Weber Carbs Diff Between IDA IDT IDTP

[Dogbreath]

I recently purchased a set of Weber 40IDTP13C carbs. I was told by the seller that the carbs were from a 1971 911T engine. Given that, I made the incorrect assumption that they were 40IDTP3C carbs from a non-USA car.

Now that I have the carbs I see that they are actually 40IDTP13C carbs. These were apparently original equipment on the 914/6 and as mentioned above and "were reversed from the original orientation of the rear engine cars". I am a little unclear on the meaning of that and basically would like to know if these carbs could be used on a 911T engine to replace the stock Zenith carbs and if so, without getting too technical, what the difference between the 40IDA and these would be. Thank you for any assistance.

[1QuickS]

They should bolt on and work fine on your T. IDAs tend to be better for engines with a little more performance due to a richer progression at transition onto the mains. The throttle cross bar on the Zeniths is different from that used for Webers so you will need to source one of those.

[DarthMJH]

I have an 1973 911T 2.4 running Zeniths, I am thinking of replacing these with Webers. Which version is the best to install IDA IDT IDS etc?

Thanks

Mike

[1QuickS]

Hands down IDAs, Made in Italy and (this is the tough part) in good mechanical condition unless you are OK with refurbishment. Expect to replace most of the jets when changing carbs. Also, the Zenith throttle cross bar is unique to Zeniths. You can source a used Weber cross bar or buy a new one from PMO.

[RWebb]

why not use PMOs? He improved on the Webers.

[Grady Clay]

Wonderfully poor 2008 non-response on my part – a 5-year ago post I didn’t see.

Originally Posted by tonybuono

Thanks Grady:
The car is a Red '67 912 soft window Targa with an '68 911T engine (ser 2080872) that was replaced by Germa(n) Equipment Co, 931 W. 5th Ave, Denver on 4/5/72. This car was originally owned by Don McDonald. The carbs are jetted as follows:
Main 1.25
Idle 0.60
Air corrector 1.80
Accel jet 0.50

In the Haynes Weber Manual, I find jets for the 40IDTP13C1 (and 3C/1) as follows:
914/6 (911T)
Main 1.05 1.10
Idle 0.50 0.45
air corrector 1.70 1.85
Accel jet 0.50 0.50

I'm also checking the float levels. There is an extra washer (a shim?) on each of the needle valves, I presume to adjust the float level. I have a PMO float level gage. Is using a "shim" washer the method of adjusting the float level using this gage? And, is this a better method to adjust the float level then bending tabs? (I bought the gage when I was going to rebuild the carbs on my '65 912 but never used it as I installed Webers instead.)

Thanks for your help. Tony (btw, I used to live in the Denver area off 285 in Aspen Park near Conifer)

Yes, that was me: dba German Equipment Co., 931 W 5th Ave, Denver; aka “The Hobby Shop”.
John Eiesebud was my first mechanic and probably did this work.
I think at this time we may have moved to 350 Broadway, perhaps still using “931” invoices.
John was a wonderful Porsche technician and after working for Rennenhaus for a number of years went off to start his own shop Eisenbuds-Fine Service of Porsche, Mercedes, Audi and VW 303.825.0322.
He is still running it after more than 30 years.
John is a good friend at our lame old ages and still one of the most skilled MFI tuners in the world. I paid for his training at Bosch in the early ‘70s.

Yes, engineering progress.
The PMOs are far better engineering than the original Webers.
Yes, original Webers can be reconditioned to be similar to the PMOs.

Best,
Grady

[911pcars]

"The carbs are jetted as follows:
Main 1.25
Idle 0.60
Air corrector 1.80
Accel jet 0.50"

My factory stock 69T had similar specs. In addition, I installed 30mm venturis (up from 27mm).

FWIW,
Sherwood

[DarthMJH]

Originally Posted by 1QuickS

Hands down IDAs, Made in Italy and (this is the tough part) in good mechanical condition unless you are OK with refurbishment. Expect to replace most of the jets when changing carbs. Also, the Zenith throttle cross bar is unique to Zeniths. You can source a used Weber cross bar or buy a new one from PMO.

Thanks for the reply. I thought the cross bar was the same for both Zeniths and Webers so appreciate the tip.

[Matt Monson]

All these years later and there's Grady still helping. I googled the carbs I have on my car and he's the first result. Thanks brother. You were one of a kind. RIP.