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Timing for the 4 cylinder engine


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If you are resetting or checking the timing on the 4 cylinder engine, assuming it’s basically in standard tune, would you follow the original factory settings or does modern petrol make a difference (I've seen experts recommend different settings for eg the Jaguar XK engine).

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I read recently somewhere that the simplest way was to start the engine and turn the distributor back and forward until the highest engine tickover speed is obtained, then retard the ignition until the revs drop by about 100rpm and lock it there. Haven`t tried it myself but its supposed to work and takes into account wear in distributor etc.

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Set it to factory first.

Then drive it and advance the timing until you get slight pinging under load or at high revs. If you get pinging then back it off slightly until you don't.

Before others argue this method I acknowledge that for some modified engines this might not be the best method. For a stock or nearly stock engine it will get you the best performance and economy without risking engine damage.

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Buy an adjustable timing light

https://www.machinemart.co.uk/p/gunson-77008-timing-light-with-advance-feature/

Check the timing mark on the pulley is correct for TDC

Mark timing pointer and pulley with white paint. - I have added a v nick in the pulley edge to align with the pointer rather than using just the hole drilled in the pulley.

GO

You are seeking less than 32 degrees maximum advance at the crank at over 3000 rpm.

My less than standard engine runs best without pinking at  28-30 BTDC.  That gives me a static advance of 8-10 degrees.  Knowing my distributor has a maximum mechanical advance of 10 degrees (20 at the crank)

Cheers

Peter W

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I do the same as Pete On my lightly tuned engines. Set the max advance to 32 degrees which leaves the tick over at 12 degrees. I set it with the manual adjustment on the vacuum advance in mid position so that it can easily be backed off if I’m somewhere where I can only get std fuel. 

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If the petrol you are using has ethanol in it then this will affect the burn profile. How much will depend upon the state of tune and particularly, the exhaust valve/extraction. Excessive engine-bay heating may be an indication and is central to the effects of modern fuel (in old engines).

One emerging view is that another 2 degrees of advance may be best suitable for E5 to E10. I think this is broadly as Andrew's post. BTDC static.The article in TR Action earlier this year and used the "Manchester" test data as a foundation. The book by Dr Paul Ireland, "Modern Fuel - Classic engines" contains the full Monty of an explanation!

After talking to experts who tune old engines (whilst researching for the article) I concluded that a rolling road test with all the supporting equipment to analyse the sensor data is the only sure way to get it right for a particular engine on a specific fuel grade.   Else, the traditional "pinking" road test still takes some beating, find the point where pinking just stops and then retard by another 2 degrees.

The data in the official TR2-3-4 workshop manuals was based on the fuel available in the 50's - very different from what we have today.  

All said, there are very many TRs out and about with settings per the manual.

 

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