Ram Air IV versus 455 HO

[SuperCars]

Ram Air IV motors seem to be regarded as top motor of choice in a Pontiac production car, but what about 455 HO motors? When you think about 400 Ram IV cars only having 10-bolt rears, and the 455 HO having a 12-bolt rear, there is significant difference. Still can't figure out why RA IV's didn't get 12 bolts though, when even SS350 Camaros got them. But obviously Pontiac Engineers recognized that 12-bolts were definitely needed due to the Torque and Horsepower in the 455's larger displacement motor.

When you look at motor ratings you see the factory rating of Ram Air IV Horsepower at 370HP/5500RPM, and the 455 HO at 360HP/4300RPM, which I wouldn't think is the 455's peak RPM. This reminds me of the GM ploy of manipulating HP rating like they did with the Chev L88, where GM under-rated the L88 by giving its rating at a lower RPM below it's peak RPM.

It would seem that 455 HO is more comparable to the Chev 454/LS6; whereas the RA IV is comparable to a 396/L78. I realize the popularity of Ram Air IV is in conjunction with the 69/70 Judges and the 455 wasn't available in a 69/70 Judge. But in 1971, all Judges had 455 HO. The compression was down in 71, but the 71 454/LS6 Vette was still able to muster 425 HP with low compression. I've always believed the saying: "there's no substitute for cubic inches".

[DaJudge]

Although rare, you could get a 455HO in a 70 Judge. Late model year introduction. I agree I don't know why they did'nt put a 12 -bolt under RA IV cars . A 70 455HO had standard d-port heads (64) and a cast intake. The 71 455 HO had round port heads and an aluminum intake (painted engine color). 4 speed 455 cars in 70 and 71 used the 068 or RA III cam. The 71 455 HO was closer to a RA IV but for performance and a great lumpy idle (527 lift cam) I'll take a IV car all day long.

[Belair62]

455HO is probably comparable to an LS5...

[Chevy454]

From what little Poncho exposure I've had, I tend to lean towards the 455HO. In Pure Stock competition the quickest Ponchos aren't the RAIV, but the RAII's and the 4550HO's. Granted, the IV's run well, but I put more faith in the II or HO combos as a whole...

[SuperCars]

This is all good feedback. I think Rob has good input from pure stock competition. Aside from lower compression, what I glean out of this is the 71 455 HO with more displacement and large round port heads had a lot going for it. Kind've like the 71 LS6 Vette, had to say that for Belair.

The RA IV's are great, and I'm not knocking them as I own a 69 and 70. But just quite surprised that Pontiac Engineers only felt a 10 bolt was needed, and that translates to performance in a round about way. The 71 455 HO W/ round port heads, and Pontiac engineers putting a 12 Bolt behind it would give me the impression that was their top performance drive train combo. Just my opinion.

[Belair62]

Didn't the 455 have a silly amount of torque ?? 500 or so...what is the diff between BOP 10 bolt and Chevrolet ?

[442w30]

[ QUOTE ]
From what little Poncho exposure I've had, I tend to lean towards the 455HO. In Pure Stock competition the quickest Ponchos aren't the RAIV, but the RAII's and the 4550HO's.

[/ QUOTE ]

Rob, I think you're confusing a few engines.

I am not sure ANY 455 1970 Poncho has run in the races where I see you race. These 1970 cars may be called 455HO in Pontiac circles, but not on the car. It always says "455 cid" and if you want to get picky, it's not a real HO car. They have nothing in common with the 455HO introduced the next year, which was basically a RAIV 455 but with low compression. The regular 455 was still available, and it received the same "cid" decals like in 1970. True HO cars received "455 HO" decals for 1971-72.

They made them in numbers marginally greater than 1969-70 RAIV GTOs, but when you factor the couple thousand T/As built, they are MUCH more common. I would not discount a RAIV just yet.

[Chevy454]

I should have been more specific, Diego! I was referring to the '71-2 HO cars that seem to multiply every year in southern Michigan! And so far, they seem to hold there own performance-wise. The '70 I referred to was the Glasgo's RAIV(?) TA.

[StealthBird]

The 1969 RAIV was the pinnacle of the factory produced Pontiac 400 engines. A few years ago, Dan Jensen assembled an absolutely box stock RAIV engine for Musclecar Review, using all NOS parts (including the heads, cam, carb, etc). His goal was not to tweak or modify in any way, but to see what a RAIV truly produced, and lay to rest all the rumors about if the RAIV was really a 400 hp engine. The engine produced over 420 hp. With the 1969 Firebird exhaust manifolds flowing a little better than the 1969 GTO's, and with the lighter Firebird weight, the peak of the Pontiac's 400 engine performance came in the 1969 Firebird RAIV, and yet those still used the 4-pinion HD 10-bolt. The 3.90 gears were standard on RAIV cars.

As stated above, the 1970 455 HO was a d-port engine with a steel intake manifold. Pontiac dropped the ball in 1970 by not having a 455 RAIV ready. Management problems, red tape, and corporate political wars came to a peak in 1970 at Pontiac. DeLorean and Wangers left for Chevrolet in 1969, the RAV program was scrapped, and the PMD engineers were told there was virtually no development money left to create a RAIV 455 due to the enormous expense incurred in their failed RAV 303/400 program. The new management felt there was no simply need for a super high hp 455 when the 400 RAIV was doing just fine. Test engines of 455 based RAIV's were generating over 470 actual hp, but they would never see the light of day. Odd, because it was so incredibly easy to make the 455 version of the RAIV. All the parts were in the parts bin, but Pontiac chose to stick with the RAIV 400.

By 1971, Pontiac was ready to unleash the RAIV 455, but with the compression ratio drop, they chose to drop the RAIV name and stick with the 455HO badge. But the 1971 455HO was nothing like the 1970 455HO. The 1971 455HO was essentially a low compression 455 RAIV, with round port heads and aluminum intake, and of course a much milder cam.

[HemiOrangeTA]

Some years ago, Muscle Car Review published an article which had Jim Wangers rate his top five fastest GTO's. Although based on period magazine tests and subjective "seat of the pants" recollections, it is nonetheless an interesting read. I believe the 1971 455 HO rated very highly.