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MG Midget and Sprite Technical - 1275 engine power increase

I am racing a frogeye sprite with a midget 1275 engine for my first season. On the rolling road I am getting just over 100bhp. For next year I want to build a new engine which can deliver more power. Firstly it has to be 1275 engine and should not be so highly tuned that it goes bang! Secondly I don't have a bottomless pit of cash. What spec should I aim for and what improvement can I expect? Thanks Peter
P B Chappell

Which chamionship are you racing in and what class so that the engine can be made legal :)
Robert (Bob) Midget Turbo

and is that 100bhp at the wheels or the flywheel?
David Smith

At the flywheel I'd imagine.
Gary Lazarus

and most importantly what have you done to the engine now?

what cam
head specs
CR!!!!
carbs exhaust
etc
Onno Könemann

Id certianly pick up a copy of david vizards book... that will help alot

Prop

http://www.amazon.com/dp/1859606202/?tag=hashemian-20
Prop

and Daniel's book for some later aditons an general midget stuff
Onno Könemann

I can advise on how to make it go bang....
John Collinson

>>>>>>Which chamionship are you racing in and what class so that the engine can be made legal :)

No point in making a legal one, no-one else will have.

Hi Peter, welcome to the wonderful world of Midget racing! It's OK, somewhere here you'll get a serious answer if you can give everyone a steer on what you're racing in. No point in suggesting you go for a big overbore if you're not allowed it.

Have you done your first race yet? Enjoy it?
Max max-at-midgetmax-dot-com

The answers are;
Classic Sports Car Club - Swinging Sixties
I purchased the engine because it hadn't been highly tuned as I want it to last a season - hopefully! So far two races complete and it runs very well - hope that is not the kiss of death!
The cam is a fast road cam and the only other improovement I am aware of is 1.5" SUs. The exhaust and inlet manifolds are maniflow. I had it set up by Peter Baldwin on his rolling road - 100bhp at flywheel.
I am hoping by next year my skill as a driver will have improved to get more out of the car with a higher spec engine, but reliability would also be helpful.
The advise I have received so far is;
Lighten flywheel and get it balanced with crank and clutch (7.5")
Standard con rods balanced
Omega cast pisons
Full race cam shaft
chain drive with vernier
Spend the money on the head - what valve sizes?

I am on the right track?

Picture of where it goes attached

Thanks Peter


P B Chappell

That looks too good for a race car!

Is the car for race use only?

In my opinion ( although limited!) if you use the car for the road going "too far" with the cam will make road driving tiresome.

choice of engine builder is important, as the wrong one can spend your money very quickly!

how is the rest of the car? (brakes tyres chassis) as this may be more important than finding another 10hp
d cusworth

The balancing and lightening is done primarly to keep it together.
Making sure it does not vibrate to bits or carry exesive weight.
This dous not actualy add performance.

The power is made in the combo pistons cam and head.
The pistons must weigh the least but be strong enough to take the bashing.
The cam must keep the valves open as long as posible without wearing out to fast.
And now the secret to real A-series power.
The head
It dictates the static CR (in combo with the pistons)
It determins how much mixture flows in the chamber.
And shapes the top of the combustion chamber.

My advice would be
Do not save on the head
Get one frome a good source (swiftune, Peter Burges, MED etc) with a high CR
Get a good race cam and maybe add 1.5 ratio roler rockers (dependend on the advice the cam grinder gives) i have seen good numbers from an SW 23 (Swiftune)
And folow your list.

Head's exact specs can best be discussed with your supplyer of choice.
if you know what camyou want and what butget you have they can sugest valve sizes and CR.

You might want to switch to a 45 Weber (if rules permit)

Please do read up with vizard an Daniel's book.
Even if you don't build yourself it gives you a beter understanding of what is being done.
Onno Könemann

Peter,
That is a very tidy looking engine / engine bay. Very nice!

I may be wrong, but that power output seems to me to be a bit on the high side for the specification that you think that you have at present. Just makes me wonder if more has already been done to your engine than you are aware of. - Maybe raised CR and some gas flowing of the head by the previous owner?

Guy
Guy Weller

100 bhp on Peter Baldwin's rollers is not that high. Was the 100bhp the figure at the wheels which you quote as a flywheel figure?

