Drilled valve lifter?

[gordinir8]

One of my valve lifters found cracked, I found a NOS 1st oversize lifter today and I bought it. I noticed that all of my old lifters have two holes drilled helping the oil to return to the engine, I was told that this is a shop modification although it looks like factory. Do you think I should live the new one as is or I shall drill it also? Is it going to be a problem if I have one drilled and one w/o?
If the 1st oversize is 20.01mm what should me the clearance of the lifter housing?

http://img.photobucket.com/albums/v11/gordinir8/20160513_221205_zpsjf7llsgd.jpg

[gordinir8]

[gordinir8]

One of my valve lifters found cracked, I found a NOS 1st oversize lifter today and I bought it. I noticed that all of my old lifters have two holes drilled helping the oil to return to the engine, I was told that this is a shop modification although it looks like factory. Do you think I should live the new one as is or I shall drill it also? Is it going to be a problem if I have one drilled and one w/o?
If the 1st oversize is 20.01mm what should be the clearance of the lifter housing?

http://img.photobucket.com/albums/v11/gordinir8/20160513_221205_zpsjf7llsgd.jpg

[rolf]

Very simple:
with extra holes are for R24 to R25
no holes for 25/2-27

it depends on the chromed parts (at your photo on the right side) "stösselführungen"....the Stösselführungen for the 25/2 (and higher) has on the inside cut-offs (like threads)....there is the oil able to flow back
For the former models (R24-25)...they are plain in the inner diameter....the oil can only flow back through the extra holes in the valve lifters

So: if you have the plain Stösselführung....you need holes in the valve lifters
I hope you understand my pidgin english.

[gordinir8]

Ok got it, mine has cut-offs in the inside so yes oil can pass with no problem, so no drill in this one.
Thank you.