8v valve clearance shims

[DamirGTI 364]

Any ideas for what purpose is the chamfered top side of the OE shims ? 

 

Something to do with the lifters ? 

 

I ran out of OE shims in the smaller increments , so i bought the lot of aftermarket ones , and neither one of those  have chamfered side .

At least i cannot feal it with my fingers . 

 

Now , during the years working with these engines i've seen people fitting OE shims wrong way round but i found no issues/wear on the lifters or the cam lobes by doing so .. lifter bores in the head , maybe , but i never measured wear on those areas .

 

Also I've quite a few OE shims which also seem/feel the same top and bottom , with no chamfer edge on either side .

 

Thus i'm not sure if it's even worth a bother dressing up these aftermarket shims , making chamfer edge on the top side ?! 

[petert 641]

News to me as well!

[welshpug 1,737]

none of the shims I have are chamfered, all oem from old engines. 

[DamirGTI 364]

Hmm, I have some which are chamfered and some which aren't .

I think the ones with the chamfer were in the early pre-'92 engines .

From what I remember, I found the non-chamfered ones mostly in later engines, so around '92 onwards .

I'd guess the chamfered edge of the shim on top might do something to cushion the sideways rocking action of the cam lobe against the lifter , or something similar.

Anyhow, I'll add that to the list of "surplus to requirements" !

[SRDT 254]

I couldn't find why some of them are rounded and others aren't but I did find what can happen if you put them the wrong way : cam noise around 2000-2500 rpm

 

[DamirGTI 364]

Interesting !

 

But If that's all , I guess you can live with a bit of engine noise now and then .

XU 8v engines aren't the quietest anyway .

 

Main thing the clearances are adjusted properly , i've had some with destroyed cam lobes and lifters , cause of way too tight valve clearances .

[DamirGTI 364]

They did some changes on the later cams as well .

 

Not sure if it's sometnihg to do with this , or simply production cost savings . 

 

The back side opposite the cam lobe nose has less surface area on later cam compared to early . 

 

'97 RGX cam on the left , '92 RGY on the right :