Cam tolerance issue

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: NB 1.8__
  2. I’m based near: Lincoln__
  3. I’m looking for technical help or recommendations on: Adjusting the cam gap. __

Hello peeps,
I hope everyone is safe and well and enjoying any good weather.
I am in the process of changing my timing belt and while I had the cam cover off I thought I’d take the opportunity to check the cam gaps. What I’ve found is that the gaps are out of spec for cylinders #1 and#4.
The gaps are too small on all eight valves.
0.152+/-mm on the inlets, 0.254+/-mm on the exhaust side.
In your opinion is this likely to cause excessive ticking noise from the engine? It’s always sounded a bit “tappety”. (145k miles).
Also, what would I expect to notice, if anything, with these gaps being too small?
Thanks for your patience so far.
From what I’ve read, I might be able to buy replacement shims to enlarge the gaps at some point but this will involve removing the cams so I’m likely to tackle this after the summer.
In the short term what do you guys suggest.
I have also read several threads that recommend using an engine flush (Wynn’s?) followed by an oil change. My only experience of an engine flush was on an old MK1 XR2 where I used Redex. The car never ran correctly again so I’m quite nervous about using flushes.
On relatively high mileage engines like the one in my car would a flush be likely to remove settled deposits and cause running problems?
I hope you guys don’t mind sharing your thoughts, opinions and experiences.
Cheers,
Guy

2

If I am reading you correctly the gap is too small? This would leave the valve open when the engine is hot. If the gap was large you would get a “tappet” rattle.

3

Yes that’s correct Richard and that’s what I thought too.
Cylinders #2 & #3 are spot on so it’s only 1&4 that need adjusting.
Any idea on why the engine ticks?

4

Gas leak on the inlet valves perhaps??

5

Thanks 999to5, that might certainly explain the ticking.

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6

A leaky exhaust manifold gasket can also cause ticking.
Because it’s escaping gas and you can access it directly, it’s easy to diagnose by using a tube as a stethoscope to pinpoint it.

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7

Having just fitted a new exhaust manifold that could very easily be the culprit. Definitely something to investigate further. Thanks for the advice :+1:

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8

Once you’ve found a piece of plastic or rubber tube, it should take you seconds to check out.