Hello chevyforum! new to this forum and wasnt sure where to post this... but ill keep it short and sweet.

I have a 1969 chevy 307 motor in my 77 pontiac bonneville. are these motors supposed to run with a lead additive or is it fine on regular gas? i seem to find little to no info that confirms anything. The car is my daily driver, usually just cruising but sometimes i get a little foot heavy as i just love that exhaust note!!

any info will be greatly appriciated, Thank you

 

Close on the year. 1970 was the year for unleaded. GM put whatever engine in whatever GM car. You are probably ok with unleaded, being a 307 86 octane is fine. I'd NOT use ethenol mix, just gasoline.

 

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Thanks for the responses, I live i Sweden so the only gas we get is 95 or 98 and in some places 99-100. With a mix of 5-10% ethanol. The engine has a edelbrock performer intake and a 1406 eddy carb. Seems to run fine. No cats, true duel exhausts with glass packs. The thing that is the most concerning is the exhaust note. Here is a video i recorded, the left bank is much quieter and kind of smoother than the right, which made me suspect compression loss. Here is the link If there is any compression loss it worried me that it could be a damaged valve seat or burnt valve. I’m a noob with old Chevy engines, this is my first.

 

Can you do a compression check? What I hear is normal, again with a 307 that vintage the only issue with unleaded gas would be the valves.

 

I’ll get a compression test done just for piece of mind. Is it ok to continue running it with unleaded? And so it’s normal for an exhaust from one bank to sound different to the other?

thanks

 

Sounds fine to me