Posted by Matt Wilson [172.69.69.13] on Thursday, February 20, 2020 at 11:25:57 :
In Reply to: 4.89's, stock 230 and 40" tires??? posted by Tweety [162.158.107.4] on Thursday, February 20, 2020 at 00:29:49 :
I ran 11.00 x 16 Michelin XZL tires (so not quite 40" tires that you're wanting to use) on my '49 Power Wagon for a few years, with 4.89 gearing and a nearly-stock 230 engine. The only things that were not stock about the engine were the head that was milled to get about 8:1 compression, the camshaft that was from Vintage Power Wagons, and was supposed to get more power at higher rpms and the carburetor, which was a Carter Ball and Ball with a mechanical accelerator pump instead of a vacuum accelerator pump. The carb was still a 1-barrel unit and I don't think it provided any more air flow than the stock carb.
I couldn't tell much difference in acceleration from a dead stop with this setup compared to when I had 5.83 gears and 9.00 x 16 NDT tires, but I'm sure there was some difference.
With the bigger tires and taller gearing, I took the truck on the highway fairly often and made it point to stay in the right lane (slow lane). It did ok and I could cruise at close to 60 mph (57 or 58 most of the time). It would do fine when the freeway was flat, and even did ok on very slight inclines, but there was no accelerating up any incline, no matter how slight, even if I was trying to accelerate from less than the speeds I mentioned above. At just a little more of an incline than that, I would start to lose a little bit of speed, and of course, I would lose speed more quickly as the incline got steeper. Keep in mind, it did not take much of an incline to become aware that the engine was challenged.
So with your engine being completely stock, and with 40" tires, I think you'll find it even a little bit harder than I did to go freeway speeds.
One thing I'll mention is that, even with the special cam I had, I wouldn't be surprised if the engine was limited by the carburetor. You can add all the lift and/or duration in the world to a cam, but if the bottleneck is the carb, as I suspect is the case with a skinny little 1-barrel unit, you're not going to get much improvement from cam upgrades alone. My only point in saying this is yuat my engine may not have produced much more power than yours would, so the fact that your engine is stock may not hurt you much. Your bigger tires may hurt a bit, though, although it may not be a huge difference.
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