[john6066]

my pistons from my 461 BB. have a T in the middle of a triangle symbol. the only marking i can find on them. the dome measures aprox. 3/16th above the flat of the piston. the intake has a pronounce relief and the exhuast a very small one. the pistons come up within .016 from the top of the cylinder and the head gaskets are .040
i formerly had closed chamber rect. 291 heads (108.0cc) way too much squeeze, i plan on running open chamber large ovals and would like to burn pump gas.

please offer suggestions on new heads and weather or not these pistons will work and still give good HP and torque. i also plan on running a hyd. roller between .650 and .700 lift.

john

ps i wanted to post pictures but the files are too big? their jpeg's, any advice on posting pics?

 

[Eric68]

I have no idea what pistons you have in there, but the Speed-pro catalog lists a .210" dome piston that makes 10.25:1 with a 108cc chamber. That's a long way from "way too much squeeze."

If you manage to stay at 10:25:1 a cam with 235'ish duration @ .050 would match pretty good.

You really need to cc that piston when you get the heads off to be sure . . .

 

[john6066]

i thought when i got this beast torn down all things would be known, wrong.
how do i cc a piston?
the dome on these roughly measure .22 and angle up to .26. they're oval pistons that "look like" speed pro #STL-H426CP30 with a dome height of 0.1 and compression distance (whatever that is) of 1.640. as listed in the summit web site.
i'm trying to line up a machine shop that i can trust, i hust want to have a pretty good idea of what's what before i get anything done.


thanks john

 

[Eric68]

I think the way it is done with a dome piston is to move the flat part of the piston down in the bore exactly .500" then close off the top using a cc jig (its a flat piece of plexiglass with a hole in it). The area above the piston and below the jig get filled with light oil (from a burret). Then subtract the volume of fluid pumped in from the theoretical total volume of the .500" tall space (1/2bore squared*pi)*.500 That would give you dome volume (plus crevice volume).

I have personally never done this and you may have to pack the crevice with grease to keep oil from leaking through the ring gaps, but I have no idea how you would get the grease out when you are all done.

Maybe someone that has done this can explain how it is done with the engine assembled (or if it even can be done with the engine assembled)

 

[john6066]

thanks eric
i found a number on the pistons L234 .030
they're 4.28 bore 1.645 comp. distance and 0.221 high with 29.40 cc.
i posted this info in the engine area too.

thanks john