Supercharging a 970 S

[Nevsmini]

I'm thinking of supercharging my 970 Cooper S. Has anyone done this before?
Looking for some advice. I was going to use a shorrock if I can find a good one!

[cheleker]

Don Racine, of Mini Mania, ran a supercharger on a 970 in his Moke for a number of years. I got to drive it a couple of times. It felt like a very well tuned 1275 for torque, but with the 970's smoothness. He was running the Mini Mania supercharger kit (NLA).

[251 ENG]

We did a supercharged mk2 1275 s for Al Vives .

Lots of torque , but it costs a fortune to get the superchargers rebuilt properly .

If you looking for a shorrock , try to get a complete kit not just a collection of random supercharger bit thrown together to sell .

[Ant Hines]

A couple of Judson superchargers on US ebay...

http://www.ebay.com/itm/JUDSON-SUPERCHA ... 720wt_1328

http://www.ebay.com/itm/Judson-Supercha ... 987wt_1328

Anyone know anything about them?

[contour51]

Ouch :!:these things aren't cheep.
http://www.ebay.co.uk/itm/SuperCharger- ... 647wt_1064

[gr4h4m]

I run a toyota SC12 on my 998. It was the oldest looking charger with the smallest carb inlet manifold. I wanted a C75 but the cost just seemed mad for an old charger that then needs a load of work rebuilding it. The car makes very good power for a 998

The kit is avaible from Aus.

[mk1]

In my opinion supercharging a 970 with a Shorrock would be totally pointless. Doing this you would not end up with an enormous increase in power for the following reason.

The Shorrock blower has an absolute maximum rev limit of 7,000 a more realistic limit for a 40 year old blower would be 5,500 - 6,000. Bearing in mind that at 3,000 rpm a Shorrock blower will give 750cc's per revolution, to give a good reliable 7 pound or so boost you would need a blower to engine ratio of around 1.2 : 1 meaning that if you run the blower at its maximum of 6,000 rpm your engine will be limited to 5,000 rpm.

As the 970 gives best results at high engine rpm where its inherent smooth rev-ability can be taken advantage of, you are never going to utilise this engine to its best advantage.

You could achieve the very same, if not better results using the much longer stroked, lower reving & infinitely cheaper 998 engine.

Contrary to popular opinion doing a shorrock supercharger conversion is not just a case of bolting it on & getting the power, it does need some thinking out.

[Pandora]

By your reasoning Mark, which engines respond best to a Shorrock? 850, 1071?

[mk1]

You get the best improvement in an 850, then a 998, a 1098 works OK.

The rev limit is something that people invariably fail to take into account, there is no point building an engine capable of revving to 10,000 when the blower will explode at around 7,250.

M.

[gr4h4m]

10k! Surely they can't do that for long....

At 6k my 998 is pushing 75-78 ATW hp. That's a reasonable spec engine that was built in 1970.

[251 ENG]

I think the Arden 999,s would go to 11,000

[gr4h4m]

No doubt, I know of grassers that hits 10k but that's a pure race engine, they get more loving care than an oil change once in a while.

What I as trying to say is why build an engine that will run to 10k when you can get good FI power at 6k. Surely even a 970 would need some serious care and £££ to hit 10k?

I know the grasser in question makes about 115 bhp out of an 1120cc. Supercharged you should beable to make that sort of power for a lot less £££.

Just a point of view.

[Nevsmini]

Well Mark, it's not what I wanted to hear but it's better finding out now than later down the road.
This idea had me pumped! I was hoping to get some torque back into the 970 engine and this was my answer! With a nice period part. Looks like I'll have to go down the rev the bol***s out of it root.

[mk1]

A guy I knew used to run a 970 S in a single seater that he reved to 13,000 it stayed together for years. It was however a very special little engine.

10,000 for a standard 970 is probably pushing it a bit but 9,500 is not out of the question. My brother used this as a red line on his 970 cranked / 73.5mm bored rally car.

My mate Will's Turbo'd 998 does round about 160 odd BHP at around 6,500rpm

[251 ENG]

Excellent point about the rev limit made by Mark .

I think post people have trouble because they over rev them or do not get the correct oiling pin .

[gr4h4m]

A guy I knew used to run a 970 S in a single seater that he reved to 13,000 it staid together for years. It was however a very special little engine.

10,000 for a standard 970 is probably pushing it a bit but 9,500 is not out of the question. My brother used this as a red line on his 970 cranked / 73.5mm bored rally car.

My mate Will's Turbo'd 998 does round about 160 odd BHP at around 6,500rpm

Wil_h's 998 has a few more ports than normal..... I think the 5 port was about 150 but then you will never get the boost from a supercharger needed to hit those figures....

My enigne was built circa 1970 with the car. In 2006 when I put the car back on the road it had 24 bhp ATW recorded at lad morecambe. It was way too slow to keep my with the modern traffic.

Twin su's, exhaust, and a 295 big valve head (too big really at the time, not that I knew then) the car made 33 bhp ATW.

Super charger bolted on, 295, hif44 with everything else the same and the dizzy retarded. 61 bhp ATW.

££ it was a very cheap way to get power.

Since then things have been refined, a bit of development to smooth things out, a few more ££ but the same bottom end and it has a few more horses. It's good fun for a little engine, I do wince a bit if you push it to 6000rpm god knows what 9, 10 or 13 sound or feel like....

[mk1]

Simon's comment re oiling pins is absolutely correct. Whenever I fitted a Shorrock blower I NEVER ONCE Used any of the original oiling pins. I always had to have my own ground. I found that around 1/4 of a thou clearance was about optimum on a well preserved Shorrock oiling system.

[wil_h]

The problem is not the 970, or short stroke and ability to rev, it's the supercharger choice.

If you are not fussed about using classic parts then centrifugal SC (Rotrex) would be well suited to a 970. Because of the way they build boost, you can run high CRs, and long duration cams. This means a great ability to rev and the extra shove you seem to be looking for.

Of course, you will need to run the carb after the compressor and I'd suggest an intercooler, so you won't have a classic look under the bonnet.

And Mark, 160bhp was so last year!!!

[mk1]

I totally agree Will, but the question was regarding a Shorrock.

M

[mk1]

Nev,

If all you are after is boosting the torque without overly increasing out & out BHP then a C75B would be a good way to go. In my earlier comments I was simply warning against the assumption that sticking a Shorrock blower on will solve all your issues in 1 go.

Its hard to estimate, but I reckon its safe to say that a more or less standard 970 that has been fitted with a C75B would be very similar to a very, very mildly tuned 1275 S. It could certainly not do much more.

M