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timt
12-05-05, 10:30 PM
With 4 star pertol increasingly dificult to find I am forced to fill up with unleaded petrol and to use lead replacement additives. Can anyone tell me whether this will cause problems with my Chevy 350 powered Cobra in the long term?
Hope to hear from you!
timt

Robin427
12-05-05, 11:44 PM
I think you can get hardened valve inserts, although you might not need them - depends on the age of the engine, I suppose.

callum
13-05-05, 05:58 AM
US engines have been unleaded for years. Are you sure you even need 4*?

route66
13-05-05, 07:55 AM
US engines (definately Pontiac and probably the rest) have had valve seats suitable for unleaded fuel fitted as standard since 1973 - that's 32 years ago!

My donor Pontiac V8 came from our old 1976 Trans Am that had a catalytic convertor fitted as standard at the factory - hence it required unleaded fuel.

Unless your Chevrolet engine is from the dawn of the SBC (ie 1955) up to say 1970 and has had no unusual head work carried out (valve seats / high compression etc), then I'd put unleaded in and maybe super unleaded to up the octane rating to 97.

Steve

bruce_mayo
13-05-05, 09:20 AM
For what it's worth, I have a 1970 SBC 350 in my Cobra which requires leaded fuel and it has run for years very happily on unleaded fuel with Millers lead/octane additive. In fact some knowledgable people have even suggested that a good additive might be better for the engine than using LRP. Whatever, it seems quite OK. Good luck.

Andy S
13-05-05, 10:15 AM
I have the same engine as you and I always use Shell Optimax or BP Ultimate, both being the highest octane available with no problems whatsoever, always carry a bottle of octane booster in case of emergencies when having to fill up with something else though.