1098 engine tune

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Captain flint
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1098 engine tune

Postby Captain flint » Tue Apr 21, 2015 8:57 pm

Hi all,
with the rarity and spiralling costs of purchasing a 1275 engine,I am sure I read somewhere in these
pages that the 1098 can be tuned to have the same output as a 1275.
Being a poor old pensioner is this a viable proposition against the purchase of said 1275?
Right,anway exactly what is involved to raise the BHP of the 1098?
Carb,cam porting? please let me know.
Many thanks for looking.
Martin.

philthehill
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Re: 1098 engine tune

Postby philthehill » Wed Apr 22, 2015 8:49 am

The weakness with the 1098cc engine is the crankshaft.
I would only advise tuning a 1098cc with a engine number prefixed with 10CC as that engine has a stronger crankshaft.
Even then to get the same power output as a 1275cc Marina engine (65.6 lb ft @ 2600 rpm) engine is going to cost money.
If you do decide to tune the 1098cc a useful book is 'Tuning BMC Sports Cars' by Mike Garton and was for sale on 'e' bay in cd form @ £1.49.
Also read David Vizard's book on 'Tuning The 'A' Series'.
Personally if I wanted to fit an improved engine to a Minor I would go for the 1275cc Midget engine as it is a straight swop but as you say they are not cheap.
The Marina Pre 'A' Plus or 'A' Plus engine are more readily available and a little cheaper; the parts required for the conversion can be sourced from the usual suppliers and are relatively cheap - but the overall cost of the conversion is not much different from buying a ready to fit MG Midget 1275cc engine.
So to sum up you pays your money and takes your chance
Phil


bmcecosse
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Re: 1098 engine tune

Postby bmcecosse » Wed Apr 22, 2015 9:20 am

The easy answer is -yes - it can be improved to the same power as a standard 1275 - but at approx 12% more revs than the 1275 - and as Phil points out - the crank is not great, and should not be taken over 6000 revs - at least, not too often! A 12G940 head from a 1275 engine can be fitted (but ask here first) and a larger single carb on an alloy inlet manifold is needed too. The head benefits from some port work - especially in the exhaust throats (but it's not essential) - and a better exhaust manifold (the 1275 Marina one is fine) and a larger bore exhaust system to match that manifold. All that will give you 60 bhp and nice mid-range power boost , which in turn allows fitting of a lower final drive ratio (3.7 or 3.9 depending on pocket depth) for more relaxed cruising. A 1098 is never going to be a racer! Of course - any upgrading should only be considered if the engine is in good condition - with good oil pressure, and not burning oil/pumping blue smoke. The MG 1100 engine gave 55 bhp on the 295 head, and the 940 head is so much better - the additional 5 bhp it gives is easy to understand.
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philthehill
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Re: 1098 engine tune

Postby philthehill » Wed Apr 22, 2015 11:31 am

bmc
I do not deny the 1098cc CAN be tuned to give better power and I agree with your comments regarding engine condition etc but and it is a BIG BUT the parts listed in your post and the work required is going to cost time & money and the original poster appears to be concerned about costs and that is why on balance if you can find a 1275cc Midget engine at a reasonable cost go for it.

http://www.ebay.co.uk/itm/MG-Midget-Aus ... 27fd712157

If not this 1275 Marina engine is worth a consideration and appears to be in good condition and at a reasonable BUY IT NOW price.

http://www.ebay.co.uk/itm/Marina-Ital-M ... 19fe3617f9

Phil


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Re: 1098 engine tune

Postby simmitc » Wed Apr 22, 2015 1:00 pm

Before you do anything to the engine, make sure that the brakes and suspension can handle things! And, for that matter, the body too

Captain flint
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Re: 1098 engine tune

Postby Captain flint » Wed Apr 22, 2015 9:23 pm

Many thanks all,
Comments most welcome!
Martin.

bmcecosse
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Re: 1098 engine tune

Postby bmcecosse » Wed Apr 22, 2015 9:44 pm

Well -I know costs have risen...and my parts were bought maybe 6 years ago now.... but my 940 head was £20, the carb was £5 and the inlet manifold also £5. A Mini Cooper 3 branch exhaust manifold was £1 , a brand new Cooper S silencer was £2 - and I welded up an exhaust from various bits and pieces... Oh and I had to buy an AAA needle - and I chose to buy a cone air filter which I think was £10. But I agree - if you can find a good condition 1275 at a fair price, by all means go that route. Still need to buy the carb/needle/manifolds/exhaust system/air filter though....... :roll: The mods to the 1098 can be done on a piece by piece basis - spreading the cost along the way. Actually I found the exhaust manifold and big bore system made very little difference....
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smithskids
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Re: 1098 engine tune

Postby smithskids » Wed Apr 22, 2015 9:57 pm

I have built up a few 1098 and 1275 engines over the years and fitted with a 270 degree cam and an increase in compression can provide quite a lively engine. 1275 engines tune better than the 1098. nothing much noticable on the 1098 under 3000 rpm where as the 1275 will pull from 20 mph with an hif type carb. A webber 40dcoe type will pull a few more rpm but wont give as good fuel consumption. :)

bmcecosse
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Re: 1098 engine tune

Postby bmcecosse » Wed Apr 22, 2015 10:18 pm

270 cam is a lot for an engine that won't be run above 6000 rpm. The standard cam is actually pretty good on the 1098, or perhaps the MG Metro cam - hard to find now.
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Captain flint
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Re: 1098 engine tune

Postby Captain flint » Wed Apr 22, 2015 10:39 pm

Just a quick PS.
I am now a bit confused as I have decided to go the 12g940 cylinder head on my 1965 1098
Morris Minor.
Many are advertised on E- bay,some Mini 1275 and some Midget type.
Three questions will a Mini 1275 fit my 1098? What about the stud patterns re some 9 stud and some 11?
I have taken on board the mods. required,is the 320thou dim.achieved by grinding?
Thanks for all your patience.
Martin

bmcecosse
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Re: 1098 engine tune

Postby bmcecosse » Wed Apr 22, 2015 11:35 pm

9 stud and the 'small' valve version is ideal . Feel free to pm me a link to any 940 heads you are interested in - if you want comments. And don't worry - I won't bid against you - I have a plentiful supply in the garage loft.... :wink:
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bmcecosse
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Re: 1098 engine tune

Postby bmcecosse » Thu Apr 23, 2015 9:42 pm

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