T&P machine shop in San Antonio,Texas ask for Barney Moravits he being racing the SD in nhra stock elem for 30 year.(210) 224-0886 :yes:

My 73 SD has round exhaust ports with the manifolds held on by 3 bolts. The ports ar so big they have steel sleeves cast in for the pushrods to go thru. The sides of the tubes are exposed in the exhaust ports. My 70 SJ Grand Prix had a 455HO but it did not have the round port heads.

I just sold a set of dated correct 71 HO heads from Kevins (Jagarang) Firebird motor. I still have the manifolds and they are round port.

I think they switched to 0 port in 71 on the 455HO.

It is clear that Pontiac did not want the 455 HO upstaging the Ram Air IV. Seems the 4 had all the goodies. Imagine the 455 HO with the 2 piece aluminum intake and the round port heads/with RA exaust manifolds. No substitute for cubic inches, unless, of course, you twin turbocharge it.

Anybody here have any idea on the true HP numbers on a 455 HO or a RAIV, not what was posted by GM to get Muncie or turbo-hydro to guarantee the transmissions behind the motors?

round port
 

68 RAII - round port
69 RAIV -round port
70 RAIV -round port
70 455 ho- d port
71,72 455ho round port
73,74 super duty - round port
71-74 had big combustion chambers
68,9,70 RA had 72cc chambers
thats all i know :willy:

Thats a big help!

Thanks :yes: