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Anything wrong with this picture? Ignition timing sprocket markings... - Engine & Ancilliaries/Gearbox - The Lotus Forums - Official Lotus Community Partner Jump to content


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Anything wrong with this picture? Ignition timing sprocket markings...


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As per the title, this seems at odds with the locations and positions of the coloured dots. Engine rotated to TDC in the photo and the static timing set at about 15 deg.

20220612_122556.thumb.jpg.68c303331a5cb713f1ad3d65ea797362.jpg

For good measure, these are the cam sprockets.

20220612_122621.thumb.jpg.2c2cc2131b93b54a77895760df6c12f0.jpg

20220612_122648.thumb.jpg.10e6ae2d79f1fa34d506bbcaa28be2df.jpg

Engine runs okay (for all I know) but a chap I took it to recently reckons it's quite badly under powered and the previous owner always said it's not firing on all cylinders.

Any thoughts?

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You could in theory have that dissy sprocket in any orientations and the car runs fine, but you may have to move plug leads round a turret or two to cope and have to turn the dissy to a place where it's awkward to remove & refit the dissy cap. As such, the sprocket isn't as per the manual but could be perfectly timed.

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  • Gold FFM

As Andy says.  So now, find a timing light!

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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Well Jono,

Unless you have something broken, there are only two systems that make it run and they are electrical, and fuel related.

Replacing spark plugs and the wires along with making sure you are getting a hot spark may help. Coil replacement may be in need also. Coils also don't last forever and become weak and this may happen during higher rpms when the load is the greatest like when you put your foot into accelerating but seem fine at lower power requirements as you drive.

Spark plug wires go bad over time and one maybe shorting out some of the juice before it gets to your plugs reducing power. Make sure your wires are separated from each other and not grounding out on any part of the engine.

You may have a fuel blockage like in the filter or a spazmatic fuel pump or even a blocked line.

Timing looks spot on.

Not rocket science but little things make a huge difference at times.

 

good luck and it probably is a simple fix. tinker tinker tinker...lol

 

Richard

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Thanks for the thoughts and good points. So am I right in thinking that all that really matters is the markings on the crank and cam sprockets being correct? And following from that, the distributor and sprocket can be in any relative orientation and the timing mark on the crank will still indicate the advance correctly (with a timing light, which is what I used to set the static timing at idle)?

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  • Gold FFM

Correct.  Except if you've checked timing at idle, that's dynamic - not static.  Isn't 15 a bit high?  You also need to check your ignition advance is functioning.

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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If the parts that @Elite 4.9 calls out are not of a reasonable age & visibly OK, then perhaps worth replacing, but if nothing obvious there then go down the diagnosis route rather than replacement route. @Sparky has already called out a couple of things on timing, I'd also want to check which cylinder(s) are not firing as strongly as the others and then work out whether that problem follows certain components like spark plugs) as they are moved. Also check for compression problems. 

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You can always do a compression check on each cylinder to see how much wear you may have and see if you have more blow past the rings than normal.

 

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21 hours ago, Sparky said:

Correct.  Except if you've checked timing at idle, that's dynamic - not static.  Isn't 15 a bit high?  You also need to check your ignition advance is functioning.

Hmmm, yes dynamic is probably the correct word, but there is no dynamic advance applied at idle so idle advance == static advance. It is a bit higher than spec, intentionally so, as I've read that the spec is way too conservative and that 12 to 15 is more reasonable. Also have a freeflow exhaust and free-er intake.

The distributor is new so it should be good.

Regarding the other components, thanks for the suggestions. The only remaining non replaced parts that could be an issue is the carbs, but I've just ordered a serious rebuild kit so will get that sorted soon. In my experience when I've had it running nicest, the accelerator pumps are very finicky.

I did do a compression test recently and the values are not great. Ranging from 10 to 20% roughly over spec.

I've also ordered a Colourtune so that might help point out dodgy cylinders.

Thanks TAR also for the diagram. The markings I was talking about are the coloured ones on the timing sprocket which do not line up with that diagram.

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  • Gold FFM

'About' 15 degrees?  If you've done it dynamically (or statically, as you call it), with a new distributor, then 'about' sounds rather vague.  However, you seem to have your finger on the pulse so I'll bow out.

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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Just check that the crank sprocket mark lines up ok when the cam sprockets are in tune, if ok and spark is  as above things should run ok, check carb balance, as a guide, if you get backfire that carb will be a bit lean.

also check that carbs are not flooding and fuel pump pressure is ok. 
a quick spark check is to connect your strobe timing light to each lead in turn, if no strobe there is no spark. 
this should do it, I had very low compression but engine ran ok you need to look elsewhere.

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Other than rebuilding the engine with new pistons and cylinder liners, you can put in some Lucas oil treatment and that will increase compression and give you less blowby making more hp and less pollution.

My trucker friends turned me on to this amazing product which also sticks to bearings and cam lobes preventing a dry start which is said to cause 80 % of cylinder wear.

These very large engines (semi) go a million miles before rebuilds and this is one of the reasons why. They buy it by the gallon.

I started using it in all my engines even from new. Truckers know !

 

cheers,

Richard

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