Valves meet piston ?????

[BrianC]

Not quite sure how to put this question so if it sounds nonsense please excuse me!!!!

Just part way through a project to solve a problem with my storm 2 - described in painful detail n another thread!!!!

The question is - could i have had a cct failure and cam chain slippage and not have damaged the valves?
Th engine will turn with apparently no mechanical clashes, but having stripped the cam covers off, and after a quick look ,it appears that the cams look a bit misaligned. I will make more observations next week!!!!

I had planned to take the head off, but will await any input from the learned people here !!!!

Brian

[tony.mon]

It's possible.
If the sprocket has moved only one tooth, usually no harm is done.
Two or more....usually at least two bent valves, most often the inlets on the front head.

One way to check without removing the head is to remove the cams on both heads and retime it properly (having sorted the CCT's- obviously).
Then check valve clearances.
If the valves are bent you will see that pair of valves have larger gaps than they should have.
Mostly it's visible- look how far down the buckets sit in their sockets, compared to the other three pairs- the exhaust valves on that head, and the two pairs in the other head.

If the gaps are bigger than they should be, pull the head.

[BrianC]

Cheers tony.

Ill give ve all that a go next week when i get back from in garage .

I will properly turn it to tdc for the ftont and see where the cams are, and take it from there.

Brian

[geeman22]

I had a front cct and rear cct fail, the rear valves were fine but when I stripped the front you could see the valve buckets were down and the cams weren't engaged. so yes that can fail and no contact happens but they can also bend so good luck fingers crossed for you pal

[lumpyv]

my front cct went at tickover and the valves survived. I got lucky

[BrianC]

I'm guessing if there is a problem I wouldn't get compression?

Might put the compression tester on it and spin it on the starter. As I say there are no clashes when I turn engine by hand

[tony.mon]

I'm guessing if there is a problem I wouldn't get compression?

Might put the compression tester on it and spin it on the starter. As I say there are no clashes when I turn engine by hand

NO.

Don't turn the engine over- reset the timing first.

If the valves are bent they quite often then clear the piston afterwards- as these aren't high compression engines they have a few mm gap between seated valve heads and piston.
So even if they aren't sitting square they can still miss the piston crown.

It's not a compression test you need; it's a leakdown test.
Although a comparison from one head to the other should give it away, there is usually some variance between them anyway.

[BrianC]

Ok tony

Thanks for the pearls of wisdom.

Ill do as you suggest

Brian

[longandlow]

Do a quick check of the valve clearances, if valves are bent even slightly it will effect the clearance.

[vardypeeps]

When doing my CCTs I managed to make a cam jump a tooth but after re-adjusting everything the markings were still out by around 3mm from the cyclinder head (didn't align perfectly, possible cam chain stretch but within limits).

We checked,
checked again and all was fine.

Popped back together an no issues with running.

[VTRDark]

Yep very rarely are any of them spot on. Then comes the decision if you want to advance or retard either the inlet or exhaust cam that 1/2 tooth to move the power around.