UPDATE: A limited supply of the original best-selling Lextreme 1UZFE EGR Delete Kit remains. If you own a 1UZ from 1990-1997, you really need to get this kit! Email me at [email protected] for help with ordering or questions. This will probably be the last kits I have made.

All other parts are SOLD OUT and won't return, including the LS400 and SC400 turbo kit, rebuild kits, supercharger and performace torque converter. We're not an auto parts supplier and I can't respond to inquries for random Lexus and Toyota auto parts.

LEXTREME LEXUS FORUMS HERE! - Post Questions For Quick Answers!

1UZFE Main Studs Vs. 3UZFE Main Bolts and Engine Studs

When I was doing GS430 Block Vs. LS400 Block (3UZ vs. 1UZ) I totally over looked the differences between the two engines.  My initial thought was they are all the same.

However, assume they are the same between the two engines is an understatement.  In fact the two blocks have major differences.

In this article I will focus on the 6 bolt main.  Although the thread and pitch are the same, but that is as far as it goes.  The 1UZ has 4 main studs and two side bolts in each main cap.  There are a total of 5 main caps.  The 3UZFE on the other hand have all main bolts.  The main bolts are the same size in the 3UZ.  However, in 1UZ, the length is different between the outer and the inner studs.  Lets look at some examples:

The first picture is the overview of the two main fasteners.  On the left are the 1UZ and on the right are the 3UZ.  You notice the different in stud length on the left.  On the right, the bolts are the same length.  The only thing both engines share one common bolt is the side bolt.

Here is a close up of the 1UZFE studs.  They are both 10mm with 1.25 pitch.  The inner stud is about .455″ longer then the outer stud.

Here are some pictures of the 3UZ Main bolts.  The main bolts are all the same length.  The exact length 3UZ bolts are 3.593″

Here is an interesting picture.  On the left is the standard 1UZ head studs, in the center is an ARP Main Stud and on the right is the 3UZ main bolt.  You can see the size difference between the two fasteners.  I would prefer the middle fastener if you a strong bottom.

Here is a closer look at those fasteners.  The diameter of both standard 1UZ and 3UZ fasteners is .293″ and the ARP Main Stud is .393″.  The ARP Main Stud shaft is about  34.1% larger

Here is something very interesting and you might not find this on the net about our engine block.  If you look at the picture below you will noticed the two holes for the studs have different depth.  The inner hole is about .145″ deeper then the out hole.

Here is a picture of the 4 bolt main from a GS430

Here is a picture of the oem side bolt and the stainless steel ARP bolt

Here is a picture of the oem side bolt.

Here is a picture of the ARP Side bolt

The picture below is a comparison between stock and upgraded side bolt.

The pictures below are a close up of the arp main studs.

Shaft Diameter .293″ .293″
Bolt/Stud Length (Outer) 3.652″ 3.593″
Bolt/Stud Length (Inner) 4.078″ 3.593″
Thread Length (Outer) .927″ 1.295″
Thread Length (Inner) 1.382″ 1.295″
Thread and Pitch 10mm @ 1.50 10mm @ 1.50
Engine Hole – Sink (Outer) .167″ .167″
Engine Hole – Sink (Inner) .312″ .312″

What does all these mean?  Stock Vs. Stock, the 1UZ has better fasteners.  Its is know by high performance arena that studs are stronger then bolts.  Therefore, its wise to upgrade your main bolts to main studs.  I have cross referenced some ARP Main Studs for the Lexus V8.  The ARP Main Studs are far superior than the standard 1UZFE main studs.  Please contact me for more information.

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

Do you have any questions? If so, please head over to the forums to get a quick answer or share your experience!

Cash App (user: $lextremeparts).
This is a freelance site with no support by huge companies.  I have been doing most of the R&D and technical write-ups by myself with my personal money and literally thousands of hours of my time.  I have taken extra steps to demonstrate in details how things are done.  Currently I am one of the few people doing Lexus V8 research and performance enhancement.  This effort comes from my personal love for this wonderful engine.  Most of the modifications are from trial and error. There's no cookbook for 1UZFE mods and its unknown territory for much of supercharger performance.  The parts, labor, web development and site hosting are 100% paid from my personal hobby money.  If you feel my efforts help you in any form, please do not hesitate to donate any amount of money to support this site. You have no idea how much I and the entire Lexus and Toyota community appreciate it!

3 thoughts on “1UZFE Main Studs Vs. 3UZFE Main Bolts and Engine Studs”

  1. im trying to get some ARP main studs for my 1uz build. i bought some from equipped engineering and they never turned up. equipped wont answer any e mails and wont pick up the phone either.
    so i have to spend the money again and buy some more.
    are you still able to get them?
    i dont need the side bolts, just the main cap studs.
    let me know what options are available

  2. Hi,

    I just wanted to say that swapping the rod and piston from 1UZFE to 3UZFE may cause a balancing problem due to the fact that the counterweights on the crankshaft are matched to the weight of the piston & rod.

    The 1UZFE LS400 from 1989-1997 are internally balanced. Is the 3uzfe ls430 and later LS460 engines are also internally balanced? I have not looked this up. But if the later 4.3L and 4.6l engine has an external vibration/mass damper than they are not internally balanced. internally balanced engines require that all rod and piston combination to have virtually the same weight.


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