dishing 3.4 (L32) pistons

[merlot566jka]

so im doing a hybrid, iron head 3.4 with gen3 heads. i want a target static compression ratio of 10.5:1.
my ideas are either to dish the stock 3.4 pistons, take 15cc from the heads, or use the 3400 pistons.

dishing the pistons...i dont know if it can safely be done. i only need the dish to be 3.15'' dia and .18'' deep. stock its 2.75 dia and .080 deep. would i be crossing the line going that far?

taking 15cc from the heads...im not to confident on this one. thats a lot of material to remove and not 'f up the burn/swirl chartacteristics of the design. anyone done it?

or use the 3400 pistons, shave .020 off the top and use the .040 gasket for a cr of 10.68.

i am having some problems with info tho. im finding on this site and others that the dish on the 3400 pistons is 33.XX cc, and the cc on the heads is 28. yet the cr calc here says 27 for the piston and 26.4 for the heads...whose right?
any help would be appreciated!

[sil]

my suggestion would be to either cheap out (go easy way) and get custom pistons made to your order

or go and do some serious research into how you can improve the charictaristics of your combustion chamber

that way you could potentially get a better designed working head and not have the detonation of the better design, have better flow... only if your serious though cuase that would be alot of research, and possibly trial and error, but the results would deffinatly be worth it

thats what i would do if i was in your situation, but right now i wouldnt even think of going that far, cuase i dont want to lol

[bszopi]

The numbers listed in the CR calc are actual measured values. You're best bet, if you have the components, is to get a burrette and measure YOUR components and go from there. There will always be some differences between castings and such.

[merlot566jka]

sil...thanks, but custom pistons in this case would not be 'cheap out'. more like 'take a loan out'....

bszopi- yea thats what i figured, and thats why i cant figure.... the car is in va, im in alaska till aug. ive got a bunch of varibles with this build, and slowly but surely it looks like nothing is going to have an easy answer. i will call the machine shop today and see what they say. theyve got my new block and are waiting for me to get back to them with the piston info. ill ask them to measure the dish on the 3400 and the 3.4, then see what i want to do. i could even cut .060 off the top of the 3400 pistons and deck the block .040 to raise the compression...wonder what that does to the lim in relation to the head?

[Superdave]

seems to me shaving .020" off the 3400 pistons is the way to go.

[merlot566jka]

ive seen that in another thread, cutting .020 off the piston and using the .040 head gasket. but i want to go higher CR than that. what about .060 off the piston and .040 off the deck? too much? this is going on the calculations that the piston is actually 33.XXcc's vs the measured 27cc

[Superdave]

ive seen that in another thread, cutting .020 off the piston and using the .040 head gasket. but i want to go higher CR than that. what about .060 off the piston and .040 off the deck? too much? this is going on the calculations that the piston is actually 33.XXcc's vs the measured 27cc

how about taking .010 off the piston :P


if you use the .045" Graphite ROL gaskets you'll be fine with .010 of pop-up. that's what i'm using with the 3500 and having no problems...

[merlot566jka]

hmmm, if i take off .010 it decreases the dish to 31.91 cc (asuming the stock size dish is 3.15 by .260, or 33 cc) that with the .045 gasket barely brings me up to 9.31 CR. thats using the gm specs, 28cc combustion chamber and 33cc piston dish.
using this sites info that will bring me to 10.37...

im really stuck untill i get actual measurements. what have you measured for piston cc and head chamber cc?