998 with 69mm bore
Turbo Mini Forums

Hi i am dav and been into minis for decades ,been advised to come over here and get some advice , i have taken in px a 998 mini engine , this is no ordinary 998 ,got it off an old boy who used to race mini stox it is bored out to 69mm offset with fiesta hcs flat top pistons and running a 1275 cam ,was wandering what kind of cc the engine would be classed as ,comes with standard 998 head as this is all he could run in the class he was in ,says it would fly if pocketed and 12g940 big valve head was fitted ,never heard of this kind of bore to 998 before so just wandered what your opinion on this engine would be .I am currently building a standard mg metro na engine ,would this 998 out perform the mg engine with the right head ect?


cheers dav

Edited by stealth05 on 23rd Dec, 2012.

69mm offset... thats getting mighty thin between the walls! im not too good with the conversion or figuring out cc, i can tell you a 68mm offset (Imp Pistons, or similar 0.134 thou OB) is 1220cc, i wouldnt think a small bore block could go much further!

Ive had a drive of a 1220cc imp pistoned small bore, sooooooo much torque! it had a 12g940 and a 45 weber, pulled out an easy 67hp at the wheels last dyno day... the engine is great! i would consider building one for an NA application, built right would be a fantastic daily motor.

Ta,
Matt

Edited by mattsmadmini on 23rd Dec, 2012.

“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

thanks mate ,def 69mm i have measured it with a vernier gauge ,he mentioned oil galleries have been sleeved or something ,running race diff of some form and heavy duty clutch ,but would have to pull it apart to find out ?

Well it won't be as big as a 1275, so ultimately it won't make as much power.

It's a bit of an oddball really, would have been a good engine in the class it was running in, no doubt. But as you're not constrained by rules, you'll make more power with a 1380 etc.

Unless you want something unusual, it has no real advantage. Personally, I like the idea.

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

www.twin-turbo.co.uk

This engines forsale on TMF for like £250 not a fan of the offset at 69mm bit mad maybe with a 940 head it out run a standard 1275

yes i have it for sale up on tmf for £180 now but i have just purchased a 12g202 head so thinking of building it and sticking it in my mini till 1275 is finished to see what it goes like .


dav

Edited by stealth05 on 24th Dec, 2012.

Large and small bore engine really rev the same. But you need a better head on the 1275. It's pretty easy to get enough breathing to make a 998 rev. Problem you'll have with this engine is a 202 will strangle it.

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

www.twin-turbo.co.uk

Yes, or an SC 7-port, or an 8 valve k head would be great.

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

www.twin-turbo.co.uk

I have a spare 940 head will just drop stright on if you want to make an offer

Will a 940 drop straight on? I wonder with that bore will it need pockets? Also I wonder what the compression ratio would be?

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'd love to see the pistons & rods and know the deck height.

Metric is for people who can't do fractions.

“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson

I've got a full-race 12G295 with 'S' valves in it - a bore this size would be magic...

Metric is for people who can't do fractions.

go 1275 more power to start off with and more to gain if wanted

Done now needs redoing lol

Stick a decent head on it and get it running - if you decide you don't like it and want something different it will always be worth more as a running engine.

Having said that, we'd all love to see the insides before you do...

Metric is for people who can't do fractions.

940 head should drop on depending on the offset small valve

and a 202 head is rubbish smaller ports that later 998 head (well mine is)

think this 202 must have been messed with then as the ports are mahuuuusive

pulled it apart and the engineering work is amazing