Does anyone know what the Red line for a Stock 302 in a 75 Maverick would be? My other question is about rear end gears. I have an 8" 2:79 rear with a C-4. I wanted to get better acceleration but still wanted to be able to go down the highway. Would 3:25 be something that I would notice a difference in acceleration and still be able to go down the highway or would that be too high/low?
3.55 is about the going rate. I run 3.80, but don't mind 3000 rpms at a slow 60 on the highway (I have a fairly laid back lifestyle, and don't punch a clock ) Red Line...Don't really know what that means. Floating valves, top end of power band, On a stock motor, shift at 4500, or it will start falling over it's own a$$ soon thereafter. Do a couple of mods, such as new intake, bigger cam, headers, and you might get away with 5000 or 5500.
My stock motor ran fine to 5500, but it would accelerate very quickly up to 4500 then the accelleration would slow down, so I would shift it there. Also, I really feel uncomfortable telling someone with a 40 year old motor "yeah, it's fine, run it up to 5500!" and then waiting for a PM saying "it threw a rod, thanks, you a-hole!"
Maximum HP in a 75 302 is reached between 4000 and 4600 rpm depending on the model. It is common and a good idea for power management to rev to 10% beyond the point where the engine reaches max power. Your redline for best performance should be between 4400 and 5500 rpm. If your oil pressure is near normal, (bearings and pump in good shape) and there is no noise from loose pistons or pins there should be no problem mechanically with turning the engine to 5500 rpm. A good compromise rear gear ratio is near 3.50. You will turn no faster than 2800 to 3000 at 60 (unless you have very small 13" tires). It will give you a noticeable gain in acceleration and won't adversely affect fuel economy much. If you were to add a new efficiency cam and lifter set you will gain some HP and fuel economy. Headers and dual exhaust will also add to the mix. Unless you go too big on the cam you won't need to change carbs although a properly selected four barrel carb can give you better gas mileage than a two barrel under most conditions. Other things that can affect acceleration and economy are tire pressures, engine temperature, oil viscosity and timing. Radial tires can be inflated to 35 psi and unless you are running very wide tires, they should be inflated to at least 32. Keeping the engine's temperature between 180F and 200F and the incoming air below 180 is a good compromise between fuel efficiency and power. Run oil with a viscosity that is just high enough to maintain oil pressure when the engine is warm. If you can do that with 5W-30 there is no advantage to using 20W-50 oil on the street. The thicker oil uses more hp to turn the pump and in street use is not needed to protect the engine. Keep your timing as far advanced as you can without preignition or detonation. That will give you the most power and best economy.
I'll go against the grain and recommend 3.25 gears. Yes, you'll notice an improvement in acceleration, especially if you're replacing 2.79s, and driving on the interstate won't be an exercise in patience.
ditto... shifted my then 34yr old 302 at 4,500 at the track.... got the best times out of that rpm, any higher slowed me due to floating.
I can tell you from experience, my valve springs have definately gotten weaker. 4bbl, spacer, duals, headers, it liked to shift around 5200, after all was said and done, seemed to be the fastest shifting just before 5500. It didn't take long tho, the valves started to float at 5500. The old girl is pushing 33 years, I think its time for a refresh.
I guess you're talking to me? I'm going to fix it, just haven't quite decided what route I'm taking. I have a set of 351 heads here, might port those, springs, etc. If one of my new projects works out, I'll be out of debt and I will have a set of AFR heads. I'm hoping to finish the floorpans and bodywork sometime this summer (I've said that before) and just get the old girl rolling again.
