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MG Midget and Sprite Technical - Installing distributor drive

I'm having some trouble locating TDC at the start of the power stroke in order to slot the distributor drive shaft in as indicated in my Haynes manual.

As described in the manual I am watching cylinder 4 for when the inlet valve is just opening and the exhaust valve just closing. However this does not appear to happen at any stage of the crank rotation. They both open and close but there is no point at which inlet just opening and exhaust just closing.

Is there another way to check this position.

This is a 1275 which I have just rebuilt. Have I made a big mistake when I timed the cam? I know I had both the dots aligned on the cogs.
tm wainwright

"Is there another way to check this position."

Set TDC via the pulley mark.

This will either be TDC No 1 firing or TDC no 4 firing.

To ensure it is TDC No 1 firing, both the valves on No 1 cylinder will be closed - ie the rockers for them will be clear of the valve stems and can be 'wiggled'. If it is No 4 firing then the rockers will be clear of the valve stems for No 4 cylinder - if the latter is the case rotate the crank through another 360 degrees.

Note: You may well have to set the valve clearances first
Deborah Evans

tm,

Forget about valve positions, etc.

Remove #1 spark plug, remove coil wire (so you don't get zapped ) and turn engine over (with a remote starter button or an assistant), put a finger over the plug hole... when the compression pushes your finger off, you're on the compression stroke for #1, then just simply turn the engine with a spanner on the altenator pully nut or crank shaft nut until you get the crank shaft pulley mark at TDC and your set!
DL Rhine

Also,

Forgot to mention...Debbie's right...adjust your valve clearances first... then find TDC.
DL Rhine

You can do it that way DL but chances are by spinning on the starter you will blow past where you need to be - at least every time I have tried it that way that's what has happened..

And it requires 2 people to do it that way - one to feel the compression and one to spin the starter.

Looking at Nos 1 and 2 rockers is by far the easiest way for one person - you can even turn the engine by slotting it in 4th gear and rocking the car back and forwards while watching the rockers.
Deborah Evans

Pull all plugs (so it turns over easy), put in gear and push the car back or pull it forward until the mark on the pulley is at TDC, pull the dizzy cap off and see if the rotor is pointing to #1 or #4, (#1 is at 3 o'clock or so, follow the plug wire to cap). Get it pointing to #1. All set. I can do it from under the bonnet just pushing and pulling a bit on the car (it helps if the engine a bit warm).
J Van Dyke

Where in Kent are you.
Alan.
Alan Anstead

Not sure if this will help or not (I have a 1500, not a 1275), but when I'm set at TDC on #1, the rotor points in the vicinity of the 3 to 4 o'clock position.
DL Rhine

Deborah, actually I do it with a jumper wire at the starter solenoid, so as not to need any help...when the compression just starts to push the finger off, I'm close enough to adjust to TDC marks...finger in the hole works every time for me!

But you're right if you have the valve cover off, when 1 & 2 rockers are free, you're also there.

Just upgraded my distributor to a pertronix breakerless unit last week and had no trouble setting it up correctly first try.

As long as the cam timing is set up correctly, tm, you can't miss using any of the above techniques.

Good luck, hope we were of some help, let us know how it turns out.
DL Rhine

Mr Rhine and Van Dyke, read the question? it is about fitting the distributor drive shaft, the distributor is not on the engine!

This is a simple thing being made very complicated.

tm wainwright, without me reading Haynes I would imagine the only reason they are asking you to look at the valves is to ensure you have the correct TDC. With regard to the distributor there are 2 TDCs of the engine, (The crank rotates twice for every revolution of the distributor shaft. Thus it is important to set the "slot" in the dizzy drive in the correct place with regard to the crank rotation.

As you rightly say ""They both open and close but there is no point at which inlet just opening and exhaust just closing."" We call that rocking and it means that that particular cylinder is is not firing where as the opposite cylinder (number 1) will be and its valves will both be closed.

If the request is as you describe then they need the crankshaft at top dead centre with number 1 cylinder on compression/firing.
Robert (Bob) Midget Turbo

oh, yea sorry, didn't read carefully, couldn't imagine what all the fuss was about, now I understand and I'll shut up
J Van Dyke

Oops, me to...
DL Rhine

Thank-you all for the advice.

Part of my initial concern was that the drive shaft didn't fit in either TDC position. However walk away, have a cup of tea and return to the shed and it slots home first time.

I will print out all the advice and check that the TDC I have is the correct one. Its a lot simpler when you remembered there were only two valve arrangements I need to distinguish between.

BTW I'm in Leigh on Sea, Essex not Kent. I will try to up date my details.

Thanks again

Tim
tm wainwright

Sounds like you've done it already but a word of warning - hold the disi drive with a very long piece of threaded rod or a bolt that is at least 4 inches long. Otherwise you'll think it's in, let go, and then have to take the sump off to recover the disi drive that's just dropped through and ended up there.

Don't ask me how I know!
Ant Allen

This thread was discussed between 22/08/2009 and 24/08/2009

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