I recently got into a bit of a discussion on another board about the "ideal" piston to deck height while building a D16 with Vitara pistons. The "calculated" P2D is approximately 0.067" when using stock length rods. I suggested that the "ideal" way to increase compression with Vitara pistons when using stock length rods was to deck the block rather than mill the Y8 head. IMO the custom rods would have been best but these are the parts that the poster had to work with.

There were a few proponents that suggested that I was incorrect but were unable to give me any reasoning. (I'm open to being wrong if I know why) The only hint at a reason was due to (what I believe he was trying to get at) bore taper at the top of the cyl. The thread was locked after any lack of intelligent discussion was going on, or they were hating im not sure....

Asking too much of the internet?

Was I simply getting trolled? Or is there some credibility to their claims, which goes completely against the need for custom length rods.

 

Im not sure wich is better but reading that thread was horrible. Is that a tech site? It seems like people are there just to make posts.

 

It supposed to be, but don't ask questions it's forbidden.....

 

That was a good example of people trying to act superior by not answering a question because they honestly don't know. Ignorance at its finest...

I don't know the exact answer to your question but I would look into what Honda says is the limit to decking that block and maybe talking to a good Honda machine shop to see what they say about decking that block. I do not personally see what the issue is since rougly 1.5mm shouldn't affect bore taper that much. It will have the same effect on cam timing no matter where you remove material so I don't know what else they could be implying.

 

X2

 

I think piston to deck or piston to head (squish) clearances would make a great thread. I know for a FI setup you want to keep the piston to head clearance on the loose side... But then again it depends on the combustion chamber design.

 

From what I have read on speedtalk and other non-import forums it's accepted that 0.040" P2H is the optimum safe range. While chamber shape does play into this both GSR and Y5/Y8 provide better quench.

Not sure how true this is but I've read:

"Squish is not a factor, it is THE factor when you are building a detonation free motor. Squish is the biggest contributing factor for detonation. You should always try to maintain at minimum the stock quench"

 

Kinda relevant

 

While I'm not an engineer, nor an engine builder...I've seen a lot of these motors come through here...with a variety of different combos of parts.

I say, if you are going to go with a vitara setup...don't worry about adding compression by either milling the head or decking the block. That slight bump in comp doesn't offer a whole lot of average HP

I don't know exactly what it is or how to explain it but these combos (stock length d rods and ycp vitaras) are extremely detonation resistant...because of the lower comp ratio. When you add to the rod to bring up piston height (fjt) the detonation resistance goes way down...remember these are not a "forged" piston exactly...and I think the greater piston to wall cleance they offer helps in the "knock resistance" you see with these

I would probably agree with you though, that decking the block will work better than changing the shape of the combustion chamber and milling the head.

 

I agree with Chris on this one but would also like to add a single layer gasket could be utilized to raise compression and not compromise cam timing but little lower compression reduces knock/detonation chances

 

i very much agree with this. i had a vitara setup a few years ago and i couldnt believe how much timing i was able to add on the dyno without seeing any detonation signs on the plugs. much of the reason they work so well is in the lower compression ratio. i wouldnt mess with it too much.