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This one common way to set the ign timing by ear, William…
All engines have an ideal ign advance, relating to rpms, loads and petrol qualities - the purpose of the distributor is to move the timing to suit. However, the dist being a crude device it is unlikely to always hit the sweet spot at all load and rpm conditions.
So advance curves, centrifugal and vacuum, may vary, usually in unknown ways, between dist models. And market priorities influences selection - not all markets aim for max power.
So experimenting with ign timing is perfectly legitimate - the spec settings are just initial timing at specified conditions…
The thing to watch for is engine ‘pinking’; which means that advance is too high for the condition that provokes pinking. And the timing must then be backed off…
As an aside; the closer to knocking point, ‘pinking’, the more efficient the engine works. Modern ign systems incorporates antiknock sensors to allow high advances…
Yup, over the next few days I’ll probably play with the advance a little and see if I can get any more out of it before it starts to ping (I have heard it said/spelled both pinking and pinging). Although the results I have now are satisfactory.
Yea I gave up on trying to see the timing marks on the damper, they are so hard to see it seems they were made for the XK before all this smog and EFI stuff came about and got in the way. And they didn’t bother to change it. It took me like 30 mins to see the timing reading properly when I originally set it to 8*. Who knows maybe I had it set to 6* or something and just didn’t know it. With this bump in timing, it feels like I legitimately added 25hp. before when starting on a hill it seemed there was almost no difference between half throttle and full, it just would not respond. Now you can steadily advance the throttle on the same hill and the engine starts pulling through the rev band. I always had a suspicion that since I installed the Pertronix unit it felt lazier but I just put it down to the old 3-speed slipping more and more.
Now off to fix my rotted mufflers that are leaking quite badly now, which makes a cool sound at idle but not in character with the car. and other fun stuff that decides to break while you’re not looking
Thanks for all the insight!
Also, this Pertronix unit claims to have a more “aggressive” advanced curve for more power. Don’t tell the government here in California though it says its not smog legal
Now that I am looking for the 0-60 specs for the car I cant seem to find a definitive answer. I can find info for cars with the higher diff ratios and earlier but not a series 3 US spec with the 2.88 rear end. I see some places claim 12.1 sec. and other 11.8.
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The ‘original’ xk ign timing were spec’ed for 98 octane, William, not readily available in the US - which also used a different vacuum advance source…
Another method for setting initial advance was using manifold vacuum readings - tuning the timing to obtain maximum vacuum. Crudely, the higher the vacuum the less air (and fuel) was required for the engine to develop necessary idling power - a parameter for engine ‘efficiency’…
In both cases; this is the initial advance at specified rpms - the rest is set by the dists advance curves. Hence the reason for keeping an on pinking…
Good to know! I advanced the timing a little more today and the idle raised to 1000 rpm at hot idle so I backed off the idle set screw to get it back down to 800-ish rpm hot idle in park. It made a difference, it feels like it has a little more power but not much. i’ll probably play with it a little more but the car already accelerates as fast as I would expect with 176hp and 220-ish ft-lbs in a 4,000 lbs car.
My euro spec did 10.5 seconds (without stalling the torque converter as in launch control) and thats with the 3.056 rear end, three speeds, in drive and with and no cats. I set the timing by backing it off until it just stopped pinging on long uphill drives. I have 95 octane most of the year and that is the non-us way of measuring. Your 92 is better than our 95.
The only time I got today was 13.99 but I used a free app that I don’t know the accuracy of. And I suspect that I have a few more degrees of advance to go before it starts to ping. But it should be way faster than that with the 4-speed.
Also doesn’t the Euro-spec have more power than the US federal spec? If I recall correctly it had over 200 hp so I am 30 hp down and I have a really long rear end ratio. I suspect the figures i found of 12.1-ish seconds to 60 are correct for my model. So in theory I should be able to do 0-60 faster than that with the 4-speed.
I don’t have experience with hearing pinging in person so what exactly am looking for with this engine. I know what it sounds like from youtube videos but never heard it in person.
You will know, especially if it goes the instant you lift your foot. It’s loud when the windows are closed and the fans are off.
The euro version has 205 horsepower but my cam timing was of and I feel it was a little quicker than it should have been.
Don’t mind the rear end, look at the overall gear ratios… what if you have a lower first gear and even reach 4th? I‘d think 12-13 seconds are very much okay. I filmed the speedo which is dead on, and pressed the button when I put down my foot.
Yea it felt like it had plenty of power I feel like with more timing and stuff I can get it into the high 12’s. the 4 speed sort of shifts to 3rd sooner than it really should for best acceleration so if i hold it in 2nd I think I could get into the 11’s
That‘d be respectable and you might match the euro spec low 11‘s with 35 hp less.
Good luck!
Also, when you set the timing off the damper: did you ever verify that the damper hasn’t delaminated and 0° is still TDC? Sometimes these wander with age. Maybe you even set it right, but the scale is off.
I have a Pertronix distributor and I set the initial to 8* like the manual states for my California car. but the car was a dog at that timing, so I have advanced it by ear, I don’t know what its at now but i’d guess around 12-14. It seems that the Pertronix system needs a lot more initial advance than the factory setup.
i have not verified that but i’ll take a look. I just hate trying to read the timing on this engine its way harder to see it properly compared to my small block ford I had.
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It sounds sort of like a stream of frozen peas dropping on a tin roof, William - but as David says you’ll know by lifting your foot…
However, It’s not given that it will pink on all cylinders. Different compression and fuelling between cylinders with the ign marginally too high may pink only on one or some cylinders. Which will influence the frequency of the pinks…
