911T- weber trouble.

[edmayo]

If nothing else those idle jets are way too big,,,,55 -57.5 maybe even 60,,,,but not 70!

[IanK]

Thanks. I will order smaller jets. Also working on electrical issues. man, this forum is just amazing.

[chris_seven]

If nothing else those idle jets are way too big,,,,55 -57.5 maybe even 60,,,,but not 70!

Totally agree and in 12 years of re-building Porsche carbs I have never used anything larger than a 60 and I would instinctively use a 55 as a starter.

The optimum position for the idle mixture screws is around 2 turns out at 'Lean Best' position.

Much less and you could reduce idle jet size and much more would suggest an increase is needed.

At '70' I am surprised if you could lean it out sufficiently and make it run - hence it is rich all of the time.

With jets this large the adjustment will be very coarse and this will also make it difficult to balance the carbs effectively.

The idle jet will also affect the progression circuit up to around 3000rpm and I am not surprised that is drops cylinders due to plug fouling.

[RW7810]

I can send you an excellent step by step tune up guide by email if you like. Contact me at robertjwilliams74@gmail.com

[1QuickS]

My guess is fuel galleries feeding the idle jet are partially blocked. Installation of larger idle jets over-feeds some cylinders while the others remain lacking for sufficient fuel delivery.

Try removing the lead plugs for the galleries feeding the idle jets, cleaning them out & then install 55 idle jets and perform Lean Best idle mixture adjustments. Check my web page for detailed instructions on the above.