Are you guys that are running really good N/A times do any type of combustion chamber reshaping or anything on your cars? I mean some of you get the block resleeved bore it out to whatever and do you leave the bottom of the head stock or I mean the combustion chamber?

 

what kind of head do you have?

I've heard of guys with B16's welding their head's like the GSR's P72, but I myself would really like some info on this as well.

 

Yea can open up the chambers on the head to match the bore size of you block.

 

Mine was taken out to 85mm, then milling it back down to 41.5cc. GSR Head.

Suprdave

 

I just chamfered the chamber to prevent hot spotting on my B20vtec

 

If you're running a big-bore, you're losing potential air flow if the sides of the chamber aren't opened up to the larger diameter.

 

Couldn't you also ruin the location of your quench pads? You need a flat spot on both sides to have 'squish', so if you don't open the head to the piston diameter, you are loosing the potential power gains, and burn quality.

Suprdave

 

You want the flats in the conventional "quench" areas, but the "squish" should come from the fit between the sides of the piston dome and the sides of the chamber. This will cause the direction of the mechanically driven flow to "loop" up high in the chamber with a more predicatble motion than is achievable with a small "flat" in those areas.

 

So ideally, you would have perfectly matched quench pads and a piston\chamber design that promoted the mixture to move from the Intake and push it towards the exhaust side with an efficient burn. I understand now, makes sense...thansk larry.

Suprdave

 

So to have a good chamber design you want to open up the combustion chamber to the bore size on the block then mill the head down some. Or you could just champfer what is left over on the head so it kind matches up with the cylinder or piston bore? Am I understanding this correctly?

 

That's correct. We generally determine how much we can mill from the head by checking piston to valve clearance in one of the (many) mock-assemblies we do with engines and heads.
On our Roller-Wave pistons we have models available with the sloping sides of the domes that extend to within .030" of the piston's bore, so we can achieve the close side clearances we need on chambers we've opened to the bore diameter. The sides of the chamber do slope, especially in the middle and toward the exhaust side, where around the intake valve, we've chosen to have the side walls almost vertical for increased breathing space.