Just wondering if its a problem that my F23 combustion chamber with its de-shrouded valves is larger than my pistons? I've tried to search but haven't found anything much related to this.

 

How much bigger? If it is going to cause sealing issues between the cylinders then it could be an issue.

How did your combustion chamber become larger than your cylinder bore? Did you do the de-shrouding yourself

 

probably 1-2 mm at most professionally done head I've seen a lot of heads that were deshrouded that look like mine. I've just never put a piston face to those heads to see the overlap.

 

the top of the piston is smaller than the cylinder bore by a bit. your best bet is to measure the combustion chamber and compare that to your cylinder bore.

 

If the combustion chamber is larger than your piston top that isn't the big issue. It will lower your compression ratio. And it could possibly cause some dead flow areas or an uneven flame front. The bigger issue would be if it is larger than the top of your cylinder bore. If it is larger than the cylinder bore (combustion chamber shaped like a mushroom) 1. The work that was done probably won't be doing a lot for flow. The head gasket & top of the cylinder wall will be blocking the flow causing an eddy effect / or a turbulent flame front during combustion. and 2. The possible sealing issue that I already stated.

When I de-shrouded mine. I marked the 89mm diameter of my cylinder bore around each of the combustion chambers. That way I would be able to see the max diameter that I could use to open up the valve shroud without going past the edge of the cylinder bore.

 

Are you referring to the top of the cylinder wall? The cylinders themselves are by far larger than my combustion chamber. My pistons are only 86.5 MM .5 mm over stock. I don't have a block handy but I'm sure the face of the bore would be outside the combustion chamber.

 

If your bore is 86.5mm make the chamber no bigger than that.

 

Can you post up pics?

On most of the F22/F23 cylinder heads that I have seen. The combustion chamber is the same diameter as the cylinder bore.


This is my F22B2 before I did the head work. The lip around the combustion chamber is the same diameter as the stock cylinder bore. I am pretty sure the F23 is a similar setup. Except it would be 86mm in diameter.

 

https://honda-tech.com/forums/all-motor-naturally-aspirated-44/300-cfm-f23-head-pics-added-2463843/

PICS. This is what I get for taking my head to a domestic porter. He made the head flow amazingly well, but now it won't work with my pistons. Looks like I'll have to sleeve my block and run 89 or 90 mm?

 

How much larger is your combustion chamber than your piston?

If those pictures are the extent of the de-shrouding you should be OK. That doesn't look like much was removed from the combustion chamber rim. Unless he made the rim larger???? If your using 86.5mm pistons and the cylinder bore and combustion chamber diameter is 86.5-87mm you should be good.

Yeah I remember that thread very well.......lol
Every Honda engine will make huge gains with 300cfm heads.

 

Compared to the other picture, that doesn't look like the chamber diameter has been opened up at all. I'd say it's fine.