F22a6 head F22b *dohc* block

[lowcb7]

Im in the process of tearing down and rebuilding a jdm F22B block. The head was in bad need head work. im planning on doing a jdm F22b block and F22a6 head setup with the larger F22b (H23) intake mani plenum with double stack Iab plates. Now my question is being that the compression of the a6 is 8.8:1 and the c/r of the F22b being 9.3:1, will this setup bump compression to 9.3. and if so in theory would it raise the hp on the a6. From my knowledge the higher c/r was due to the f22b pistons rather then the head. If anyone has any knowledge or insight please let me know.

[deevergote]

A higher compression ratio will result in a little more horsepower.
According to a calculator I found on Google (I did not research at all to see if it was truly accurate), raising the compression ratio of an F22A6 to 9.3:1 would result in a gain of 2.21hp, with all else stock.

Without delving into engine theory that is beyond my own understanding, it's usually pretty safe to assume that all engine mods will enhance the effects of all other engine mods, as long as they are compatible. In other words, the compression ratio increase might give 2.2hp, and the intake manifold might give 7hp (made up number... I don't know how much it actually gives), but the two mods combined could result in a 12hp gain (again, made up... simply using it as an example.)

You'd need to know the combustion chamber volume of each head to accurately calculate the new compression ratio. It may be different with the A6 head.
According to HondaFan81 (who I trust to be very accurate) in this thread, The F22A's combustion chamber volume (head only) is 50.5cc. The F22B DOHC's combustion chamber volume is a smaller 47.2cc. Therefore, the compression ratio is going to be lower with the F22A6 head than it is with the F22B head.


In messing around with this calculator, plugging in known specs from HondaFan81's thread above, I determined that the final compression ratio of the A6 head on the F22B block would be somewhere around 8.91:1. Using the other calculator I found to determine horsepower gains given by a compression ratio change, I arrived at a gain of .5hp. You'd likely see a better gain by farting in your intake!

It seems that the F22B block is much more similar to the F22A block than previously believed. Much of the compression increase is in the head itself.

[lowcb7]

Sweet and to the point Thanks Deev, yeah i wasn't expecting massive gains just curious. i had entertained the idea of making a G22 Frank out of the F22b block but would rather have a hard running SOHC than to be part of the DOHC fanboy club. Due to convenience of the F22b block being in near mint shape inside figured my best bet would be to to just stick SOHC. That way if i wanted to delve in to the frenkenstein hellstorm i could use the spare f22a6 block i have that could probably use a good bore anyways

Edit: Deev now correct me if im wrong but shaving the head will bump C/R?

[deevergote]

Shaving the head will increase the compression ratio a bit. As will using a thinner head gasket (OEM is 3 layer.)
Shaving the head can be risky, though. Shave too much, and you'll never be able to repair it if it warps in the future. Also, shaving the head can have a negative effect on valve timing. You'd need an adjustable cam gear to get it right again.

Also, "g22" makes my skin crawl. The G series has 5 cylinders! Someday, I hope that term disappears!

[Jarrett]

The DOHC F22B head I have is close enough to 50.5cc as measured with a cheap plastic graduated pipette that I just accepted it. The 47.2cc figures that perpetuated this site have never been duplicated by anyone else. I can;t remember if it was PirateMcFred or someone else who measured, but it seems they had a head that was milled previously.

[lowcb7]

Yeah i also wouldn't want my pistons to kiss my valves after all this work. trying to keep it simple and maybe have everything in before AFM14.

Also just wondering if replacing injectors would be worth it in something of this nature. I.e H22 / DSM injectors or is PT6 ecu would not run them properly, or if i should look for another chipped ecu to tune. I want to say PO6 is the one i keep seeing recommeded in threads.

Unfortunatly "G22/3" is probably gonna be here forever lol. that would be something i would attemp in a car that i dont need to be reliable. Some thing that you run down a track a couple dozen times and start over

[Jarrett]

You don't need to replace your injectors. People have gained power from RDX turbo injectors because of a much more refined spray pattern, but you're not to the point where you could really utilize a 410cc fuel injector.

[deevergote]

Yeah. Unless you do considerable work to the engine, the stock injectors are adequate.


If the F22B head has roughly the same volume, then I suppose the overall compression ratio wouldn't change much (or at all) with the F22A6 head in place. In that case, expect that whopping 2.21hp gain

[lowcb7]

Right thats what i figured. 2.2hp soounds bangin' to me!!!! lol Thanks gentlemen

Edit: plus whatever power a port match will give. Hahaha +5 hp here i come