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blackhat

Hey all!

I've finally got my manual in so I don't feel so lost looking under the hood now. But, I'm still confused on the vacuum stuff.

The CIS system was pulled off and a single Weber carb sits on what looks to be where the top of the intake was. I'll post pics of it tomorrow so it all makes sense.

Where I'm confused at is the vacuum system now. There wasn't a really good vacuum diagram in the book. I found a great post a little bit back about how there are to vacuums that go to the distributor so that made a huge difference. The previous owner had manifold vacuum going to the advance and nothing going to the retard. I found the ported vacuum on the carb and hooked that up to the advance and moved the manifold vacuum to the retard. That's right...right?

So, now she doesn't backfire out of the carb but, it seems like she backfires out of the exhaust. No matter how far I advance it, she'll backfire out of the exhaust manifold. It's only on a deceleration. She accelerates pretty strongly, but when I come off the throttle, there's kind of a steady thing of backfires till it comes back down to idle, kind of like a gurgle. Is there too much vacuum coming from either the manifold or ported vacuums on the carb?

Once thing I did notice is that the PVC port on the crank case is just cut at the elbow and going no where. I'm read that the PVC hose shouldn't go to manifold vacuum, but what about ported? Since I don't have the whole intake system anymore, I can't really run it back to the intake system before the air filter. Could not having any vacuum to the PVC port causing any decrease performance or be causing the back fire? Should there be vacuum to the PVC system or just pop a filter on it?

Also, my vacuum system is just a FUBAR'ed mess. These guys had no idea what they were doing with the car before me (the idle fuel screw was backed all the way out for cryin out loud). Does anyone have a decent vacuum diagram I could use?

Thanks all!
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My First Porsche
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1978 Porsche 924 N/A

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

The retard function is only there as an emission control measure. Euro spec cars dont have one.

Try disconnecting the vacuum retard line from the distributor (and block off the hole at the manifold) and see how that goes.

If it's a legal requirement for your smog tests (or whatever) you can always reconnected for the test and remove it when you get the car back home.

_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

blackhat · Posted: Wed Apr 30, 2008 10:11 pm Post subject:

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

I don't think you need to go to the length of getting a Euro dizzy. Once the retard vac connection is removed, it'll work pretty much like a Euro dizzy anyway, provided you set the timing in the same way. i.e. set 10° BTDC with both vacuum connection removed (and plugged at the manifold end).

As for the PC, it would normally go into the inlet tract or the air filter box. Is there any way of connecting it in upstream of you carb...? If you do that you ought really have a valve to protect it from the vacuum under WOT conditions... Otherwise just have it going into the outside air via a filter, I suppose...

I can't comment on the vac. tanks. I've never seen that on a Euro set-up. Sorry.

_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

blackhat · Posted: Wed Apr 30, 2008 11:45 pm Post subject:

Thanks for the tips on the dizzy. I'll be sure to time it tonight with both lines off and capped @ 10° BTDC and then hook the ported vacuum line back to the advance.

With the PCV stuff, I was thinking of how to bring it back up to the carb but there isn't a cover around the air filter like in older cars. It's just an air filter on the throttle body. I thought about drillin' out a hole on the bottom plate inside the air filter and putting a barb on it and running the line up to that. But, then it's inside the air filter and it's supposed to be outside the air filter I though. Should I just put a PCV valve on it and a filter?
_________________
My First Porsche
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1978 Porsche 924 N/A

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

From what I can remember of older carb set-ups, the PCV usually goes inside the filter. Otherwise the filter would clog with oil very quickly. So if you're able to fit a barb there, that's a pretty good place for it, I would say.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

Lizard · Posted: Thu May 01, 2008 1:19 am Post subject:

that sounds like a standard amc pacer intake manifold.
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3 928s,

blackhat · Posted: Thu May 01, 2008 3:45 am Post subject:

Is there going to be any performance increase to hooking the PCV back into the intake (creating a slight vacuum)? I'm not really looking at an emissions stand point since I don't have any smog tests here. I'm just tryin' to get her to run a little stronger.
_________________
My First Porsche
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1978 Porsche 924 N/A

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

If you reinstall the FI the engine is going to run better, and stronger. when cold as well as warm.

The engine only produces 110hp, just are you expecting in performance? Every modern car out there is going to out drag it. 924s are made as touring/turing car, as ware most of it's relatives. That's the way it is..

The Mickey Mouse carb you have is never going to work right. Id you want the engine to run the best it can, restore the car to original configuration.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

On the other hand, if you really like carbs and want to improve performance, I have a dual Weber as well as dual Dellorto carb setup, each complete with manifold, that I could be persuaded to part with...
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erstwhile owner of just about every 924 variant ever made

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

blackhat · Posted: Mon May 05, 2008 3:09 pm Post subject:

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Yes, plus:

...air meter (usually comes with the fuel dizzy), filter box, aux air valve, cold start valve, injector seats, fuel pump relay, banjo bolts, return fuel line back to the tank, accumulator(s), fuel filter, in-tank pump (poss.), hot start valve, thermo switch, thermo-time switch, intake boots.

Maybe some of these items are already on your car...

Your cheapest option might be to get the whole shebang from a scrap car. Then, of course, you'll have to set the whole thing up from scratch...

It intrigues me when you say 'the rest of the manifold'. The 924 inlet manifold is a one-piece unit that joins to the throttle body with a vertical face. You seem to be describing something with a top-mounted carb. Either the original manifold has been severely modified, or you have a manifold from a different car... Either way, you'll need the 924 unit if you're going back to CIS.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org