3 replies to this topic

[cap'n crunch]

I ran a 12G295 (with standard vavle seats not hardened) for about 13-15k miles, checked the head today and all of the exhaust valves and the valve seats in the cylinder head were pitted. Is this a surefire sign of unleaded petrol so i need to get hardend seats? or is there something else happening?

[jonny d]

didn't you use an additive for unleaded fuel?

[Davethepioneer]

I ran a 12G295 (with standard vavle seats not hardened) for about 13-15k miles, checked the head today and all of the exhaust valves and the valve seats in the cylinder head were pitted. Is this a surefire sign of unleaded petrol so i need to get hardend seats? or is there something else happening?

this sounds like valve seat recession you could take the head to a specialist and have hardend seats put in so you can run it properly on unleaded or dependant on how bad it is run an additive in your fuel but if there severly pitted then you may need new valves also, so it might be best and cheaper to go for an exchange head with new valves.

[bmcecosse]

'Pitting' is not down to recession - when that happens you actually get very good smooth seats - but the gaps close up! Had your gaps closed at all ? I would grind them in - you may need new valves - and set the exhaust gaps to 15 thou.