Slightly bent rod?
06-16-2023, 09:59 PM
#11
Registered
Starting with fresh pistons and rods is cheaper than scrapping the engine when a rod breaks trying to save $$$ when reality says you have to bite the bullet (or pay big $$$ later).
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06-17-2023, 11:08 AM
#12
502Nova,
I just did a quick and dirty sketch on AutoCad, to represent what a bend that yielded a .020" reduction in C-C length of a 6.385" rod would look like. It requires a 1/4" deflection at the midpoint of the rod beam, assuming a single point bend and straight chords between rod ends and the bend. You should be able to see that from space, so to speak. I'm no engine guru, but my math tells me you can rule out a bent rod.
Thanks. Brad.
I just did a quick and dirty sketch on AutoCad, to represent what a bend that yielded a .020" reduction in C-C length of a 6.385" rod would look like. It requires a 1/4" deflection at the midpoint of the rod beam, assuming a single point bend and straight chords between rod ends and the bend. You should be able to see that from space, so to speak. I'm no engine guru, but my math tells me you can rule out a bent rod.
Thanks. Brad.
06-17-2023, 11:16 AM
#13
VIP Member
VIP Member
That would be my guess. But that’s all it would be. I’m no engine builder.
If I were spending your money, I’d go with new rods and pistons. Molnar and JE, respectively. Really can’t go wrong there.
Thanks. Brad.
06-23-2023, 09:20 PM
#14
Platinum Member
Platinum Member
All MkIV 502's came with forged pistons. Period.
I want to say that ALL 502's with Mercruiser badges on them came with forged pistons but there may be some weird combination out there that would prove me wrong.
MkIV 502
Early ones had the Bowtie standard deck block, later MkIVs had a 502 siamesed block that was not technically a Bowtie block.
All 502s up thru 500EFI has rectangle port GM iron heads, steel crank, steel 7/16 dimple rods, and forged pistons. Early ones had low tension oil rings.
I want to say that ALL 502's with Mercruiser badges on them came with forged pistons but there may be some weird combination out there that would prove me wrong.
MkIV 502
Early ones had the Bowtie standard deck block, later MkIVs had a 502 siamesed block that was not technically a Bowtie block.
All 502s up thru 500EFI has rectangle port GM iron heads, steel crank, steel 7/16 dimple rods, and forged pistons. Early ones had low tension oil rings.
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articfriends (06-24-2023)
07-14-2023, 01:29 PM
#15
Registered
Last time I had to deal with pressed pins, I used a good piece of oak and machined a matching profile to the piston. They were stuck hard I was using a 12 ton arbor with a pipe extension and I put all of my 200lbs on it to get them apart and I didn't damage a single piston.
