Morris Minor Owners Club

Does anyone know if when having unleaded seats put in do the exhaust valves need changing for a different type / style to the standard valves or are the standard valves fine for the job.

you could say the bigger the valve the faster you go(well up to a point)

If it was my car I'd like to have new valves anyway. As far as cost goes, it is probably cheaper to get new ones than have the machine shop grind the pits out and re-lap them. Once they've worn or been cut back a bit they can become a bit 'thin / pointy' around the edges which increases the tendency to get damaged in future so a new valve is a better option.
There may be improved materials when getting new valves, but on the basis most spares are poor compared to original parts there's no guarantee that new ones will be as good

As for special valves for unleaded - I could only guess (the guess would be no, unless it's a modern engine not an A-series)

I think ordinary valves will do - but in good condition of course. I bought some on ebay recently - £5 for 4 brand new standard size exhausts. generally for more power it's the inlet that needs enlarging - the exhausts are not ideal - but less important.

If it was my car I'd like to have new valves anyway.

Agreed Ray but it just that I have a unused set of standard valves for my midget engine and wondered if the would be ok to use them with unleaded seats.

If it's exhaust valves for a 948/1098 Midget then they will do fine !

I was supplied with stainless steel exhaust valves when my head was fitted with hardened seats, so that seems to be the option.

Stainless valves should only be run in bronze guides !!

Good job I fitted bronze guides then!!

Absolutely !!

And me!

Trubble is - they wear out much more quickly than the iron guides !

Standard valves will not last in an unleaded engine.
Hardened valves (or stainless) need to be fitted.

I converted my sidevalve in 1996 to unleaded & couldn't get a definitive answer from anyone as to which valves to use. Hardened seats were fitted with standard valves.......20000km or so later during an engine strip down (for a different matter) the exhaust valves were found to be badly pitted .
New hardened valves fitted now .

Sidevalves were 'unleaded' as standard ! They were made in the days before lead was added to petrol !!

Well............ leaded petrol came in in the '20s I think, and the engines were different back then. The sidevalve Morris 918cc engine (USHM series) was designed to run on leaded fuel (designed in the 30s I think) and will suffer VSR if you just use 'normal' unleaded.

As far as I know POOL petrol was not leaded. But of course - the engines were not driven as hard in the 'old' days!!