Flow gains outweigh the loss of compression when swapping from 516's to 906?

[GearAddict]

I am finally starting to dig deeper into the 383 that the PO dropped in my RR. Looks like a 66 block, with 516 heads.

I have a good dealon a set of re-done 906's and was thinking about pulling the trigger as the valves need work in the 516's.

My question is, will the flow of the 906's help me, when I'm looking at loosing compression from the open chamber design? or is it better to have the CR with the restricted flow of the 516's?

 

[1wild&crazyguy]

If you can fill the cylinder more with the 906 over the 516... you are doing better than not filling the cylinder as much and squeezing it harder.
Think of the effects of forced induction, the idea is similar in that the compression go's up with more airflow filling the same area.
Id get the 906 heads.

 

[Badvert65]

I did the math and (with a little fudging/estimating) came up with a loss of about 0.7 compression ratio when going from the 516 heads to the 906. While not necessarily exact, it will give you a good ball park figure. The 66 engines had anywhere from 9.4 to 10.5 compression, depending on engine purpose.
Personally, I would also suggest swapping to the 906 heads.

 

[Meep-Meep]

Just looking at the 906 head vs. the 516, the 906 is a better head, but I doubt you would have any earth shattering difference between the two. Assuming the 516 have been cut to 1.74 exhaust. 452's have the same flat intake port floor as the 516 and they can be made to work well. Also the old DC stage IV and V are flat floor heads. Much of what you are talking about is controlled by the cam anyway. If the 906's are indeed a good deal I'd get them.

 

[Charger686970]

Just looking at the 906 head vs. the 516, the 906 is a better head, but I doubt you would have any earth shattering difference between the two. Assuming the 516 have been cut to 1.74 exhaust. 452's have the same flat intake port floor as the 516 and they can be made to work well. Also the old DC stage IV and V are flat floor heads. Much of what you are talking about is controlled by the cam anyway. If the 906's are indeed a good deal I'd get them.

funny you mentioned the old direct connection stage IV heads, I have a set that came off my 68 charger when I got it and the other day I was just thinking of what those heads might be worth? I was thinking of possible selling them since I have been using indy or edelbrock alum. heads. Was thinking of doing a package deal with the heads and a N.O.S. str low deck intake with the single 4bbl thermoquad top, or do I keep the heads for a just in case, if I get something that need heads and I do not want to put alum. heads on. Do you know what those heads might be worth? they supposedly only had 1500 miles on them when I pulled the motor out and sold the short block to a friend and I threw the stage IV heads on a shelf and that was 19 years ago.

 

[Herr_Poopschitz]

Much of what you are talking about is controlled by the cam anyway.

This^

 

[Meep-Meep]

funny you mentioned the old direct connection stage IV heads, I have a set that came off my 68 charger when I got it and the other day I was just thinking of what those heads might be worth? I was thinking of possible selling them since I have been using indy or edelbrock alum. heads. Was thinking of doing a package deal with the heads and a N.O.S. str low deck intake with the single 4bbl thermoquad top, or do I keep the heads for a just in case, if I get something that need heads and I do not want to put alum. heads on. Do you know what those heads might be worth? they supposedly only had 1500 miles on them when I pulled the motor out and sold the short block to a friend and I threw the stage IV heads on a shelf and that was 19 years ago.

I have no idea on value, but I do know much of the old DC parts were just assembly line parts repackaged. The chrome valve covers that were new in the 80's were just late 70's valve covers that were chromed. I never liked the style of those so I never got a set. It would stand to reason that the stage IV heads were pretty much late model 440 heads since many features were the same as production line parts. Flat intake port floor for example. It's a fairly well known fact the 915 head was designed for better flow (over the 516 and Max wedge port design at the time) so one would think that DC should have sold a new version of the 915 head but with hard seats.

 

[Charger686970]

I have no idea on value, but I do know much of the old DC parts were just assembly line parts repackaged. The chrome valve covers that were new in the 80's were just late 70's valve covers that were chromed. I never liked the style of those so I never got a set. It would stand to reason that the stage IV heads were pretty much late model 440 heads since many features were the same as production line parts. Flat intake port floor for example. It's a fairly well known fact the 915 head was designed for better flow (over the 516 and Max wedge port design at the time) so one would think that DC should have sold a new version of the 915 head but with hard seats.

Thanks for the info. I guess I will just keep them around since they are pretty much late model 440 heads, never know when I might pick something up that needs a set of heads. Thanks again.