Weber Carb Fouling Plugs

[mduck]

I have Weber 40IDS carbs on my 1965 911 and one of them is fouling all three plugs on one side only. When the carbs were swapped side to side the fouling problem followed the carb. Any ideas? The carbs were both rebuilt by Pierce Manifold and the problem carb was sent back to be gone through again but it is still fouling plugs.

Also, on a separate note, which MDS ignition system would be recommended for a '65 911?

Thanks!

[1QuickS]

Hi Mike,

If the Colortune I sent indicates idle mixtures are good and the fouling occurs during driving then one thing I didn't mention earlier is that there may be a fit-up issue between the auxiliary venturis and the main throttle body that allows unmetered fuel to be sucked into the throttle bores.

Also, it bears repeating that float levels need to set using the vial gauge and that they be observed with the engine running, static setting is not adequate. Fuel pressure should be checked to be 3.5 psi, again with the engine running. There is also the issue of the tabs on the fuel floats having divots from wear, these divots can cause side loading of the needle tips which will affect fuel metering. You can see the divots I reference here: http://performanceoriented.com/technical.htm#FuelFloat. And finally, if the geometry of the floats has the tab adjusted so that it is not nearly perpendicular to the axis of the needle then this will also contribute to side loading of the needle tip. Of course, if the floats are installed upside down then the geometry is way off. I can send a drawing of the float geometry id you like.

[mduck]

Thanks Paul! I appreciate the time you spent with me and Karl on the phone too. We are on a mission to figure this out. Also, I called Pelican about an MSD ignition but they were unsure of the correct model. If you know which MSD I should get, I would appreciate it. I ran into another local mechanic at the post office and he said that was one thing he has noticed in common with all early 911's that run well - that all have MSD ignitions.

[sithot]

MSD 6A or AL; Most any parts warehouse can get one in a hurry. JEGS, Pegasus, Summit Racing etc.. Shop around.

[mduck]

Paul - your are our hero! For you to properly diagnose our Weber 40IDS problem as having the wrong idle jet holders OVER THE PHONE is impressive. The car is finally running like a Porsche. We appear to still have a distributor problem but we hope to get that taken care of this week and we are installing an MSD 6A so I'l let you know how it goes. Thanks again for all your help. I would recommend you to ANY early Porsche 911 owner!

[vickcraw]

Glad to hear that you are making progress on this.