Hypothetical engine build... input please!

[GhostAccord]

If you look at some chamber designs they are only a tub shape and don't even cover the diameter of the piston. All depends on the quench areas and how much clearance you have between the piston and cylinder head.

This build being a boosted one I would assume that the pistons are dished/stock. Therefore there is no real danger of piston to head or valve clearance issues. The piston to deck height is -0.002 (out of the hole) stock. so I don't see this as even being an issue really.

IMO if you were to go the other way around it would be more of an issue. The mushroom head = 85mm bore with an 87mm cylinder head chamber. For example the H22 head on F22 block swap. This actually puts a dead spot in the chamber for carbon to build up in. In turn this could cause hot spots. Not a real issue when you go 86mm bore 85mm chamber.

Just my 2¢ worth!

Good luck ether way!

[Jarrett]

Yeah clearance definitely wouldn't be an issue with this with a factory compression height/rod length/stroke. Simply design of the quench area.

[wed3k]

i know no one asked for my opinion but i wouldn't be too worried about it. chamfer the edges and be done with it.

[Jon]

i know no one asked for my opinion but i wouldn't be too worried about it. chamfer the edges and be done with it.

Always appreciate opinions.

[deevergote]

Wow, I forgot there even WAS a non-VTEC F23A! I can't remember the last time I saw a 6th gen DX.

Still, I think everything needed to make the head work will end up being just as expensive as modifying the F22A head, if not more so.

I wonder how the F23A5 port design is in comparison to the F22A...

[GhostAccord]

lol...... #11....

F23A1-5 are all PAA castings, same as the F22A1-6 are all PT3 castings.

[deevergote]

Yeah, I did read that this morning (as I was halfway out the door... ) But I wasn't sure if it was the same casting. I suppose I assumed the VTEC heads have different castings than the non-VTEC heads.

[GhostAccord]

In the F23 the only differences are the rockers and cam. They use the same cam caps and everything. Honda was being crafty when they designed the F23 series engines.

It would be pretty easy to convert a Non VTEC F23A5 into VTEC. Swap out the rockers and cam. Remove the oil passage cover and install the VTEC solenoid and pressure switch.

[BurtonRiderT6]

Wouldn't milling the head bump up the compression?

[Jon]

Wouldn't milling the head bump up the compression?

The short answer, yes it would. But you would eliminate the issue at hand (CC bore size matching with the cylinder bore size).

[BurtonRiderT6]

I too have been planning my build and I never really thought about the mismatch.

[19dabeast85]

I am pretty certain your "issue" isn't really an issue. When the head bore is LARGER than the cylinder bore you get major issues if not planned carefully. But with the head bore slightly smaller than cylinder bore you will be perfectly safe just chamfering around the bore in the head.

However, looking at the flow numbers of that F23 head, if you are deciding between oem F23 head or oem F22 head with NO porting, and IF everything on the F23 head lines up....in stock form it will flow better than the F22. But who does a full build without porting the head?

[GhostAccord]

As far as the F23 head goes.... It too can be ported to gain some fairly good flow numbers. As good as the F22 maybe not.... But I can't see anyone complaining about a street/strip port and +1mm valves flowing 300cfm.

F23A ported w/+1mm OS valves
Lift - Int. - Exh.
0.1" - 96 - 79
0.2" -178 - 151
0.3" -246 - 202
0.4" -289 - 215
0.5" -303 - 221

That's good for up to 270-300hp N/A with a proper intake and exhaust 90-100% VE. The exhaust being 73% is kind of a low. However, it could work very well with a proper cam.

[Jarrett]

Proper intake in this case being ITBs.

[GhostAccord]

Yes! If you want to make use of 300cfm and get 300hp N/A out of any F series head, be it an F22A or an F23A. It will require some sort of aftermarket or custom intake and exhaust setup. A pair of double Weber carbs would work as well.