924Board.org

[Motorheadmike]

Does anyone know if a brake booster from a 924S/944 work for a 931?

Thanks, Mike
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1981 931 series2

[gohim]

The brake vaccum booster has been transplanted in 924 chassis before by the guys that have done V8 conversions. It is shallower in depth, and larger in diameter, which makes it fit closer to the firewall.

I don't know if it has been done reusing the original 924 master brake cylinder. The swap to the 944 vaccum booster is usually accompanied by a changeover to the 944 master cylinder as well. The 944 master cylinder is machined with a step, meaning that the front and rear sections are different diameters, and different amounts of fluid are pumped to the front and rear brake circuits when the brakes are activated. Since the 924 is plumbed for diagonal braking, and the 944 has front and rear braking circuits, this means to use the 944 master cylinder, you must rearrange or replumb the braking circuits.

Also, if the 924 master cylinder can be sucessfully used with the 944 vaccum booster, you may find the brake pedal overly sensitive, since you will have boosted the amount of vacuum available without increasing the amount of effort needed to activate the brake pedal.

Go to the engine conversion discussion area, and leave a message. A member by the name of Porschev (or another member who has done a engine conversion) can better answer questions about brake modifications of this sort.