Ignition timing and unleaded fuel

[Ian]

I'm sure I am right in saying (Hopefully someone will tell me) that when you covert a car from leaded to unleaded petrol, in addition to hardened valve seats, an adjustment needs to be made to the timing? Do you advance or retard the timing?
Many thanks in advance

[TerryG]

You retard the timing slightly.
I normally set the timing where it "should" be and go for a drive up a hill, if it pinks I retard a bit, if it doesn't I advance it until it does then wind back slightly.

[Ian]

You retard the timing slightly.
I normally set the timing where it "should" be and go for a drive up a hill, if it pinks I retard a bit, if it doesn't I advance it until it does then wind back slightly.

Top man, cheers Terry

[JPB]

As Terry says, with the proviso that, where inserts are already present, they must by metallurgical default be hard enough and as such don't need to be replaced. The Triumph/Saab slant 4 and V8 along with the Rover V8s and indeed anything else with an aluminium head or - in the case of US market Volvo B18/B20/B30 and the Standard/Triumph IL6s - a cast iron head with induction hardened seats, in that case you clearly won't see inserts but then you'll wonder why that end mill that was only changed at the start of the first period has already been turned into a paperweight by what appeared to be a stock iron head from a student's SoCal import TR250.
Schadenfreude? Maybe, but it's really quite funny to watch.

[mr rusty]

Depending on the car, it may or may not run like the proverbial bag'o'nails with retarded timing- I know my Vitesse does. I use unleaded, with castrol valvemaster plus to boost the octane rating: the car was meant to run on 5 star fuel and really doesn't like anything less, and with the booster I can run at factory timing settings and full performance, retarding it makes it very sluggish, so depending on the car even if you do have hardened seats fitted you may still need to retain factory timing with an octane booster to make the car driveable. The lead substitute is a side issue, these old iron headed Triumphs don't seem to suffer from having no lead, even with the original decades old valve seats, but other makes react differently.

[JPB]

Probably because later IL6s (1968 on ringing a bell) had induction hardened seats for non-export cars too. The numbers were published in a bulletin from around that time that was [much] more recently put in with a recent copy of a specialist Triumph Magazine.
The small journal 4s suffered badly with recession, indeed the engine found in the Herald 13/60 and the FWD 1300 used to suffer that way even before lead content was first reduced in the late '80s. The large journal 1300s seemed to suffer less but when they were still within warranty and I was starting out, they were still presenting with some seat recession issues but we worked on more and had fewer incidents than with the remaining small journal OHVs.