Time for an engine overhaul??
pewe - 13/10/21 at 01:28 PM
Guys, I need some advice.
A bit of a saga but bear with me please.
When I bought it the hairdressers, 1.6 NA 1991 20k miles, it showed about 170psi on all cylinders.
Eight years later and showing c.130k miles but having had a hard life - supercharged, trackdays, solos etc. etc. they are down to 142/140/135/140.
Putting oil down the bores brings them up to 180/173/160/180.
The main reason I've been questioning the engine's performance is that due to a numpty error I mixed up the valve stem oil seals when I did
them last year using the rope method (if you haven't tried it - it really works!).
Of course the engine smokes on over-run given I apparently randomly mixed up inlet & exhaust seals - different diameters - never too old to learn
etc.
Anywho I would appreciate some input as to whether:-
a) I simply replace the seals with new ones (on the correct stems of course) OR
b) bite the bite the bullet and go for an engine rebuild over the winter OR
c) buy a low mileage engine (if such exists) but existing one's showing good oil pressure and I've replaced a lot of the ancillaries OR
d) overhaul the engine from the spares car which has done 120k miles but is largely unknown and has sat in the car under a tarp for 8 years.
Any suggestions gratefully received.
TIA.
Cheers, Pewe 
Mr Whippy - 13/10/21 at 01:44 PM
So you've put on 110k miles? yeah I'd give it a good rebuild before you damage something that can't easily just be replaced. I'm
impressed you've managed to do such a mileage tbh
I'm sure it will seem much faster once done. Hopefully it will just need new rings & the valves. I always replace the valves these days as
it's so much less work 
Would be good if you did a full thread on it.
perksy - 13/10/21 at 01:59 PM
Good time of year to strip and rebuild...
Perhaps a few upgrades aswell
pewe - 13/10/21 at 02:15 PM
quote:
Originally posted by Mr Whippy
So you've put on 110k miles? yeah I'd give it a good rebuild before you damage something that can't easily just be replaced. I'm
impressed you've managed to do such a mileage tbh
I'm sure it will seem much faster once done. Hopefully it will just need new rings & the valves. I always replace the valves these days as
it's so much less work
Would be good if you did a full thread on it.
Thanks for that.
I kind of know its the way to go but find it difficult to do majors nowadays - been there, done that, got the T shirt etc.
That's not helped by the fact the F27 has occupied the garage space since I bought Maz - should really sell it and at least I'll be indoors
to take the lump out.
I'm surprised at the abuse Maz has taken, however that 1.6 engine was developed for the Mazda3 turbo so the bottom end is particularly strong.
Only drawback is coolant circulation given it went from East/West configuration to North/South so that was part compromised - not that I've had
problems.
I'll keep you posted.
Cheers, Pewe
theconrodkid - 13/10/21 at 02:44 PM
sounds like compression isnt too bad, prolly a quick hone and a set of rings would sort it out
pewe - 14/10/21 at 10:37 AM
Thanks for the replies.
I've spoken to Toby @ O'Keefe Motors, Hurst (all round good guy, knows a thing or two about MX5's and generous with his advice).
His take is that being supercharged the compressions aren't currently a major issue.
He has suggested replacing the valve stem oil seals again but on the correct valves this time!
Also using a sheath over the stem when sliding the seal onto the stem, presumably to protect the lip.
Evidently it does come with some kits but not with the ones I've recently bought.
I'm thinking an old biro bodu should be OK unless someone has a different suggestion?
Reading the manual this time it suggests the seal should be a precise height above the head, repositioning if necessary.
Also Toby suggested using Mobil1 10W-60 and a new filter.
I know No1 son used this on his much thrashed Integra to good effect so will give that a try and hang the expense.
So it looks like that's next weeks job.
I'll keep you posted.
BTW I'm carrying a Javelin Events voucher over into 2022.
It was bought so I could do a track-day at Mallory where I spent a lot of time hanging over the fence in my yoof watching racing. Anyone else fancy
that?
Cheers, Pewe
pewe - 14/10/21 at 10:41 AM
quote:
Originally posted by theconrodkid
sounds like compression isnt too bad, prolly a quick hone and a set of rings would sort it out
Thanks for that Conrod.
If it was possible to drop the sump and work with the block still in place that could be an option.
However AFAIK it's not so if the lump does have to come out I might as well do the Full Monty.
Hopefully the above will sort it for now.
You OK? About time we had a catch-up.
pewe - 9/11/21 at 04:38 PM
I think its sorted for now.
A new set of valve stem oil seals and the smokiness has all but gone - hooray.
I think the problem could have been a seal becoming detached for its housing.
Certainly when I pulled one off with the long nose seal pliers the seal and spring were missing.
Could be I nipped them off as I pulled upwards but unlikely.
Certainly no sign of them in the cambox so God alone knows where they went but I sure ain't stripping the engine on the off chance they have
found their way into the sump!
The other live and learn - sliding the seals onto the valve stems using a lubricated sheath(!) to avoid nicking them on the top of the valve stem.
There wasn't a sheath supplied with the seal kit but a 6mm diam drinking straw cut in half and folded in on itself plus a short cut in the tip
meant smooth application.
All for now guys.
Stay safe and well, Pewe