998 with big overbore
Turbo Mini Forums

Newbie here (although i've been lurking for a while) - just starting to build my first turbo motor and i've got a few questions.

The plan is to go for a big overbore on a 998 and take it to 69mm giving me a capacity of 1140cc. It's a hillclimb motor so with the 1.4 equivalency that would give me 1596cc and just keep me in the 1600 class.

Has anyone got any experience of overbores this big on a 998? What are the pitfalls/problems i need to be aware of?

I have never gone that big on a 998, can you even get the pistons?

However, if you do this the car will probably be in sports libra class and probably not very competitive. As the Mini was never built with a bigger motor than 1275cc it is not eligible for any class above upto 1400cc class. That is unless your specific club/championship allows it.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I'm planning to get some forged pistons made for the engine. According to Vizard it used to be a common mod on 1100s using Imp pistons - these pistons are no good for a 998 though.

What I was wondering is if anyone had done such an overbore and what level of success they had (how many blocks will successfully take the overbore).

I should have mentioned that the engine isn't actually in a mini - it's in the back of a Terrapin (yes, the one that competes in the Aldon HSA championship Ben).

For those of you who are thinking what the hell is a Terrapin, it is a single seater using many Mini components designed by Allan Staniforth in the mid 1960's. Most have been converted to bike power but mine remains faithful to the A-Series.

Oh, well now I know who you are it all makes sence. I can't help you with the overbore side, but any turbo forced induction questions are all well covered on the site.

Good luck with the build, hope to see you out next year.

Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Wouldnt it be easier to start from a 1275 platform and de-stroke it ??

You would benefit from the much better 1275 cylinder head casting too, unless you are intending to fit a 1275 head to the 998cc block..

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Pete has an """850 block with 68.8mm bore using custom pistons""" by all accounts, but I'm not sure if this engine ever got built?

If I were you Mike I'd speak to Simon at Morspeed as he did the machining for Pete as far as I know, 01530 830369.

The other options are a 1071 bored out to 74.5mm (not sure of cc of that, and this will be expensive) or a 998 with a +80 and these pistons http://www.minispares.com/Product.aspx?pid=38612 . This gives 1061cc (so 1485cc with a turbo). Ok it well within spec, but it has the potential of 180bhp. don't ask me how to get to 180bhp though as I'm stuck at 140.

Wil

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

www.twin-turbo.co.uk

Thanks for the info. I think for now I'm going to try the +.080 pistons - 1485cc equivalent with a turbo is still much better than the 1330 N/A I've got at the moment!! It also has less potential problems than the 69mm bores of the 'big' engine and can be bored out to the larger size at a later date.

I've posted a few pics of the car taken at Prescott last year in the photo archive.

http://www.turbominis.co.uk/index.php?p=14&album=511

Edited by mike_jenkins on 28th Jan, 2007.

I like you thinking Peter. I was considering E85 as the 107RON is very tempting.

I still havent checked the Bule Book though. I know that it is now 'pump fuel' but not sure if it's actually specified.

Also, I'm not sure about using it with a carb!!

Wil

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

www.twin-turbo.co.uk

Wil,

I know we are going O/T now, but E85 is only permitted with specific MSA approval. I have asked the MSA and it needs the championship organiser to apply - I have asked Paul R - will let you know what happens.

Cheers Mike.

Don't worry too much about going off topic on this forum. There aren't any OT Nazi moderators!!

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

www.twin-turbo.co.uk

does this overbored 998 as been tried or left in the dark?
fab