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MG MGB Technical - Oselli 1950cc

Hello after selling my MG last year to a Frenchman and regret it im looking for another Roadster .The early models have increased in price so a later car with the chrome bumper conversion would be perfect.Im going to look at a well sorted 76 with the conversion ,the guy as spent a fortune and a lot of time on the car.Its got a new Oselli 1950cc engine with a new single Weber carb.How would this engine compare to my old Peter Burgess 1860 with fast road head and 285 cam 106bhp.After having a MG with a more powerfull engine i don't want to buy one standard Thanks Daz
DCP Parker

Perhaps it's like this one (128bhp) http://www.mgcars.org.uk/news/news289.html
Geoff E

Yes it has the suspension upgrades 123 dizzy etc
DCP Parker

I imagine the Weber is the 45DCOE. This carb flows more that 2 HS4 SUs but uses more fuel and is less tractable in road use. 1950cc is close to the limit these bocks can take, mine "squirms" a bit and burns some oil but it was done 20 years ago its possible Oselli have learned a lot since then. I know someone with a 1950cc Oselli engined MGA and no complaints about the engine generally, and esp how it goes on SUs.
Stan Best

You may find as Stan says, that your low end torque may be a little down, but in comparison to standard? Which from all accouts you have not driven for some time. The other thought is a long induction track with the right cam can give you good low torque, but a short induction track pushes the torque band higher up the revs range. So with the wber relatively short track, etc and beacause there is no balance pipe between the 2 intake ports etc,etc All in the Tuning the 1800 article we've talked about on this chat page. Mike
J.M. Doust

Daz, you need to establish what cam is fitted initially. Also state of tune of the head. A good cam for the road would be a 285. If it has that you will find it more sprightly than the 1860, and more torque. And more thirsty!

But it depends what Pete did to the 1860!!

I would think the 1950 would be a quicker engine.

Colin
Colin Parkinson

DAZ,
The bodywork is everything as you know - if power is important, the later body will give you options - a V6 or V8 transforms the MGB. Try one first.
R Walker

Im not after that much power just a bit more pep than standard .The chap selling the car told me that the engine spec is oselli 1950cc fast road stage 2 lightened and balanced with clutch and flywheel (fast road cam)but does not know the cam spec.uprated suspension and brakes etc.You mentioned more fuel,can't see it much different to the 1860 or is the Weber carb not so economical.Forgot to say it as a full ss sports exhaust one silencer and a tubular manifold.

DCP Parker

Daz, I am afraid economy and Weber do not go together well!

Cam spec is important I think.

Colin
Colin Parkinson

If i don't get on with the Weber i could sell it and fit 1 3/4 SU carbs..
DCP Parker

A properly calibrated Weber DCOE can still return good mileage. They are probably the beat carburetor ever produced, with a throttle shaft that is supported by ball bearings. Everything inside the carb is able to be changed out to a different size, to allow for increased performance or better fuel mileage. I ran one for over 10 years before fitting a supercharger system to my car. RAY
rjm RAY

Your very lucky .We are paying over £6 a gallon and you only £2 so economy is not so important for you !
DCP Parker

Your very lucky .We are paying over £6 a gallon and you only £2 so economy is not so important.
DCP Parker

Daz, the 1950 will always burn a bit more fuel everything else equal , its the 2nd law of thermodynamics and you dont get loopholes in those laws with objects the size of an MGB. However you are correct that its not enough to worry about. The cam and carb will make dramatic differences. The car sounds great, and you can always re-cam it and as you say put it back to SUs.If the guy cant tell you the cam fitted why not get the cost of putting in a reasonable fast road knocked off. Persanally I would ring Peter Burgess for advice.
Finally , not dissing Eduardo Weber, his carbs are masterpiecs and any weber carb same model same jets will will perform exactly the same and one 45DCOE flows more that 2 HS4s, but for road use I prefer the constant depression SU.
Stan Best

I've got a Roadster in 1848cc and a GT which had a 1995cc/DCOE Oselli until a while back. I'd make the decision based on how you are going to drive it. Roger Parker gave the best description: whippet versus bloodhound.

The Roaster is always eager and puts a smile on your face, the GT felt powerful but less keen, unless you were prepared to use full throttle all day (the Weber effect). It was so good that often I was, only then the fuel consumption figures would end "-teen".

One footnote is that the larger engine seemed to lose its tune faster than the standard. It more sensitive to ignition timing. Other than that it was perfectly reliable and only started to use oil after I'd done more than 60,000 miles.

Steve
SteveP

I have a 1973 B roadster with an oselli. conversion and mines 1995 cc the car has a standard head and an oselli cam a B271 and standard SU carbs at the time of buying this car I was more interested in getting a car with a decent body and paint work.
It was a few weeks later that it began to dawn on me what I had bought, the one point the previous owner made to me before I drove of with the car was that the valve tappet gaps should be set at 20-21 thou, which I thought was excessive as notes on this cam say 16-18 thou he said the engine had been tuned for low down torque,
The only problem I find is that I have to drive the car which is fun but if I let the revs fall below 2300 in 2,3,or 4 gear then I find the engine prone to pinking this I try to avoid, This car loves a hill to climbe.

Do you think having a standard head on this car makes for a higher compression ratio as apposed to a stage 2 head. The other thing I have noticed is this engine requires the highest octane fuel I can buy on 95 octane it performance is poor and the engine tends to run on when switched of. On 97 octane the car performs but I still feel like I should be adding an octane booster to get rid of the pinking.

I would appreciate your comments on the standard head and ways to elivate the pinking.
A race enthuseast said to me adjusting the carbs to give more fuel might help sugesting more fuel might make the cylinders run cooler,

Regards Patrick Tighe
P.T. Tighe

Going from a standard worn engine to Peter Burgess engine
1860
Fast road head
285 cam

the difference was unbelievable

It made 106bhp at the wheels Peter supplied the head and cam and i had it built by a pal of mine.It was balanced so that made a difference.
Once the cam came in there was a sudden surge of power almost like a turbo kicking in.I managed to get 35mpg on a run to Devon so it must be more efficient.
The flame thrower coil electronic ignition and Aldon dizzy made some difference,could keep up with modern traffic and sit a 80mph all day..A lovely little engine.
When i get another car i will be doing the same all again..Who knows he may have some more tricks up his sleeve different cam spec etc...
DCP Parker

This thread was discussed between 12/03/2011 and 18/03/2011

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