How can I get a little more from my standard 1098?

[Jaywhy]

I am relatively new to the forum but keep in touch with most bits that appear on the message board. I have a 1098 mm 1966 and wondered how I could get a little more power from the the engine without fitting a 1275? At the moment it is running very well but found it difficult when going up hills. Would a different carb help? E.g. Hif 38 For instance or am I wasting my time ?? Perhaps BMC has a view on this?

[bmcecosse]

A better cylinder head and yes that carb with an alloy inlet will help considerably. Carb on it's own won't make much difference - but would be a step in the right direction. 12G940 head is best by far - but needs a little care when fitting. 12G295 is more straightforward to fit - but not as good result....and tend to be v expensive these days!

[MarkyB]

Check that the vacuum advance is working properly.

[bmcecosse]

As Marky says -I was going with the 'running very well' - but an overall check of everything (including valve gaps and compression) and the whole ignition system to make sure everything is as good as it should be, won't go wrong.

[irmscher]

I have a 940 and a 295 for sale if you are interested and a bigger carb

[Jaywhy]

Thanks to everyone for their comments.I will certainly be taking on board the engine and ignition suggestions made and feedback any results. Can I ask BMC about the extra care I need to take if I decide to fit a 940 head? if I take this route of fitting the head do I need a hif 38 carb? Am I going to see any better performance by fitting the head and the carb or will I get the performance by fitting the head only?

[Jaywhy]

Irmscher - what sort of price are you looking for the 940 head and the carb? Do you have manifold for the carb?

[bmcecosse]

You could fit the 940 and acceleration will be better up to say 4000 rpm, but then the small carb will limit it. You need to realise it's the head from a 1275 engine - so it has larger valves, and they are wider apart. This means that the exhaust valve can hit the block if there is not enough clearance. So - you need to measure and check there is 320thou (8mm) clearance between the top face of the ex valves and the surface of the head - and if not, you need to sink the ex valves in to the head until there IS that clearance. Many heads have now developed 'recession' and will have that clearance now. Otherwise it's a 10 minute job in a machine shop. 1275 gasket must be used - also 1275 rocker set (or spend ages re-aligning the 1098 rockers on the shaft so they act directly over the valve stem tips - actually a v satisfying job when you get it right!) and file some metal off the top of the water pump (1 minute filing max!) to make sure the head can sit right down on the block. Curved top water hose needed too - I cut mine from an old bottom hose. Simples !!

[JOWETTJAVELIN]

Many heads have now developed 'recession' and will have that clearance now.

Is this an admittance of something many of us have denied for so long?

[bmcecosse]

No denial on my part! It's the reason I suggest 15 thou ex valve gaps........and check/reset every 3000 miles.......

[Jaywhy]

Hi BMC
Thanks again for your reply. Very informative. Can I further ask if I manage to get a 940 head how will I know if it is suitable for unleaded petrol? Also with this upgrade of head and carb how will this affect MPG?

What sort of realistic price do you think I could pick up a hif 38 carb and head for?

Thanks again.

[bmcecosse]

Don't worry about unleaded - if you drive the car harder, it WILL use more fuel - so if you want best economy - don't do it. Plenty on ebay - prices vary wildly so just keep bidding what you can afford....

[Jaywhy]

BMC - again thanks for reply it is much appreciated. Further questions - With regards to 12G940 heads I have had a look on ebay and notice there is this model of head for Mini's , Metro and MG sprites - so if I manage to pick one of these up, are they all the same e.g. Valves recessed the same OR are they somewhat different for each of these models? If different is there a particular model you would go for?

Also the ones that I viewed seem to have no rocker gear, so am I best to bide my time till I can get one with rocker gear or will my 1098 fit with some adjustment?

[bmcecosse]

The 'MG' and 'Cooper S' heads may have larger inlet valves - ideal on a 1275....not really what you want for a 1098. They also command a higher price... You can pick up rocker gear for v little - or spend ages re-aligning the 1098 rockers.
This is still well worth buying... http://www.ebay.co.uk/itm/171155587900? ... 1423.l2649

[irmscher]

Jaywhy I have sent pm

[Jaywhy]

Irmscher - I have replied to your PM. Let me know if you have not received it.

[Jaywhy]

Hi BMC

Missed out on the cylinder head link you gave me, however will this one do the job even though it is cooper head?

Look forward to your reply

http://www.ebay.co.uk/itm/CLASSIC-AUSTI ... 162wt_1172

[bmcecosse]

It would - but it's a bare head, and by the time you buy all the bits it will cost you a fortune....plus, you will need to out-bid me on it! I have a box of 'bits' so I can build it up ok if I win it.......... But I am honestly expecting it to go way beyond my limit anyway.....

[MarkyB]

Bare is right, how much will a full set of valves and springs cost on top?
The seller likes to call stuff classic, race and Cooper on his adverts, doesn't seem to be cutting much ice at the moment.

[bmcecosse]

And spring caps and collets......