|Originally posted by Joseph Upson:|
Do not lower compression if it's only 9:1 compression and you intend to run no more than 15 psi, it would be counter productive. Remember these motors are designed to run 87 octane so premium fuel and programming should be sufficient to accommodate a good level of boost. As for using the 3" stroke 2.8L crank in place of the 3.31" stroke 3.4L crank, don't do it, unless you're planning on custom pistons, otherwise you'll ruin the quinch area (distance between the outer top perimeter of the piston and the cylinder head) which can cause spark knock. The piston should be no more than about .040" from the cylinder head especially on the old iron heads which are not as efficient as the aluminum heads. The rods are the same between the engines at 5.7" as well as the journal diameter.
I'd not be so quick to say don't do it,, yes the way the o/p asked, would not be a good idea...
but a 3" stroke with a longer rod in a 3.4 might be just the ticket.. finding a rod to work tho, hard isn't as hard as it used to be...
all of them use 5.7" rods (2.8/3.1/3.4) same length as the chevy v8 , the v6 •Rod journals are 1.998 to 1.999" The v8 are 2.00" small journal or the 2.1" for much of everything after '67 ish
The 3.4 bore is 3.62" the 262v8 was 3.671 and the 265 was 3.75
making the 262v8 piston an opinion maybe. 3.4 60 over is 3.68 30 over is 3.65 40 over is 3.66" and 50 over hits the magic 3.67" almost the same size as the 262v8 of 3.671 so a 3.4 50 over and a hone to get it from 3.67 to 3.671 .. now nascar chevy v8 rods use a rod journal size of 1.89" and the 60*v6 it's 1.998/1.999" offset grind the v6 crank to get the 1.89 make up the stroke difference of the 2.8 crank of 2.99" to the 3.4's 3.31( a .32" difference) and you are mighty close, as the v6 deck height is 8.819" and the v8 9.02 for a difference of .201" straight grinding the crank rod journals gives you .109 add that with the deck height differences and you get .31 out of a needed .32" offset grind the crank a tiny tiny amount, and BOOM.. you are there..
a short stroke, 50 over 3.4ltr using cheap parts, as used nascar rods are cheap and will be overkill in this.. If a 3.4 block will go to 3.75" it opens huge piston options, as far as cheap.. 262 pistons are cheap also, but forged ones might be a one off..
oh you could have tons of fun building oddball stuff.. offset grind the v6 crank, nascar 6.25 rods, and pistons with the correct pin height.. the 3.4 piston height is 4mm less than the 2.8
[This message has been edited by E.Furgal (edited 02-24-2015).]