MX5 black spark plug?

[mx5 shaun]

Hi I have a 1992 eunos roadster and its done over 200,000km I brought it as a project thinking the valve stem seals were gone I have since given the car a top end rebuild and replaced the valve stem seals and all the gaskets around the area. It was still smoking when I did the first start but after awhile of letting it warm up it didnt smoke as much and only smoked when put under load or heavy acceleration. Today I have had number 1 spark plug out to check and the plug was very black and a little wet aroung the edge, however the tip of the spark plug was not very black at all. Does anybody know what could be the problem, and do you think that the piston rings or oil scraper ring could be gone, and if the rings are gone how much would you say its goin to cost about to get another engine and get it fitted as I am not confident enough to do a engine change.

Thanks shaun

[J-Tuner]

I've had a fair few drinks so go easy on me

Is it oil? Maybe rocker cover gasket?

[mx5 shaun]

dont think its rocker cover gasket as that was replaced 2 weeks ago with a genuine mazda one, however my spark plug socket was very oily from the last job I did with it so that may be the reason its oily on the outside.

[ronime]

Failed oil control rings on older Mazda engines is becoming increasingly common. I rebuilt my '92 Mk1 engine over the winter because of the very same problem.

Having a good used engine fitted and serviced was going to cost me over £500 with no guarantee as to how long the rings in the replacement engine would last so I decided to have a go at rebuilding my own engine. You can get a set of decent aftermarket rings and shell bearings for less than £100 but a genuine Mazda full engine gasket set costs over £200. I also needed 8 new exhaust valve guides and the valve seats and faces recut.

All documented here: http://www.mx5nutz.com/forum/index.php?showtopic=1...