First off, don't tell me not to build this motor. I know the f-series have no potential and are **** motors. lol

Here is the setup that I intend to build:
BLOCK:
F23A1 block
K20A2 pistons (11.0:1 stock)
F23 rods

HEAD:
F22A1 ported head
Bisimoto non-vtec pro springs
Bisimoto F22Ax cam gear
Bisimoto Level 2.3, F22A/B Nitrous cam

INTAKE:
H23 intake manifold, gutted and ported
H23 throttle body
3" intake with a bpi 3" vstack

EXHAUST:
Custom header
3" exhaust with a magnaflow muffler

NITROUS:
NX direct port
1 gal fuel cell with a 130gph pump and carb dead head regulator
Mallory 685
2 steps colder plugs

TRANNY:
H23 5 speed
Haven't figured out a clutch yet

My goal is to run around 11.5-11.7 in the 1/4 in an EG. I could give a **** what the dyno numbers are, just want to run a solid time.

My main question is about the K20 pistons. I have heard that they fit in the F23 block pretty well. They have the same bore atleast. ***What is needed to fit these on a F23 rod?
Also, what do you think the compression would be?***

I have searched this topic quite a bit and I haven't found a DEFINITE answer.

Thanks for your help guys.

 

Go forged if your gonna spray heavy. After flycutting the exhaust side of the oem k 20 pistons they weaken so nono with the spray if you want it to last. Everything else looks ok, I would go 12 points of c/r with the level 3 cam before spray since your running a seperate fuel cell for race gas. Also maybe a different i/m

 

Didn't know that I would have to flycut.
**** it I'll just get some arias pistons then. lol

The reason why I don't want to go higher than around 11:1 comp is because of the shitty 91 octane gas we have here.

C16 will be in the cell, the motor will be getting a healthy dose of the giggles.

 

If you're not going to machine the K20A2 pistons' exhaust valve reliefs to fit the intake valves and rotate them in the bores 180˚ then I wouldn't use them. You don't have to "flycut" them and if you clay the engine you might be able to get away without the machine work as long as you maintain .040" minimum piston to valve clearance. If you can't get .040" clearance then you'll need to enlarge the valve reliefs.

Also, the K20A2 piston pin offset is shifted to the wrong side for use in the F23. I would also not use cast pistons for nitrous, at that compression (~12.5:1CR) and expect it to last. The simplest solution to the above issues would be to run some aftermarket forged 86.5mm pistons, without a pin offset, with a 0 cc dome to get you ~11.5:1CR.

Otherwise the OE pistons will fit on F23 rods no issues. Installs like any other F23 piston on an F23 rod. If you get an aftermarket piston you might have to hone out the LE rod bushing to fit the pin.

my 2¢

 

looking forward to seeing the outcome.
i am running a f23/f22a4 right now. I kept the bottom end stock and milled the head .045". but i am boostin it.
how much hp from the spray?

 

That was one of my main questions, the compression. Thanks man!
Thanks for telling me what it would be. 12.5:1 is wayyyy to high for 91 octane.
Their goes the idea of K20A2 pistons lol.

Although, one thing I disagree with you on is that cast pistons do not last on nitrous. You would be surprised how long an OEM built motor lasts with a good tuneup. I'm not talking about dyno tuning a nitrous setup with a wideband (worst thing to do). I'm talking about good street tuning and reading the plugs. I have seen some insane nitrous setups that made peoples jaws drop. Guess what, they were all on stock motors.

The couple things they all had in common:
Direct port
Standalone fuel system for the kit with C16 gas
2-3 steps colder plugs
Real world nitrous knowledge, not reading the bullshit nitrous FAQ that's on every forum.