Timing mark confirmation

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OK, took the rotor off, of course the woodruf key just fell out so I couldn't tell anything. However, when I re-install the rotor, the timing mark is still is off according to the pistons. I wonder if my rotor has taken to rotate the center part on the rotor itself? It does feel a bit loose, that is, I can take a tapered shaft, put it in the rotor and I feel a bit of slop between the center rotor part and the outer rotor part. Here is a picture of the keyway in relation to the timing mark. Can anyone verify that is about where it should be. I am thinking something on the rotor has changed. Maybe its time for the Sparx.

Timing mark confirmation


Dave
69S
 
I wonder if my rotor has taken to rotate the center part on the rotor itself? It does feel a bit loose, that is, I can take a tapered shaft, put it in the rotor and I feel a bit of slop between the center rotor part and the outer rotor part.
Click to expand...

Yeah, that can't be a good thing, but how much movement could there be? Enough to cause it to be off that much?
 
Gday DogT, mmm... sounds like there's only one thing wrong with your rotor, its rooted! Have heard that some pin the centre in place and others welded? I,d buy a new one.
Foxy
 
This may be redundant Swooshdave but,
The piston stop is a ridgid screwed in point through the plug hole at which the piston bumps and stops somewhere near TDC. You then turn the crank in the opposing direction till it comes to rest. splitting the difference on the degree wheel should indicate TDC. This can prove to be more accurate than a dial indicator due to the lash effect coming over the top and the indicator reading "0" over a range rather than an absolute point. I think.
 
Dave,
You may have one of the bad batch of rotors from that era. They were known to loosen on the insert and even disintegrate. The welded ones, Lucas #54202298 are a replacement.
 
I've been trying to find pictures of Lucas rotors and they are hard to find. The ones I do find seem to have the timing mark pretty much in line with the keyway, just like mine. So at this point I am still not sure what is going on except maybe static between the earphones, but it may take me a couple of days to recover from that. I'm giving it a rest for tonight. Not discounting anything at this point, as usual.

Dave
69S
 
Dave,

Here's a picture of a rotor from Old Britts, and you're right that the marks are just about lined up with the key.
http://www.oldbritts.com/11_068100.html

I found it very difficult to catch TDC with a dial indicator. The movement of the piston at TDC is so small compared to crank rotation. The dial indicator is at an angle so there is scuffing and maybe some flex too. Stops are cheap. Set it to around 45deg before and after TDC, split the actual difference and that's TDC. Very accurate.
Piston Stop: http://www.amazon.com/Competition-Cams- ... B000A8FNLI

Degree wheels that you print out are notoriously inaccurate. They aren't that expensive, the bigger the better.
Degree Wheel: http://www.amazon.com/s/ref=nb_sb_noss? ... _121&fsc=6
 
pvisseriii said:
This may be redundant Swooshdave but,
The piston stop is a ridgid screwed in point through the plug hole at which the piston bumps and stops somewhere near TDC. You then turn the crank in the opposing direction till it comes to rest. splitting the difference on the degree wheel should indicate TDC. This can prove to be more accurate than a dial indicator due to the lash effect coming over the top and the indicator reading "0" over a range rather than an absolute point. I think.
Click to expand...

Since that's the case then you just take the measurements with the dial indicator at either side of TDC. I just don't like the idea of turning the engine over until it whacks something, no matter how slow you go.
 
Hi all,
just so as I get this right using a piston stop, please don't all mock at once, just bear with me!!!!!

Put piston stop into spark hole,
  • 1, Turn engine, slowly, 'til piston makes contact with stop.
    2, Note on the degree wheel the number of degrees before TDC it has stopped.
    3, Turn it the other way, again noting where it has stopped.
    4, And therefore TDC should be the exact miday point, e.g. if there is say a 74 degree swing TDC would be at the 37 degree mark
I take it it's easier to determine the amount of degrees moved between the two points if you set the degree wheel at 0 when it has stopped at 2 above then count the number of degrees passed 'til it has stopped in the other direction, once that's done and TDC determined you can reset the degree wheel to read 0 at TDC and make any further timing marks you may need to on the rotor or indicator plate.

Cheers
Robert
 
Yes but don't discount the action of the valves. Using a TDC dead stop that is long enough to stop the piston at about 30 degrees ether side of TDC can find contact with the valves as you go about this task. Just look in the spark hole while turning the motor. So it may be better to add a few sentences to your list.” Back off the pressure on the tool and remove the tool and once you’re near the point piston coming back up add the tool again”. A good dead stop tool has an air bleed hole and is ridged. I just put it in snug by hand and mark the tool with a marker as to make a repeat easier.
Dog T if you feel it loose on it’s core replace it.
 
What's the difference between a piston stop and a dial indicator?


The piston stop is more accurate than a Dial indicator, at TDC a degree movement is a very small vertical movement which is also compromised by any slack in the small end/piston pin and the rock of the piston in the bore, a piston stop is acting further down the bore where the movement per degree is more. But a dial indicator is the next best to the piston stop compared to the rest.
 
Using a dial indicator for this purpose can produce errors of at least 3-4 degrees if not more. It is not an accurate way to do this and in essence, it's a waste of time. You are trying to find out the specific accuracy of the oem timing marks but even if the marks are off, they are probably inside the error of the dial indicator method.
 
Good question Dave - one I was asking in my head. Here's an answer from a hotrod forum... I like the reason part.. :D
Using the piston stop rotate the engine carefully !!!

Find something to use as a pointer. Does not matter where if making your own TDC mark so pick something strong and easy to see with a timing light.

Roll the engine tiill it hits the stop, make a mark at your pointer
Roll the engine in the opposite direction till it hits the stop, make a mark at your pointer.

EXACT TDC will be in the center of those 2 marks. You will not be able to roll the engnie there until removing the stop.

The reason you have to stop the piston before TDC is that the crank rotates a few degrees while the piston is stationary at TDC. So you cant just run the piston up top and set it.

Same with finding a cam lobe centerline. the cam rotates a few degrees with the lifter all the way up top.
Click to expand...
 
Duh, Double Duh. When I realized that the drive side crank rotates anti-clockwise it all makes sense. I knew that last month but forgot in the meantime. Everything is cool. Timing mark is real close, push rods go up and down in the correct fashion. Contact points work fine with the AAU. Just needed a brain adjustment which was 180 out.

Dave
69S
 
An image that helps is that of the back wheel rotating. Viewed from both sides it never matters. It's a miracle we can see when you think of the eye bringing in everything upside down and backwards.
 
That's what it finally took. Thinking of the rear wheel and the drive chain and the primary chain in conjunction. It's so amazing your mind can play these tricks on you, especially at my age I appreciate it.

Dave
69S
 
norbsa48503 said:
An image that helps is that of the back wheel rotating. Viewed from both sides it never matters. It's a miracle we can see when you think of the eye bringing in everything upside down and backwards.
Click to expand...

Not at all. I have tiny images that travel up my optic nerve...

Greg
 
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