valves
Turbo Mini Forums

a real fast question ! can i use any valve small or big bore in a small bore head?
are the lengths different?
are the stem widths different?
wish i had a big bore head to compare with/use!

im looking for the largest exhaust valve i can fit in my 12G202 head ill probably
looking for a ratio of something like 85% ex to in valve


ive found me a local guy that is well known and respected for his work

length is different. I know bodgers do fit big bore valves in small bore heads, but great care is then needed when setting up the rockers.

Paul Ivey once told me that there was no point in a 29mm exhaust valve in a small bore casting. I'd buy a 27mm from him.

http://www.gsvalves.co.uk/sourcehtml/RECMa...veCatalogue.pdf

Bigger than this and you might have to pocket the block.

Stems are all the same bar Metro Turbo exhausts.

so id need to use off set rocker bushes to correct the geormatry?
any idear on hight dirrence?
i did not think about the darn block getting in the way! that messes things up! gah some times i just want to dump the a series for a modern lump but then its not a mini !!

i can get some 34mm 27mm formula junior valves in small bore 998/1098cc size i was just really looking for a big ass exhaust valve as recommended by my head guy

WHy does he reccomend such a large exhaust valve? Have you looked at the exhaust port? Not massive my any means.

Sounds as you should go 940.

its my understanding that the biggest restriction in flow is the valve also immediately before and after it so if that and the bowl is brought up to scratch with the best flowing part the port then you have a winner my thoughts are to target the mosr restrictive part

surely the port can out flow the biggest valve you can fit?
the valve, before and after the seat, and the bowl are the real restrictions right?

i was told that lots of turbo engines use huge exhaust valves at the experience of intake with good results
as the intake only need to flow well until boost is built up then it just needs to flow enough for the power to be made
by making the exhaust free flow you get boost early and with out restriction so im told

My question to you then:

Why does Paul Ivey which is an engine building guru not produce bigger small bore exhaust valves than 27mm?

is that regarding na or boosted?

my guess is that bigger than 27mm may hit the block with regular (over)bores

and all gurus have thier own findings/thought/religion about valve size

fair point i keep thinking in terms of normal engines..

perhaps i could use some off set guides that will bring them closer the opposite of what is normal done with off set guides
i dont think digging out the block is the right way to get clearance as it exposes the rings to boost

so sticking to the NA valve sizes should be just fine for boosted use ?

If your goal is lots of power, the 202 is a dead end street.

I spoke to Paul on this when I needed some new valves he did say for n/a cars then anything over the 26 ex valves saw a loss in power however, when I mentioned forced induction he was more understanding on the larger valves...

Really nice guy, at the time he had to run as he was meeting a guy from cosworth to deliver some f1 stuff to him...

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

i am looking for all this little 1098cc can give basically.
i thought the chamber/valves where the only real difference between small and big bore heads didn't realize the ports where any different?

27 will be a good increase in valve any way i think same for 34 intake

Again, a 34mm inlet in a small bore casting is just silly. Look at the cross section of the ports and valve throat.
You need to stop dreaming. If you want the most of your 1098, fit a 940. Seriously!

The ports sizes & shapes vary hugely between between the 202, 295 & the other 998/850 heads & the 940 is different again.
As V said, if you're after everything your 1098 can give I'd fit a 33-29 valved 940 casting.

Phil.

WWW.TURBO-MINI.COM

hmm... can one still call it a mini with the ARDEN 8 PORT bolted on? seems a good way to do things altho it has its problems... cam push rods rod clearance manifolds also has its good things too

The simple and quick answer is yes. But you need to take on what had been said. Fit a 940 casting. I have no idea what sort of power you can achieve from a 1098 but the figures 1293 and 12g940 in combination has produced monster power. But that being said innovation takes vision.

Own the day

“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

well at this stage im thinking the sensible thing to do is
get my 202 to flow well enough to make good low end and make about 150+ hp and hopefully equal to torque due to long stroke and ex manifold bla bla..
then when ive saved up get an nice 8 port head, cam to match, efi, new manifolds to match head, proper modern turbo list goes on but hell i might be happy with the ft pounds the turbo gives out so thinking just getting it going and making half decent power seem the best thing atm

that said what size are the turned down 1275 cooper s ones? being turned down what ever i need?
happy to spend my cheep time setting up rockers and stuff i anyone can do with some time and little knowledge..

will turn down to whatever you need. Height isnt such a drama, most of the valves are single collar type, so getting the little collet things is a bit of a pain, but looks the biz. give one of them a call, they'd love to hear about turbo'd a series

“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

cool ill keep that in mind once ive found out the magnitude of this hole that the shop is gonna blown in my wallet lol