Kenny Bradley

Just out of interest I have just cut open 2 hydraulic tappets. I have included a photo, a very amateurish drawing and my interpretation on how it works. Please correct me if ive got it wrong.

Pressurised oil inside the cam housing enters the 1.5mm port then the 2.5mm port where it has access to the 1mm port in the piston. It will open the check valve and fill the space behind the piston pushing it out untill all tappet clearance is removed.

The oil pressure, however, is not enough to force the engine valve open. When the cam starts to press down on the tappet the check valve closes preventing any oil from escaping from behind the piston. The tappet cannot compress because of the trapped oil and the engine valve opens.

This system looks quite robust. The 2 I opened showed no signs of wear but I was surprised at how light the check valve spring was. I would imagine the biggest problem would be dirt clogging the ports or check valve and air trapped behind the piston.

As I said before this is only my interpretation. Please let me know if ive made any mistakes.

Cheers Kenny
1991 944turbo

OZ951

Nice work Kenny..... youve got too much time on your hands

Peckster

Wow. That was worth your time. Thanks!

What does the encapsulated rubber seal do? Does it contact the piston at all?

Ski

Nice view but you should have painted the edges red just like the factory cutaways , again nice job.

TonyG

Nice work.

TonyG

dmoffitt

awesome job!

Kenny Bradley

Peckster,

I have labeled the encapsulated rubber seal in the photo. It appears to seal between the outside of the piston bore and the plate above it. It does not come into contact with the piston at all.

Hope this helps.

Cheers Kenny

Peckster

So there's a seam between the plate and the bore? I guess the outer piece had to be cast in two sections, but where's the other seam?

Jay Wellwood

Excellent.....might be interesting to the 'other' water cooled Porsche owners as well.

Well done!

Tony

I love that kind of stuff..thanks. I linked this to the 928 board as well.


Jay!! Something you need to tell us!! Cool...details details

Kenny Bradley

Peckster,

It looks like its pressed together a "A" and the rubber seals it at "B"

Cheers Kenny