Another Weber Carb question

[Xavier PJB]

Greetings,

I have a 1968 2.0S engine would a set of 40IDA (new) perform less, equal or better than a set of 40IDS ?

(I ordered a set of 40 PMO from a USA reseller but no joy after nearly 8 weeks)

Cheers

[Richy]

40IDS' perform a little better between 6,000 and 7,000 rpm because of the enrichment tubes . The IDAs can be jetted so the difference is negligible .

[1QuickS]

The first 500 2.0 911S engines used 40IDA3C Webers and experienced detonation at max revs and full power due to high piston dome and the inability for the spark to burn the fuel across the dome. To richen the mixture for these engines the IDS was developed using High Speed Enrichment tubes. The earliest 2.0 911S engines used IDA Webers and subsequently suffered piston failure due to weak mixture at top RPM. So the IDS provided a richer mixture at top end without making the main circuit unduly rich, this was accomplished by reducing the main jets size from 135 to 125 and changing emulsion tubes from F26 to F3.

So, yes 40IDA3C Webers will work but be aware that if you push the engine at high RPM you may experience a piston failure.

Disclaimer: The info is to my knowledge correct but is based upon input from knowledgeable sources that I trust and actual factory info regarding the switch from 40IDA3C to 40IDS3C Webers for the 2.0 911S engines after the first 500.

[Xavier PJB]

Thank you for all the inputs.
Have fully restored the IDS and let them a chance to operate on my 2.0S engine - went to a rolling bench for tuning and output is awesome (166 HP)
I also have received a brand new set of 40IDA which I will probably return back to the vendor.

Xavier

[sttoronto]

Can you let me know what you use for all the jetting? Is that with F3 tube?

Who did you use for the IDS rebuild?

Thank you for all the inputs.
Have fully restored the IDS and let them a chance to operate on my 2.0S engine - went to a rolling bench for tuning and output is awesome (166 HP)
I also have received a brand new set of 40IDA which I will probably return back to the vendor.

Xavier

[Xavier PJB]

I did rebuild them myself - took time and patience.

I use :
Main air jets: 187 (custom)
Main fuel jets: 130
Emulsion tubes: F3
Idle jets: 55

X

[sttoronto]

Thanks

Did you use stock Venturi of 32?

Did you have hesitation problem when parked for few days when the engine not warm. If I park for few days, the first 10-15 minutes of the drive I get hesitation over 3k rpm, After 10-15 minutes than it run fine.

[Xavier PJB]

Yep, 32 venturi.

Well, that 2.0S Weber engine is not linear and smooth for sure. It takes 15' to get it running well from cold start, a bit longer in winter of course.

Thanks

Did you use stock Venturi of 32?

Did you have hesitation problem when parked for few days when the engine not warm. If I park for few days, the first 10-15 minutes of the drive I get hesitation over 3k rpm, After 10-15 minutes than it run fine.