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timing and tdc?!
Posted: Mon Sep 30, 2019 7:47 pm
by RubyRed65
Hello all!
Have just done a top end rebuild on my 66 912, didn't think to check distributor before taking apart but TDC is at 7 o'clock or possibly 1 o'clock?!
It should be 5 o'clock shouldn't it?
I didn't rebuild the bottom end so I haven't taken the crankcase apart and it hasn't run or been on the road for about 20 years.
Is this right or what am I doing wrong?!?
Thanks
RubyRed
Re: timing and tdc?!
Posted: Mon Sep 30, 2019 8:00 pm
by mycar
Important to establish top dead centre on number one.
Remove the plug on #1, stick a wooden chopstick into the hole and hold it with your left hand, carefully turn the engine cw by the fan-nut with your right hand while feeling the stick. When movement stops, remove the stick, remove the distributor cap and note the position of the rotor. The rotor either points to the notch (Meaning TDC on piston #1) or 180 deg opposite. If it points to the notch, mark the crank pulley with chalk in reference to the case seam, re-insert the chopstick and carefully, slowly, keep turning the crank a tiny bit more cw until you feel the stick moving away again. Make another mark on the pulley. Inbetween the 2marks is TDC for #1 cylinder. It should coincide with the Z1 mark on the pulley and both valve-rockers for #1 should be slightly loose meaning compression-stroke for #1.
Re: timing and tdc?!
Posted: Mon Sep 30, 2019 9:16 pm
by RubyRed65
Thanks for the quick reply... I've found what I think is TDC but the rotor arm is pointing towards 7 o'clock, I'm sure it should be 5 oclock... am I wrong and does it matter?
Thanks again, much appreciated.
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 8:42 am
by Ashley James
RubyRed65 wrote:Thanks for the quick reply... I've found what I think is TDC but the rotor arm is pointing towards 7 o'clock, I'm sure it should be 5 oclock... am I wrong and does it matter?
Thanks again, much appreciated.
Doesn’t matter as long as plug leads are long enough and they’re connected correctly.
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 8:56 am
by RubyRed65
Thank you, I was concerned that someone in the past put the camshaft gear in the wrong position so have been building myself up for a total stripdown!
Do you know why it is a 7 o'clock rather that the 'usual' 5 o'clock... or more to the point is the 5 o'clock position actually standard?
Thanks again.
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 9:32 am
by Ashley James
It’ll be because the distributor drive gear hasn’t been meshed as per the manual. If you’re feeling brave and you have a workshop manual you can lift it and remesh it to the book. I can photo the book if it would help.
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 9:38 am
by RubyRed65
Thank you... I'm not feeling particularly brave but I'd like it to be right and it sounds better that a crank stripdown!
I do have a manual so I'll look it up but if I understand correctly it's the distributor pinion shaft that needs taking out and position adjusting??
Thanks again.
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 9:46 am
by Ashley James
Yes. Take out the distributor and the fuel pump then jam a bit of tapered bar in the hole in the centre of the drive shaft and cautiously lift it, rotate it and mesh it again. The worry is that there’s a washer on the end that doesn’t need to fall into the works, so bear that in mind and that it doesn’t matter if number one is in the wrong place, only that the leads lead to the correct cylinders.
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 10:02 am
by RubyRed65
Thank you again... much appreciated!
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 10:16 am
by RubyRed65
Done!!!
Thank you so much, as always simple fix and not as bad as my sleepless night made it out to be!!
Thanks again, today's a great day!
Re: timing and tdc?!
Posted: Tue Oct 01, 2019 5:03 pm
by Ashley James
Well done! Glad it worked.