Biggest valves in a 12G295 head
Turbo Mini Forums

I feel like a bit of a numpty posting this but I can seem to find the answer anywhere. Does anyone know what the biggest valves sizes are that can be used with a 12G295 head without pocketing the block (998 without a rebore) or offsetting the valve guides?

Cheers

Rob

PS. I wasn't sure if this should go in help needed or technical chat, so feel free to move it if it's in the wrong place.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=8029

still has a little info, pete seems tohave overlooked this one!

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

and heres how mine ended up, very similar to wil_h's head

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=134463

Edited by joeybaby83 on 19th Jan, 2008.

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

I've used 33mm inlets and 26.5mm exhausts on Sturgeo's NA 998 12G295 head, and am doing another set for Axel's.

I think any bigger than 26.5mm on the exhaust with a skimmed head may start to hit the block.

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."

You'd need a severly skimmed head and high lift cam to get the valves to hit the block on a 295.

I had standard 1275 valves in a 295 with a Kent 266 and it was fine. Head was skimmed to suit non cooper too.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=8029

in this thread slater has had an experience that contradicts this...

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Done a bit of maths:

Standard 12G940 inlet: 1 5/16
Standard 12G940 exhaust: 1 5/32

1 5/16 + 1 5/32 = 2 15/32 = 2.468"

998 Bore = 2.547"

So it should be OK (depending on the offset of the valves) but there's only 80 thou of clearance in total so it may well be touch and go!

Yep i put the valves from a 940 in my 295 and they touched the block. Head was skimmed but not excessivly as it had flat top pistons and was only 10:1.

The valves overlapped by about 1mm

Im running a Kent 276 and 1.3 rockers with a overbore of .060 too so not too excessive there either!

Measure the distence from the valve face to the head face. You'll be surprised.

so maybe 266 cam lift is ok and 276 not ok ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Mine had a 266 and the head had the usual (80thou?) off it to suit the non-cooper 998. But alas I can't say much about the head becasue it was done (badly) by the previous owner. Maybe he offset valves or something?