Tappet Time - Mick's Tips 429

By: Mick McCrudden

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A little noise isn't necessarily a bad thing

It’s inevitable that your engine’s head is going to need a little care. When it comes to valves, recession through wear and tear is common and that means you’ll need to adjust the tappets. If it’s let go too long, your tappet clearances get too small, and in extreme cases disappear altogether, which in turn means your valve is being held open too long. That can lead to the valve burning out and we don’t want that.

What you might want to worry about is not tappet noise, but that it’s getting too quiet. The old saying from Grand-dad was a noisy tappet is a happy tappet! A rattly tappet isn’t necessarily causing any drama, it’s just annoying.

On an older vehicle, every 18-24 months pop off the rocker covers – and don’t be cheap, buy new gaskets. Don’t try to re-use the old ones as they will always leak on you.

Pull out the sparkplugs so you can turn the thing over. If it’s possible, do a compression test while you’re in there. That’s not critical, but it is an opportunity to check on the engine’s health.

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Bring a piston up to top dead centre (on compression), so both the tappets are loose, and do your measurements from there. I have several sets of feeler gauges on hand, some with a bend in them for access in tight spots. They don’t cost a fortune and it makes life so much easier if you’ve got the right gear. We have all sorts of fancy tools in my game, but this job is very undemanding.  A screwdriver and spanner, or Allen key and spanner, is about all you need to the job. Oh, and a gentle touch!

The clearances should be readily available – they’re different for inlet and exhaust on a Holden Red motor, while a lot of the Japanese four-cylinder engines used common clearances. In any case, it’s not complex.

With the piston at top dead centre, you back off the locknut and adjustment. Then you bring it down on to the feeler gauge so there is some resistance when you go to remove it. You’re looking for a reasonably firm fit. The trick is, when you go to tighten up the locknut, ensure that your adjuster doesn’t move. If in doubt, just redo it, as it’s a task that sometimes takes a little practice to get the right feel.

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You’ll find that once you’ve got the adjustment spot-on, what you thought was running okay suddenly feels a whole lot better.

Now even if your engine is running hydraulic tappets, it doesn’t hurt to reset them. I set them 90 degrees, which means the oil will bleed off and it will sound a little ‘tappety’ when you restart it, but it should soon settle down.

Of course these thing don’t last forever, so here’s a tip: If you get to the point where the heads need a strip and rebuild, you might just want to crunch the numbers. Sometimes it’s cheaper to buy a new unit than it is to recondition it.

Note: Mick runs Glenlyon Motors in Brunswick, Vic.
Tel (03) 9380 5082.

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