Minimum octane for L84?

[Duke W.]

Re: Minimum octane for L84?

I think Don has the right answer above. It is my understanding that when '63 / '64 L-84s were new, owners had a lot of complaints about knocking. This was back in the days of 100+ octaine being available at every gas station. As I recall Sunoco had pumps where you could dial the specific octaine you wanted. I read that the dealers during that period added an extra head gasket to give a total of ~.040 thickness, thus reducing the compression ratio. At disassembly I found 2 steel gaskets on each cylinder head, sort of confirming this practice. When I rebuilt my engine I installed 0.040" composition gaskets.

Doug

Flint began double gasketing 340/360HP engines during the 1962 model year, and this continued through the '63 MY. There was a TSB published on the subject.

I believe single shim gaskets were used beginning in '64. The valve relief machining for the 2.02" inlet valve added about 2 cc to chamber volume, and the 30-30 cam reduced DCR relative to the Duntov cam.

Introduction of the 462 heads dropped CR another couple of tenths due to the elimination of the small quench zone on the spark plug side of the chamber, which increased head chamber volume another cc or two.

Duke