[IhaveNoPantsOn]

I’d be shocked if I got anywhere near 80 more horses just by converting to EFI. Even half of that would be worth it. I’m also thinking of getting the head ported and polished at the same time, depending how much it’s gonna cost me.

 

[Mad Max]

I don't remember how big the valves are for your 6 hole-er, you might be able to go larger.
Some of the projects I worked on had "drop in" larger valves available. Open the valve seat and install bigger valves. Easy.

Did you change the valve springs when you added the cam?
I have an 85 TVR 280i (look it up) that has a Ford 2.8 V6 in it. I got a set of replacement heads that had the most skrewed up valve springs I have ever seen.
There were 4 different spring heights! I bought a set of performance springs... HUGE difference.

 

[IhaveNoPantsOn]

I’ll ask the machine shop about the valves. It’s a place that has a good reputation for building engines for decades, so I think they’ll be able to guide me in the right direction.
Stock valve springs, still. If I had gone with any bigger of a cam, I would have needed to change them. So it might be needed after the head work. I’m sure they’ll know.

 

[Mad Max]

They can check the spring pressures.
As springs age, they tend to sack out.
Springs can also act like a "rev limiter"... If they are tired, the valves will float at higher RPMs, limiting the engine RPM at high revs.

I have a tired Olds 350 engine that has this happening. It revs really quick, but stops right about 6k RPM.
I know you don't want to wind this engine past 5K, so this may not be an issue.

 

[Mostizzle]

That could be an Olds thing. Both my Cutlasses big block and small block both had penchants for floating valves near redline. Both were semi fresh builds using GM parts. My buddies Skylark of the same vintage didn't do it.