Quote:
Originally Posted by Bill D
I'm leaning towards the . 63 as it's less wear and tear on the engine for long cruises.
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Less wear and tear on your ears as well, although you may be planning on going the earplug route regardless of RPM.
Especially with a 4.10 rear, I would say 0.63 is the way to go. It may depend on what your main driving plans are as well. I guess I’m thinking that unless you are planning on a significant amount of track time, the 4.10 might even be a bit much, but that may already be a done deal. But if the engine isn’t happy cruising at 70 mph at 2267 RPM, I don’t think it would be much fun trying to just cruise around at lower speeds in any gear, so maybe the 4.10 is OK. Hard to tell without knowing where the peak HP and torque are occurring. I would also be curious of what the compression ratio of the engine is.
For a good simulation of the difference in these RPMs, maybe you know someone with a car that has an engine similar to yours, or that would be about as loud as yours, who could take you for a ride and cruise for a while at the two different RPMs, even if it means dropping down a gear to keep from exceeding speed limits, depending on their gearing. If you can’t find someone to accommodate the experiment, then use your daily driver. Although engine-wise, this may seem like comparing apples and oranges, it will at least give you some feel for the DIFFERENCE of these two RPMs. It may feel or sound like 2627 is screaming and something that you know you would not want. Although this engine is probably significantly different from your daily driver, you may have already noticed that at 70 mph it is somewhere well below 2267 rpm, depending on the vehicle of course.
While your cam’s power range may be 2500 – 6800, I think if you were in a situation where you wanted the power, you would be downshifting anyway to raise the RPMs farther up into this range. And if you have to downshift because your speed drops to 60 or 50 mph, going through the gears is half the fun anyway.
Here is a gear/RPM calculator I was looking at recently, just to give you another point of reference it not the one you are already using.
Tire Size and Gear Calculator | GTSparkplugs
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