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MG MGA - how to find tdc

hi

i put a late mgb front cover over the cranckshaft with the timing marks at 11 o clock, now how can i find top dead centre.i tried with a screwdriver, but that doesn't work.

thanks serge
serge

Serge, you need to make a piston stop from an old spark plug. the stop will stop the piston some way before TDC. You turn the engine forwards until you feel the stop, and mark the pulley. Then you turn the engine backwards until you feel the stop again. Mark the pulley. Then split the distance of the two marks and you have exact TDC.
To make the stop, take an old plug and drill out the electrode. Replace it with I think a piece of 1/4 rod and weld it in place. cut it off with about 3/4" sticking out, and file the end round. Insert in No 1 cyl.You may have to play with the distance to get it suitable. And of course turn the motor by hand using the front dog nut and a long bar.
Art Pearse

Yes as described by Art. I used to o something similar with a screwdriver until I heard the technique with the old spark plug described and thought I will have one!!

Anyway why did you not use the MGB pully as well, then the marks would have been correct?
Robert (Bob) Midget Turbo

These look like a good idea.

http://advanceddistributors.mybisi.com/product/mgb-timing-tape-kit-1962-1971
J Bray

Easiest way to find TDC on the compression stroke is to put your thumb over the #1 hole and have someone turn the engine over by hand. When your thumb pops off the hole, you have reached TDC.
Cheers,
David DuBois

Tape doesn't work on MGA as there is no wide flange on the pulley. For the piston stop, consider tapping the spark plug shell and using threaded rod to be adjustable. You want to stop about 20 degrees from TDC on either side. Any higher and you may damage the piston from too much mechanical advantage.

John Twist has a nice tech video on doing it with a hose fitting and viscus oil. See here: http://www.youtube.com/watch?v=Aw7IdW4Qxcc
Barney Gaylord

Dave, that is not an accurate method for TDC.It will tell you that you are on compression stroke, that's all.
Serge, also take all the other plugs out to get a better feel
Art Pearse

Art - "that is not an accurate method for TDC" - I will grant you that, but the other methods do not tell you when you are on the right up stroke. Both procedures need to be used together. Cheers - Dave
David DuBois

This thread was discussed between 03/02/2012 and 05/02/2012

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This thread is from the archive. The Live MG MGA BBS is active now.