You might want to ditch the dynamo for an alternator and save some weight.
Daniel Thirteen-Twelve

Peter

To be competitive in the Swinging Sixties series you will need a full race 1380 on a Weber/Dellorto 45.

With race engines you can follow peoples recommendations on head/cam etc etc and just end up spending a lot of money on what will quickly turn into scrap metal... Racing breaks engines (ask JC...). My best advice is to either 1) find a good engine builder that you can work with and wait until you can afford to buy a ready to race 1380 or 2) find one of your competitors who knows what they are doing and has a track record of competitive finishes, and try to persuade them to advise and help you with an engine build - in my experience of Spridget racing there are very few people out there who will actively give out duff info...

Good luck, and don't forget to keep the greasy side down... ;o)

James B
James B

Welcome Peter, I was admiring your car at Brands, I'm a bit nearer the front of the grid than you, but also light on funds (and talent, for that matter). James speaks wise words; the best thing I ever did was go to Steve at MED with a fistful of cash and buy a complete ready-to-fit endurance spec engine. 1380, 286 cam, 1.5 rockers, 36/29 valve head, Weber 45, steel flywheel, rally clutch and 118 bhp. It ran faultlessly for 3 seasons of FISC, so impressed I went back for a second one. Your 100 does sound high for the spec... but as long as you always use the same r/road it doesn't matter as once you have a benchmark it's all relative.
David Smith

Will throw my hat alongside James and Dave on this one.

If you are starting out, then get the peripherals right first, brakes, suspension and the skills to handle the power that will come. Then (or whilst) save some money up and buy a RTR race engine.

I tried doing it in bits and bats and didn't get anywhere, then decided (after about 15 years of competing) to get a proper engine sorted out. James and his mate Dave built me a superb unit that actually lasted for SIX.... yes SIX seasons doing FISC and would probably have still being running if it hadn't been for the driver (me!) who absolutely ragged it down the long straight at Zandvoort and snapped a valve clean off.

I went back to the old engine and did okay, but not brilliant, so another unit was purchased last year and we are happy again now.

But too much power and not enough talent to harness it CAN seriously damage one's pocket, hence our new car this year. The new car with the old engine has bitten me already, so just be careful!

Come and say hello to us at Oulton Park CSCC if you are going.

Andrew
Grey Midget Orange Stripes, No. 56.
Andrew McGee

That's 3 of us voting for speaking to engine builders and buying a complete set-up rather than doing it piecemeal.

I've spent/wasted a great deal of money over the years trying to build my own engine, I wish I'd bought one. And it's not so expensive. I was refreshing the engine in my last car before I sold it, and the value of the parts and machining alone was little less than an off-the-shelf rock-solid MED 1380.

Enjoy! Oh and keep us in the loop!
Max max-at-midgetmax-dot-com

Thanks everyone for the advise - a lot to think about.I will keep going this season as my sole intention is to keep out of everyones way and finish - oh yes and have fun. I shall be at Oulton on the 12th June so any further advise would be most welcome. Thanks Peter
P B Chappell

See you at Oulton then.

Andrew
Andrew McGee

heres a piece of advice you wont like, its from the david lieb thertical school of racing.

instead of spending money on the engine how about spending money on track time, hire a good driver and several hours of track time to theach you the finer details of racing, Im always amazed how a great driver with 1/2 the car of a rookie can still keep up with the best of them...

there is something to be said for driving ability and skill, its sorta like golf if think about it.

Prop
Prop

Nothing theoretical about it - David is spot on. You can spend thousands of pound/dollars on a top notch race engine, the best tyres and whatever tuning gizmo's are flavour of the month - however the greatest improvements will always come from the 'nut behind the wheel'.

There are very few cars in club motorsport that are driven to the maximum performance of the car as opposed to the maximum capability of the driver - driver training with a decent driver coach is always going to bring about the greatest decreases in lap time...

You still need a decent engine to be competitive however...
James B

True. I learnt so much more by following you James and also some others in FISC racing.

Track time is paramount.

Andrew
Andrew McGee

Andrew

Blimey don't follow me - I spend far too much time crashing...

:)
James Bilsland

that'll explain it Andy...
;-)
David Smith

This thread was discussed between 23/05/2010 and 27/05/2010

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