Shim over, or under bucket...or shimless?

[cribbj]

I'm pondering upgrading my 1UZ valvetrain, since we'll be putting in some Lextreme Stage 1 reground cams, and I understand this motor has a tendency to spit shims after cam/spring upgrades. After fixing the problems in the bottom end, I really don't want to start having cam/valve problems. So the way I see it, I have the following choices:

Stay with shim over bucket - not a good idea IMO.

Shim under bucket options:
2UZ buckets & shims
RB26 buckets & shims (a la Paul Carey)
Possibly 3UZ buckets & shims?

Shimless bucket options:
SZ motor (Prius & Yaris?)

Any others?

Appreciate any feedback from those running any of these combo's. I know Erol is running the shimless bucket setup with lash caps on the valves, but is planning to do something different soon.

BTW, did a shim bank ever get established in the USA? These puppies are expensive @ nearly $7.50 each..... Even if we do have a shim bank, it's probably for the shim over bucket setup, and I'm sure the shim under bucket setups are different <sigh>.

 

[Lextreme II]

John,

One way to solve your problem would have a set of custom cut valve stem length to eliminate the shims.

 

[cribbj]

Good idea David, but it's a little late for that. I'd prefer to keep the existing valves and their stem lengths "as is".

Anyone know if the 2UZ shim-under-bucket setup fits well on the 1UZ valves with 1UZ collets & retainers? I found some old threads on this, but there weren't any firm conclusions.

 

[Lextreme II]

Hi John,

If I remember correctly, the 1uzfe (pre 98) is 6mm and the post 98 is 5.5mm valve stem. What from I experienced, the later backet will fit into the early springs. However, you would need post 98 retainers. Post 98 has a special groove for the shim. I can take some pics for you if i can find some laying around. But again the post 98 retainers are smaller in diameter and you might have to bore it out to fit the 6mm stems.

 

[4000GT]

Isnt it the 1NZ and 2NZ shimless buckets that fit?

 

[cribbj]

Pass. Erol & I were having an email discussion about it last summer when he was looking to source some shimless buckets from the 1SZ/1NZ/2NZ motors.

I assumed they were all essentially the same, as he said he wound up sourcing locally, and using 1SZ buckets.

 

[200sx-v8]

I have measured the 3sgte under bucket design, and they are ca 1-2mm lower then the 1uzfe buckets. Have thought about making custom shims that is higher (4-5mm) but that might generate other problems.

 

[cribbj]

I'm having some email correspondence with a Nissan mate about using RB26 buckets, shims, retainers, collets, etc. and he's asking approximately how tall does the installed bucket & shim need to be for our motor.

I'm 5000 miles away from my motor at the moment, so can't measure one. Does anyone have this dimension handy?

Note, not looking for the overall height of the bucket & shim, but the dimension from the top of a valve stem to the base of one of the lobes on the camshaft.

 

[cribbj]

Here's a bit of trivia for anyone (else) who may have thoughts about using bike buckets.

Didn't know anyone in the GSXR community that could give me info on their buckets, so I picked up a few just for sh*ts & grins to see if we'd be lucky enough that they're the same as the 1UZ. Well they're not......

GSXR buckets are 25mm, while 1UZ's are 31mm.

But they are definitely a shim under setup, not shim over like ours.

BTW, our buckets have a pad thickness of 4.35mm, so with a shim of, say 3.00mm, you can have 7.35mm of lash adjustment.

Edit: The 4.35mm was measured with a digital caliper, but with an outside mike, I measured 4.5mm pad thickness. I think the mike measurement is more accurate.

Haven't measured the 2UZ or 3UZ buckets yet, nor the 3SGTE's.

 

[cribbj]

I've just received samples of a 2.5mm and 3.0mm lash cap, but I've measured their depth and they require 3.0mm of valve stem above the collets for a good fit.

Unfortunately, I only have 2.0mm of stem above the collets.

What's the collective opinion on grinding the lash caps down to 1.5 or 1.75mm so as not to interfere with the collets? Is this still sufficient overlap with the valve stem to keep it from rocking, and more importantly, to keep it in place?

 

[rms]

John,
Been a bit busy lately, so I will reply to your PM here.
The engine with the lash caps fitted should ????? be ready to dyno in a couple of weeks. We only have 1.5 mm recess to locate the lash cap on the valve stem. Is it enough ? I think it will be (fingers crossed) unless you run into valve bounce or valve spring harmonics.

Guess we will find out !

Erol

 

[cribbj]

Cheers Erol, I think you'll be on the dyno before me, so I'll wish you luck in advance, and hope all your lash caps stay lashed down......

