Larger Venturi for Zenith TIN40 on a 2.4L? Options

[Tdskip]

The 74 914/6 build has a 2.4 L MFI engine in it that came to me running Zenith 40 TIN.

I spoke with a Zenith specialist and he said that a 34m Venturi would be a bette match for that engine displacement and it’s an easy change to make along with some jetting changes etc.

This seems a whole lot more cost effective than going to Weber 40ida that are $3,000 +/- just for cores.

Anyone here have experience with this they can share?

Thanks!

[930cabman]

I have twice overcarburatored Porsche engines. Once with a 2056, went with 36 vents, just wouldn't draw, ended up with 32's, runs great and gets great gas mileage. A fresh 2.7 I went with 36's and again, tooo large. Also ended up with 32's

My suggestion would be to try 28's and go from there

All the above is with Webers, 40 IDF and 40 IDT 3V

[Superhawk996]

I have twice overcarburatored Porsche engines. Once with a 2056, went with 36 vents, just wouldn't draw, ended up with 32's, runs great and gets great gas mileage. A fresh 2.7 I went with 36's and again, tooo large. Also ended up with 32's

My suggestion would be to try 28's and go from there

All the above is with Webers, 40 IDF and 40 IDT 3V

(IMG:style_emoticons/default/agree.gif)

America is the land of overcarburation.

The chart below is for Horsepower not drivability. Usually 4-6mm smaller than this chart recommends for good vacuum signal, air velocity, and driveability. You give up a tiny bit in the top end but unless you’re on track - you’re not running at redline for any significant part of a drive.

The TiN were for 2.2L and they come with 27.5mm Venturis. So are we to believe that Porsche didn’t know how to tune? By the time you get to 32mm you’ll start trading throttle response for top end gains.

For a 2.4L you’re going to be about 30mm which will probably work a little better with the MFI cams (assuming that’s what’s still in it).