Hello all,
I wanted to secure my parts before I posted. I am building what I guess could be called a G21, consisting of H23A1 block and head, F20 crank and rods, and H22 Type S pistons. Displacement should be just over 2100 cc, compression around 11.5. This will be a nearly square engine with a bore of 87.635 and stroke of 88. The 1.65:1 rod ratio should be quite nice in terms of making a smoother power curve as well as help me with the high compression ratio (for a street car at least.) This wil be going into my 1992 Accord EX.

Other parts accumulated so far:
Lightweight crank pulley (a la UR)
OBX header
H22 P/S pump
ECU + TCM

I did have an idea of taking the "butterfly box," the unit with the vacuum operated butterfly for secondaries (IAB?) and adding a second one with the butterflies removed underneath the first one for longer ports and possibly more torque (hopefully.) Seems to hold more promise than a throttle body spacer does. Anyone tried this?

Thoughts/comments on the build?

 

That sounds like it should be a fairly badass setup while retaining near stock reliability. I've never seen anything with the "butterfly box" modded, but I agree it should be a better setup if done correctly than a throttle body spacer.

You might want to invest in a mild port and polishing of the stock H23 intake manifold to free up some extra airflow, you might actually achieve better power gains in that setup than switching to an aftermarket one.

 

Thanks for the feedback. I'm looking into some adjustable cam gears as well, to get the most out of the stock cams. I wonder if an air fuel mixture controller (SAFC, VAFC) would be a wise investment? Any experience with them?

 

you're probably going to need a whole new computer setup to handle this

 

You think so? What would be wrong with using the H23A1 computer? Also, I just finished the port matching and mild porting of the stock upper plenum, located a 2nd IAB to construct my long runner manifold and the teardown begins today.

 

I didn't think about it until recently, but when changing the stroke, one must also change the balance shafts, so I ordered up f20 blance shafts to go with the change in stroke. Also, F and H balance shafts are interchangeable. The H23A1 shafts are the same as the F22 with 95 mm stroke.