Vacuum hoses for a late 75 2.0l Porsche 914, Is it ok ? Options

[Villemi]

Hello

I have december 75 2.0l Porsche 94

My car is an US one and had a canister and air pump.

For late 74 diagram it was this one

(IMG:http://www.914world.com/bbs2/uploads_offsite/i48.servimg.com-23807-1640074350.1.jpg)
I don't have any more the canister and the air pump

My car has no anti flash back valve too.

Are you agree with the new diagram for my late 75 car ?

(IMG:http://www.914world.com/bbs2/uploads_offsite/i48.servimg.com-23807-1640039023.1.jpg)

It's difficult to understand when you have a 46years old !!!

[BeatNavy]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi in Hg (EDIT: corrected to in Hg) at wide open throttle to somewhere over 22 psi in Hg (EDIT: Corrected to in Hg) during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 in Hg?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

[Villemi]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi/bar at wide open throttle to somewhere over 22 psi / 1.5 bar during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 psi?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

Yes thank you,

And for the fashback valve ? Mandatory ?
I don't understand where the hoses ar connected on the engine
Pics possible ?

[DRPHIL914]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi/bar at wide open throttle to somewhere over 22 psi / 1.5 bar during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 psi?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

Yes thank you,

And for the fashback valve ? Mandatory ?
I don't understand where the hoses ar connected on the engine
Pics possible ?

@Villemi

in 1975-1976 the factory did not put head vents on these cars and therefore no antiflash back valve, futhermore if you look at the research on this by LN engineering, Len Hoffman and Jake Raby did they found it better NOT to vent the heads( i just found this out last week and read thru all their research and documentation they did)
- so you can follow the diagrams but if your heads are US heads with no vent then you will not hook up the anti-flash back valve.

ALSO 75-76 US cars did not have a PVC the factory deleted it. I would not use a PVC , the stack at the oil filler is different, but what i would do and oh i did do is i connected the crank case vent hose to a catch can and that to the air cleaner. That will keep the oil vaper out of your air filter like Jeff said. If you put the hose to the manifold like the early cars had you are going to have what will amount to a high idle due to pulling too much air , just like a vac leak.
- so - late cars had no PVC no head vents and no flash back valve.

Phil

[TX914]

I have a 76 and I'm in agreement with @DRPHIL914 . I also recommend running the decel valve.

[DRPHIL914]

I have a 76 and I'm in agreement with @DRPHIL914 . I also recommend running the decel valve.

(IMG:style_emoticons/default/agree.gif) i left that off but i think that is the general concensus that with Djet you should have the decel valve hooked up, to help prevent an issue with the MPS- i need to put mine back on.
one other issue is that in the US these cars had the smog pump too but those are long gone and i have never seen a car with one on that worked, so there would be that air injection port on the head at the exhaust port that would be plugged if all the smog stuff is removed.