Unleaded Valves

Post by **Kevin** » Fri May 06, 2005 4:42 pm

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.

Post by **turbominor** » Fri May 06, 2005 5:28 pm

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

Post by **rayofleamington** » Fri May 06, 2005 6:43 pm

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)

Post by **bmcecosse** » Fri May 06, 2005 11:19 pm

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.

Post by **Kevin** » Mon May 09, 2005 1:47 pm

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.

Post by **bmcecosse** » Mon May 09, 2005 9:18 pm

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

Post by **les** » Mon May 09, 2005 9:39 pm

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

Post by **bmcecosse** » Mon May 09, 2005 10:29 pm

Stainless valves should only be run in bronze guides !!

Post by **les** » Tue May 10, 2005 9:30 pm

Good job I fitted bronze guides then!!

Post by **bmcecosse** » Tue May 10, 2005 10:45 pm

Absolutely !!

Post by **Cam** » Wed May 11, 2005 10:21 am

And me!

Post by **bmcecosse** » Wed May 11, 2005 9:05 pm

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

Post by **Scott** » Fri May 13, 2005 4:52 am

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

.

Post by **bmcecosse** » Fri May 13, 2005 8:25 pm

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

Post by **Cam** » Sat May 14, 2005 11:39 pm

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.

Post by **bmcecosse** » Sun May 15, 2005 11:25 pm

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