12 replies to this topic

[1987_ParkLane]

Hi all,

With a bit of money coming in son, with starting my new job, I was thinking of doing a an engine build ready to be fitted in the summer of '09 ready for most of the mini events. It is going to be a 998cc engine, and I think my mini could do with a new engine anyway, so I am going to treat her. So here is what I would like it to include:

• +120thou Pistons
• 1100 Crank
• 1275 Ported and Polished Head (Double Valve Springs, etc)
• Turbo Clutch
• Straight Cut Gears (With Centre Pick up)
• Lightweight/Lightened Flywheel
• HIF38 Carb
• Supercharger
• Performance Diff
• 1.5 Roller Rockers
• Cam (Not Sure Which One Yet)

I can't think of anything else at the moment, but what I'm really asking is if anyone can think of a reason why this wouldn't work, what to change or what to add.

Thanks

[Sleepy Stu]

I would start out with a 1275 block if i were you so you are not always playing catchup?

Edited by Stewart_GT, 05 September 2008 - 01:34 PM.

[1987_ParkLane]

I would start out with a 1275 block if i were you so you are not always playing catchup?

I knew someone would say that, but I want it to be different, not just a 1275 or a 998. But I'm sure with all these mods it would be quick.

[cap'n crunch]

i would imagine with that set up you would be pushing 100bhp depending on the boost you will be running, though +120 overbore is a bit much though? i would have thought there would not be a whole lot of space between the cylinders and did not realise you could get such a large over bore?

[Tomf]

Sounds good, but why not just use a 1275 block as there would be so little space betweent the bores i woudl imagin you would be re-building the engine every year...

Edited by Tomf, 05 September 2008 - 03:24 PM.

[Sam Walters]

oh you can go quite abit more then +120 but why bother really when you can make a 1293 that will be less stressed to make the same power out put.

bmc had

[Retro_10s]

i would say the 1.5 roller rockers don't need to be on that list.

There's a supercharger on that list,.. really you should build the engine around that idea.

[jayare]

If you intend to use the 1098 crank, you'll need pistons with a smaller gudgeon pin to crown height than if you used a 998 crank to account for the increased crank throw without the pistons sticking out of the top of the block at TDC.

As has already been mentioned, 1.5 ratio rockers don't tend to work too well on small bore engines - 1.3:1 ratio would suit much better. Keep the cam relatively mild - the charger will give you plenty of power without needing a wild cam.

Good luck with it and enjoy it!

JR

[Jammy]

What do you intend to use the car for?

[mk1leg]

Your block and pistons will need alot of machiningyou will be better off not wasting your money and going for a ready built and tuned 1380 and then put on a supercharger.............140+bhp................

[1987_ParkLane]

Its not all about the power, I want my mini to be ifferent too.

[Dan]

Absolutely right, it's not all about the power. It's about where the power is developed in the rev range and what the rev range is. The 1275 engine is far too undersquare to enjoy a really good range and while boring it out helps, it doesn't help enough unless you also destroke it fully. Having said that of course the 1098 crank will make the small bore very undersquare too. If you do fit a supercharger, that will help overcome the problem. If you drive about town a lot then a small bore, squarer engine is far better than the big bore. If you spend more time cruising at maximum revs on the motorway then the big bore is better, but will use more fuel.

I can't remember how many people over the years have been shocked that our car is a worked-over 998 but in Germany this year I got asked the question several times again and several more people got the answer they didn't expect. How well you build it is just as important as what you build.

[1987_ParkLane]

Absolutely right, it's not all about the power. It's about where the power is developed in the rev range and what the rev range is. The 1275 engine is far too undersquare to enjoy a really good range and while boring it out helps, it doesn't help enough unless you also destroke it fully. Having said that of course the 1098 crank will make the small bore very undersquare too. If you do fit a supercharger, that will help overcome the problem. If you drive about town a lot then a small bore, squarer engine is far better than the big bore. If you spend more time cruising at maximum revs on the motorway then the big bore is better, but will use more fuel.

I can't remember how many people over the years have been shocked that our car is a worked-over 998 but in Germany this year I got asked the question several times again and several more people got the answer they didn't expect. How well you build it is just as important as what you build.

Thanks, nice reply