HELP INSTALLING 40ida on 1973.5 911T

jyporscheboy · 08-31-2011, 08:32 PM

I am considering putting 40IDA Weber carbs on my 1973.5 911T .. Anybody have experience in this project .. Any help or suggestions will be greatly appreciated ..

Bobboloo · Bobboloo's Garage

Great picture. Beautiful car.

Carbs could be installed but in my opinion your much better off with the CIS induction. Carbs are great for throttle response but they come at a price. Reduced gas mileage, tempermental cold running and starting.

CIS when calibrated properly is much easier to live with.

Should you decide to go the carb route you'll need the 32mm intake manifolds that Weber made for the 2.0 and 2.2T motors. Your ports are 30mm so it'll be a slight mismatch but it's the best you can do off the shelf.

Then I suggest you have a reputable shop that's familiar with these old Porsches and has an old fart who knows how to tune Webers and have them set them up with the proper jetting. Even better buy a set of PMO's and tell them what motor they are for and have them jet them before they ship. Then only minor adjustments may be needed.

Again if it were my car, I'd keep the CIS but it's not so do your thing.

E Sully · E Sully's Garage

Here is a link for the cis if you need information on getting it set up. The 73.5 is a little different from the later ones, no thermo time switch and injectors in the head instead of the intake runners.
CIS Primer for the Porsche 911

lindy 911 · lindy 911's Garage

I have 46 Webers on my 3.0 and love them. I have no problem with cold starts and the low mileage thing is confusing to me. If you keep a steady throttle on the highway and stay out of the accelerator pumps mine gets around 20 mpg. No, it's not 26 like some claim they get, but I've never seen 26 mpg with my car even stock.

Carbs, whether Webers or PMOs, add so much character to a 911 it's hard to explain. It will definitely wake it up. Tuning takes a little practice but you can become an expert in little time. Once the carbs are jetted and adjusted properly, you're done. If you need specific parts list information look for "onequickS", Knightrace or Henry Schmidt at Supertech. They are all very knowledgeable people.