1UZFE Vs. 3UZFE Piston

This is another interesting article that I am writing.  If you haven't read the 3UZFE Rod vs. 1UZFE Rod than this article might not make too much sense.  However, I will try to compare the two pistons here.  On the left we have a GS430 with 3UZFE piston and on the right we have 1990 LS400 1UZFE piston.  From the measurements, the 3uz is little thicker from the center of the pin to the top of the piston.  However, the 1UZ is taller in over-all height from end to end.

The picture below demonstrate the side profile of the two different pistons.  The 3UZFE seems to have a special thermo coating.  I am not sure what type of coating it is, but pretty impressive.

Here is another picture of the two pistons side by side.  You can clearly see the ring lands on both pistons.  The 1UZ have thicker ring lands then the new model piston.  Do you see anything wrong with the 3UZ piston from the picture below?

Here is an impressive view of the 3UZ piston.  Its a very complex design and I am sure John Brady can explain all the tech details about the pistons.

The above and below pictures are incredibly different.  From my limited experience with engine materials, I think the 3UZ piston was forged and the 1UZ was casted.  I am not 100% sure, but I should take the pistons to a local engine builder and let him validate them.

The oil system in both pistons are very interesting.  The 3UZ piston has 4 little openings from the oil rings for oil flow from the outside of the piston to the inside.  Please see the picture below for more graphical descriptions.  The 1UZ has 4 huge openings slightly below the oil ring and enter near the piston pin.

The 1UZ have something that the 3UZ don't have.  A special ported opening feed oil to the pin for cooling and lubrication.  Very interesting design.  However, the later model deleted that configuration.

Here are the huge two openings right below the ring land and near the piston pin.  1UZ piston design seems to have better oil flow.  The openings are large and allow massive oil to flow in or out of the pistons.  These large openings also have less chance of being clotted if the oil is dirty.  However, the 3UZ oil system is more sensitive to dirty oil.  Clotting is much greater in the new model pistons.

Here are few more pictures of the 1UZ oil system. Below is a picture taken from the inside of the piston.

Another look at a close up picture of the 3UZ piston oil system.

If you didn't catch it earlier, now you can see the weakness of 3UZ piston.  I was told by an experience engine builder about Lexus piston ring land weakness.  He stated that is the biggest problem with Lexus pistons.

Now which piston was well made and designed?  I don't know.  It seems like FI the 1UZFE would be better, but NA form the 3UZFE have bigger bore.  Personally I would prefer 1UZ for FI application.  From what we found the rods for the 3UZ are also weaker then the 1UZ.  I guess the GS430 owners can get the 1UZ rods as an upgrade for FI application.  For oil circulatory system, the 1UZ has higher flow and increase piston cooling and lubrication.  Secondly the design of the 1UZ piston has more meat on top of the piston and more material around the shirt of the piston too.  I guess you can ask your questions in here. 

Here are the specs of the two pistons:

1UZFE vs. 3UZFE Piston 1UZFE 3UZFE
Piston Diameter (Bore) 3.426" 3.560"
Pin to Deck (edge of the pin hole to the top of the piston .917" .960"
Ring Land (1) Top of the piston to the first ring land .315" .388"
Ring Land (2) Top of the piston to the second ring land .512" .388"
Ring Land (3) Top of the piston to the third ring land .688" .533"
Pin Diameter .867" .867"

Here are some pictures of 3UZ piston with 1UZ rod.  Its a great combination for the 3UZ owners.  Its a perfect fit.  You can use the stock 3UZFE pins.  Its a direct fit.  The 1UZ rod is much beefier and able to handle more hp then the 3UZ.  The 1UZ rods are dirt cheap.  You can get less then $50 usd for the whole set.  Much better then custom rods.  You will save thousands on the rods.

Other articles of interest:
Lexus 3UZFE rod vs. Lexus 1UZFE rod
GS430 Block Vs. LS400 Block (3UZ vs. 1UZ)
1UZ Vs. 3UZ Main Fasteners

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