Your stock 318 should run on Regular grade gas, these mods will require Preumumn grade so ANY MPG gain will be eaten up buy the extra $0.40 per gallon costs.
All these mods to a 0.030 over 318 will put out just a bit more power than a stock 5.9 Magnum with a good tune. But do a few bolt ons to that 5.9 Mag and now you really gain power for your heavy truck. Stroke is the win here for a heavy vehicle.
So, I didn't really consider the octane issue. What compression level do y'all think I would start needing to use the higher oct? Does hardened valve seats allow the compression to go higher (like on the 302)? I do prefer to burn low octane, not just for price, but because the ethanol is so bad for the fuel systems. I have replaced the 2bl carb 3 times since I got the truck in 09. And that is with a can of B12 poured into the tank ever other month. I hate ethanol, I'm literally writing a thesis on why I do for a class right now.
I'm kinda up in the air between doing 302/8 heads on my 318 or dropping a 5.9 like y'all said. I could keep my 318 for a light Duster or something someday later. After pricing 5.9s on FB marketplace, there's like 3 of them within 200 miles from me for 400 bucks. Would my fuel economy go down with the bigger Magnum? If I hopped it up a little, or decided to put a carb on a Magnum, would I run into the same octane/detonation problem?
I really appreciate y'all's input. You have saved me from putting together a motor for the wrong application.
