Frank Acampora
Supreme Mariner
- Joined
- Jan 19, 2007
- Messages
- 12,004
I have been asked a couple of times if new pistons will fit in older Chrysler engines. The answer is YES--but with conditions.
Look at the first photo. It shows a newer type piston flanked on either side by an older style with needle bearings in the piston itself. The wrist pin on these old style pistons is pressed into the small end of the rod and rotates in the bearings.
Now, note that all three pistons are the same height AND the wrist pin is in the same location. The reason Chrysler and Force rods are so short, is because there needed to be room for three rings and the bearing in the piston. When Chrysler changed to the newer style with two rings and no needle bearings, to save costs, the rods, pistons, and wrist pins were kept the same. Blocks had only minor changes through the years but the bore and stroke was kept the same for each engine.
SO: Later model aftermarket pistons (Wiseco, for example) will fit in the early block no matter that the representatives say that they won't. HOWEVER: The rods must be changed.
Now look at the second photo showing the difference between the old rods and the new ones. Note that the old rods have the wrist pin pressed into the small end and they locate the wrist pin in the piston. Note that the newer rod has a much larger small end to accomodate 26 loose needles.
While Chrysler changed the small end, the length and big end of the rods was kept the same. Additionally, the same rods were used in every engine from 20 up to 150 horsepower with a couple of exceptions (Chrysler 2 carb 55, 60, and 65, and late Force 75 and 90.) So, if you wanted to use new aftermarket pistons in a 1960s Chrysler you could use rods from almost any later junker engine.
While the old rods can be made to fit, there will be no bearings in the new piston and the wrist pin will wear the holes egg shaped.
Look at the first photo. It shows a newer type piston flanked on either side by an older style with needle bearings in the piston itself. The wrist pin on these old style pistons is pressed into the small end of the rod and rotates in the bearings.
Now, note that all three pistons are the same height AND the wrist pin is in the same location. The reason Chrysler and Force rods are so short, is because there needed to be room for three rings and the bearing in the piston. When Chrysler changed to the newer style with two rings and no needle bearings, to save costs, the rods, pistons, and wrist pins were kept the same. Blocks had only minor changes through the years but the bore and stroke was kept the same for each engine.
SO: Later model aftermarket pistons (Wiseco, for example) will fit in the early block no matter that the representatives say that they won't. HOWEVER: The rods must be changed.
Now look at the second photo showing the difference between the old rods and the new ones. Note that the old rods have the wrist pin pressed into the small end and they locate the wrist pin in the piston. Note that the newer rod has a much larger small end to accomodate 26 loose needles.
While Chrysler changed the small end, the length and big end of the rods was kept the same. Additionally, the same rods were used in every engine from 20 up to 150 horsepower with a couple of exceptions (Chrysler 2 carb 55, 60, and 65, and late Force 75 and 90.) So, if you wanted to use new aftermarket pistons in a 1960s Chrysler you could use rods from almost any later junker engine.
While the old rods can be made to fit, there will be no bearings in the new piston and the wrist pin will wear the holes egg shaped.
