7 replies to this topic

[cap'n crunch]

The two cams i have been looking at have been the SW5 and the cooper 997 cam (948).

The engine specs i am looking at is:

998 or 1098 (depending on funds)
12g295 cylinder head
Twin HS2
Cooper freeflow and RC40

The Usage is a Daily Drive (roughly 20miles round trip, though the roads are all 50-60mph limits for 80% of the time though there somtimes slow moving traffic).

My aim is a car which will be sensible in traffic(some lopeyness acceptable) and give good power through the range from between 1000-6000rpm, but i am looking for acceleration over maximum speed.

Now the question is this, after trawling though the yellow bible and these forums, which would you recomend

Option 1

SW5 with 1.3 rockers
Duration: 244/244
Overlap: 28
Lift at cam: .281/.281
Lift with proposed rockers: .365/.365


or

Option 2

948 with 1.5 rockers(yes i know 1.5 rocker on small bore what am i thinking! BUT read the specs)
Duration: 252/252
Overlap: 37
Lift at cam: .250/.250
Lift with proposed rockers: .375/.375


As you can see both have similar specs with the Option 2 with slightly more duration and lift. Would this be detremental on a 998 and need a 1098? or to much for any small bore to act as a daily drive?
Would Option 1 be the way foward? considering i am looking for Torque over Bhp (yes i know they go hand in hand and HP is a a calcualtion on torque) and needed as a daily drive?


Congratulations if you have got this far after all the questions, brackets, numbers and demands All suggestions and opinions welcomed with the exception of "why don't you just get a 1275" and "what about the insurance cost".

Edited by cap'n crunch, 15 October 2007 - 08:41 PM.

[redhotmini]

from experience i would go for the SW5 cam. im sure quite a few other people would too

[minimanclive]

The 1098 was always a more torquey engine than the 998. (got one in my clubby estate) That with a SW5 cam and a decent unleaded head would make for a nice daily driver. I'm not sure on the long term use of the 1.5 ratio rockers on a daily driver. (i'm thinking of changing my 1.5s for 1.3s) As the SW5 has quite a lot of lift anyway you'll be fine with the 1.3s. Too keep things simple i'd have a single carb, with that engine spec either an HIF38 or HIF44. Match that up with a gearbox with a 3.44 Final drive and it'll be pretty quick.

[cap'n crunch]

i have already bought and recondition a set of twin HS2 so i will use them, and my mini currently has a 3.44 final drive which i intend to keep.

so it looks like the SW5 with 1.3s? but why is that? would the other set up i suggested be to much on a small bore? or not suitable to drive on a regular basis? or is the SW5 THAT good?

thx for the info/opinions so far guys keep it comin

[jayare]

The 997 Cooper cam, whilst a very good cam was designed somewhere in the region of 45+ years ago, whilst the SW5 is a very modern design using higher lift and faster valve opening rates which allows the duration & overlap to be minimised and still get the desired results and with more MoT friendly emissions. As you note, you can use this with 1.3 ratio rockers which will put less side loading on your valve guides.

JR

[Dan]

The problem with high ratio rockers in 998s is mainly to do with the timing of exhaust pulses, exhaust gas speeds and overlap. It's the same reason the Freeflow is a better manifold design for this engine than the LCB. A longer cam duration and higher ratio rockers too will only make it worse. The reason the 998 can work better in race trim using an LCB and 1.5s is not to do purely with the engine design but also its use. Race engines spend all of their time high up the rev range and don't really have to idle well or crawl about in traffic. I think you'll have trouble idling or normal driving and parking with that engine. But maybe not, the only people who would know are those who hve already built one and lived with it. It may be better on the 1098 and you'll certainly have to skim less off your head on one. I can thoroughly recommend the repro Cooper S 1.3 rockers from Mini Spares. You could also get them rebushed with offset bushes if you want to increase it a little more. Standard sintered rockers are about 1.27 I think and not too reliable throughout the range of movement.

[cap'n crunch]

thanks for that dan, that was very informative and answered the question perfectly. So the SW5 with the 1.3 rockers is what i shall opt for.

by the way is it possbile to have a link to the 1.3 coopers repros? as they sound like a better option then paying looooooads of money for roller rockers

Thanks again!

[Dan]

Unfortunately not, the Mini Spares website is working about as well as usual at the moment. Just ring them. The rocker is part number 12G1221, sold individually. They use the same adjuster screw and locknut as the standard rocker but you may as well get some new ones.