Shim size for AM cams
12-16-2017, 12:53 AM
Post: #1
Shim size for AM cams
Hi all.

I've done a bit of reading around and getting conflicting results. Whats the cam size limit before having to go shim under bucket?

I've also seen that the 1NZ runs the SUB set up already but again there is a variation in sizings. How would you go about finding out the correct size properly for the shims?

and does anyone have a list on what you need to go SUB from shims to valves and seals?

TIA
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12-16-2017, 09:24 AM
Post: #2
Shim size for AM cams
First, 1NZ buckets are NOT shim under, but shimless -> you have to order the correct size for each valve.
The only thing you need to go standard to 1NZ buckets are ... the buckets. Nothing else change !
As to how do you find the proper size ? the same way than with any other setup-> you measure
But instead of measuring only the shims you have to take the buckets them-self into account. (A good micrometer is recommended at that stage)

As for the cam size, past 9mm of lift brands like Toda recommend to go shim under (or shimless)
But there are no rules set in stone. I have seen peoples run high lift cams with the standard shim over bucket.
As long as the profile (duration / ramps) is not crazy it might not cause any problems.
(Personally I would not risk it...)
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12-16-2017, 06:10 PM
Post: #3
Shim size for AM cams
Someone on the forum has a set of 8 NZ buckets (smallest ones) that you could use to measure the size you'd need. I bought them ages ago but can't remember who has them right now.

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AE86 ex-daily
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12-16-2017, 07:47 PM
Post: #4
Shim size for AM cams
(12-16-2017 09:24 AM)Project D Wrote:  First, 1NZ buckets are NOT shim under, but shimless -> you have to order the correct size for each valve.
The only thing you need to go standard to 1NZ buckets are ... the buckets. Nothing else change !
As to how do you find the proper size ? the same way than with any other setup-> you measure
But instead of measuring only the shims you have to take the buckets them-self into account. (A good micrometer is recommended at that stage)

As for the cam size, past 9mm of lift brands like Toda recommend to go shim under (or shimless)
But there are no rules set in stone. I have seen peoples run high lift cams with the standard shim over bucket.
As long as the profile (duration / ramps) is not crazy it might not cause any problems.
(Personally I would not risk it...)

This is perfect info and exactly what i was looking for. Thanks for this!
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12-18-2017, 05:34 PM
Post: #5
Shim size for AM cams
a LOT (your need for shim under) depends on the valve springs!

If you have enough spring to follow the cam, then shim over works just fine (albeit it is heavier).

The issue with shim over is, ***IF*** the spring doesn't follow the cam, but instead begins to "bounce" - THEN you have a problem! The shim being on top is the easiest piece to dislodge. If it becomes dislodged, then it can pop out causing catastrophic damage.

There is no lift limit, the problem/issue is more based on rpm levels (the spring can't respond quickly enough)

Dan -

You can |Sad .... OR you can ask for help!!!

OST Porting service - http://hachiroku.net/forums/showthread.php?t=19991
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