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Discussion Starter · #1 ·
Hi All-

I have a single carb 1967 Kadett and am having a bit of an issue with a flat spot between the idle and main circuits in the carb. I've adjusted the accelerator pump to max and it helped but I think there might be an ignition component to the issue. I set up the vacuum advance to run off manifold vacuum so it's more of a vacuum retard but switching it to venturi vacuum doesn't seem to help the stumble. I have the timing set to about 36 degrees total with the vacuum advance disconnected.

What is the best total timing for a 1.1 and am I crazy to use manifold vacuum instead of carb vacuum?

THanks
 

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Can Opeler
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For most cars around 36° is fine. I can’t speak for the 1.1L in general, but I bet you are fine.

I can answer your vacuum advance question though. Hooking up to manifold vacuum will give you full (or close to full) vacuum advance at idle instead of waiting until just after the carb throttle plates open. This is bad for gas mileage and might mess with your tuning of the idle circuit a bit. It’s terrible for emissions too, but a lot of those hot rod v8 guys do it too.
Also it’s not acting as vacuum retard in this set up. It’s still advance. The vacuum retard port on the distributor pulls the breaker plates a different direction is why it retards. Not because of the different manifold port

It’s not your issue though. Does it bog down when it transitions (overly rich) or does it completely die if you hold full throttle and then slowly sputter back (lean)?
 

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Discussion Starter · #3 ·
It's for sure going lean. If you crack it open fast it dies and will recover if you pump it. The car has a free flow exhaust and air cleaner so I have to guess it needs larger jets but I was wondering if there was an ignition component to my problem. I have some bigger jets I'll try tomorrow and will report back.

anyhow, I thought having the ignition advance under high vacuum was good for burning more efficiently but caused more emissions at idle.
 

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Opel Key Master
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Pull the idle jet out of the carb and make sure it is clean and you can squirt cleaner through it. These are usually the problem child with these engines. Also if you are still running points, that could be causing some of your issues. Pertronix is a great idea there. Yes, you should not be running full vacuum all the time from the manifold. You do not want to have the advance circuit going on during idle. You need to establish a solid baseline, and if you have constant vacuum pulling your advance, you will have it backed off to much, because you are compensating.
Digital timing lights are great for seeing where your mechanical advance is at, and then the vacuum advance.
 

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Discussion Starter · #5 ·
Thanks for the reply!

The car has a Pertronix 3 igniter in it already and that seems to work well. Nice to have a built in rev limiter.

Just to be clear, I'm setting the timing using a dial equipped timing light. I have it set to 36 deg at 4k rpm with the vacuum advance disconnected and capped. I am not looking at the idle timing at all since this is a race car and all I care about is what the advance will be at working RPMs. I found that the car is a bit crisper on transition with the vacuum advance connected to main manifold vacuum and seems to burn more of the charge on lift throttle. This would not be a setup I would use for street because of emissions concerns though.

I did some jetting work yesterday and reduced the stumble a lot by going up two steps on the main jet. Car is pretty decent now and makes good power. Let's see how the race this weekend goes though....
 

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Can Opeler
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Sorry to revive an old thread, but this one came up when I searched for the issue I was having with my 1.1L Kadett. It did indeed end up being the idle yet on my car (as Opelspyder suggested to the original poster)

Right after I did a valve adjustment it started running like crap. It was running fine during the adjustment.

The Kadett would start, but randomly started started having a very unpredictable idle that I could compensate for by adjusting idle speed and mixture. Eventually I couldn’t keep up with it and it would start but die immediately after the key was removed. The Kadett doesn’t have a 12v start power to the ignition coil like a GT so I knew it wasn’t ignition related.

Turned out my idle yet got clogged! I cleaned it back up and it idles and runs like a charm. It was just a coincidence that the issue started right after adjusting valves.

I like simple solutions!
 
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