Exhaust valves

Post by **MarkyB** » Mon Jun 08, 2009 8:29 pm

While putting the head back together this weekend I found that the exhaust are not attracted by magnetism.
I just found an ordinary exhaust valve in the shed and it is highly attracted by a magnet.
When I bought the car I was told that it had been converted for unleaded which I took with a large pinch of salt when I found out how poor the "regular servicing" had been.
Now I'm thinking it was taken somewhere honest for the unleaded conversion unlike the cowboys that did the servicing.
I can't see any signs of the exhaust valve seats being done.
Any thoughts?

Post by **bmcecosse** » Mon Jun 08, 2009 8:37 pm

They have simply fitted the later stainless exhaust valves - and are claiming that as 'unleaded'. What collet arrangement do the valves have ?

Post by **MarkyB** » Tue Jun 09, 2009 8:43 am

Bog standard single groove collets with pesky little spring clips.
Maybe I'll pop one out and have a closer look at the seat, but I'm fairy sure nothing has been done to them.
How obvious would it be?

Post by **bmcecosse** » Wed Jun 10, 2009 9:21 am

If the seats have been changed it will be very obvious. Must indeed be 'special' valves then - the later Mini exhaust valves have different collets and caps - you can throw the spring clips away anyway!

Post by **MarkyB** » Wed Jun 10, 2009 7:52 pm

Gah! on the way to work this morning I realised that the head I've been talking about isn't the original one.
That is one I was given that I've replaced the valve guides and skimmed.
So I've brought the original one out of the garage into my living room and removed an exhaust valve.
It certainly isn't stainless steel but I'm not 100% sure the seats haven't been done.<br>

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2,3 and 4 have a noticeable groove round the seat number 1 is completely flat.
It seems to me that I'm a lot better off with the head and stainless valves that I'm going to fit than bothering with the original head.
Should valves and seats both be changed in an ideal world?

Post by **bmcecosse** » Wed Jun 10, 2009 7:59 pm

Not really - you don't need to do anything! the Minor will run fine without 'unleaded' valves/seats - for many many thousands of miles. Set the gaps to 15 thou - and keep an eye on them. What can kill them is constant hard driving on the Motorway. If that's your use of the car - then consider adding Tetraboost - which is the ONLY additive containing lead tetra-ethyl, and effectively convertst the fuel to genuine 'leaded' petrol. But your stainless valves will be the best ones to use. The marks you show are quite normal - possibly caused by sometime re-cutting of the seats - but likely just the original factory machining. Unleaded seats will show best down the throats of the ports - where a clear line will show where the new seat has been pressed into the machined casting.

Post by **MarkyB** » Wed Jun 10, 2009 8:25 pm

Sounds about right, I'll have a look in the service records and see how much the previous owner got charged for doing nothing

I'll see how it performs on the motorway once it's all back together then decide if I'll need an additive or not.

Post by **bmcecosse** » Wed Jun 10, 2009 9:57 pm

Well - fitting special stainless valves is not 'nothing' - certainly better than putting some metal tablets in the fuel tank - or fitting an 'inline' unleaded fuel conditioner! Which some 'specialist' companies seem to think qualifies as an 'unleaded' conversion!!

Post by **MarkyB** » Thu Jun 11, 2009 9:13 am

The head that was originally fitted has had nothing done.
The stainless valves are in a replacement head I'm going to fit.
The car does have some kind of miracle economy device in the fuel line. Maybe that's what they did for the "unleaded conversion"

At least the stainless valves should help.

Post by **bmcecosse** » Thu Jun 11, 2009 9:22 am

" some kind of miracle economy device in the fuel line. " - excellent! The only one that would work would be a flow restrictor with a tiny hole - to limit the quantity of fuel into the carb. Of course - the pistons would soon fry due to weak mixture, and you would be very fed-up with it constantly stuttering and cutting out!