911T distributor
 

Hi,

I have a theoretical question regarding the distributor on my 73.5 T.

In theory, what would be the problems if some previous owner scrapped the CIS injection, installed 40IDA's and done nothing to the distributor?

I have a vacuum advance unit that works but there is nothing to plug into it. It's set at 5ATDC

I've rebuilt the carbs, set the float levels and tried various size jets but am still fouling plugs. Now I'm thinking the ignition may me a problem due to the curve.

It drives well, always a difficult starter when cold and fuel consumption seems lower than I expected...and the fouled plugs.

Many thanks
Mark

I'd try a hotter plug

I've tried that, started with an NGK 8, went for a 7, then a 6. Not really an awful lot of different.

To be honest, it probably was slightly better with a hotter plug, but not much.

Do not focus about the idle timing. Should be 36 BTDC at 6,000+ rpm with the vacuum disconnected and plugged.

Carbs will deliver poorer gas milage than fuel injection.

IDA's do not have a choke, hence hard to start. Someone who knows more about them can give you a decent starting procedure. This thread may be helpful: https://forums.pelicanparts.com/porsche-911-technical-forum/1039078-weber-carb-woes-cold-start.html

There other threads as well. Try a search with the terms "weber cold start"

Before you set the timing, put a few drops of oil on the felt pad in the distributor shaft, points grease where the rubbing block contacts the shaft, and set the Dwell angle to 40 degrees.
The 5 degrees ATDC would be with the vacuum pod connected and working. As Harry stated, since you are not using the vacuum set the maximum advance and let the idle fall where it may.
http://forums.pelicanparts.com/uploa...1734469967.jpg

I would add that it is my understanding that the 5 ATDC was part of early attempts to meet emissions standards.

I can set the timing at 36 at 6k, but the question I would like to know is what would the problems be, if any, not using the vacuum advance on an engine set up that is supposed to have one from the factory?

If it idles ok and it runs good off idle vacuum advance is not your problem. I think you need a smaller jet .. are you running at higher altitude than the previous owner?

I'm not sure, it had 60 idles, I've got down to 55 and it drove better. Have ordered 52's and 50's. 130 mains.