I've been a lurker for a about 3 years and finally seriously considering a stroker. Lots of info here that makes my brain spin. I've searched and didn't find my answer. I have an 86 AMC Eagle with an 81 shortblock with a 4.0L head milled .050, Comp 68-232 cam, with a Motorcraft 2150 carb. I've got over 20k miles on this combo and it runs pretty darn good. I had it dynoed before and after. In Colorado, on a Land and Sea dyno it had 112hp before and 180 hp after. It was a night and day difference but I questioned the after numbers. After moving closer to sea level and monkeying with the carb, it doesn't quite feel as fast or I may have gotten used to it. I had it dynoed a few months ago on a Dynojet and it was 135HP. The shortblock had 80k original miles on it when I installed it. It has always had an oil consumption problem since installing it. Mostly only on road trips though, since it has a 3 speed auto it revs about 2700 at 70 mph, using about a half a quart between fill ups(325 miles). I have a 4.0L long block that I got for $40. I wouldn't use the head that is currently on the 258 since it is milled and has the coolant passages welded. I do have everything to go EFI via Megasquirt but need the time and sack to do it. Does the .5 liters make that much difference?
Eaglefreek wrote:Does the .5 liters make that much difference?
The bigger displacement will make some difference but the real HP/TQ gains come from all the external bolt-on performance mods that help the engine breathe, porting the head, and adding a performance camshaft. I did everything except the last and the result's in my sig.
Thanks for the replies. The engine in the car runs fine now, so this will be a slow build while time and funds come available. My number one priority right now is getting rid of my KLX650R and replacing it with a KTM 300 XCW.
It's about a 10% increase in displacement if you are going from a 4.2 to 4.6 and you can set your compression right where you want it so it should realize all of or slightly more than that with the proper accessories. Going to sea level that thing should have picked up unless you lived in Death Valley.
I've read that the larger bore of the 4.0 block matches better to its head than the smaller bore 258 block, you can imagine an eddy around the parts where the head is wider than the cylinder, so a stroker creates less turbulence and better overall flow. So it's not all about cubic inches. Dino's success of using the stock cam and improving the low end torque shows how the combination of more air, still at the right velocity, but lower rpm, is a better solution than stock, especially for our heavy, brick rigs, trying to tow or turn big rubber.
What's your Eagle weigh? What gears do you have? My Mother-in-Law's 2002 stock GC is pretty spirited on the highway. You may like the mileage and ease to rebuild the 4.0 for how you drive, but you've got the stroker pieces except for the pistons.
I had it dynoed a few months ago on a Dynojet and it was 135HP. The shortblock had 80k original miles on it when I installed it. It has always had an oil consumption problem since installing it. Mostly only on road trips though, since it has a 3 speed auto it revs about 2700 at 70 mph, using about a half a quart between fill ups(325 miles). I have a 4.0L long block that I got for $40. I wouldn't use the head that is currently on the 258 since it is milled and has the coolant passages welded. I do have everything to go EFI via Megasquirt but need the time and sack to do it. Does the .5 liters make that much difference? 
