big block head question

[383RRwill]

first let me say this is a great site. the best mopar site i've found yet.
ok, here's my question, i bought a 68 roadrunner with a 383 last summer, i've always wanted one. it has a '67 383 in it that is running better now (considering the guy that had the car rigged it up 6 ways to sunday). i know 906 heads were on 68 383's, which i have a set of that needs rebuilding, and i also have a set of 452 heads. anyways, the last three digits of the heads currently on my 383 is 516, if i remember correcly.
i know of the 906 and 452, good performance heads, but i dont know anything about these 516 heads. would they be of any use in a high performance engine, or should i build my 452's?
this is going to be a build up for the street, but it's not my main mode of transportation so i want to use heads that can make the most power.
this is my first post of many as i am going to start building my baby up soon. man! this is a great site! i could read these posts for hours.
thanks a lot

[MopART]

Welcome...

The 906 and 452's are so close in performance in stock form that one would serve as well as the other. The 906 and 452 are open chamber heads. However, the 516(I believe '67 - '68 440 equipped) is a closed chamber head and do not flow as well in stock form as the 906 or 452. You would benefit from the compression of the 516, but not have the flow of the 906 or 452.

On the flip side of the coin, high flow is not always the best nor are big valves. Depending on your combination, ie cam, intake, carb - you may benefit from the compression and velocity of the 516. By the way the 915 closed chamber is, to me, as good as the 906...only a bit difference in performance with the 906 having the advantage.

If you want the performance, best for stock, use the 452 or 906 and weigh your cost vs performance to use whichever pair you decide. Additionally, the 452's will more than likely have hardened seats and the 906 not.

ART

[silverstreak383]

If your 383 was rebuilt with over the counter pistons that sit way down in the cylinder, you will give away a lot of compression and lose performance by switching from those 516's even though they have small valves and ports compared to the 906 and 452. That may be why they are on there. I had to mill my 906 heads and use steel shim gaskets to get cylnder pressure up to 130 on my 383, I still could use more.