Having specialized in automotive oil seals for nearly 3 decades allow me to lead you down the path of undisputed truth......

The seals you have on there are just fine for your application and what I would recommend to you and would also use on my own engine if I were running triple springs.

I suspect an installation error on the seals. This design seal with the all metal body and sealing element at the top only has 2 areas of sealing off oil to the guide.

1) interference on the valve stem and 2) it also seals along the top edge of the valve guide.

Excess oil down the valve guide can be contributed to the following....

Lack of clearance between the retainer and valve seal at max lift [should be .060" - .080" minimum]

Valve guide is not long enough for the seals skirt length. This condition will not allow the valve seal to fully seat down on the guide. Sometimes they are not driven on enough and other times it may be a spring locator that is interfering with proper installation.

Seals could have been driven on crooked and are now loose on the guide allowing oil to migrate up the guide O.D. and under the seal. If the seals are loose they can actually act as a pump and shove oil down the guide every time the valve opens similar to not enough retainer to seal clearance.

Are you having this problem on all 8 cylinders? Is it the intake, exhaust or a combination of both?

You have some investigating to do but either way do not use Teflon seals like the link to Goodson. If you need seals they are listed in our catalog...... part #732FP (.341" x .530")