Not long ago it's had all new gaskets etc, but over the last month it's started tapping and gained a misfire on idle and whilst driving. Changed all plugs, leads dizzy etc, but still has the misfire.

Nipped off the rocker cover today for a quick look and noticed that the inlet lifter over number 4 is really soft, and the rocker arm above it is quite lose being able to turn it and lift it by hand. Turned it over by hand and it doesn't change.

Would a dodgy/worn lifter cause a misfire atall? Or just the tapping?
The head was meant to be good when fitted and was quiet for months before this.

 

Sounds like your cam is fecked. Whip it out and have a look.

Yes would cause misfire/tapping. Make sure the threads aren't fecked on the rocker stud too.

I bet if you take the lifter out it's concaved.

 

Nipped the lifter out today and it's fooked. It's worn out with a pin hole at the bottom so it's not holding it's oil.

So a new cam and lifters will be bought at the end of month when payed.

Cheers mate