[screamingchief]

Well,that depends,are these heads getting ported?

If not than there is really no need to be overly concerned with lifts much beyond what has been discussed here already as the head really wont flow any better at higher lifts.

What sorta cam are you thinking about?

Like has been advised,the crower #68404-16 springs are the best for more or less stock IH heads (1.60" appx.).

And like I said the crower "recommended" retainers for those springs add some extra clearance while still sealing with the OE O-ring valve stem seals and shields,this is when the crower retainers are compared to the OE retainers,the other alternative is the OE retainers can be "ground" for some more clearance,and they too will still seal,but that is time consuming IMO and I prefer to just buy the crower retainers myself.

And if you machine for the viton seals often there is a little bit more room to be found if it's done correctly.

But if your after lifts much beyond say .550" lift or so,yeah your probably gonna be machining the spring seats or adding longer valves and corresponding longer pushrods to use the 1.70" installed height and the corresponding springs for that IH.

Does that help?