If yours survives the dyno with only 1.5mm fit on the stems, I'm sure mine should too ;-). Did you source yours from Crow there in Oz, or ?

I have a sample from VAC Motor sports, and another sample coming from Supertech in Canada.

 

[rms]

Precision Shims

http://www.precisionshims.com.au/index.html

 

[cribbj]

Thanks; I thought he just did shims, but apparently he does lash caps and perhaps buckets too? Contacting him now.

 

[cribbj]

Apparently he does lash caps and a wide range of shims for mounting over and under buckets.

UPS just dropped off my package from Curt @ Elmhurst, and here are some photos:

1st photo is a standard 2UZ bucket for use with a shim underneath. I've got the mike set to show how thick the bucket pad is. This is a 31mm bucket that will fit right in our 1UZ motor.

2nd photo is a Prius shimless bucket, in the thickest pad available which is 5.74mm.

3rd photo shows the thickest 2UZ shim available which is 2.8mm. Not shown in this photo is its OD, which is 10.8mm.

4th photo shows the total thickness of the 2UZ bucket & shim together, which is 8.23mm, so if you run reduced base circle cams, this is the maximum clearance (with 0 lash) you can have between the stems and the cam, unless you go to Precision Shims.

Chris can probably make custom shims up to 3.2 or 3.5mm thick, which will accommodate nearly 9mm of stem/cam clearance (at 0 lash again).

The 2UZ bucket, and the Prius shimless bucket appear to be nearly identical, except that the contact pad on the underside of the shimless bucket is about 6.6mm diameter where the 2UZ bucket pad is about 7.3mm.

One interesting solution to get more lash adjustment could be to run the thickest shimless bucket @ 5.75mm pad thickness, plus the thickest shim available @ 2.8mm, which would then accommodate 8.55mm stem to cam clearance (with 0 lash). This could be easier & potentially more reliable than fitting lash caps.

Weight wise, the smaller shims are "about" the same weight as lash caps, so no advantage there.

 

[XR8tt]

Are the 1uz buckets ok with std base circle ??
As in billet cam, 9.5mm lift. Std base circle..

Whats the limit on spring tension ??
I was told 85 and 185Lb spring pressure at max lift..
With std 1UZ buckets..
If so ?? The option is to use cam that works with in these specs ??

 

[cribbj]

I would think std buckets & shims ought to be OK with new billet cams with a stock base circle, but IIRC someone had experienced bucket collapse at high spring pressures and/or high lift or RPM. Also, I don't know exactly at what lift the stock springs bind, but isn't it somewhere around that figure of 9.5mm? I take it you'll be using different springs, but it's something to watch for.

Nice thing about these shimless buckets is that they're steel vs the 1UZ's ally buckets, so no worries about bucket failure.

Weight wise, I just measured the combined weight of the steel shimless buckets and lash caps, and they're within a gram of the OEM ally buckets and steel shims, so no weight penalty!

 

[XR8tt]

The std springs are weak as p!ss.. From memory 40 / 80 ..
http://www.lextreme.com/Tundra-Valve-Springs.html
It seems these engines have VERY mild cam and spring specs..
From working on other turbo engines.. Cam doesn't need to be all that wild to make power.. Sure a crazzy wild cam will up top rpm...
They seem to go well with as much lift without stressing springs etc...
Seems 14 to 15 Lb boost is about as far you can boost without upgrading springs... Several 1UZ experts I have contacted in N.Z say the std buckets are o/k up to 180 Lb with billet cams up to 9.5mm lift..

 

[rms]

XR8tt,
I believe the bucket/shim failure is related to rpm. If you retain the stock intake plenum you will be limited to around 6500 rpm. In this case billet cams and 180lb springs are probably OK.

However, it is a different story once you get rid of the std inlet manifold. Even with stock cams and springs the engine will run to 7500/8000 rpm and then the aluminium bucket shows signs of collapsing under the shim. I have had this problem.

The questions I keep asking are 'why did Toyota set a rev limit of 6200 ?' and 'why did Toyota change to steel buckets and shim under ?'

Anyway, since going to the 3UZ type bucket and shim we have had no problems, apart from cam gear drive pins fretting. Now running 2 pins much deeper into cam and gear.

Max power at 8400rpm, max torque at 7800rpm, rev limiter 9200 rpm

 

[JustenGT8]

I am planning to run the VVTi UZ shim under bucket with kelford billet cams in an early UZ. There have been so many different combos compared on this forum i have to confess i'm not sure what issues this combo is going to have?
Non VVTi collets not having a suitable recess for the shim? anything else?