Looking for Info / Specs on Obsolete Mopar Piston
Thanks for all the responses, I need to read through your responses again to absorb all the info.
My car is a real 1970 Challenger TA 340 - 6 with 727 Torqueflite, Turbo Action torque converter, 2500 rpm stall, Mopar Performance Electronic Distributor with Orange Box. The car doesn't see any track time, just basically a nice cruise night car.
The original motor was gone when I bought it around 1992. The current motor is a 340 block cast in July 1970 with the "O" heads, 2.02 intakes. Has the original 6 Pack setup.
3500 miles on the build. Bored 0.030 over, still has the crosshatch pattern in the cylinders.
When I bought the car, the motor was fresh but the heads were off the motor, i.e., needed some final assembly. The cam in the motor was the purple cam P4120233, 0.508 lift.
I thought this cam was too radical for a Torqueflite equipped street cruiser, so based on recommendations from Mopar Performance, I installed the P4452761, 0.455 lift cam.
This was before I knew anything about the concept of "Dynamic Compression".
The "233" cam has 76 degrees overlap vs 50 degrees in my "761".
I'd like to switch to a retrofit roller from Howards (711915-12, 221/225 @ 0,050, 52 degrees overlap, lift = 0.475 I / 0.500 E), but the block has the chamferred lifter bores.
I know Hughes makes a retrofit roller that is supposed to work with the chamferred bores.
Still sounds like a roll of the dice if it works and you still might need to get the lifter bores bushed. ($700 ?)
If I went with the Howards roller, I'd probably just have the pistons machined to get the compression in the range of 9.5 to 10.0. Not sure what kind of power it would produce with the open chamber heads. There's no quench in the open chamber heads. The quench pocket in the heads runs about 0.080 / 0.090 inches depth. I've been looking for a forged "step-dish" design piston that would improve the quench with these heads, but haven't found anything suitable.
More homework to do.
Thanks for all the responses, I need to read through your responses again to absorb all the info.
My car is a real 1970 Challenger TA 340 - 6 with 727 Torqueflite, Turbo Action torque converter, 2500 rpm stall, Mopar Performance Electronic Distributor with Orange Box. The car doesn't see any track time, just basically a nice cruise night car.
The original motor was gone when I bought it around 1992. The current motor is a 340 block cast in July 1970 with the "O" heads, 2.02 intakes. Has the original 6 Pack setup.
3500 miles on the build. Bored 0.030 over, still has the crosshatch pattern in the cylinders.
When I bought the car, the motor was fresh but the heads were off the motor, i.e., needed some final assembly. The cam in the motor was the purple cam P4120233, 0.508 lift.
I thought this cam was too radical for a Torqueflite equipped street cruiser, so based on recommendations from Mopar Performance, I installed the P4452761, 0.455 lift cam.
This was before I knew anything about the concept of "Dynamic Compression".
The "233" cam has 76 degrees overlap vs 50 degrees in my "761".
I'd like to switch to a retrofit roller from Howards (711915-12, 221/225 @ 0,050, 52 degrees overlap, lift = 0.475 I / 0.500 E), but the block has the chamferred lifter bores.
I know Hughes makes a retrofit roller that is supposed to work with the chamferred bores.
Still sounds like a roll of the dice if it works and you still might need to get the lifter bores bushed. ($700 ?)
If I went with the Howards roller, I'd probably just have the pistons machined to get the compression in the range of 9.5 to 10.0. Not sure what kind of power it would produce with the open chamber heads. There's no quench in the open chamber heads. The quench pocket in the heads runs about 0.080 / 0.090 inches depth. I've been looking for a forged "step-dish" design piston that would improve the quench with these heads, but haven't found anything suitable.
More homework to do.
