[Clan]

That was certainly the case in the 1980's when i was doing official Volvo LPG conversions on 200's and 300's but alas not today ..Actualy the Volvo Bi-Fuel heads are different to normal, their valves and seats are supposed to be even harder than standard but there was a batch in 2002 which weren't and the valve clearances were reducing to zero .volvo were changing heads on 4 cylinder Bi-Fuel cars due to valve seat recession under a Policy action . I have seen non-volvo LPG conversions causing this problem too on a 960 and a S 40 the problems became apparant on both cars around 50000 miles after conversion ...