MX5… Which Rocker’s Which?

Not that you’d need to know, but incase you’d like to for extra scene points or whatevs…  But there are some fairly obvious difference between NA and NB cam covers.

Which is which? 

Fresh back from Chemical Strip, three of these covers fit the NB/ MK2 mx5 models. But how can you tell?

Firstly, the NA/ MK1 covers are simple to identify by the lack of crankshaft position sensor or CPS, found on the front, only on the NB onwards. Mounted on the nose of the crankshaft, it was introduced for the detection of misfire in the ODBII engines.

Telling the NA 1600 and 1800 covers apart from eachother is most noticable by the lettering… The NA6 has recessed letters whereas the NA8 has raised letters. (This is only The case with N.A. engines…. NB engines are ALL recessed.) The NA8 is also slightly longer.



The NB models however, arent that simple. On both the 1600 and the 1800 MK2 covers, the lettering is recessed. If you put them side by side, there are some notable differences to tell them apart…

NB6 vs NB8 

Firstly the most obvious difference here is the length. Just like the MK1 models, the 1600 is shorter than the 1800. You’ll also notice the difference in the positioning of some holes…

But the most obvious way to tell them apart – especially if you dont just cssually happen to have one to compare with – is the cut out on the back of the cover for the CAS. The NB6 is on the Inlet side on the left, and the NB8 is on the right for exhaust.

They will both have the sensor in the front in the same place.

So. Going back to the original pic… In order from left to right are….


So now you know. 

This Week… Its an Oil Leak…

So I changed the rocker cover last week, reused the gasket thinking it would be OK. Swapped them over, torqued the bolts back in and away we go… Wasnt very long before the smell of oil was periodically passing through the car on trips. Quick look in the bay when checking oil levels, there was an obvious leak back left of the cover. Shouldnt have reused the gasket. Doh! Clive at Autotronix was sound enough to order me in a gasket, picked up a CAS (cam angle sensor) Seal as recommended to change at the same time, £1.50 and a 5 minute job whilst the rockers off.


Glad I picked up a CAS seal (from David Manner’s Group J2 M5 Birmingham, real helpful guys), on closer inspection it had also been leaking fairly bad. If you havent changed one before, its not really difficult.. Its a good idea to mark up the CAS before removing it, that way the marks can be re-aligned and timing is unaffected. Unplug a few plugs, undo the 12mm bolt on the back of the rocker, slot the CAS off, switch the seal, (I had an awesome picky tool and a spare set of hands to pass me the new seal)  line it up with little adjustments, a little firmer to push in with the new seal, push it on into place and line up your timing marks. Job done. I couldnt get it out from behind the head but there’s enough room to maneuver a simple O ring change, so it doesnt need to come fully out of the bay. 


There’s been a bit of a blow on the stock exhaust system, so whilst I was down at Reddicap Performance Garage today, Philip put it up on the ramps and had a look. One of the Cat gaskets had disintegrated so he let me loose with the sealant.. Oh dear… 


So that was another little fix off the list and half a tube of sealant gone. Lol. Whilst it was in the air, I took some brake cleaner to the leaked oil spots (had made its way down the back of the engine, round the sump and gearbox) and cleaned it all off. Its in the air frequent enough to notice any more oil leaks under there, be easier to spot on a clean slate. 

Anyway, all work and no play is no fun at all. So quick once over with the fairy liquid and off to a local gathering. No burning oil smell, no blowing zaust, just smiles per miles roof down 🙂


Till next week…

With thanks to Autotronix Developments, Sheffield and Reddicap Performance Garage, Sutton Coldfield