340 compression ?

[hoosierdaddy]

What was the biggest change that dropped the compression on the 72-73 340 engines ?

 

[mcodecuda]

They moved the wrist pin location on the piston. If you replace the pistons with the 68 - 71 pistons you can regain the compression that was lost.

 

[oldkimmer]

..............Actually the 72-73 340 pistons r totally a different piston than the 68-71........the compression height is .100 thou shorter which is a 2 point loss.........kim............

 

[D-mailman]

OldKimmer...you are correct sir ! They infact did lower the piston .100 in the bore. Piston change is all. If you have an early and late piston opn hand, slip a wrist pin into both at same time and you will see.

Terry

 

[fourspeed]

Early pistons actually stuck above the deck by .010

 

[388dart]

actually .018 if all was correctly machined.

 

[mikedevore]

I think the 1972 & 73 pistons also had 4-valve releifs in them & the pin height was different. The low compression pistons could be used for left or right installation. The 1968,69,70, &71's had the piston offset, you had left bank pistons & right pistons & only two valve reliefs.