So I wanted to calculate the RPM to see if I ran the engine too hard. From what I have calculated, I don’t think so. The speedo was 11MPH off according to my VZW Navigator GPS. I checked the tire size on the bus VS the tires that came stock. The stock tires were 6.40 - 15, which according to a vintage tire size conversion they were P195/75R15, or P205/70R15. The tires that are currently on the bus are P215/75R15. Why is this important? We need to understand the what the tire diameter is in order to know the speedo correction. By using the handy-dandy tire size calculator tells me that the im either 4.5% or 7.5% too slow. Which tells me something else is wrong with my speedo, or there is another variable I’m not considering.
Now for the calculation. The variables i need are the following.
tire diameter - 27.7
4th Gear ratio - 0.82
Ring & Pinion - 4.125
Reduction Gearbox Ratio - 1.26
Constant - 336
RPM = (MPH*336*Drive Ratio)/Tire Diameter
Drive Ratio = (ring & pinion * Gear * RGB Ratio)
Given that I kept the speedo at 50 to 55 MPH, which translates to 61 to 66 MPH. That equates to 3153 and 3412 RPM. From what I can gather, as long as I keep the engine under 3500 RPM I should be fine. However I have read that the best cooling is around 2800 to 3000 RPM, so I was probably pushing it some, but I don’t think I ran the motor too hard unless the tuning was off. That I’ll never know at this point.











Wow did I get schooled Saturday. Woody sent us some pictures of the inside of the bus and asked what we wanted to do with the upper vents in the bus. Well we want then sealed, but I thought I would consult the experts on 



