MICK’S TIPS
TAPPET TIME
IT’S INEVITABLE t hat your engine’s head is going to need a litt le care. When it comes to va lves, recession through wear and tear is common and that means you’ll need to adjust t he tappets. If it’s let go too long, your tappet clearances get too small, and in extreme cases disappear a ltoget her, which in turn means your va lve is being held open too long. That can lead to t he valve burning out and we don’t want t hat.
What you might want to worr y about is not tappet noise, but t hat it’s gett ing too quiet. The old say ing from Grand-dad was a noisy tappet is a happy tappet! A ratt ly tappet isn’t necessarily causing any drama, it’s just annoying.
On an older vehicle, ever y 18-24 months pop off the rocker covers – and don’t be cheap, buy new gaskets. Don’t tr y to re-use t he old ones as t hey will a lways lea k on you.
Pull out t he sparkplugs so you can turn the thing over. If it’s possible, do a compression test while you’re in t here. That’s not crit ica l, but it is an opportunit y to check on the engine’s healt h.
Bring a piston up to top dead centre (on compression), so both the tappets are loose, and do your measurements from t here. I have severa l 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 t he right gear.
We have a ll sorts of fancy tools in my game, but this job is ver y undemanding. A screwdriver and spanner, or Allen key and spanner, is about a ll you need to t he job. Oh, and a gent le touch!
The clearances should be readily available – t hey’re dif ferent for inlet and ex haust on a Holden Red motor, while a lot of t he Japanese four-cylinder engines used common clea ra nces. In any case, it’s not complex.
With t he piston at top dead centre, you back off the lock nut and adjustment. Then you bring it down on to t he feeler gauge so t here is some resistance when you go to remove it. You’re look ing for a reasonably f irm f it. The trick is, when you go to tighten up the lock nut, ensure t hat your adjuster doesn’t move. If in doubt, just redo it, as it’s a task that sometimes ta kes a litt le practice to get t he rig ht feel.
You’ll f ind t hat 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 t hem. I set them 90 degrees, which means t he oil will bleed of f and it will sound a litt le ‘tappet y’ when you restart it, but it should soon sett le down.
Of course t hese t hing don’t last forever, so here’s a tip: If you get to t he 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 t han it is to recondition it. Note: MickrunsGlenlyon MotorsinBrunswick,Vic. Tel(03)93805082.