thanks. That's helpful. Just so that I am clear and order the correct parts...
In your pic back right the chrome tube is a flame trap and or PCV valve which would connect via a tube to the PCV port on the front of the Edelbrok carb. This is effectively the ventilation port for the crankcase gasses.
The mushroom with plastic cap and filter is a fresh air intake and can be replaced with a pipe to the underside of the carb air filter (possibly if I can get the mushroom off and replace with a pipe).
The chrome jobbie is just a breather with flame trap mesh inside. The black jobbie is also a breather with a smaller hole. This will allow vapours in and out as will the chrome one. But its mainly for filtering air into the crankcase if the crankcase pressure goes negative. Neither of these are PCV valves. As that setup stands the black one stays as it is and the chrome one should be piped into the air filter. If you pipe either of those into the pcv port on the carb the engine will lean out and probably have an out of control high rpm idle.
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
Finally got my solution for this. I didnt have clearance under hood for the same style of breather so have used an in line one as per landrover I think. This is then piped to an oil catch can as I want to minimised the amount of oil going back through the carb. The catch can in turn is connected to the carb air filter. On the other side I have the small mushroom filter.
When I can work out how to post a single pic I will
When I can work out how to post a single pic I will
Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten
Porsche 944 2.5 Lux gone but not forgotten
Final mock up of the breather system
After a lot of research, and head scratching it is finally sorted. I ended up having to create my own cap for the left hand rocker cover because the TVR one was too tall. I separated the cone filter the car came with and used the base, into which I inserted a rubber grommet. Into this is inserted a pipe union with sealing washers either side of the grommet then nipped up from the underside with a nut, this should create a decent seal and is pretty sturdy. To the top side of the union is fitted with a 90 degree fixing onto which is scewed a hose barb. I am using ID 15mm (1/2 inch) hoses for this part of the setup. As stated before, this connects to an in line firetrap then to 3/4 liter oil catch can and finally back to the carb air cleaner.
The blue hose in the pics was supplied wiith the catch can, it will be replaced with black hose. I'm going to use this blue hose initially because it is see through so I can easily check that the setup is working as it should. Once happy I will switch the hoses.
https://www.flickr.com/photos/144556909 ... res/18Zyg2
The blue hose in the pics was supplied wiith the catch can, it will be replaced with black hose. I'm going to use this blue hose initially because it is see through so I can easily check that the setup is working as it should. Once happy I will switch the hoses.
https://www.flickr.com/photos/144556909 ... res/18Zyg2
Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten
Porsche 944 2.5 Lux gone but not forgotten
Looks pretty good so far Sean!
But remember the hose fittings have a smaller bore than the hose. The elbow looks to be 8-10mm bore? There is plenty of metal that can be bored out here.
The old 3500 engines had two rocker breathers via flame traps into the air filter area as well as the small breather filter at the back of the lifter gallery.
These lines were the same bore as the in line flame arrestor you have fitted.
So at the moment you have a system that is about 50% smaller in air flow / vapour flow potential than it could be.
If you are going for a simple breather system like that with no pcv setup you may as well make another breather for the other rocker cover. The small vented filter wont really do anything with what you have now so you may as well run a larger breather from the other rocker cover as well with a flame trap like the other side.
If you intend to keep the single catch can then increase the inlet and outlet connection sizes. Make sure the inlet connection has a port with a free area the same size as your two small hoses. Then make sure the outlet hose to the fliter has a bigger bore to suit.
I'm not trying to be a killjoy mate. I've been through this many times with breather systems.
It may be that your engine and what you put it through wont need a big breather system. I can only comment on my past experience with my engines. If your engine is tip top and doesnt suffer much blow by under load then what you have may be ok for your application. But as you are talking aobut a track day car I'm assuming the enigne will be running high rpm for good chunks of time? If this is the case then Breathers need to be as big as possible.
The restricted "IN" breather on one rocker cover with your setup wont do anything. If you find after some miles that the filter in the restricted breather becomes clogged with oil, that means the other large breather isnt big enough?
Just my thoughts mate.
Regards
Perry
But remember the hose fittings have a smaller bore than the hose. The elbow looks to be 8-10mm bore? There is plenty of metal that can be bored out here.
The old 3500 engines had two rocker breathers via flame traps into the air filter area as well as the small breather filter at the back of the lifter gallery.
These lines were the same bore as the in line flame arrestor you have fitted.
So at the moment you have a system that is about 50% smaller in air flow / vapour flow potential than it could be.
If you are going for a simple breather system like that with no pcv setup you may as well make another breather for the other rocker cover. The small vented filter wont really do anything with what you have now so you may as well run a larger breather from the other rocker cover as well with a flame trap like the other side.
If you intend to keep the single catch can then increase the inlet and outlet connection sizes. Make sure the inlet connection has a port with a free area the same size as your two small hoses. Then make sure the outlet hose to the fliter has a bigger bore to suit.
I'm not trying to be a killjoy mate. I've been through this many times with breather systems.
It may be that your engine and what you put it through wont need a big breather system. I can only comment on my past experience with my engines. If your engine is tip top and doesnt suffer much blow by under load then what you have may be ok for your application. But as you are talking aobut a track day car I'm assuming the enigne will be running high rpm for good chunks of time? If this is the case then Breathers need to be as big as possible.
The restricted "IN" breather on one rocker cover with your setup wont do anything. If you find after some miles that the filter in the restricted breather becomes clogged with oil, that means the other large breather isnt big enough?
Just my thoughts mate.
Regards
Perry
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
mgbv8 - no worries mate I appreciate the input, I'm on a steep learning curve with this engine so the input is welcome. The fittings on the cap I made are 10mm ID and at least as big as the flame trap ID. On the catch can I have used the largest fittings it came with which are ID 12mm I think. At least with this approach I can revert to the cone filter if needs be until I come up with something else.
I originally wanted to go for a PCV set up but getting hold of suitable components proved very difficult.
I have a lot of other jobs and projects to do on the car so I will leave this as is for now as I want to get it driving again before the MOT runs out so that I can test and setup brakes and suspension ect. I'll run it for a few hundred miles with this config of breather and see how it goes. If needs be I can modify it over the winter.
cheers
so the input is welcome. The fittings on the cap I made are 10mm ID and at least as big as the flame trap ID. On the catch can I have used the largest fittings it came with which are ID 12mm I think. At least with this approach I can revert to the cone filter if needs be until I come up with something else. I originally wanted to go for a PCV set up but getting hold of suitable components proved very difficult.
I have a lot of other jobs and projects to do on the car so I will leave this as is for now as I want to get it driving again before the MOT runs out so that I can test and setup brakes and suspension ect. I'll run it for a few hundred miles with this config of breather and see how it goes. If needs be I can modify it over the winter.
cheers
Porsche 924 GTv8 Track-day car project
Porsche 944 2.5 Lux gone but not forgotten
Porsche 944 2.5 Lux gone but not forgotten
Stick with it Dude!
You only learn by doing it for yourself and seeing what happens eh
You only learn by doing it for yourself and seeing what happens eh
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
