'74 911 CIS install question
 

I have a 1974 911 with a stock motor using CIS injection system. Currently my airbox is blown thanks to a back fire. Yes, I had a pop off valve installed! Turns out a previous owner had glued the airbox back together so the pop off saved it a few times but eventually my number came up and the glue job cracked!

When it failed it split between the lower box into which the 6 intake runners flow and the upper larger box on which the fuel distributor and other parts are mounted. Thus disassembly was with the air box in two parts while reassembly will of course be with the air box in only one piece. Which (finally!) brings us to my question.

Is it best to mount the 6 metal intake runners to the air box before or after installing on the engine? I see two possible reassembly procedures:

1. Remove runners from engine and assemble them to air box on bench leaving clamps on rubber tubes connecting runners to air box loose. Drop CIS/airbox/runners onto engine, align runners to intake studs, tighten nuts on runners, tighten clamps on rubber tubes connecting runners to air box.

- OR -

2. Leave runners on engine and assemble them to air box in engine bay using clamps on rubber tubes connecting runners to air box. Success depends on clearances between ends of runners and their mating flanges on airbox being wide enough to allow me to get the three on the left connected then push the airbox hard left to allow the right side rubber tubes to be installed then center it up and tighten all the clamps.

So, anybody been there done that and taken away some advice for an old DIYer and new 911 owner?

Hi there. Very soon, there will be a tech article on doing this, and also replace a bunch of other seals (replace your other seals, thermostat, and oil pressure, etc. when you replace the box).

I would attach the runners to the manifolds,and then place them on the box, without tightening. Then, place the system on the engine, and make sure that you have them aligned so that you can tighten the clamps. Bolt down the manifold, and then tighten up the clamps. That seems to be the best solution for me.

Hope this helps,

Wayne