14 replies to this topic

[MiniBK]

I have a Mk1 Austin Mini 850, and I'd like to increase the power and speed to be able to keep up with modern traffic. I don't want to physically change the engine but upgrading the carburettor and inlet and exhaust and and other upgrade I'm up to other upgrades as well but I don't know where to find it or what else to do to get it keeping up with modern traffic!

Thanks!

Ben

[Cooperman]

Whilst you can improve an 850 a bit, you will never get a 50-year old car with a very small and old-tech engine to keep up with a modern car.

To get any sort of meaningful improvement will mean a re-build of the engine with a better gas-flowed head, a different cam, a 3-branch exhaust manifold, a 1.5" carb and some lightening of the flywheel. Done wel it could give c.45 to 48 bhp up from the lowly 34 bhp

Of course, you could build a 'screamer' of an engine which would give much more power for a short while until it needed re-building again or until the crankshaft snapped.

The only other option is to fit a bigger engine, like a 998 which is much easier to improve. but that would make it non-original and no longer the true classic a 1967 car is now. Or you could fit a Shorrock Supercharger which is a period modification.

Best, maybe, to make sure the engine is performing as well as it can and then just enjoy the true retro-driving experience which only a true classic can give. I'm in the middle of an 850 restoration at present and look forward to the day when I can come to remember just how slow those cars really were   . But they were so much better than the other small cars of the time such as the Ford 105E, Triumph Herald, Vauxhall HA Viva, VW Beetle, Renault Dauphine, etc.

[SteveDW]

All the usual tricks work. Get a stage 1 kit and 1.5" SU. When buying an exhaust manifold you need one that will clear the driveshafts, I can't recommend one but have heard that some foul the driveshafts. Don't go too large with the exhaust, RC40 is more than enough. You can also fit a Cooper 998 head or one from a 1098 engine, it will need skimming to get the correct compression ratio. If you tune an 850 lots then you need proper camshaft bearings as the standard ones are not up to much.

Let us know what you decide.

Steve

[Spider]

For the money spent & effort involved vs result, you'd be better off doing an engine swap to a 998 or an 1100 engine.

[OzOAP]

I've just done an 850 for a customer. Have a look. I'm only a couple of miles from East Grinstead so get in touch if I can help.

www.facebook.com/ozoap

[Stevie W]

+1 for an 1100 engine. These are relatively torquey little engines in standard form but with a gas flowed/reworked head and a cam like an SW5 or equivalent and a small bore LCB/RC40 exhaust system will make for an excellent little road engine.

 

The SW5 cam will work well with the 1100 and give a nice flat torque curve and an engine you don't need to rev the nuts off of to get any performance!!

 

Cheers, Steve.

[whistler]

+1 for an 1100 engine. These are relatively torquey little engines in standard form but with a gas flowed/reworked head and a cam like an SW5 or equivalent and a small bore LCB/RC40 exhaust system will make for an excellent little road engine.

 

The SW5 cam will work well with the 1100 and give a nice flat torque curve and an engine you don't need to rev the nuts off of to get any performance!!

 

Cheers, Steve.

Be aware that if you transplant an 1100 engine and box from an 1100 car then the diff. ratio is likely to be too low for normal road use, 4.1:1 so would need changing to maybe a 3.44:1.

[Dusky]

If you really want to keep a 850cc engine you could Always fit a Fiat 850..
57 bhp from factory on the specials.

Jokes aside, Id Just fit a stage 1 kit and maybe rebuild the engine. It ll Be a Nice motor to have the real Classic experience

[absx2]

Wise words in favour of an engine swap and you can keep the original motor safe.

 

But there is something great about squeezing a bit more out of an 850.

 

Being on a serious budget back in the day I used a 1 1/2" carb including the standard 1000 air box with a snorkel to keep the girlfriend happy.

I separated the inlet from the exhaust manifold to remove the hot spot whilst keeping the small inlet manifold for port velocity. I kept the standard exhaust and cast manifold but changed the back box for a middle box as it was straight through.

The best improvement was slightly deshrouding the valves and removing part of the beak in the combustion chambers with a carbide cutter ( copied from a mountune head picture in a Vizard book )

Then I removed the guide bosses and opened the ports on the exhaust`s. The inlets only had the funnel shape smoothed out at the start of the port.

It needed a .060" skim to give me 10:1 compression.

I few runs up the road and as many adjustments and needle swaps later it was a little flyer regularly hitting 70 mph in third and it took a bit of catching.

All this fun for the princely sum of a fiver to a mate for surfacing the head and what ever a head gasket set cost back then.

 

Its probably all the fun you need for local driving with nose to tail traffic and national speed limit signs being swapped for 30 mph limits .

Its hard to legally drive a ride on mower to its limits let alone a rip snorting fire breathing monster :)

You also keep the fine art of sling shot going which can be as entertaining as it is frustrating but hey anyone can just put there foot down and overtake in a modern car ;)

[MiniBK]

Thank you for all your help I really appreciate it. I think we're going rebuild the engine and go for the stage 1 kit and a bigger carb and see how that goes! Once again thanks a lot for your time to help me ;)

Thanks

Ben

[Cooperman]

I did once fit an MG1100 engine into a 1962 Mini 850. I should have fitted a 3.44 FDR but kept the 3.76.
The other thing was the brakes - or rather the lack of them. I put a set of 998 Cooper discs on later with DS11 pads and Amber fluid and it was much safer.

[JBW]

Back in the day, I fitted an HS4 carb on an 850 automatic manifold (the auto was the only one to use an HS4 back then) a 12G295 head, home modified, then skimmed to get CR correct, a Servais stright through silencer, the front drum brakes were fitted with Ferodo AM4 (?) linings, all inspired by Clive Trickeys book and articles in CCC magazine. Money and parts were a bit tight back then.

It went quite well, much better than a standard 850,  & stopped better than my mates 998 Cooper,even on a tarmac stage event, brakes never faded like the original linings used to.

[Turbo Phil]

The cylinder head is the power killer on these motors. The poor chamber design and minuscule intake valve should be your first target. Some basic head work will yield some decent gains.
I could go into all the details here but it will take me ages, the best bet is to have a look at Vizards "Tuning the A-Series engine" it's covered in great depth in there.
The above mods coupled with a 1.5" SU, mild cam and a proper stage one kit will increase performance nicely without going wild.

Phil.

[Mini Manannán]

 a snorkel to keep the girlfriend happy.

 

 

[absx2]

 

 a snorkel to keep the girlfriend happy.

 

 

 

 

I also kept the long pipe on the air box to reduce induction noise