Give Me More Head - solid exhaut valves V;s sodium filled valves
Turbo Mini Forums

Chaps ..

I am head pondering even more ...

I know there are many different views out there ; but would be interested in any comments. Assume a head with 28cc , plenty more boost say 14 PSI .. what Valves should i go for ?


solid exhaut valves OR sodium filled valves ???


My Mini will not really see many miles ; prob. no more than 3k a year


Cheeeeeeeeeeers
S

TurboLessTosser

My understanding of the sodium exhaust valves is that they are used as they conduct heat away from the valve head more quickly, thus attempting to avoid burning the valve seat away.

They also have a larger stem diameter and I think a fairly bulky underhead design, again to provide a good path for the heat to soak away from the valve head.

I don't think that wear over mileage is affected either way so doesn't make any difference if you do 3000 or 30,000 miles etc.

Obviously running more boost produces more heat, so making their use important?

As a side note, my Avonbar St4 turbo head (27.5cc) uses the sodium valves. Not sure what other heads (e.g. MED) use.

Please correct me if I am wrong anyway, that is just my understanding of it.

Cheers

I still have the sodium valves in my head.
The next head i make will not however....
I've seen the heads coming off the valves once too often!
I would just use a conventional valve, but with a nice wide seat area to dissipate the heat. This is more effective than relying on the stem to take the heat away... It's not ideal for ultimate power, but i've never got to the stage when there is 'nothing more' i could do to drag the very last hp from my engine...

Completely up to you, but decent 'one piece' valves are ideal!

Tom is right its all about heat transfer...

but that directly effects how long the valve lasts, they dont just suffer seat wear. The valve also wears.

This can be in the same form as seat errosion, or it can manifest itself as fatigue and valve failure (head drops off).

Alex

AlexF

I thought that most valves were made fron 2 pieces.

Who makes one piece valves. Had plenty of heads drop off in my time on all types of valves.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

most valves are... but head drop is normaly poor quality or more likly over heating.

alrx

AlexF

Well I always thought that all valves were two-piece aswell, but Jim told me that MorSpeed have just fitted some new one-piece valves to his head...

nah you can make them out of a single lump of metal...

but they arnt cheap!

AlexF

Tell us more then!
Are Rimflows one piece?
What about valves like the ones minispares sell?

I'll have to do some digging... not sure on mini specific valves.

Alex

AlexF

No Dave rim flow valves are 2 piece!

which is another reason for keeping with the standard ones, i know people say the head fall off, but i've also heard of the same with rim flow valves:(, so what do you do!

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ive heard but not seen the turbo valves' heads coming off ,somtimes it can be put down to using old valves with vague history ,work hardening , fatigue etc, use new rover - some replacement parts are solid valves -,i use solid stainless two piece - the two parts are the valve main shape and a harder metal'stellite' section friction welded to the top where the rocker touches - not the head and stem being joined as most people think ( and chrome stem - 3rd part !!?) most valves are made this way , either stamped from stainless rod (about 10mm dia ) like a nail ,or a form of casting /forging as most standard type valves and both methods require turning or grinding to shape to finnish

I always thought that the Minispares £10 "race" valves were one-piece. I've used these in high rpm engines and had no problems. No racing though. Then again, the standard Rover valve's stems never seem to wear. They must be good, although two-piece.

Wouldn't a water injection system help keep the valves cool?

think that the water injection is tricky for similar reasons to injection.

not 100% sure though, i know a few people who have tried it and not found it to be that good. or atleast their not still running it now so that says something!

Water injection supresses det more than cools valves.

Alex

AlexF

it suppreses det by cooling the mixture though ?
these days almost all valves will have a stellite or similar tip added to stop the rocker 'mushrooming' the end
and the rover valve stems have good wear properties because they have been hard chromed
about 70 % of heat in the head of a valve is transferred through the valve seat , wider seats or short duration cams will let the valve stay cool

It supresses det by slowing flame speed and hence pressure rise...

Your def right about the seat width... just use a std valve and widen then seat. Yes you loose flow but we have forced induction to help with our volumetric efficiency!

alex

AlexF

A small thing i will say is sodium filled valves weight more thus sapping a little bit of power compared to the solid valves. Not much tho so don't bite my head off.

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