350/450 V8 unleaded Ron fuel

[osc]

I believe the early 1972 350/450 V8s run on unleaded does anybody have any thoughts on unleaded vs. super unleaded?

I know unleaded will make the motor run hotter, and my engine becomes slightly unstable when idling for a long time - does anyone have any experience with different ron petrol?

 

[turbopete]

most early cars running on unleaded needed harder valve seats as they burnt out as there was no lead in the petrol to lubricate and protect them. if your car was designed to run on unleaded from new, that shouldnt be a problem. if not, you can have hardened seats machined into the cylinder heads or use a lead substitute additive. regarding the fuel itself, the only difference between 98 and 95 is the RON or the octane rating. the higher the octane, the SLOWER the fuel burns, meaning you can run more advance on your timing. your car may run smoother on super as the timing may be set for 4 star (97 RON). im not sure if its electronically controlled via ecu etc or has a switch to swap between the 2 (leaded and unleaded), your car is older than me!

to give you an idea of what i mean, if you took a 1985 ford escort, the timing was set at 12 degrees before top dead centre (tdc) for 97 RON 4 star. this could still be used for 98 RON super unleaded. when unleaded was 1st launched though, there was no super unleaded, just 95 RON. using the above example, the timing has to be retarded to 8 degrees before tdc if it was a carburettor fed engine and 6 degrees before tdc for a fuel injected engine!

long story short, it depends on how your engine is set up, whether you want max performance or if you just want to cruise as cheaply as possible, as you really have to be able to justify the extra cost of the super, unless you will be doing very few miles in it, in which case try super and see if it runs smoother.