I'm planning to rebuild my f20 block with a f22 crank & rods, and USDM Ap1 pistons.

Is this exactly the same as a 2004 f22 block? I'm deciding if I should just buy a new F22 short block from Honda and fit it to my ap1 head, and not worry about a margin of error or not to spec with the f20 rebuild

thanks in advance

 

you'd want to use an ap1 block if you are using ap1 pistons, from what i can find out ap2 blocks have a slightly bigger bore.

doing this will give you about 12:1 compression due to the longer f22 stroke.

the heads all bolt up the same, no problem there.

 

No , they have the same bore, doesnt matter what block you use. The AP2 gets the extra displacement from the longer stroke, not piston size.

It is a direct swap, you dont need a new short block. F22 crank, F22 Rods and the USDM AP1 pistons will do fine. Actually you will have more compression than a regular AP2 so that be nice. Why dont you try and get yourself a set of JDM AP1 pistons? Thats the route I would go if I were looking to do this. OEM Honda Reliability, Higher Compression, More Torque than an AP1 motor. Cant go wrong.

 

"Why dont you try and get yourself a set of JDM AP1 pistons? "

what compression will JDM pistons net me if USDM pistons are 12:1? what compression rate can I safely go to using pump 91?

thanks

 

JDM AP1 pistons should raise the compression ratio to ~12.5:1.... from what I have read here. I think you will be fine with 91 to be honest, but you might want to consult a better engine builder than myself. Go with whatever makes you comfortable and whatever your engine builder thinks is gonna work.

 

He's planning to rebuild it, so he's the engine builder.

 

the set of ap2 pistons i have are about 0.0025 bigger than the ap1 pistons i have, thats pretty significant.

jdm pistons would give you about 12.7:1 compression, USDM ap1 pistons would result in 12:1 compression, and if you know where to get em i need a set too.

jdm pistons is pushing on 91 octane.

 

You might get away with 12:1 CR on pump gas (91 or better) with a stock ECU, but no way you're doing that with 12.7:1. You will need tuning, or at least, bigger injectors to increase your margin.

Check the bores but unless you're starting with a new block you will likely need to hone it, and if you do so, you'll probably have to hone up to larger size (OS) pistons. Used blocks are normally out of spec, especially if you hone to make for good ring seal.

OS AP1 pistons are currently on national backorder.

 

just buy a used f22 short block.

 

Not to thread jack, but how much material is removed during a honing procedure? Is there a set amount or just the minimum possible to restore wall finish?