Bored G149 vs G160

Which engine will make more hp, a stock 160 or a 149 w/ 3 9/16 high dome pistons? Has anyone dynoed an engine with the pop up pistons?

Dr Allis, I have a stock G149 with 160 carb and manifold right now. So what would win, bored high comp 149 with 160 carb and manifold or stock 160?

Been there done that.  I have a D10 block that I've installed the domed 3-9/16 pistons, 155 CID. The exact compression ratio is unknown, however it really doesn't like regular gas. This engine had slightly bigger valves when it was built. With it install in a CA chassis it does just a tic over 40HP at stock PTO speed. the 160 in the same chassis did closer to 50. When the 160 was tested it was still factory stock, before I did head and cam work. 

All I know are the results. I should have also mentioned that both above mentioned motors are available, I'll answer PMs for the details.  Both are currently able to hear running. 

There are so many variables to change to get higher HP, adding fuel may get SOME, adding more valve opening may achieve SOME but not a lot for either, simply adding higher compression probably will not. HP is a factor of Cu. In. displacement, compression ratio against fuel supplied and timing efficiency where RPM is the major player in gasoline engines and on diesels the amount of moving mass denotes higher torque for a given HP against the other points.

Leave RPM at the same point, the same amount of mass moving within the engine(flywheel, rods, pistons, crankshaft) and not change the rest of the equation and you gain very little with what seems major changes for fuel, compression, etc.

It would be interesting to actually run a cranking compression test on both engines and see which one has the most compression. D-15 S2 will run 170 to 180 psi with the Power Crater piston design.

Rod length is the same between those engines. You'd have to hold the two pistons side by side to see why things are as they are. Power Crater designed pistons work well with a flat cylinder head. It sounds like the dome design may have more of a detonation problem with a flat cyl head.

I've written about this before, but here it is again.  25 or so years ago, I was asked to overhaul a Customers WD. It was his twice daily cattle feeding tractor that was never unhooked from the feeder wagon. It had the original design flat top AC aluminum pistons. I did some calculating and figured a set of 175 pistons and sleeves would yield the same compression ratio with the standard 4 inch stroke crankshaft. I had a 175 motor kit on the shelf.  Realizing the HP risk was very small (he didn't plow or disc with it) that's what got installed. Cranking compression was right at 100 psi, just like a WD should be. The surprise was this:  the sound of the exhaust was much more like the "crack" of a WD-45, not like a normal WD. Why would this be????  My $$$$ has always said the Power Crater bowl design is what changed the sound of the exhaust.  Believe it or not, I choose to believe it does.