Valve clearance to smal

[Pieke]

Dear forum,
I'm rebuilding from scratch a 911 2.2 E engine 1971. This is the constellation: because the old cylinders and pistons were no longer usable, I had to buy new ones. And because the 2.2 was not available, I had to take 2.4 E pistons from Mahle, OE-Nr 911 103 943 02. I kept the crank and rods from the 2.2 E. I had to put 2 copper gasket rings to get a deck height of approx 1.2 mm. The valve lift at TDC overlap is within specs, 3.10 mm.
And this is my problem: the valve clearance.For the intake valve of cylinder 1, at 360° it is 2.5 mm, at 368° it is 2.5 mm, but at 375° it goes almost to zero.
What can I do? Put more gaskets under the cylinder?
Or is there a problem with changing the 2.2 to 2.4 Cylinders?
Thx for your answers.
Pieke.

[Trackrash]

From what I can understand by your description, your cam timing is not correct.

At TDC firing on #1 intake your valve clearance should be .1 mm. At TDC overlap you should have no valve clearance as the valve should be slightly open.

At TDC firing on #1 the punch mark on the cam should be at the top.

I don't see how the cylinder base gaskets have anything to do with the valve clearance.

[Eagledriver]

He’s talking about piston to valve clearance.

You don’t need a lot of clearance. .8mm is enough. You can try retarding the cam slightly. If you have to, you can get deeper pockets cut into the pistons.

-Andy.

[Pieke]

Sorry, Trackrash, that I wasn't clear enough. But it was indeed valve to piston clearance.
@ Eagledriver: I am following Wayne's book, and hè persists that for intake it should be 1.5 and for exhaust 2 mm?
I will first try what the effect is by retarding, since cutting out the heads is a bit more work... .

[Pieke]

Here I am again, about retarding the cam. Since I have replaced the 2.2 by 2.4 pistons, and since they have different specs, which one should one take? And retarding means that the valve lift at TDC overlap ( within specs ) is bigger or smaller?
Thx.

[Eagledriver]

The Porsche workshop manual for the early 911 engine specifys.8mm minimum clearance. Others recommend bigger clearance to be more conservative. Retarding the cam means using a smaller value of intake valve opening at TDC. I don’t know if the problem is from the switch of pistons.

-Andy

[Eagledriver]

I would use the spec for the 2.2 engine. You still have a 2.2 just with different shaped pistons.

-Andy