Rocker clatter

Here's a Q - 2.25 petrol ex-MoD in my 109 which I've only run a little whilst readying the shed for her MoT.

The top end - inside the rocker cover, 2/3 of the way from the front occasionally gives a loud !!CLAT!! then returns to normal for several seconds, then another loud !!CLAT!! - repeat ad nauseam.

The !!CLAT!! is detectable with fingers - it's an impact on the underside of the rocker cover - I can feel it.

Something has let go - though surprisingly the engine's still running on all four...

Any suggestions, team, before I dismantle the beast?

It may feel like that but is possibly not that bad. It could be a sticking valve or the rocker shaft might be loose. You may have a sticky tappet or a worn cam follower. The cam followers are simply discs that roll over the cam and push the tappet up and down you can end up with a groove worn into these which means that as they spin sometimes they work ok then others the rocker gap is huge.

First thing I'd do is get a pair of safety googles and run it with the rocker cover off to see if you can see what's going on. A length of hose to use as a stethoscope is a good thing to try. It may just be a sticky rocker.

Try reducing the idle speed as low as it will go to help identify which rocker/valve/tappet it is.

To fix the valves or tappets you'll need to remove the head. There are inspection plates on the side of the engine which allow you to see/feel the cam and the followers but in my experience unless it is really really bad you'll not get a sense until you've fished them out for a proper look which means the head might need to come off.

Take rocker cover off 1st and look to see if you can see any impact marks .
Tappets can be reset without taking the head off.
Check all valves look ok might be a broken valve spring.

A loud clatter at the front of motor can be a failed timing chain tensioner the chain then hitting the casing.

Blackburn - I think you misunderstand my post. Rockers are not tappets . Tappets are the things between the followers and the push rods and they cannot be got at without removing the head. "adjusting the tappets" is a misleading phrase.

The round bit is the follower - that is the bit that can get grooves worn in it causing erratic rocker/valve clatter. The brass thing is the tappet and they can jam in the guide (the bit at the top).

As I said earlier though don't be scared to take the rocker cover off - it might squirt a bit of oil about if you rev it but should be ok at idle....just watch your fingers.

Team - thanks. I haven't found the time yet to strip the beast - and yes, I thought initially that it was the timing chain hitting the cover - it sounds very similar.....but I can feel it so it ain't.

We shall see in due course - I shall report back.

And having taken the rocker cover off, all became clear..... a pushrod waving in the air, and an inlet rocker completely upside down.
Five minutes and order is restored and it runs like a sewing machine....
I bought this thing after it had been sitting in a barn for ten years - the engine's a MoD recon and it didn't look to me like the rocker cover has been off in years - I wonder how long it's been like this and how it got there?

Apprentices friday afternoon job?

An apprentice would have to try quite hard to get it that wrong...

It is *spectacularly* wrong. Really.

A valve that stuck open even just for a moment could let the push rod escape and the rocker could be then free to rotate. This is just my guess as to how it happened given it had been sitting a long time. Cheers.

tottot said:

A valve that stuck open even just for a moment

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That's probably the most likely scenario - there's no damage that I can see and she was running sweetly. I shall do the old school tuning routine this morning and bung her in for MOT next week.

Wish her luck!
My granddaughter calls her Queen Elizabeth The Shed.

Castor said:

That's probably the most likely scenario - there's no damage that I can see and she was running sweetly. I shall do the old school tuning routine this morning and bung her in for MOT next week.

Wish her luck!
My granddaughter calls her Queen Elizabeth The Shed.

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Good luck for the MOT.

your valve or rocker shaft springs might be a bit weak

dominicbeesley said:

your valve or rocker shaft springs might be a bit weak

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Thanks - yes, I think they probably are, but the engine's done less than an hour since resurrection, and in hindsight I suspect the pushrod came out in the first couple of minutes.
In time I'll pick up another head, get it hard-seated and flow it - but that's for another day....

Passed?

John S said:

Passed?

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Not yet!

I may get it dropped off tomorrow evening, logistics permitting - and I know she won't pass because there's some little bits of chassis welding/fettling that are needed. My friendly MOT station can mark those up and my chum will work his magic with the result.

However the engine is now happy I suspect the only thing there is that amiss there is timing chain and tensioner. It's on the list......