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MG MG Y Type - More power - yes please?

There is an interesting item in the December bulletin of the MG Octagon Club concerning overheating and petrol vaporization in summer.

I don't have either of these problems on my YA but the interest is that both of the solutions seem to offer a small increase in power, which, lord knows, I could do with.

The writer proposes that modern high octane petrol does not burn as fast as the petrol available after the war. "Pool petrol in the late 40s was about 72 octane. So the petrol is not fully burned and maximum power is not developed.

His first solution is to advance the timing to 13 degrees BTDC (on a TC. This sounds extreme, but I have seen it suggested before that an increase of 5 degrees will improve power safely).

The second solution is to reduce the octane rating of the modern petrol from 90+ to a lower figure by mixing it with paraffin (kerosene for the heathens in the Americas - greetings to you all).

I can find little on the internet except an article suggesting that the octane needed is in proportion to the compression ratio, so our 7.2:1 engine needs 72 octane fuel.

Has anybody got information to confirm either of these as practical solutions?

If anyone wants the article, I'm sure the octagon Club would not mind me sending a copy on request. I would ask them first, of course.
Michael Nicholson

I can recommend simply raising the compression ratio to 8.6, a mod I did in the 1970s

Remove the head and have 3/32 inch skimmed off so that the head top to bottom measures 74.37 mm.
Remove frazes.

You will need 4 off 1/16 inch spacers under the rocker pillers drilled to match those holes at the base of the pillers. [these were available as part number M.G.862/459 ] however they are simple to make.
also 10 off 1/16 thick washers for the studs.

Then the rest is straight forward assembly, a weekend job if you prepare the parts before hand.

Ignition and carburation may need slight adjustment.

You will be most pleased with the the result.

As a note the TF was 8.1 compression.
Bryan

As a follow up to my recommendation, if anyone is in any doubt please consult someone like Mr Gammon or Eddney & Son since they know their way round an XPAG better than most. I base my advice on many years and miles of, at times harsh treatment of my YA.
One thing is for sure is that the car will cruise at 60 - 65 with ease and the fuel consumption will reduce.
Bryan

Dear Bryan
Can you explain further the "slight adjustment" to carburation: different needle ? If so, which one ?
I raised my ratio to 8.5 by fitting domed pistons, and fuel economy did not improve at all.
Remo Peter

I must confess that when my YA was last used it ran on leaded fuel then as I remember it returned 30 - 31 mpg. May I suggest that if you are now on lead free that some experimentation is needed or perhaps you are using the extra performance. I remember a long time ago a fuel brand called Clevaland which contained alcohol, it played havoc with ignition timing and carburation.
I suggest the afore mentioned tuning specialists may help. { I must correct my error, it is George & Peter Edney ]
Bryan

This thread was discussed between 13/12/2007 and 16/12/2007

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