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Old 02-23-2004, 03:19 PM
SuperCars SuperCars is offline
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Default Ram Air IV versus 455 HO

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".
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Old 02-23-2004, 04:53 PM
DaJudge DaJudge is offline
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Default Re: Ram Air IV versus 455 HO

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.
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Old 02-23-2004, 04:58 PM
Belair62 Belair62 is offline
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Default Re: Ram Air IV versus 455 HO

455HO is probably comparable to an LS5...
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Old 02-23-2004, 05:20 PM
StealthBird StealthBird is offline
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Default Re: Ram Air IV versus 455 HO

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.
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Old 02-23-2004, 05:23 PM
Chevy454 Chevy454 is offline
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Default Re: Ram Air IV versus 455 HO

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...
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Old 02-23-2004, 06:15 PM
SuperCars SuperCars is offline
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Default Re: Ram Air IV versus 455 HO

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.
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Old 02-23-2004, 06:19 PM
Belair62 Belair62 is offline
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Default Re: Ram Air IV versus 455 HO

Didn't the 455 have a silly amount of torque ?? 500 or so...what is the diff between BOP 10 bolt and Chevrolet ?
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Old 02-23-2004, 06:27 PM
StealthBird StealthBird is offline
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Default Re: Ram Air IV versus 455 HO

The RAIV cam was the first computer designed camshaft in the industry. It was so effective, the camshaft is still widely used even today in Pontiac rebuilds, even with 35+ years of aftermarket cam grind technology available. Besides, we don't know any better.

The predecessor to the 1969 RAIV was the 1968-1/2 RAII. The RAII was basically a RAIV, but without the RAIV 1.65 high lift rocker arms, and without the nifty RAIV two-piece aluminum intake. On paper, the RAIV was a stronger combo.

But Jim Mino's 1968 RAII Firebirds seem to tell a different story. There has been a lot of speculation as to why the RAIV doesn't seem to do as well as the RAII and 455HO in the shootouts. In all honesty, I firmly believe that no one has really taken a RAIV to the same level that Mino took his RAII Firebird (or Jensen with his 455HO car). Those guys had a firm understanding of the Pontiac drivetrain, head flow, etc., and spent a great deal of time and effort assembling their combos. It appeared as if they were cheating, but they weren't. It was hard to believe a little 400, rated at a measly 340 hp, or a low compression 455 rated at 335 hp, could beat up on on so many high compression, big cube, solid lifter cars, 400 + hp cars, but they did. Mino's 68 Firebird was a lightweight, and so was Jensen's GT-37, but not "cheater" lightweight. They just found cars that were originally ordered in a street racer way. Jim Mino did a thorough teardown of his RAII a few years ago for a magazine, and showed every conceivable part of his 400 to the cameras. It was absoltely bone stock, unported, unmolested. He just assembled the engine with great care.

Pontiac 400's and 455's are low revving combos. They were so effective on the street because most street races lasted about 5-10 seconds, and during that time a person cannot take advantage of a 6000 + redline. Pontiacs focused on a broad torque curve rather than peak hp, and that made for a great street racer.
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Old 02-23-2004, 07:53 PM
yellowjudge yellowjudge is offline
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Default Re: Ram Air IV versus 455 HO

Hi, the 71 455 HO TA only received a 10 bolt, 3:08,42,73 ratios. I think the 455 H.O. great street mtr, just does not have the mystique of the RAIV. I have both, the H.O&gt; a better cruising car.
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Old 02-23-2004, 08:22 PM
Charley Lillard Charley Lillard is offline
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Default Re: Ram Air IV versus 455 HO

The Pontiac 10 bolt is stronger than a Chevy 10 bolt. Might have 10 bolts but it is better.
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