Turbo smallbore and 12G295
Turbo Mini Forums

Hi guys,

I'm at the point in my project where I'm getting the cylinder head work done. I've read and re-read Vizard's thoughts and read any tid-bit of info on here and so far this is what I have come up with...

I'm going to get them to blend in the guide bosses and fit bullet nosed guides, blend in the locater ring, remove the steps around the valves in the combustion chambers and fit larger valves. Also give the ports a general tidy up and polish the exhaust ports.

How does all this sound? Can you recommend valve sizes for the boost I'll be running? Any other recommendations before I give 'em my hard earned?


My motors going to be 1098 +.060" with a 12G295 head running around 8.0 to high 8 C/R, EDIS and intercooled on 10 or more psi. Still tossing up between EFI and carb ( but I'll make another thread for that )

Let me know your thoughts :)

Cheers,
Sam

Sounds good to me.

I'm using 31mm inlets and 26.5mm exhaust valves.

You could push the inlets up to 33mm. If you go bigger on the exhaust, then you may need block cutouts, depending on your max valve lift.

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."

Cheers,

How big can one go with the exhaust valves on a smallbore head without having to pocket the block?

The 12G295 flows a fair bit more than a normal smallbore head so I don't think ( at this stage ) it's worth my time or money to go reshaping the chambers and porting the shiz out of it... or is it? lol

I forgot to mention I was going to get them to do a 3-angle valve seat for the intakes and 30deg seats for the exhausts, thoughts?


My long term goai is to achieve 160 engine horsies which I think is attainable with enough boost and heat control. I know there's a member on here with an 1100 turbo making 140hp, heck I'll even be happy to get that!

On 9th Feb, 2008 spraycanmansam said:
Cheers,

How big can one go with the exhaust valves on a smallbore head without having to pocket the block?

The 12G295 flows a fair bit more than a normal smallbore head so I don't think ( at this stage ) it's worth my time or money to go reshaping the chambers and porting the shiz out of it... or is it? lol

I forgot to mention I was going to get them to do a 3-angle valve seat for the intakes and 30deg seats for the exhausts, thoughts?


My long term goai is to achieve 160 engine horsies which I think is attainable with enough boost and heat control. I know there's a member on here with an 1100 turbo making 140hp, heck I'll even be happy to get that!

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."

Ok good to know. I'm going to be using an RE13T camshaft, I'll have to get the specs. The heads bog standard, never been skimmed. I'm going to get it lightly skimmed, just to make sure it's all flat :)

The only reason I suggested 30deg seats on the exhaust and not the inlets was because Mr Viz reckons the inlets expand with heat and 45deg seats keep the valves seating better.

i have fitted 33mm inlet stainless race valves and 29.5mm exhausts stainless race valves in a 295 head de shrouded the chambers for the valve size in question

in this head i would opt for 1mm 45 deg seats not three angle

hope this helps

sounds good to me and the cam choice is good for a small bore engine

Don't use 30degree seats. The centering will be rubbish, and the seats will wear out. I'm fitting A+ inlet valves as exhausts in my own 202. That'll be excellent along with Rimflo 31,8mm inlets. There is no reason to fit bigger valves than 31ish. The head won't flow air for more, but it's very cheap and crude to fit big bore valves.

Okay so scratch the 30deg seats. So with the 45deg seat they just cut a straight 45deg angle, not 30/45/60(?) like a 3-angle? Do they blend it in at all?

Those valve sizes sound pretty good, with that size exhaust do you have to worry about hitting the block?

I'm thinking 31mm inlets and 29.5mm exhausts...

Think about it as 'how much valve lift can i have before it hits the block.'

Even with standard big bore valves the valves overlap the edge of the bore and will touch with a high lift cam.

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."

IIRC the RE13T is basically the same as the N/A version just with a lot less overlap. I think the lift is around .380" or more? I'm using 1:3:1 roller tip rockers as well which will bump it up a bit higher...

So 31-32ish mm inlets and 26.5mm exhausts with 45deg seats sounds like the go?

Where are you going to purchase the RE13T? Have have searched but been unable to find them online. How much do they typically go for?

Direct from the man! 8-) Graham Russell makes them here in australia. He has a website but he's more of a phone/face to face person.

He has a site ( not finished ) with some contact details ---
http://www.destinymedia.com.au/GR/Index.html

Or I'm pretty sure Keith Calver reproduces them over in the UK, not sure on the RE13T version though...

GR does normal regrinds or new billets, but I'm not sure of the cost.

Hope that helps

i think the re13t is just the re 13 with a wider LCA, if so calver can do them as he does the RE13's with custom LCA's depending on the engine.

Also thats a cracking website LOL

Edited by Joe C on 10th Feb, 2008.

Ok went to talk to the fella doing my head today. I had the head cleaned and crack tested and it has a few cracks in one of the seats, but that'll be fixed with new seats.

I had a look on Mini spares and couldn't find any 31.75mm inlet valves but I found some 33.3mm stainless ones which I'll get him to turn down to 31.75 mm.

He also has a machine that puts a radius on the seats as opposed to "3" angles.

Edited by Vegard on 11th Feb, 2008.

Apparently the cracks in the seat were only minor and he thinks it'll be no worries with new inserts, fingers crossed...

Potters wha? Lol, I'm in Australia so If that's some funky place in the UK, I haven't heard of it

So 31.8 Rimflo's for the Inlet's and I was planning on running these exhausts --- http://www.minispares.com/Product.aspx?pid=33367

You wouldn't happen to have a Minispares part number for those inlets would you?

C-RIM104 from the top of my head :) Those exhausts are perfect!!