12g295 valve sizes.
Turbo Mini Forums

Hi all, a quick question can you fit 29mm exhaust valves into a 295 head and run on standard 998 (no overbore) without having to pocket the block?

I think so but I'm just checking.

Thanks for any help

Graham

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

No you cannot, but that doesn't matter, DON'T do it. The port wont flow that much, and you'll ruin the head.

so whats the largest you can run 26.5mm??

I was thinking that when boosted a better exhaust flow would help get all those gasses out.

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 have Grahams head here & it already has ex valves over 27mm fitted. But whoever fitted the unleaded inserts originally has cut them stupidly wide and the valve is sitting very low in the seat. The idea of fitting the 29mm valve was to allow the valve to sit up properly in the seat and so the seat could be radiused nicely into the throat.

WWW.TURBO-MINI.COM

I have 29mm exhaust valves, and 33mm inlets in one of my 12G295 heads:

http://www.turbominis.co.uk/forums/index.p...tid=138402&fr=0

I need someone to fit some exhaust seats and I might give this a try.

EDIT: You will need to check that the exhaust valve sits deep enough, so that it will not hit the block on full lift.

Edited by Paul S on 8th Feb, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Just measure the ex again & the appear to be 27.9mm. Maybe they were sunk into the head on purpose, to allow clearence from the block ?

WWW.TURBO-MINI.COM

I'd fit new seats in that case. I REALLY don't like the 940 valves fitted in 295s.

morspeed strike again. I originally purchased this head as a fully recon'd 295 head. Looks like the jammed any valves in they had lying around... worst thing is the exhaust valves are actually inlet valves...

Anyway thanks to Phil for helping me out and answering my stupid questions.

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've used A+ inlets ground down as exhausts. It depends on the quality of the valve.

The cheap and east way is to fit 940 valves, but it's far from the best way.

I'm lost again.
I bought:
C-AEG587 Exhaust (1.040")
C-AEG588 Inlet (1.218")
They fit perfectly the original (not modified) 295 I've got.
Why to bother with 940 valves ? Or are they for overbored seats ?

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

The seats in the 295 wear like mad because of shit alloy. The cheapest way to fix this is to fit OS valves. The cheapest OS valves are 940 ones.

It's a bodge.

That's right. On both 295 I bought intake seats are 0.5mm below the initial level, while exhaust ones are just fine.
May be that's because intake seats are 1mm wide, while exhaust are 2mm wide ?

Edited by alpa on 11th Feb, 2010.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

So which valves to use ?
Are C-AEG569 1.311" (33.3mm) the good ones ?

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Paul Ivey still does 295 valves largest 33.3 inlet and 26.5 or .9 I can't remember but you can only send a cheque or postal order. They were a good price at about £11.00 each I think

Kingswood Farm Kingswood
Albrighton Wolverhampton
West Midlands, WV7 3AQ
West Midlands County
Contact: Paul Ivey
Race engine components
01902 373770

a very nice chap...

but I haven't gone with them due to my issue.

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

oh the rim flow valves off of Paul direct are a fair bit cheaper.

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

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

27 mm ex valve is OK but 29 will hit the block ???

that is just 1 mm on radius, is it that close ?

Rusty by nature

I know I have them both in my hand and hey look very close...

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

Vegard, supercharged my head made very good power with 33.3 and 27.8 with a std cam. In fact I think this is why it was so good, (61ATW) as it shocked us at the time, however I didn't know the valve size then.

IMO the sizes work well on a FI car. I understand that they are a little big NA.

IMO you need a good exhaust size to get all those gasses out when your forcing everything in.

On the 1275 length valve:
My car ran with odd size valves from 06 until now, when I'm taking the opportunity to have the head ported. I had the head rebuilt 12 months ago because I was trying to trace a problem I think the guy reamed them out too much as is smoked ever since.

Maybe I have been lucky on a couple of fronts like not blowing a hole in the wrong spec inlets being used as exhaust valves. I have used a std cam.
I have to point out that I'm running shims under the rockers and for the last 18 months I've been running 1.5's. the car does about 3-5k a year inc some track days. I drive it with good sprinkling of mechanical sympathy. Probably been lucky with Morspeed sinking the valve seat.

After loads of chats with Phil and my RR operator. I have gone with all stainless race spec 1275 valves 33.3 inlets and 29mm exhausts which I have at a machine shop for them to turn down to match the old ones removed.

Is this the correct way to do it maybe not, it would be nice to have 295 valves, but I don't want to go back a size to 26.x mm, for the points above.
I might be wrong in all this but it has worked well since 06, I hope even better with a cam designed for a supercharger and a bit of Turbo Phil porting magic. I will however check the clearance before I fire it up... maybe with the blue tac test.

But with my luck recently, and if the exhaust valves do touch the block I'm not sure of my next move..

Edited by gr4h4m on 12th Feb, 2010.

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

Well thinking about it I would have to get a pic of Turbo phils sister and well it on here to fund a new engine or block pocketing... :)

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

You'll be lucky ! She's just a figment of everybody's imagination.

Edited by Turbo Phil on 12th Feb, 2010.

WWW.TURBO-MINI.COM

What about Phil in a Dress...

Help me out here Phil :)

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