So I popped a pair of big block #516 heads for sale on another forum and checking my email this morning, I found I had half dozen guys have reached out to buy them. I know the close chamber helped bring up compression, but is there anything else about these heads that makes them desirable?

The closed chamber is the big selling point , especially since they can be had cheaper than 915's. they need the exh valve upgraded to at least 1.74 and porting to come alive .

thanks John. Yeah that tiny ex valve looks restrictive.

There is nothing desirable about them other than the cheap price.
If you can sell them great. I've thrown away a lot of those heads in the past since there wasn't a market for them. I used to take them to swap meets and try to sell them for $100 a pair with no takers. Lowered my price to $50 a pair and still not takers so they all went in to the recycle place.

I went 10.40’s with them back in the late 1970’s with a set in my 69 dart. I wouldn’t scrap them.

if you want good improvements from swapping heads step up to a cheap set of aftermarket aluminum heads with the bigger, better flowing valves and ports

Some guys on a budget want them.
Some regions of the U.S. are pretty lean on old cast iron cylinder head cores.
I ran a set on my 69 RR, added the 1.74 exh valve, bowl ported them with the MP templates, gained 2-3 mph through the traps.
It ran low 13's @ 105 mph. Just a warmish 383 B-motor, 833, 284/484, TM6, 750 AFB, 4.30:1, 10" slicks, 1.99 60'.

If you're on a budget, they're great in my opinion. Big exhaust valve, a little porting, and they will run decent numbers. Not aluminum head numbers, but not aluminum head $$$$ either.

For me to consider them, there would be two key questions to answer first:
1. What do I have to spend to make them usable in the first place (e.g., valves, seat & guide work, milling)?
2. If I want more than as-cast performance, how much do I have to pay to have someone do enough porting to reach my goals (assuming I can't do it myself)?

I wouldn't want to put much money into 60 year-old castings in this day and age...

I look at it as……. How much less than a set of aluminum heads would the “all in” price for any old iron heads have to be for you to go down that path?
And……. Can that be realistically done(price wise) in your area?

Machine shop labor prices keep going up……… but so have new aluminum heads.

By the time you put hard seats in, new 1.74 valves, port them, guides and a valve job you could just as well buy a new set of aluminum heads. Having said that years ago I did a set for myself, plus I shaved them .060. I ran 12.19@106 in my old truck with them. I put a lot of work into them but they guy worked real cheap (me).

Yeah, 50 years ago they weren't a bad choice

My days of sitting in a cold garage learning to port on a set of OEM iron heads are decades behind me

My expected combo (65 426 wedge) is the 516, 452 or Eddy head with 1.60 ex valve. Cam is limited to .431 lift and any duration no porting but any valve job. I’m thinking of running 40 degree or less seats (more flow in overlap with the low lift). What about nail head vs tulip valve shape? I have a few extra 516 heads to experiment on but still looking for the 67 small valve heads.

30deg, & a nailhead valve, works great on a low lift setup

Ahhhhh one of many “boneyard performance” upgrades of our youth. Grabbing a set of those was akin to crawling under a van or truck and scoring some 3.9 or 4.1 gears.

Some of these guys don’t understand the fun we had making this stuff go fast. Lol

My scores were 915 casting.big or small exhaust valve

Thanks