400 hp heads or 383 hp heads?

[71butterbee]

Im restoring a 73 Ralley Charger and Im wondering on which way to go..... I have the original 400 HP heads but I also have a set of 906 heads off a 68 motor. Is there a big difference between the two heads?

[Nacho-RT74]

I think mainly the hardened seat valves and open chambers on 73 ( 452 heads ). 908 heads gives more compression because closed chambers

[firefighter3931]

Both heads will be open chamber so there is no compression advantage to be gained by swapping. The later 73 heads will have hardened exhaust seats for unleaded fuel which is an advantage. In stock form....the flow is near identical in all BB iron wedge heads.

I would use the later (400) heads which are most likely 346 castings. A good 3 angle valvejob and some new springs/seals 



Ron

[Nacho-RT74]

Both heads will be open chamber so there is no compression advantage to be gained by swapping. The later 73 heads will have hardened exhaust seats for unleaded fuel which is an advantage. In stock form....the flow is near identical in all BB iron wedge heads.

I would use the later (400) heads which are most likely 346 castings. A good 3 angle valvejob and some new springs/seals 



Ron

OOOPs, my bad... I must confuse the 906 Heads with earliers... sorry

[71butterbee]

Both heads will be open chamber so there is no compression advantage to be gained by swapping. The later 73 heads will have hardened exhaust seats for unleaded fuel which is an advantage. In stock form....the flow is near identical in all BB iron wedge heads.

I would use the later (400) heads which are most likely 346 castings. A good 3 angle valvejob and some new springs/seals 



Ron

Thanks!

[hemihead]

The difference was not in the head castings for emissions, it was in the compression and the cams.

[AKcharger]

Older closed chambers had smaller vales too...