40flier Posted October 8, 2018 Share Posted October 8, 2018 I see the 68 430 was 10.5 compression, do these cars adequately cool on 93 octane? I've had to enlarge combustion chambers on a Pontiac to stop spark knock and overheating, but that was on an earlier car with a vertical flow radiator. Thanks Link to comment Share on other sites More sharing options...
NC1968Riviera Posted October 8, 2018 Share Posted October 8, 2018 (edited) My 68 430 runs between the 1/4 and half way marks on my temperature gauge no matter what octane gas I use, never getting any higher than the half way mark. I ran both 89 and 93 non-ethonal gas in my car this weekend in 90 degree heat and it never ran hot. Edited October 8, 2018 by NC68Riviera (see edit history) 2 Link to comment Share on other sites More sharing options...
68RIVGS Posted October 8, 2018 Share Posted October 8, 2018 . . . same here - never had an overheating problem, even on 120 octane avgas ! 2 Link to comment Share on other sites More sharing options...
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