I can't remember what it was but something with the design of the l98 heads that stops you from going over .50 on the valve lift?

what can i do to get some more lift out of these heads?

They are worth putting a bit of money into because they were mildly ported two owners ago, not sure the extent tho going to ind out this weekend when they come off.

 

.050" offset locks are a cheap way to do it.

otherwise, machine your guide boss down, with a comp/crane cutter that also lets you use the positive stem seals in the .530"OD size.

 

i had the spring seat milled down, but i had my heads 100% fully redone.

I managed to sqeeze .600 lift out of these heads with my current setup.

 

klumb15 had this done to his aluminum vet l98 heads

"I had my spring pockets bored and deepened, and i had single groove valves installed, instead of the stock 3 groove ones, the single groove allows the spring to install higher, making more spring travel"

I assume thats more or less the same thing? just enlarge the spring pocket.

What is the main factor that limits lift with these heads? is it just as simple as having the pockets enlarged?

 

well, basically its the width of the spring "bore", larger springs allow more lift and higher spring rates. larger installed hight allows more lift as well. Bunch of different factors.

 

The problem is the clearance between the bottom-most surface of the retainer and the top of the guide boss with the factory setup (heads, valves, retainers, etc). At about .480" is when clearance issues become worrysome. About .050" of added clearance is desired when calculating lift.

There are parts you can buy, as mentioned, offset keepers and retainers. that move the increase the installed height of the spring. Milling the guide boss is another option. Longer valves is yet another option. Just be sure to get springs that tolerate the increase in installed height.