I am still trying to run some numbers on my 383 build. My last post some one gave me a link to a compression cal. My problem now is am am DUMB when it comes to numbers. I need to know what my .400'' dome pistons convert to in CC's, which is what the calculator needs to compute the ratio. Also I am slightly confused about what rods I'll need. If some one could enlighten me in the difference between long and short rod applications. :hail:

 

I've never seen such a thing.... most domed pistons have .100" or .150" of dome.

Be that as it may, measure the actual dome height with a micrometer or something, thereby avoid all sorts of guessing errors. Or, if you know the part # of them, look them up or post it.

A domed piston in a 383 will probably result in an unuseably high CR.

As far as rod length, since you already have the pistons, you're kind of stuck. You need to find the "compression height" of the piston, which is the distance from the center of the wrist pin to the nominal top of the piston where it's even with the deck; then subtract that number, and half of the stroke you want to use (for a 383, that would be 1.875"), from 9". That will tell you how long your rods have to be.

 

Yeah .400'' dome is uncommon, but they are designed as a "semi-finished" piece that must be machined to your desired height. I'm still trying to figure out my desired height is. I want to be at about 11:1...

 

That would depend on your heads' combustion chamber volume, the block's deck clearance, and the head gasket you use.

Sounds like you needed to have already done a bunch of the basics of planning this motor. It's not a real good idea to buy pistons without knowing what rods they're made to work with and what chamber size they're for and stuff like that.

 

well, as for my planning on this whole prodject, I cant argue that. if someone could awnser the part of my question about converting the dome height(.400") into cc's, I would know what heads I am going to buy(planning).

 

You can approximate it if you know the area of the dome; multiply that by the height, then multiply that by 16.387 (the number of ccs in a cu in). There's no "magic conversion factor", since if the dome is small (covering a relatively lesser portion of the top of the piston), the volume for any given height would be smaller than if the dome was large and covered more.

Without knowing the area, there's no way to calculate it. It'd be better at that point to contact the mfr and ask them. Or, measure it with a buret, like you would a head chamber.

 

RB83l69, thanks for that last bit of info, I think I have it figured or at least I'm in the right direction. I have been trying to get a hold of the manufacturer, but nothing so far. Thanks