As Skidpan mentioned, the Yamaha-developed 1.6 engine requires camshaft removal to make adjustments.

As a general rule, the valve clearances on engines with bucket & shim adjustment reduce over time, because the valve seats in the cylinder head gradually wear. Ultimately this leads to the engine taking longer to start, and reduced performance because the valves eventually stop closing properly.

However, the tapping could also be from a worn cam bearing or perhaps a worn cam lobe & bucket top.

You could get a price from a trusted independent garage for checking / adjusting the clearances, then weigh up what the car's worth to you. If you like it and intend to keep it, and the job is not too costly, I'd be tempted to get it done. If you're not that bothered and / or the job is expensive, then leave it.

Unfortunately, cam removal is necessary on the Yamaha/Ford 1.6 motor. Possibly because of Yamaha's motorcycle engine development experience: the majority of DOHC bike engines from the mid-80s onward have shim-under-bucket adjustment.

Just checked in the manual and for the Yamaha Zetec shim removal is possible with Ford Tool 303-563, the same tool used on the 1.8 and 2.0 Black top Zetecs.

On a tangent, we had two 1.8 Mondeo Mk1s (a '93 and a '95) with the alloy cam covers and both had hydraulic tappets. Wonder why Ford changed to conventional bucket & shim for the later 'black top' Zetec engines?

I used a couple of the earlier Silvertop Zetecs with the hydraulic tappets in the Caterham on the track and road with a rally cams and did not have an issue even using 7500 rpm. Made changing cams a simple 1 hour job instead of a days work setting up shims. Now have a Black Top Focus 2.0 Zetec in the car and since its not used on the track any longer it has standard cams.

When I changed to the later engine I spoke to a Zetec specialist who agreed that for road cars and sensibly tuned track cars hydraulics were fine but as always there are limits. His race cams used solid lifters of a larger diameter which required extensive head work before fitting, not cheap.

There seemed to be 2 opinions as to why Ford changed to solids, which is true no idea, probably a combination of both. By the mid 90's the Silvertop was the only "modern" Ford UK petrol engine using hydraulic tappets. The Yamaha Zetec and V6 Duratec used solid lifters and the i4 engine already on the drawing board used from 2001 in the Mondeo and 2005 in the Focus (Mazda design) also used solid lifters thus the Sivertop was the odd one out. More likely was emissions, hydraulics place limits on cam lobe shapes and on factory engines the opening phase of the solid lifter engines is more aggressive and overall lift greater probably as part as the need to keep emissions down. Its all guess work.

A totally standard 2 litre Silvertop on throttle bodies, aftermarket ECU and a nice exhaust gives about 165 bhp when set up. A totally standard Focus Blacktop with the same ancillaries gives about 175 bhp when set up. Ford quoted virtually the same figure for both engines but its clear that the Blacktop was being strangled by the extra emissions kit. The blacktop has a stronger midrange.

Edited by skidpan on 07/04/2021 at 09:49

The 2.0L Zetec Black Top engine on my previous Mondeo did just over 200,000 miles. I never had the tappet clearances checked and/or adjusted and it ran just fine.

Unless the engine is being rebuilt after a major overhaul I've never heard of this work being done.

Every 8 years or 100,000 miles is the official interval but if they are quiet its fair to ask why on earth would you even bother to check them. On the other hand if the clearances close up due to the valve seat wearing away they would not get noisy and eventually you would start to loose compression and performance.