timing

[fsk658]

what is the general opinion on the timing for a 1098cc engine fitted with a lead free cylinder head. I know the manual states 3 degrees btdc with leaded petrol and the advice given for unleaded petrol is to retard a couple of degrees for the lower octain but what is really is the best setting.I have run up to 5 degrees without pinking ? John

[Cam]

Well, the limit on advance is when it starts pinking, so if it doesn't pink at 5 degrees then it's fine.

[Packedup]

I always thought the static figure was between 8 and 12 on most old pushrod engines (using decent octane, not the normal unleaded crud we have now). 3 sounds very very low! You could always run on super and get a bit more out of it, if you're willing to pay the extra for the fuel.

Agree with the above, if it runs fine at 5, then don't worry about it

[bmcecosse]

Advance it till it 'pinks' - then back it off very slightly. Don't be fooled by very light short-lived pinking as you initially press the throttle- this is just the vacuum advance 'letting go' and does no harm - the real pinking that you DO NOT want is when the engine is working hard up a hill with the foot to the floor. Pinking then is very bad news and this is what must be avoided by slightly retarding from the setting that brought it on !

[MikeNash]

The general drift of the above seems to be the more advance you can stand without distress the better. I don't agree. If the octane rating of the fuel is high enough then you can easily have more advance than is best for max power before you actually get the onset of pinking. I've just done this with an accidental set up of 10 degrees static on my 1098 which went OK but a bit harsh and "tight". The tick was faster which seemed a good sign and part throttle seemed bettter, but I had a near disasterous bout of pre-ignition on prolonged full trottle. Reset to 3 degrees and all sunshine. (Now using NGK BP7ES plug with great success.)
5 degrees might be OK, but I wouldn't want to hand swing 10 or 12 dgrees static! Let us know how it goes. Mike N.

[chickenjohn]

I just set the timing till the timing strobe light is in the middle of the three timing marks and the car then goes great!

[jojax64]

Rosie has one of these broquet thingies in the fuel tank ( from a previous owner, over 10 years ago).
I use Castrol Valvemaster additive. The car runs sweetly enough, but pinking is evident on steep hills. Where should the timing be set?

[Cam]

Like John says, the middle mark is fine which is 5 degrees I think. The 1098s seem to be OK there, but my 1380 likes 8 degrees and so does my MG B (my two Minis did too - 998 and 1293).

[bmcecosse]

Modern engines have a device thta 'listens' for the pinking and constantly advances the timing till it pinks and then backs off again - hundereds of times per second of course ! Maximum advance without serious pinking gives best performance and economy. Slight 'tinkle' can be ignored - but you DO NOT want hard pinking when slogging up a hill. If you never hear a tinkle then it is too retarded.

[Cam]

Well.... you should adjust until you hear no tinkle (pinking). I don't agree that if you never hear a tinkle it is too retarded. I would say that if you heard a 'tinkle' and then you retarded the timing slightly and you no longer hear it then that's spot on.

Of course I agree about the slogging up a hill bit.

[Blunt]

Rosie has one of these broquet thingies in the fuel tank ( from a previous owner, over 10 years ago).
I use Castrol Valvemaster additive. The car runs sweetly enough, but pinking is evident on steep hills. Where should the timing be set?

we did Broquet a while back, but since then I've found this useful site http://www.fuelsaving.info/catalysts.htm

off topic I know, but I can't find the old thread to revive it

[bigginger]

Cheers for the link - v. interesting read.

[bmcecosse]

Cam - my engine gives just a very slight 'tinkle' as I press the accelerator - but this is just the vacuum advance (which has pulled the timing forward under high vac conditions) not quite letting go quickly enough. I find if I back the timing off then the engine is definitely less 'lively' - but I have NO pinking under heavy load - even though I have removed some metal from the internal stop to allow extra centrifugal advance.

[Cam]

Well, if you are happy with it then that's all that matters. But the vac advance unit does not have a delay (unless it's knackered and sticking). It's instant in operation (well, probably around 1/10th of a second or less which to all intents and purposes IS instant in human terms).

If you are finding that your engine is less lively with less advance and you can live with the slight 'tinkle' (pinking), then ok.

I would not want TOO much advance at very high RPM as that's a pretty good way to damage the engine. So, I'd be wary of letting it advance too much centrifugally, but I'm sure you know what you are doing.

[bmcecosse]

It's survived my worst efforts so far !
The vacuum in the advance unit can only decay back to the manifold - and it's a long thin pipe. I think it can take about 1 second - going from cruise with high vac to sudden flooring of the throttle and virtually no vac. This is when I get just the slightest very short 'tinkle' from the engine as it picks up speed.

[Cam]

Well, you can see it's operation with a strobe lamp on the timing marks.

[Dru]

*dumb question time*

...when you're adjusting the timing using the micrometer click wheel at the base of the distributor, do you need to slacken the distributor clamping bolt first? -my little handbook isn't clear on the subject, and the Haynes doesn't even seem to go there....

[bmcecosse]

No. It's there for easy (but relatively tiny) adjustments to be made. It's actually connected to the vacuum advance mech - in effect you are stealing a little bit of the possible vacuum advance!

[ndevans]

"Even dumber question" time

When we say "retard the timing", do we mean towards TDC? ie from say 3 to 1? Or is it t'other way round?

cheers, Neil

[Dru]

Ha. Something I can answer

Advancing is increasing the degrees BTDC, so that the spark pulse happens earlier in the cycle; and retarding is the other way. So going from, say, 3 to 1 is indeed a retarding. Retardation? Oh, you know...