998 turbo parts advice
Turbo Mini Forums

Hi,
Im just ordering the parts i need for my engine build as i want to see can i send off my engine to the machine shop in the next couple of months but not too sure about a couple parts that i need.

Im fitting a 12g295 head to the engine but i want to get the valve guides changed as well as changing the valves to stainless ones and maybe fitting unleaded valve seats, my origional plan was to go with these valves C-AEG587 and C-AEG588 but im worried that the inlet valves wont be big enough as the standard inlets in the head look to be sitting too low, dont fancy having to get unleaded valve seats fitted in the inlets too,
i attached a few pics but i wondering if the minispares valves are slightly bigger than the standard ones and if ill get away with them or could ye reccomend a bigger valves size.
Also would fitting unleaded valve seats increase the chance of the head cracking as ive heard there prone to doing this.
I also need to get a timing chane setup, have minispares any race one that would be ok, cant seem to find any suited to modified engines,
Im missing the inner valve sping on one of the valves, would i be better off just getting a full replacement set or is it worth inspeacting the rest of the springs first.
Im sure alot of simular questions have been asked before but cant seem to find what im looking for.
Any help would be great

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A job worth doing is a job worth over doing

For the head the best I have found is 33 inlet and 29 exhaust with unleaded seats on the exhausts.

Problem is that you have to use the valves from the 1275 head as they are the only ones available. Someone on here will tell you the trick to fitting them, as I don't know.

Yes just buy a new set of springs.

Any timing chan will do the job, stick with steel though if you plan on doing some miles.

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

www.twin-turbo.co.uk

The 29 exhaust valves will hang over the block so you either sink them into the seat a bit or pocket the block.

The 1275 valves are longer so you have to put shims under the springs. Turbo phil sorted mine out but I had the 29mm valves cut down 27.something

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

Edited by Advantage on 17th Jan, 2012.

Rusty by nature

If you are not planning on running high boost, then a set of machined down 1275 valves would be OK.

Say 32mm inlets to deal with the seat recess and 26.5mm exhausts that should clear the block. However, if the head is not skimmed then that wont be an issue anyway. Open up the throats to suit.

I can let you have a set of washers to space up the valve springs. I bought 100 when I only needed 8 !

Edited by Paul S on 17th Jan, 2012.

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."

I use 29mm valves on a +20 and it clears ok.

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

www.twin-turbo.co.uk

Cheers for all the replys,
This is my first engine rebuilt so was hoping for a more straight forward solution.Im gong +20 too so will this mean i wont have to pocket the block or anything if i fit 29mm exhausts. Im aiming for the region of 100bhp if thats achievable, Was thinking of going with a gt1544 with 10 - 12 psi boost. But it would be nice to be able to up the boost a little for thoses special ocasions
So want to do it right while im at it.
Whats the biggest valves available for a small bore, the only thing is i dont know what it will take to get the inlets sitting right, This might be a stupid question but is the valve stem diameter the same in the 1275 valves as in the small bore ones.
Is opening up the throats something you could do yourself,
Would these inlets the ones your on about http://www.minispares.com/Product.aspx?ty=...id=37567&title= or would the standard 1275 one do.
and are these the exhausts http://www.minispares.com/Product.aspx?ty=...id=35889&title=
Thanks again

Edited by jdisel on 17th Jan, 2012.

A job worth doing is a job worth over doing

The 29mm exhaust valves will be OK provided that the head has not been skimmed and you are not going too high with the valve lift. They could hit the top of the block.

On one of my builds I'm using a heavily skimmed head with a highish valve lift and the valves go into the bore at maximum lift. 26.5mm is the largest valve that you can use on a +0.020" bore in that instance.

A set of second hand 1275 valves would be OK. Stems are the same as the 998s.

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."

Edited by jdisel on 18th Jan, 2012.

A job worth doing is a job worth over doing

If you are using that ladyboy cam :) , then you've only got around 8.0mm lift, so makes like a bit easier.

As for exhaust valve size vs performance, then all I can say is that I'm running 120hp on 26mm and the new build should do 150hp with 29mm valves by just allowing it to breathe easier and rev a lot higher.

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."

In that case these should be more than up to the job for my planned hp.
http://www.minispares.com/Product.aspx?ty=...id=33367&title=

I got that ladyboy cam was i thought it was a decent cam for a 998 turbo, alot of people seem to be running them, do you think its not suited.

So would anyone have a decent set of 33m inlets that they would sell, or am i beter off going new

Oh ya, would the standard cast duplex timing gear from minispares be ok to use,
Thanks again lads for all the replies.

Edited by jdisel on 18th Jan, 2012.

A job worth doing is a job worth over doing

Nothing wrong with the MG cam, it's a safe bet. I would just like folks to try something else, so we can get a bigger picture.

Not sure what you can do for short, small bore 33mm valves.

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."

What sort of cams would you like to see used? Any specific ideas?

one day boost will be mine!

I've got good results from the MD274, but I would like to see if others do too.

Then theres the RE13T or whatever it's callled, although probably a bit too much for a 998.

I'm currently doing a 998T build with a short duration scatter pattern cam and I'll post the results as soon as I have them.

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."

Safe is good for me at the moment, ha
Its my first build so want to go with something that i know works, i can always experiment after.

A job worth doing is a job worth over doing

Paul Ivey does the "Rimflo" valves.

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."

I use the 266 in the sprint. and on my hillclimber I use 33 29 valves and that has more than 150bhp. I tried bigger with poor results.

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

www.twin-turbo.co.uk

Would the 33mm rimflo ones be alright to use as the inlets.
Another thing, what kind of main and big end bearings would be the best, Ive been looking through the fourm but still not sure would i need to fit the earlier type ones and get some maching done or will the standard later replacement ones be ok. the less maching the better so would like to see can i get away with the later type.

A job worth doing is a job worth over doing

Rusty by nature