Quick question on timing

Wilfred Oldtimer said:
Just wondering, you mentioned a rebuilt of your dizzy, so I guess the position of the part I circled red could be misaligned and the timing way out of what it should be.
You can rotate them relative to each other, so much more then the fine tuning.

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It all looks okay however I have double checked to be sure and it is…it’s all back just as it was…
 
Hmm,

What I did after the rebuild of my XK Jaguar engine was set the engine to “0” degrees, so TDC, then find out which of the cilinders had both valves closed, looked what position the rotor in the distribution was pointing at and connected the appropriate kabel to the engine. By turning the dissy you can fine tune the position of the rotor to the corresponding cable.

Then I connected the rest according the firing order. ( it’s important to know which direction the rotor is normally moving, clockwise or anti-clockwise)

Now the engine should start and you should be able to adjust the timing.
 
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The offset drive dog on the base of the dissy fits into a shaft with gear teeth machining into its base. It is possible to pull that out with the dissy and have it drop back in one tooth over.

The fluctuating idle can also be caused by a vacuum leak (especially if accompanied by flat spots in acceleration). If you have the dissy set at 6 degrees BTDC leave it there for the moment, you should get some sort of idle there.

To check for vacuum leaks I would look around the carbs first - especially as you mentioned having removed and rebuilt them recently. With the engine running, spray starter fluid or brake/carb cleaner around where the carbs meet the manifold. Also around where the manifold meets the cylinder head. If you see any change in idle speed there's your leak. Also check the breather hoses going to the engine are fitted correctly.
 
sdibbers said:
The offset drive dog on the base of the dissy fits into a shaft with gear teeth machining into its base. It is possible to pull that out with the dissy and have it drop back in one tooth over.

The fluctuating idle can also be caused by a vacuum leak (especially if accompanied by flat spots in acceleration). If you have the dissy set at 6 degrees BTDC leave it there for the moment, you should get some sort of idle there.

To check for vacuum leaks I would look around the carbs first - especially as you mentioned having removed and rebuilt them recently. With the engine running, spray starter fluid or brake/carb cleaner around where the carbs meet the manifold. Also around where the manifold meets the cylinder head. If you see any change in idle speed there's your leak. Also check the breather hoses going to the engine are fitted correctly.
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What you say about the tooth jumping is quite possible I guess, (I did wonder if it could be withdrawn) how would I ever know? I guess I could lift it out with a telescopic magnet and move it along one tooth, perhaps? Might this cause any internal damage to my engine?
As for the tick-over I have been through all of that spraying carburettor cleaner around everything and it doesn’t make any difference. It did before I had the carburettor rebuilt, and that’s why I had it rebuilt. however, since refitting the fully refurbished carburettor spraying the whole area does not effect things…, I still have this varying tick over…. Very strange.
 
Wilfred Oldtimer said:
Just wondering, you mentioned a rebuilt of your dizzy, so I guess the position of the part I circled red could be misaligned and the timing way out of what it should be.
You can rotate them relative to each other, so much more than the fine tuning.

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Click to expand...

Your dist does not have a skew gear, that arrangement you have can only be installed one way, so no confusion there.

You do say to get the timing marks to align you have to turn the dial on the strobe light to 50 odd degrees, that means your timing is out.

Slacken that pinch bolt with the screw slot in the lower part of your pic.

Set the strobe dial to zero, point at the timing marks at idle and turn the distributor until your strobe aligns at 8 deg before TDC.

Tighten the pinch bolt

That clamp assembly should be bolted to the engine through the hole that is above the pinch bolt.
 
Speedfreak
Sorry I thought I replied to your post with the pic, I now see it was by oldtimer.

Info given should still be useful :rolleyes:
 
Update…. having followed all the above advice and getting nowhere, I’ve decided to send the Distributor back to the company that did the refurbishment along with the coil, so they can test everything on the bench. I put a lead on a plug today to earth, and the spark appear to be a little weak and inconsistent. We will see what they say…
 
Had an alternator rebuilt once, and had lots of trouble trying to refit to the engine. In the end I found they had refitted the rear body wrong way around, and the mounts didnt line up.
 
Timing marks are largely irrelevant these days, as the combustion characteristics of modern fuel is markedly different from the petrol of the period. It combusts slower, for a start, so you need more advance, but the shape of the optimum advance curve will also be different - steeper primary (ie faster advance).
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I thought new petrol was lower octane and therefore burns much faster, hence pinking unless the ignition timing is retarded?
 
Well, the Distributor was tested and was found to be fine, the car is now running, the moral of the story is, Don’t presume that your spark plugs and HT leads areas good as you think they are.
 
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