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 Spark plugs- hotter baby?
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Derek
V4 Guru

United Kingdom
2018 Posts

Posted - 24 Sep 2020 :  11:39:46 Show Profile Reply with Quote
The dribble could well be due to too high a float level. Yes it is showing as on the line but you could try it a fraction lower. I noticed a similar dribble when I had a leaky and heavy float in the FoMoCo. The dribble floods the manifold. Obviously an electric pump will do this easily with the ignition on but with the mechanical it will also flood the manifold if it doesn't start immediately and you keep on churning.
Would the Nikki needle valve allow you to add a washer to lower the level? Some floats don't have an easy to adjust tab to set the level.
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Jimmys old Saab
V4 Beginner

United Kingdom
98 Posts

Posted - 26 Sep 2020 :  18:31:01 Show Profile Reply with Quote
Hello again; the fuel level is exactly on the line- apparently it is critical for fueling that it is on these Nikki carbs.
However I have taken another look at the 96 this afternoon. I had already found out that winding the idle screw out several turns seemed to help starting. This time around I blipped the throttle a couple of times- sure enough, I could see the accelerator pump squirting fuel into the secondary venturi. Then I pulled the choke and she started.
As I said earlier I suspect that now starting is relatively easy the car will idle too rich. So the carb and engine do not match as well as I'd have liked but that's no surprise, it will do for now until the car has gotten some miles under it's tyres.


Saab 96 1971
Datsun 120y coupe 1975
Saab 9000 CSE turbo 1993
VW T5 LWB 2012
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Jimmys old Saab
V4 Beginner

United Kingdom
98 Posts

Posted - 26 Sep 2020 :  18:33:30 Show Profile Reply with Quote
Melle- what is your email? I will send you some pics of the carb in situ.

Saab 96 1971
Datsun 120y coupe 1975
Saab 9000 CSE turbo 1993
VW T5 LWB 2012
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 26 Sep 2020 :  19:35:14 Show Profile Reply with Quote
saabv4[at]saabv4[dot]com I think I have a Nikki manual PDF, if you email me, I'll send it with my reply if I can find it.

www.saabv4.com
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Jimmys old Saab
V4 Beginner

United Kingdom
98 Posts

Posted - 23 Apr 2021 :  22:51:22 Show Profile Reply with Quote
The problem with starting appears solved. Firstly, the rocker cover to carb intermediate plate hose is not in position so the port to the plane was open, hence a source of air to the inlet manifold. I plugged the hole. That may make some difference but there are oily fumes going in there anyway so maybe not...I would imagine that would alter the fuel/air mix anyway?
Secondly I am convinced that air velocity into the engine is much reduced from normal because of the size of the venturi of the twin choke carb. At start up the engine struggles to pull enough air into the engine. A bit like trying to suck lemonade through a hosepipe as averse to a straw. What made a difference was adding an air filter to the carb and pumping the throttle at least three times. The carb is so much bigger than the original FOMOCO that I'm convinced that the engine's volume is insufficient to gain enough velocity on start up to draw fuel from the jets into the mix. Choking the venturi with am airbox is sufficient to increase the speed of the charge.

Saab 96 1971
Datsun 120y coupe 1975
Saab 9000 CSE turbo 1993
VW T5 LWB 2012
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 24 Apr 2021 :  09:18:22 Show Profile Reply with Quote
quote:
Originally posted by Jimmys old Saab
Firstly, the rocker cover to carb intermediate plate hose is not in position so the port to the plane was open, hence a source of air to the inlet manifold. I plugged the hole. That may make some difference but there are oily fumes going in there anyway so maybe not...I would imagine that would alter the fuel/air mix anyway?
Not a good idea not to have a functioning PCV system in my opinion, the pressure will build up and eventually escape somewhere (through a seal, rocker cover gasket, dipstick tube etc.). See https://en.wikipedia.org/wiki/Crankcase_ventilation_system and/ or the workshop manual.

