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MG Midget and Sprite Technical - 1275 valve setting and timing

67 midget, 1275 engine.
How do you rotate the engine to set the valves and the timing. All of the manuals say to use a wrench on the crank pulley nut. What size is it, and how do you get it in there?
Thanks,
Joe
Joe M

Put it in top gear, hand brake off and push. Quite easy to nudge the engine round by small amounts quite accurately this way. Just make sure the ignition is off!
Guy Weller

Or take out the plugs and turn the engine by the fan.
Matt

I set mine by the rule of 9 method. I have always set the gap with the opposing tappet (i.e. 1 + 9) fully down. If I rotate the engine a little, the gap gets bigger. Should I set the gap at maximum gap, or when the opposing valve is fully open? (High lift Kent cam)
Shawn

if i'm interpreting your post right shawn, do you mean when #1 is down, adjust #8, # 2 is down do #7 .. etc?

if thats what your saying then thats also how I do it too. Bearing in mind that the rocker doesnt have to be all the way down, just a bit as theres a long range of degrees on the opposite of the cams on the camshaft where a valve gets full clearence. Clear as mud that in't it!?
Nick

What Guy said but with Matt's plug bit, and I use second gear because you get less engine movement for a given car movement.
Jeremy Cogman

Too muddy for me Nick. So do I set it at the max gap?
Shawn

Theoretically the base circle of each cam lobe should be circular, so it shouldn't matter where you set the clearance so long as it is clear of the ramps.

In practice, the lobe profiling process can result in quite a few thou run-out if car is not taken in the set-up, so for this reason it pays to set the clearance when the oppsite valve (in the rule of 9) is fully open.

If you set the clearance when the opposite valve is within 30 deg of fully open, that should be safe enough. A useful way to achieve this derives from the fact that on any given stroke there is one inlet and one exhaust valve open, but at slightly differnt phasing (ie one is fully open shortly before the other). Which valve is fully open first depends on whether you are turning the engine forward or backwards - when turning with the fan, backwards works best; (when pushing in gear it depends on what's in front or behind you!)

If you turn the engine until the first of the pair of valves just starts to close while the other is still opening, that is a godd point at which you can then set two clearances rather than one at a time between turning the engine.

If you have a dial indicator and a non-standard camshaft, it is always useful to measure the base circle run-out and note it for future reference. Less than .003 usually doesn't create clearance hassles; more than that can be an issue in ensuring that the take-up and let-down points of the cam action still occur on the opening ramps. When they don't, the result is always accelerated wear on the cam lobe and/or valve train.
Paul Walbran

This thread was discussed between 23/07/2008 and 24/07/2008

MG Midget and Sprite Technical index

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