Thread: SBC mileage

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Well just to keep the thread going I will mention that yesterday my family attended the Va State Fair in Richmond and I had a chance to look over the stealth Camaro of one of the local counties (Henrico). It is an unmarked maroon 2002 Camaro with a lot of internal gadgets including a PC. The thing of interest is that their sign advertised the car as their 159 mph cruiser with a LS1 engine and a automatic 4 speed. The main feature of interest is that it has only a short stub antenna externally but both forward and backward looking radar with the ability to pick out the fastest vehicle from a pack. Chatting with the officer, he admitted he had only taken the car up to 131 mph and the 159 mph number may be only due to the highest reading on the speedometer dial. But, assuming a 0.7 overdrive gear in my roadster with a 2.79 rear ratio and 735/75/15 rear tires I calculate a theoretical top speed of 197 mph at 4500 rpm! Clearly with 1929 full fenders and a square top I suppose anything over 100 mph would be difficult as well as illegal on the street with a Model-A roadster. I imagine the wind buffeting at high speed in a Model-A would be severe (based on memories) so I am only interested in the 70-80 mph range for "passing" on the Interstates. I looked up the LS1 350 specs and see that the bore is less at only 3.900" but with a longer stroke than my old '76 350. Also as noted above in the 2004 Corvette site the Corvette uses a 2.73 ratio rear with the automatic 4-speed and 0.7 overdrive. The question is when I run the calculation for my tires with a 700R4 0.7 overdrive and my engine, the rpm comes out around 1500 at 70 mph. The question is whether the car will actually run at that low rpm with the non-aerodynamic roadster body and will I have to change the rear to a lower ratio say 3.55? This is just a conversation piece, but I wonder how those 0.7 overdrives can run in the 60-80 mph range with such low rpms and is this only possible with the greater torque of the LS1? On the other hand with lockup in the 4th gear and the automatic making the decision when to shift I guess it works great for a slick body, but will it work easily for a roadster body? Maybe tinkering with the shift point for the OD gear will be necessary?

Don Shillady
Retired Scientist/teen rodder