Porsche Enthusiasts Club Forum

Hi everyone, as my topic title suggests, I think I may have bent a couple of valves. The reason I think this is because; A, I adjusted the valve clearances recently and I think the cam moved round (or I may have had the cam in the wrong place) when I put everything back together. B, after doing everything up and moving the cam back to where it should have been in the first place, it started getting a misfire under 3000 rpm and is a bit hesitant on acceleration. C, I did a compression check and got 8.5 bar on cyl 1, 9 bar on cyl 2, 6.5 bar on cyl 3, and 8 bar on cyl 4. This is on a 924 2.0 N/A.

Would it be bent valves or could it be something else troubling the engine?

Any help or advice appreciated. Matt.

There is nothing that would cause the cam to move when you adjust valve clearances.

For some reason did you remove the cambelt?

This may sound a bit daft, but I removed the cam to adjust the tappets then refitted it to check the clearances.

That was a bit daft as they are adjusted with the cam in place by turning the engine over till the valve is fully closed and rotating the follower so that the hole where the adjuster can be seen.

Recheck the clearances and the cam timing

It might be that you haven't adjusted the valve clearances correctly. Start from scratch and do it again..... taking more care and doing it properly - you may be lucky.

i may be wrong but i think the 2.0 litre engine is non interference, ie valves don't hit the pistons

Hi

Take my word...IF you bent the valves the car WOULD NOT drive....it would be missfiring appallingly, with a total lack of power....you wouldn't even get round the block...

If you are unsure about cam timing and belts.....or what you have or have not done...

Do this....

DO NOT start the engine...

DO NOT drive the car...

Do get someone round who is a qualified mechanic to look at it...

That could save you a fortune...

All the best Brett

As already posted; the 924 engine is a non-interference type, so the valves wouldnt bend even if the belt snapped at 7,000rpm!

Hi

I have seen so called "non inteference" engines of all makes WITH BENT VALVES !!!

Usually when an amateur mechanic decided that he "knew" about timing lol....

So my advice stands.....

All the best Brett

...and I have seen a number of 924s which have suffered a belt failure and every one has been completely undamaged.

Have been and checked the valve clearances today all seem ok, the valves on cyl. 3 have about 0.15mm clearance on the inlet and about 0.45mm on the exhaust on a cold engine. I think they may be a little on the big side, but would they actually result in a loss of compression (not done a second compression check yet though)?

Big valve clearances aren't going to help getting a decent compression reading. It really needs correcting before you run it as it'll damage the cam & bucket. Set the clearance correctly & retry the compression test. Also try a teaspoonful of engine oil down each bore & retry it.