After rebuilding my '76 engine about 3 years ago, the only fuel it likes to run on is premium 93 or better.  However, with the current prices of fuel, it's going to break the bank just to take a drive around the block.

I know it's a mortal sin to say that I would sacrifice performance to be able to run 87 octane fuel, but the economics of enjoying my Vette verses paying for premium fuel are too great.

Does anyone know what could be done to lower the octane requirements?  I know the compression of the engine obviously isn't easily changed, but what about retarding the timing? or different spark plugs?

Any tips would be helpful...

Thanks.

when the engine was rebuilt, did you get any info on the new compression ratio, did they put a hot cam in it?

 

I was told the new compression was estimated at 9.3:1 which I know is on the edge to run 87 octane.  I had them put a Comp Cam (270H or 280H maybe) in it, but only one that would still work with the stock heads and pistons.  Unfortunately, the person that owned and rebuilt my engine passed away only a few months after rebuilding my engine, so the above info is all I have to go on.

I don't thing the cam is too aggressive, considering my dad has a '63 Impala SS with 300+ HP, with an even more aggressive cam, and he can run 87 all day (maybe not to optimum performance, but he doesn't get any pre-ignition that I get.)

 

The easiest thing is to retard the timeing.  Performance will suffer, but that's life.  You could also reinstall an EGR valve if it has been removed, or never there.  This would may require a new intake, valve, and vacuum controls.  It's not too difficult to hook up.   The entire purpose of and EGR valve is to control knock/ping/NOx emissions.  That will allow you to run lower octane.  The last choice is reducing compression.

I'm definitely going to try retarding the timing.  Yeah, it really is going to stink losing performance, but it will still perform better than under a car cover in the garage all summer. 

I didn't know the EGR controlled all that, I though it was just emission gas recirculation.  I still have the EGR on the manifold b/c the bolts were too rusted and rounded off to take it out.  I'll try hooking it back up.  I believe it still works.

I still have some premium fuel mixed w/ CAM 2 from last summer in the tank (I sometimes add a gallon or two of the CAM 2 just for the smell, Not really for performance) so it will be a while before I can fill up with just 87.

Thanks.

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