mg midget engine 1500 swap ??

[timetraveller]

i just been looking on the su site to try and get an aaa needle for the carb
turns out ill have to ring them monday morning to order so before i do will i need any other parts ie...uprated spring,different jets etc....
thanks
neil

[bmcecosse]

No - just swop the needle. A decent free-flowing air cleaner helps obviously - so NOT a pancake !

[timetraveller]

hi
got a call from the machine shop to call by for a chat
2 stuck valves that took quite a bit of removing and a few choice swear words apparently
original valve seats are knackered so he didnt really want to grind that far down as he thinks there would be nothing left and kept telling me if he cut out the exhaust valve seats then the inlets would need doing as well ????

ive been advised by a friend to try another place he knows and get the old seats removed,ground down and some unleaded seats fitted

have i just landed unlucky with the head i bought
its stamped 12G940 it also bears a 905 mark and a 17A mark......any ideas of origin ???
or is this the only type of 12G940 head that cant be converted........probably.......never was lucky

thanks
neil

[bmcecosse]

Knackered original seats are IDEAL - just tell him to get it done - until you get that 320 thou clearance. DO NOT do the inlet seats (maybe the lightest touch to make them smooth) - if you sink them down you will lose too much compression ratio - ONLY sink the exhaust seats (and then ONLY if you NEED TO) - don't get conned into 'unleaded'- you don't need it. Obviously stuck valves suggest it has been stored damp (or the valve stems are bent) - just fit new valves and guides - very easy to do. I suggest the 'machine shop' are making a meal of it all to increase the value of the job for them ! My head cost me £10 I think - and we seated the exhausts down in ten minutes at work - in the lunch break, of course !

[timetraveller]

finally got the head back today from the machine shop all ground down to the magic 320 thou clearance and then i set about setting and spacing the rockers up

as i was reading the morris manual the exploded diagram shows the standard valves as having a groove for a hairpin clip however the ones that came with the head have collets and as everything came in bits im not sure how it goes together and holds
any help or tips gratefully received
thanks
neil

[GeorgeHurst]

hey neil,
some valves use collets and clips, and some just use collets. Both in fact work without the clips. The collets are just held in by the pressure of the spring pressing on them from below.
HTH
George

[bmcecosse]

The clips were thrown away about 50 years ago....... Ideally you want to add packers under the exhaust valve springs - the same thickness as has been ground out of the seats. Best way to judge is with a trial assembly - you will see the exhaust valve stems are sticking up more than the inlet stems. Measure the distance - and that's the thickness of packer you need. In practice - a steel washer does the trick........

[timetraveller]

hi
another quick question for you
looking at the standard block breather pipe thats screwed into the inlet manifold i was wondering where would this now be located or will i need to drill the new inlet manifold out and put it back in its original location??

neil

[bmcecosse]

Sorry - you've lost me there! Sure you aren't looking at a servo connection ??

[SGTBILKO]

I have been following this thread with great interest and have nothing positive to contribute (some would say I should keep my mouth shut). Whereas I can understand peoples' frustration at the relative low power of a Morris Minor but aren't they missing the point? I am old enough to remember motoring in the fifties and sixties when often there were long streams of traffic on the open road and invariably there was a dear old Morris Minor at the head doing a steady forty in the crown of the road!

My father was a victim of polio as a child, the upshot of it was his left arm was totally paralysed and he owned a standard Traveller with no mods. His method of changing gear was putting his right arm through the steering wheel, hardly conducive to rapid changes! So lost seconds between changes and that hand was off the wheel which was held by his arm! Try doing that today! I can't remember him holding the traffic up but then the pace of life was slower then and to think at the time the sixties were considered 'fast'!

Well I will stop digressing and go back to my slow old bog standard Minor.

Keep it up!

William.

[timetraveller]

i think its a breather outlet pipe but im probably wrong[frame][/frame]

[bmcecosse]

Yes indeed - that is the 'closed circuit' breather. May be needing a new diaphragm by now. If your alloy manifold doesn't have a suitable tapping - then it will need to be drilled and tapped. Or - just discard it - and connect the breather directly to the pipe on the side of the carb - it will work just as well.

[timetraveller]

hi
just a few questions to clarify before i dive in
does the head need skimming to make a good seal (by the way.....its not warped) ?????
why wont the inlet valves slap the block ?????
doesnt grindining out the exhaust valves lower the compression ?????
wouldnt the heated manifold stop the juice freezing ?????

i know some are mentioned in previous posts but they are only mentioned
so some detailed answers would be good to put my mind at rest before i start

cheers
neil

[bmcecosse]

As long as it's flat - then no need to skim it. The inlet valves go down the bores - fortunately not when the pistons are there! Yes - grinding down the exhausts drops the compression slightly - BUT - it was too high anyway due to the small chamber capacity of 21.4cc on the 940 head against the standard 206 head capacity of 26.1 cc. Hopefully only a very small 'grinding down' was needed to get the 320 thou clearance required. The heated manifold 'may' give slightly better economy - although I doubt even that. For best performance you want the inlet charge going in there as COLD as possible. And no - it won't stop carb icing either - because any heat in the manifold can never hope to travel 'upstream' back to the carb. But - do feel free to try it with and without the water heating. Do set the exhaust valve gaps to 15 thou - and the inlets to 12. Did you put packers under the exhaust valve springs to make them equal compression to the inlets ?

[timetraveller]

hi all
its been a while but finally found the time and got round to sorting this lot out and hopefully with the next few bank holidays it will be installed and done
im having to do it in stages to keep the car on the road as its my daily driver
the exhaust manifold has been modified and fitted to pass through the chassis leg and the rest of the exhaust has been hung
the hif 38 carb has been fitted and luckily needed little adjustment to idle nicely,so hopefully thats the breathing side sorted out
i tested the car and theres an immediate noticable difference in acceleration already and obviously a meaty exhaust note

next job will be the installation of the head which im dreading
the head is ready to go on valves lapped in,rocker shaft is set up,new coolant hoses ready is there anything else i should do or need before i take the final leap

thanks
Neil

[bmcecosse]

Make sure you have a 1275 head gasket - and 1275 rocker assembly ? You may need to file a little off the top edge of the water pump to ensure the head can clamp down without touching the pump. It WILL go very much better........

[timetraveller]

im gonna use the standard 1098 rockers spaced to suit
thanks
neil

[bmcecosse]

Oh yes - that's the best way forward, provided they are correctly spaced to land directly over the valve stem tips.

[timetraveller]

im gonna put the head on next friday,i may as well make use of the holiday as i certainly wont be getting involved in the royal wedding shenanigans
what are the best valve clearances 12 inlet and 15 exhaust or different ??
cheers
neil

[chrisryder]

did you get an unleaded head or not?

if it's unleaded, run 12 and 12.

if leaded, 12 inlet, 15 exhausts.