quote:
Originally posted by Jimmys old Saab
Choking the venturi with am airbox is sufficient to increase the speed of the charge.
If the air filter is indeed that restrictive it's either horribly dirty or way too small too small I suppose?

www.saabv4.com
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Derek
V4 Guru

United Kingdom
2018 Posts

Posted - 24 Apr 2021 :  14:32:05 Show Profile Reply with Quote
The hose from the cover to the carb should probably have a very small metering valve or a one way pcv valve or both. An open hose will have really bad effects on the mixture being effectively a massive air leak. The hose from the cover can go to a spigot on the engine side of the air filter as per original. There is a thread on doing this with an aftermarket filter for the Weber ICH on here somewhere.
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Jimmys old Saab
V4 Beginner

United Kingdom
98 Posts

Posted - 24 Apr 2021 :  18:19:54 Show Profile Reply with Quote
quote:
Originally posted by melle
quote:
Originally posted by Jimmys old Saab
Firstly, the rocker cover to carb intermediate plate hose is not in position so the port to the plane was open, hence a source of air to the inlet manifold. I plugged the hole. That may make some difference but there are oily fumes going in there anyway so maybe not...I would imagine that would alter the fuel/air mix anyway?
Not a good idea not to have a functioning PCV system in my opinion, the pressure will build up and eventually escape somewhere (through a seal, rocker cover gasket, dipstick tube etc.). See https://en.wikipedia.org/wiki/Crankcase_ventilation_system and/ or the workshop manual.

quote:
Originally posted by Jimmys old Saab
Choking the venturi with am airbox is sufficient to increase the speed of the charge.
If the air filter is indeed that restrictive it's either horribly dirty or way too small too small I suppose?

www.saabv4.com



You've mixed up what I was saying there; I have plugged the carb plate, not the hose on the rocker cover, that is just venting to atmosphere.

Saab 96 1971
Datsun 120y coupe 1975
Saab 9000 CSE turbo 1993
VW T5 LWB 2012
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 24 Apr 2021 :  18:41:44 Show Profile Reply with Quote
I sort of assumed you plugged the rocker cover too, but either way you no longer have a functioning PCV system. The oily fumes that normally go back into the intake are recirculated within the engine, so they're part of the metered (by the carb throttle plates) air intake volume. If the port is left open unmetered air messes up the mixture (i.e., leans it out). Was there any particular reason for removing the PCV valve?

www.saabv4.com

Edited by - melle on 24 Apr 2021 19:16:23
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Jimmys old Saab
V4 Beginner

United Kingdom
98 Posts

Posted - 25 Apr 2021 :  16:27:20 Show Profile Reply with Quote
I just dont have a suitable piece of hose, it needs a piece with a 90 degree kink in it. The PCV I still have from the old set up and will re-use. No reason why you couldn't vent to an oil catch pot though is there?

Saab 96 1971
Datsun 120y coupe 1975
Saab 9000 CSE turbo 1993
VW T5 LWB 2012
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 25 Apr 2021 :  16:46:43 Show Profile Reply with Quote
You can vent to a pot, but then you won't have the advantages (for both your engine and the environment) of a fully enclosed PCV system. I have a catch can between the rocker cover and the PCV valve, it catches rather a lot of oil, so worth fitting in my opinion. john-saab on here stocks the original shape hoses I think, they're a weird shape and pretty much nothing else will fit as most hoses will easily kink due to the compound narrow bends. Samco may also do them in silicone iirc?

www.saabv4.com
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EdinburghJoe
V4 Fan

United Kingdom
119 Posts

Posted - 26 Apr 2021 :  12:56:22 Show Profile Reply with Quote
Someone on this forum a few years ago suggested inserting a spring into a normal length of silicon hose to prevent it folding flat on the tight bends for this pipe. It locks very firmly into position on the bend so it won't move up and down the pipe. I used the spring from a door stop - pretty much the right size and it has been doing the job for me over the last few years.
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 26 Apr 2021 :  13:24:27 Show Profile Reply with Quote
That's a clever solution Joe.

www.saabv4.com
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