New Piston to pin clearances

[Abbypathy]

Does anyone have experience with rebuilding a VG33E and buying a new piston, pin set with a different wrist pin to piston pin hole clearance? Nissan's specifications call for a clearance of between 0" to 0.0002" for piston pin to piston fit. I bought a set that has a clearance of 0.0008". So its quite a difference but that's new piston manufactures specs.

Nissan is almost calling for a press in pin.  All I can find are floating wrist pins. The piston pin to connecting rod bushing(small end) is within Nissan's specs. So will this new engine geometry be a issue? All the lubricating holes on both the old Nissan pistons match with the new ITM pistons. Except agian the wrist pin hole diameter in the piston.

[ThatOneNissanGuy]

Recommend Going To A Junkyard And Find  A Infiniti Q45 (that has working pistons and good compression) as it makes the vg33 a vg34 and bumps from 168hp (1997-1999) to 230hp (or 170 to 232hp on 99.5-2000)

[ThatOneNissanGuy]

VH45DE Pistons Should Fit 

[Slartibartfast]

I wish making a VG34 was that simple! There is a fair bit of machine work required to put Q45 pistons in a VG33.

 

0.0008" clearance from the wrist pin to the piston is definitely out of spec. A VG33 should not have clearance there at all.

 

The writeup I linked above claims the VG33 has full-float wrist pins, but the '97 and '01 R50 and '02 and '04 WD22 service manuals disagree. The spec is listed as 0-0.0002" interference. Looks like you have to get the piston hot to get the pin to drop in. The pin is constrained by two snap rings, so they're not counting on that interference to retain it, but clearly they're not intended to float.

 

The '95 WD21 VG30 specs 0.0003-0.0005 clearance between the pin and the piston, and the '96 Z32 VG30DETT specs -0.0002 to 0" interference, which is an odd way to say 0-0.0002" clearance. So wrist-pin-to-piston clearance is spec'd in some VGs, but not that much.

 

That said, I'm a service manual nerd, not an engine builder. Hopefully someone who knows more about engine internals can chime in. In the meantime I would reach out to the manufacturer and ask them why their spec is looser than Nissan's. Maybe it has to do with their manufacturing tolerances. Or maybe they were tired of people sending back busted pistons with stuck pins after trying to hammer them in cold.

[Abbypathy]

Its a very bewildering specs to grasp. Its not configured as a normal press in pin. And the oem clearances clearly are not fully floating and just barely would be considered a press in clearance.

I thought press in wrist pins are pressed into the connecting rod (small end)all the time. In my engine its showing 0.0002 and 0.0009 clearance on C.R. to pin clearance and 0.0000-0.0002 on piston to wrist pin. In other words, wrist pins are pressed into pistons as opposed to being pressed in the connecting rod.

 

I can only think of asking every possible engine builder I can find for advice

Edited April 5 by Abbypathy
Edited for clarity

[Abbypathy]

Hate to answer my own question. I think it appropriate here.  So in my research replacing the original semi pressed in piston wrist pins with a set of pistons with fully floating pins will be fine.  There is no engine perimeters in the VG33E that would forbid this.  Its a engineering and performance issue more than anything else. My understanding is pressed in pins do have an advantage and also some draw backs compared to floating pins. And vice versa.  Way to technical for me to discuss any farther.

 

Never the less after market pistons will be floating more often than not.  Probably due to ease of installation like you said Slartibartfast.

 

So I see at this point no need to worry about the new pistons being the floating type.  The retention clips seem to be solid, and that's important.

I may put in new small end bushing to close up the gap there.

[Slartibartfast]

Sounds reasonable. Good luck with your rebuild, and let us know how it goes!