I have a v8 engine that came in already disassembled (mopar)
the wrist pins are offset about .080" in the piston from center
4 rods were hung one way, 4 rods hung the other.
I do not know which way this offset should be oriented in the V during assembly.
is this offset/orientation relationship the same for all V style engines?
offset wrist pins
Moderator: Team
Re: offset wrist pins
As installed by the OEMs the pin offset is toward the major thrust side.
Monty Frerichs
B&M Machine
B&M Machine
Re: offset wrist pins
As per SupStk, In a petrol engine the offset goes to the thrust side of the bore. [opposite to the cranks rotation, in a ccw the right is the thrust face.]
If there are unequal piston reliefs, that will dictate orientation, but it is highly unlikely this would be contradictory.
Cheers.
If there are unequal piston reliefs, that will dictate orientation, but it is highly unlikely this would be contradictory.
Cheers.
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Re: offset wrist pins
thanks fellows.
also, per an article in engine professional - Mike Mavrigian
The pin offset is biased toward the major thrust side of the piston. In a clockwise-rotating engine, the major thrust side is at the intake side on the left (driver) bank and the exhaust side on the right (passenger) bank. In a reverse-rotation engine, the thrust sides are opposite: the major thrust side will now be at the exhaust side of the left bank and the intake side of the right bank.
also, per an article in engine professional - Mike Mavrigian
The pin offset is biased toward the major thrust side of the piston. In a clockwise-rotating engine, the major thrust side is at the intake side on the left (driver) bank and the exhaust side on the right (passenger) bank. In a reverse-rotation engine, the thrust sides are opposite: the major thrust side will now be at the exhaust side of the left bank and the intake side of the right bank.
Re: offset wrist pins
The same as SBF engines?!
Old trick was to swap pistons from side-to-side to improve angle of piston-to-crank pin.
Pick up a few HP with the cost of a little more noise on cold crank up. (no big deal when running headers!)
6sally6
Old trick was to swap pistons from side-to-side to improve angle of piston-to-crank pin.
Pick up a few HP with the cost of a little more noise on cold crank up. (no big deal when running headers!)
6sally6
Re: offset wrist pins
Not the best example; the vast majority of car engines rotate CW as seen from the non-flywheel end, making the left side of the bores the thrust side.
Felix, qui potuit rerum cognscere causas.
Happy is he who can discover the cause of things.
Happy is he who can discover the cause of things.
Re: offset wrist pins
to lessen any confusion re major thrust face etc, OE-type piston makers usually permanently mark each piston crown's edge with a dimple, F, notch, arrow etc to denote that side of piston should face FRONT of motor ... installed accordingly, pin offset will be to major thrust side & correct per OE. afaik OE purpose is to lessen slap.
reversing offset was also a smokey yunick thing (in restricted motors which required OE-type pistons) ... more piston dwell thus restricted cam behaves as though it has a tiny bit more duration.
reversing offset was also a smokey yunick thing (in restricted motors which required OE-type pistons) ... more piston dwell thus restricted cam behaves as though it has a tiny bit more duration.
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Re: offset wrist pins
Reversing offset was also a fairly standard practice in the MOPAR Performance/Direct Connection tech papers for all engine families.
A little power at the expense of noise.
I'd be prepared for the possibility of some risk of un-intended consequences with an early days unsophisticated knock sensor.
A little power at the expense of noise.
I'd be prepared for the possibility of some risk of un-intended consequences with an early days unsophisticated knock sensor.