9 replies to this topic

[logan]

hi guys this maybe a stupid question to you lot but if you were building an engine to race which one would you opt for and why considering that you cannot rebore,change the cam,lighten components but you can skim the head,basically standard with head skimmed.would be nice to hear your opinions on the gearing aswell as the wheel size.

[Ethel]

1100, slightly better head as standard and more cc's = more power. In standard form neither will rev high enough for that to make a difference.

[logan]

ok what about if you were to use the 295 head and were able to change the cam without rebore etc.thanks for your input.

[Ethel]

1100 wins on everything apart from its ability to rev. Stay under, say, 6k rpm and it comes out on top.

For a crude comparison the difference is 10%. 10% more cc's for power, 10% longer crank for torque but 10% more stress on the crank.

[Cooperman]

I agree with what 'ethel' has said but with one proviso. If you are really aiming for a full-on race engine with a cam such as a 286 or better, you will need to be pulling up to or over about 7000 rpm in race applications. An 1100 crank just won't take those sort of revs and, really, 6000 rpm is a safe max for an 1100 crank. A 998, however, can be bored to 1061 cc which is +0.080" (or, some say, even bigger is possible) and, balanced and lightened will safely pull upwards of 7200 rpm.
If you are going to build a race car you also need to have in mind the class structure. With an 1100 you'll almost certainly be up against 1275-engined cars, but a 998 is in the up to 1 litre class and the only Minis with a better engine will be any that have the 970 'S' engine.

[logan]

hi again thanks for your input,i doubt that the engines will be reving to 7200 revs as it is for juniors and is not involved in the normal specs of grassing as it would be a locally run club with limits as shown in the first posting,i was just wondering if there was a mass amount of diffrence between the two engines but after reading the input there isnt a lot of diffrence and i would imagine the little diffrence there is could also be put down to the drivers as well.would there be anything that you could do to check that the engines are within the limits of a club without going into to much trouble or expence.ie bore size,cam profile,compresion test etc without the need of stripping down.

[Cooperman]

It's easy to scrutineer the stroke. An old scrutineer friend of mine had a pencil which he used to poke down a plug hole. He would make a mark at TDC, then turn the engine to BDC, make another mark and measure. a 998 has a 3" stroke and a 1098 has a 3.2" stroke.It's also easy to measure maximum valve lift by taking off the rocker cover, screwing one rocker down to zero clearance and using a DTI on a magnetic base to measure the valve lift.
Of course, neither of these will tell the actual capacity and the only way to do that is to remove the head. Also, a cam can have the correct lift for a standard engine, but have more valve overlap which is much harder to measure.
For any competition use, a bored out 998 will be better than a 1098 and even if it's not intended to rev over, say, 6000 rpm, it's easy to miss a gear and go to a lot higher, with, possibly, a snapped crank and the resultant mess of the bits going down through the box.

[logan]

hi guys thats realy helpfull and i appreciate your input very much,its just that i already have 4 1000cc engines but would be able to race 1100cc thats why i asked the questions but after reading your input im on the understanding that there isn't a great deal between them to run them as standard units so i think i will go down the route of the 1000cc engines as you will very well know the expence that you can go to.

[Cater_Racer]

Logan I run a 998cc witha +40 overbore 276 cam and 12G295 head skimmed and ported, HS2's LCB etc.

It therefore runs in the 1000cc class but still gives 70BHP so very competitive in that class, unfortunatley I frequently get pushed into the "Mini's Class" and find myself against 1380cc Cooper S engines, not nearly so competitive then, but great fun.

[logan]

hi yes i would have bored to + 40 but because it is only a single track run club the specs are diffrent to what you guys are used to,basically we are allowed up to 1100cc without rebores or cams or lightend items inside,but are allowed to skim the heads,i think the guys who run the club are aiming at fairness for all the young ones because you will always get people who could afford to spend quite a bit on them and then you get people who can't afford to spend as much so in fairness that is why we cannot rebore etc.the young one raced a standard 1000cc last year and was quite competetive considering he was allegegedly (if you know where im coming from)racing against 1400cc fords and pugs etc.hopefully they are to clamp down this year so i would exspect a very good season.as we all try and do i was after just that little extra and hopefully after joining the forum and reading the input of your guys i found it absouloutly fantastic and the amount of knowlege is unbelievable.as with the racing side of things i dont think its all about winning but the taking part and like you said its good fun and people just love the minis.