[71ModelJ]

Had my first great ride in a 69 triple blackG.P. 428 H.O. car. But my buddies 72 SSJ seemed to pull a little harder. anybody ever straight up race a 428 vs. a 455 in a good street race or at the track? Curious.

[north]

I remember reading a period article about a 70 gp and the author noted that it was a "stronger feeling engine than last years 428)

While a 428HO was a higher performance engine as compared to a 70 455, the longer stroke and milder tuning of the 455 would give it more grunt at lower rpm.

[Lloyd-TX]

All else being equal, the '69 HO SHOULD smoke any 455 GP!

[71ModelJ]

I don't know. I mean I took a ride in both cars. I was just wondering if they were ever tested heads up.

[Lloyd-TX]

Just do the math . . .

'69 428HO - UNDER-rated at 390 gross HP. 068 cam and NICE streamlined exhaust manifolds. Probably 3.23 gears if auto. Lower if a stick car.

'70 455 GP. Rated at 370 gross HP. 066 (auto) or 067 (stick) cam and log manifolds. 3.07 gears.

'71-'72 455 GP. Rated @ 300 gross or 250 net HP. 066 cam and log manifolds. 3.07 gears.

All 4 would weigh close to the same if similarly optioned.

Unless worn out or woefully out of tune (or piloted by a rookie driver), the '69 would smoke any of the 455 cars.

[Region Warrior]

Good question.
C.I. vs HP vs Torque vs RPM vs Gearing vs Wieght.
C.R. not as big a factor as most think until you go over 230-240 duration.
Not much diff between an 067 and 068 either.
Any true stock test comparisons from mag's back in the day?

[71ModelJ]

Thats what I want to hear. A comparison from back then. I know the 455 had lower compression but it pulled harder than the 428. Pontiac made up for the compression loss with cam, timing and head flow. And what I can remember it didn't have log manifolds. That 455 was blueprinted at Hurst. It was a real 72 SSJ. It had 3.08's and a 12 bolt posi. Not great off the line but at 50 and punch it, Great pull. That car was just a blast. Oh and the heads were 7F6 round ports and had ram air exhaust manifolds.

[north]

69 HO only had the 068 with the stick, auto's had 067. Also no AC on stick HO's so 3.55 gears.

Btw, those long branch exhaust give a HO GP a really nice sound, better than a RA GTO IMO

[428ho4spd]

Originally Posted by 71ModelJ

Thats what I want to hear. A comparison from back then. I know the 455 had lower compression but it pulled harder than the 428. Pontiac made up for the compression loss with cam, timing and head flow. And what I can remember it didn't have log manifolds. That 455 was blueprinted at Hurst. It was a real 72 SSJ. It had 3.08's and a 12 bolt posi. Not great off the line but at 50 and punch it, Great pull. That car was just a blast. Oh and the heads were 7F6 round ports and had ram air exhaust manifolds.

With both engines in stock form and running right, the 428HO should walk away from 455. Obviously your friends SSJ was far from stock with round port heads, HO manifolds and being blueprinted. I'm sure it ran very well and it should have!