Morris Minor Owners Club

Can anyone tell me how far the stndard 1098 engine can be bored out by?

+.040 inches, according to the workshop manual. You can, however buy +060 pistons - the experts will have to tell you about those though

what cc would that bring the engine up to?

I seem to remember reading somewhere that the 1098 has piston sizes only in increments of +.020", unlike the 948 that goes up in +.010" sizes. Please correct me if I'm wrong Ginger!

Oooooh - judging by the ESM site, you're right

Vizard goes into offset bores & Imp pistons to take it up to 1215cc if you want to go that far (no point for you lucky guys who have fairly easy access to 1275s ).

Unless you live WAY up north in BMCland. Apparently.

Indeed - 1275 in-line is scarce fare up here. Hardly worth boring out more than you need to. Risk of it going porous! Power increase will be negligible - there are easier ways to get more power!

tell me the easier ways of getting more power? i have a set of twin 1.5 inch su's can i jet these to suit the engine?

Turbo it! Pity Iain doesn't come here that often anymore. That's mr Turbominor. But I think mr Ecosse was referring to the 1098. If you upgrade a 1275, there is a lot more to play around with.
Ask Cam, he has a very nicely tuned 1380cc in his 4 door

the only problem is that the 1275s are gettin very rare over here.I would have to spend £200 to get a burnt out unit and then start rebuilding it. any other options anybody

I think that they weigh too much for hand luggage on RyanAir too....

okay without blowing a fortune on the engine what would be easy done and give me a few more horses. Iam putting on fibre glass wings to cut down on weight also the interior is going to be the minimalist type. But i am going to use it on the road. But not for a little while yet as she is gettin a good restoration

A cheap easy way of getting more power.. being 17 i find the prospect interesting

paul.kissick wrote:tell me the easier ways of getting more power? i have a set of twin 1.5 inch su's can i jet these to suit the engine?

Buy David Vizard's Book: Tuning BL's A-series engine and read it from cover to cover. That will tell you all you need to know.

With the correct tuning, a 948cc motor can outperform a 1275, but of course if you start with a 1275 then the potential is greater.

Twin carbs are not really worth the hassle to set up as they don't really give any advantage over a single large SU carb.

Also there is no 'jetting' as such with the SU carbs. Just a change to the fuel metering needle.

So does a 1098 need bringing up to 1275 before you can do anything else?

Hello Cam,

"Twin carbs are not really worth the hassle to set up as they don't really give any advantage over a single large SU carb."

Perhaps not discernable on a road car but mini racers used to chop two Weber DCOE units to use a twin DCOE (single choke) set up, not cheap, but the manifolding must have given some gain over a single DCOE for them to go to the trouble?

Alec

The twin weber trick was to get the very last 1or 2 hp from a full race engine ! Best way for more power is a good big valve head (12g295 or better 12g 940) then change the cam for something with a bit more timing - MG Metro cam is excellent and then carbs and manifolds. You could use the twin 1.5" carbs (after the head and cam mods) - they are slightly too big - but the good thing about SUs is the variable choke - so it only opens as much as is justified by the airflow. You could get up to ~ 75/80 bhp if all done nicely - but do remember 1098 engines break the crank if revved continuously over 6000. A crankshaft damper is essential !

Won't this put strain on all the engine parts? more to the point how much are you looking at paying for those parts?

Tris wrote:So does a 1098 need bringing up to 1275 before you can do anything else?

No. Think of the engine like an air pump. The more air it can pump then the more power you get out. The trick is to change the engine parts so that it can get more air in and more out. changing to a bigger pump (1275) is an instant way of getting more power, but getting the smaller pump (1098) to rev faster and make the incoming air have an easier path (modified head, bigger valves, change of cam, etc) and an easier route out (decent manifold & exhaust system). Of course this is a simplified way of looking at it but you get the gist.

A carb is a device that meters the fuel to match the air flowing through to supply the correct ratio that the engine needs. It does this for all the different air demands that the engine requires. If the carb is large enough to supply the engine with all that it needs then there is no advantage of having more smaller units that are trying to make up one large one. A lot of the big A-series engine tuning places don't recommend twin carbs now, just one big one. Usually a HIF44 is sufficient for most applications. Twins might look better but they won't give a performance advantage over a correctly set up single as they can't!

Also, comparing Webers to SUs is not like for like and so not a fair comparison. Webers can give slightly better top end. But they loose out further down the scale and they don't offer anywhere NEAR the economy that an SU can.

If you are running a FULL RACE engine and are competing at high RPM round a track then I can just see the point in a Weber, but for 'through the gears' racing an SU is just as good (if not better). For a road car I would not fit a Weber personally.