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My Audi A5 had some bent valves after the chain tensioner broke. I have replaced the bent intake valves and a single broken rocker arm.

When I reassembled the top, I noticed the first pair of valves on the intake side does not open simultaneously. It seems like one of the two are delayed. I would say they are about 300ms out of sync of each other. They do however not touch the pistons.

2nd valve on the intake side from the front goes down a bit faster than the first one, and goes up faster if i'm remembering correct. This is only checked by manually turing the crankshaft gear by hand -So not very fast.

We already assembled the engine when we spotted this.

Since the valves did not touch the piston, we decided to do a test start. It sounded normal, but it seems to lack some compression at the last cylinder.(This valve offset issue is on the first cylinder) I believe this is the standard issue regarding oil consumption on these 1.8t engines.

Is this normal, or do I maybe have to change the intake camshaft?

As stated above, the engine seems to run normally (only tested on idle 5-10s w/o coolant). Is it responsible to use this cam, or will it cause engine failure down the road?

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    Welcome to Motor Vehicle Maintenance & Repair! What year is your A5 and which engine does it have in it? When you say one is about "300ms out of sync of each other", are you saying one opens before the other? At what engine speed? Does the same valve close earlier than the other (otherwise stay in time) or does the first close later than the second? I'm wondering if you might have more damage than you thought you did. – Pᴀᴜʟsᴛᴇʀ2♦ Dec 16 '19 at 18:58
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    The most common camshafts that I've seen have pairs of valves open/close at the same time but there is no requirement that they work this way. It seems conceivable that some engines may be designed to open one valve before the other one but in that case you should see the difference in the cam lobes. Another possibility is that the camshaft is bent (i.e. twisted) from the chain tensioner issue and should be replaced. If you find that ALL the intake cams have a similar offset, then it's likely as-designed. – jwh20 Dec 16 '19 at 19:24
  • Thank you for your answers! The A5 is a 2008 model with an 1,8t CABD engine. – Sølve Tornøe Dec 17 '19 at 14:30
  • I updated the question with some more info – Sølve Tornøe Dec 17 '19 at 14:55
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Dual valves can be designed to open at the same time or at different times to each other depending on engine speed and power required.

This applies to inlet and exhaust valves.

This is relatively easy if there are two camshafts and each one of the pair of inlet, or exhaust, valves are on a different camshaft.

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  • I did not know that, thank you! Regarding the "this is relatively easy" part. Do you mean it is relatively easy to change the intake camshaft, or? I did not understand the reference to that paragraph. – Sølve Tornøe Dec 16 '19 at 12:18
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    I'd say that if you replaced the bent valves yourself, you should be capable of replacing the camshaft. But doing so without verifying that it's actually damaged is wasted money. – jwh20 Dec 16 '19 at 19:26

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