1970 455 "HO" Engine question
 

Did the higher compression 455 from the 1970 GTO, w/ the 64 heads, come with log exhaust manifolds or the HO / Ram Air 3 400 versions?

I believe the standard log versions but wished to make sure.

Log manifolds.

2x on the logs .
I have an original car that still had the lock tabs on the exhaust manifold bolts.

If they had only used a 87 cc ra4 head,, aluminum intake,ra exhaust manifolds and ra 4 cam on that 70 455. Wouldn’t of been much to touch it.

I suspect the fact that they couldn't sell the 455 in the F bodies was a reason they didn't make a true high-performance version of the 1970 455. Also, the long stroke of the 455 on the stock bottom end of the 1970 455 wasn't compatible with the high rpm characteristics of the RA IV cam and valve train.

The closest to that was the 73-74 455 SD, it doesn't take much to imagine what 25% more compression and the high lift duration of the RA IV valvetrain would have done to the power band.

My 70 455 has its original 64 heads ported to 254 cfm, port matched iron intake and a ra4 sized hft cam. Made 490hp at 5200/570 trq. I would think that’s well within the rpm safe range ,,, no need to spin anymore the 5500 rpm’s.

RoundPort heads and IV cam with 1.65 rockers will spin past 6,000+ rpm
That's why most Ram4 cars have replacement engines.

Guys would have been doing the same thing with their 455's if Pontiac put all the goodies with them.
Which they should have, and had plans to, but didn't.
Would have been a lot of warranty repairs even with better rods.

067 and 068 camshafts with stock springs were like built-in rev limiters