69 911T with S pistons. Plug Fouling.

[wintersurf]

My recently rebuilt 69T has S pistons and E cams.
I have the Merelli distributor, points, condenser, coil set up.
NO CDI

It suffers from plug fouling. Especially if I let it idle too long.

Reading thru all the pelican and early S threads I see that plug fouling was a common problem with the S type engines but, was resolved when they went to CD ignition.

Most of the threads indicate that going to a MSD or Crane system will resolve the plug fouling.

I would also like to go electronic with my Merelli distributor . Yes I know that I am on borrowed time with the Merelli but I have a good cap and rotor and it works.

alot of the threads I read are 10 -15 years old. Electronics change.
So as of today. What are best solutions available today?

What would you all recommend to accomplish the following.

1) plug fouling - MSD or Crane or ?
2) going electronic with Merelli distributor. - pertronix or Crane Or leave it with points?

Regards.
Doug

BTW -- I did contact thru PM jluetjen and blau911... thanks guys!....who I had followed on some old threads dealing with plug fouling. They both had successfully gone the MSD route.

[911pcars]

Assume you're using the T engine's Webers. Get a baseline confirmation of engine health/integrity with a compression and/or leakdown test before your tuning attempts. Then check your air-fuel ratio (AFR) and adjust the carbs, fuel level, etc. and/or jet accordingly. S cams are peaky and the valve overlap might contribute to a slightly rough idle. A better ignition box will help reduce low-speed plug fouling, but first confirm your idle and low speed mixtures/adjustments are within spec.

BTW, don't think a Pertronix or ? pointless unit is compatible with the factory T Marelli distributor of that vintage. Others might know more.

A Bosch distributor from an E or S would provide a more compatible ignition curve and is physically compatible with a Pertronix, Crane or equivalent pointless unit.

Sherwood

[eastbay]

I'd look into the programmable CD boxes and/or the programmable distributors now available, that is what has changed in the last few years.

[wintersurf]

Sherwood
Thank you for your thoughts.
Just took the car in and had the leak down and Carb adjusted. carbs needed some minor adjustment but are good now . Leak down all less than 2%.

Good thought on the ignition box I just ordered a Bosch CDI box from Bob Ashlock.

Regarding the merelli dist.
I agree ... I am going to look for a Bosch dist from an E or S.

Sherwood
Do you know what model number Bosch dist I should look for?
2.0 Webers.
S pistons
E cams.

Bosch 008 ?
Bosch 002 ?

Regards.
Doug

[911pcars]

It seems Pertronix claims their pointless ignition module fits into all '69 911 distributors (T, E and S). However, I would call and confirm. E and S engines used a Bosch distributor while the T used a Marelli. Back in the 60s/70s, there wasn't a pointless module to fit the Marelli. Maybe now?

The most desirable (and hard to find) distributor is from a 67-68 911S Bosch due to it's aggressive mechanical advance curve, but any of the early 911, 6 cylinder Bosch distributors are good candidates.



The mechanical advance weights/springs of any early distributor can be modified (at cost) if desired. Some are equipped with vacuum advance units, some not. Find one that has little shaft wear. The condition of the cam lobe isn't important since breaker points won't be used.

I'm pretty sure any of the pointless ignition module manufacturers have a distributor compatibility list that accommodates their product.

Hope this helps,
Sherwood

[Quickstep192]

I think if I were replacing the distributor, I’d consider one of these.

https://www.123ignitionshop.com/gb/porsche/94-123Porsche911S.html?search_query=Porsche+distribut or&results=185

[kent olsen]

It's been a long time but I think I ended up putting a Pertronix in my 72T with the Marelli but it did have a CDI box.