compression calculations help

just wondering how accurate the compression calculations that 440 source has listed for there stroker kits.

I'm building a 440-512 kit 30 over (505) with the .17 dished pistons and trickflow heads.
They say I should be at 10.6. With pistons .015 in the hole. I went 0 deck and I'm trying to figure out what my compression is going to be and I'm having a hard time. Even when I enter there numbers in summits compression calculator get a lot higher numbers than what they say. Any help is appreciated. My goal was 11.1 or so. Thank in advance

A 505 with 17 cc dish and zero deck and 78 cc heads will be 10.9 compression with a 0.041 gasket.

You made some sort of input error. I used the Summit calculator and got 10.85 compression ratio. You probable used the wrong sign on the dish volume.

10.85 sounds just dandy.
If you wanted to figure area above the top ring, and head gasket void, you are going to be lower, which is a good thing.
It would really be bad if you had your build be on the verge of detonation every time it was a little hot, or pump gas wasn't up to snuff.

When I was figuring CR on several motors, Summit’s calculator was always wrong. All of the ones online seem to vary somewhat. I finally found a formula and just did it on paper.. it worked better and I could compare the changes and see how much different numbers changed the ratio.

good to know that the online calculators ain't right (I woulda never thought). I will figure out that formula & use it

The Summit calculator works fine for me.

Try using the United machine on line calculator and or the Wallace on line
Using the same numbers will result in slightly different results on both sites
Make sure and try using the - and+ sign on the piston deck heights and piston dome volume, you should get less compression with the dish than with the same amount of dome volume. Which ever sign gives you the less compression using the dish volume will be accurate, if using the + sign on the disc volume gives you 10.5 to 1 and the - sign gives you 13.5 to one then you know which sign to use on THAT sight
Both will get you in the ball park though
Have fun and learn

One of the areas most mistakes with this happen are around chamber volume and down fill volume. Many simple step calculators just use published figures from piston and head manufacturers and should be fairly repeatable if you use the right figures. That isn't to say they will all be exact, but they should be within a narrow range of each other.

One I like to use for static figures is here: https://www.rbracing-rsr.com/compstaticcalc.html

Once you have accurate static numbers, I use this one to account for cam, altitude, and boost variations to figure out what needs to change for pump gas livability: https://rbracing-rsr.com/comprAdvHD.htm

Thanks for the help. I should be good at that comp ratio. Now to finish assembling it and getting it on the dyno