Re: The 283
Greetings,
I've enjoyed being enlightened as to the tendency of today's "high test" gas to detonate/or not under real world conditions. I'd be very happy if I could get by with little or no lead substitute. "My" '66 327 block was rebuilt with Icon pistons of either a 5.3 or 6.3 cc dome. Head gasket measures about .037-.038" and the deck height about .030". This engine (a block I bought to save my original engine for the next owner to decide on how to deal with originality) was bored .030". My cr computation may not be fully accurate but with the above numbers I come up with 10.4:1, which, given that the factory used a thinner head gasket than aftermarket of today but the deck height was likely significantly higher, is probably close to what left the factory. Back in the late '60s when Uncle Sam said I was free to leave (and, no, not free from a federal prison!), I bought a used '66 coupe with the L79 option. I was fortunate at that time to live in an area being marketed by Sun Oil and so I used Sunoco 260 and occasionally 250. It may have been my imagination but the engine didn't seem to like other high tests (Standard Oil/Amoco, Texaco, Shell, etc) and so the question is what was the octane of Sunoco 250 back in the day? Ninety eight or ninety nine, perhaps? I'll follow Duke's advice as to whether or not I get detonation on 91 octane--I have assumed that I would. Initially, during the break in, I used exclusively 91 octane but, with nothing other than gentle acceleration and no high ambient temperatures, I had zero detonation. However, now that the break in period is past I'm less than confident without as additive. The machine shops seem to be of the opinion that nothing higher than 9.5 or 10 to one could be built without detonation concerns. I'm happy to learn that Duke does not subscribe to that theory. HOPEFULLY, Biden's gas prices will not get much higher during the summer months--good luck there!
Bill
Greetings,
I've enjoyed being enlightened as to the tendency of today's "high test" gas to detonate/or not under real world conditions. I'd be very happy if I could get by with little or no lead substitute. "My" '66 327 block was rebuilt with Icon pistons of either a 5.3 or 6.3 cc dome. Head gasket measures about .037-.038" and the deck height about .030". This engine (a block I bought to save my original engine for the next owner to decide on how to deal with originality) was bored .030". My cr computation may not be fully accurate but with the above numbers I come up with 10.4:1, which, given that the factory used a thinner head gasket than aftermarket of today but the deck height was likely significantly higher, is probably close to what left the factory. Back in the late '60s when Uncle Sam said I was free to leave (and, no, not free from a federal prison!), I bought a used '66 coupe with the L79 option. I was fortunate at that time to live in an area being marketed by Sun Oil and so I used Sunoco 260 and occasionally 250. It may have been my imagination but the engine didn't seem to like other high tests (Standard Oil/Amoco, Texaco, Shell, etc) and so the question is what was the octane of Sunoco 250 back in the day? Ninety eight or ninety nine, perhaps? I'll follow Duke's advice as to whether or not I get detonation on 91 octane--I have assumed that I would. Initially, during the break in, I used exclusively 91 octane but, with nothing other than gentle acceleration and no high ambient temperatures, I had zero detonation. However, now that the break in period is past I'm less than confident without as additive. The machine shops seem to be of the opinion that nothing higher than 9.5 or 10 to one could be built without detonation concerns. I'm happy to learn that Duke does not subscribe to that theory. HOPEFULLY, Biden's gas prices will not get much higher during the summer months--good luck there!
Bill
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