20Rs have a 80/81cc combustion chamber, early 22Rs 82/83cc. 20R valves measure 43mm/intake 35mm/exhaust, 22R valves 44.5mm & 36.5mm. By putting a stock 20R head on a stock 22R block you have decreased you combustion chamber by 1 or 2 cc's, but you now have smaller valves.

But you've also raised the compression ratio 0.5~1.0:1.0

79coyotefrog is trying to tell people you'll have this tremendous hp gain by swapping all stock parts. This is simply not true.

There have been no written results of his or mine or anyone else's hp numbers because it's not worth spending money or time for a dyno. There IS hp gained, but the number depend on your build. and using stock 20r parts is not completely worthless. I was running stock 20r head and there WAS a hp gain (again no actual numbers to verify, but the truck was faster just based on a stopwatch (0-60 time decreased) I had an exhaust manifold leak and wasn't gettin all I could out of the motor and noticed a good increase.

Those of you who "estimate" you have a 150+ hp 22R. Have you ever drove a 3RZ. A 3RZ has around 150hp stock. I have seen very few "built" R series motors that will even compare to a 3RZ. Hmmmmm?

see, you can't compare the 3rz unless you're comparing a 22r stroker 2.7L > 2.4L so yes the 3rz is going to be better - no replacement for displacement. But why stop with the 3rz, have you ever tried a SC'ed 3.4L..it's apples vs. oranges again

As for my motor I can't give you 100% factual hp numbers but it's close to 140.  My specs from what I can remember: 20r head - 46mm,38mm valves, port/polish, 3 angle valve grind, comp cam 268s (may be 260s). 22r block - bored 0.20 over, stock stroke. Thorley header, Weber carb.

Nothing said here is the bible of engines. Just opinions and experinces. Don't believe anything??...don't do it. Some people say it's worth it some don't. It's just like some say that 37's are too big, or synthetic winch rope is better than steel cable.