need help figuring out compression - Honda Prelude Forum

arctic93 · 04-28-2002, 10:14 PM

i wanna mill the head on my h23 but i don't know the formula for figuring out how much to mill it to get what ratio. does anyone know the formula or has anyone milled there head and knows what their compression is now? any info would be helpful. thanks

-tim

marcucci · 04-29-2002, 03:18 PM

More importantly you need to figure out how far you can mill it before you smack the valves with the piston. You'll also need to correct for your change in timing with cam gears.

Still want to mill?

arctic93 · 04-30-2002, 12:57 PM

yes, i do still want to mill. i know all about valve clearence. i just don't know the formula for figuring out how much compression i will get out of it. also i don't know what you mean by change in timing. correct me if i'm wrong, but it should stay the same if i set the crank and the cams to TDC. the t-belt will still have the same tension because the tensioner is spring loaded. the only difference is they'll be a little closer together. at least thats my take on it. thanks for the advice though.

marcucci · 04-30-2002, 03:14 PM

The timing is dependent on the belt... reduce material/distance from the cam and crank pulley and you change timing since you've reduced the leading (tension) edge of the belt. The tensioner is on the trailing edge, it's to keep slack out of that side.

To figure out the change in compression you figure out the change in your compressed and uncompressed volumes. In other words, 2.2L/4 = .55L uncompressed, your old "compressed" volume is .55/old CR. Figure out your new volumes and divide to get the new CR.

You need to add in the CC volume to these volumes to be exact, but this should be fairly accurate. You can probably find the CC volume on the web somewhere.

arctic93 · 05-01-2002, 09:37 PM

cool man. thanks alot.