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". https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

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 https://www.yenko.net/ubbthreads/imag...lins/dunno.gif . 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. https://www.yenko.net/ubbthreads/imag...lins/beers.gif https://www.yenko.net/ubbthreads/imag...ins/3gears.gif

Re: Ram Air IV versus 455 HO
 

455HO is probably comparable to an LS5...

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.

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...

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. https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

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. https://www.yenko.net/ubbthreads/imag...ns/burnout.gif

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 ?

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. https://www.yenko.net/ubbthreads/imag...mlins/haha.gif

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.

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> a better cruising car. https://www.yenko.net/ubbthreads/imag...mlins/flag.gif

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.

Re: Ram Air IV versus 455 HO
 

Is the BOP 10 bolt like the later Chevrolet 10 bolt?

Re: Ram Air IV versus 455 HO
 

Hey Mike! Talk about your good running Ponchos! I'd still love to see that 'Bird of yours in action! But only if I get a "spot"! https://www.yenko.net/ubbthreads/imag...iggthumpup.gif

Pete can jump in here if this is wrong, but I *believe* the Glasgo's have a '70 IV TA that they run at the PS events. If I'm not mistaken, it's in the high 12-range, and looks KILLER. One of Minos old RAII 'Birds is running PS with us, as well as another RAII 'Bird. I was sandwiched between these 2 cars in Stanton last year with my 12.47. And Jensen's HO car is sleeper if there ever was one...but you'd better choke up if you're gonna tangle with that T-37! Hard to go wrong with any of those packages.

Re: Ram Air IV versus 455 HO
 

Hey Charlie, you won't get any static from me on that. https://www.yenko.net/ubbthreads/imag...ins/3gears.gif https://www.yenko.net/ubbthreads/imag...mlins/flag.gif

Re: Ram Air IV versus 455 HO
 

When did they go to the corporate rears?

Re: Ram Air IV versus 455 HO
 

There was also a BOP 12-bolt, which was essentially a 10-bolt with a 12-bolt cover. This was the rear end that made it into the BOP heavy duty applications in 70-72. It uses bolt in axles, not c-clips, and the cover has a different shape. This is what's under my 69 Firebird.

Rob, thanks for the https://www.yenko.net/ubbthreads/imag...iggthumpup.gif I really have to make the trip to see these Pure Stocks in person. BTW, they just released those coveted RAII/RAIV exhaust manifolds for the 67-69 Firebirds, and believe it or not, they have a version with a 3" collector! I was seriously thinking of going back to RAIV heads and using these manifolds to see what would happen, but I realize some of the really serious "stock" guys have a lot more serious internal engine mods than I care to perform right now. I still have a hydraulic cam, cast rods, and big ol' TRW slugs. https://www.yenko.net/ubbthreads/imag...mlins/haha.gif

Re: Ram Air IV versus 455 HO
 

You Poncho guys got it all...bolt in axles, 3" mani outlets! What's next, pre-ported intakes! LOL!

Don't count out that ole 'Bird! That thing would be in the hunt no matter where you run. But, some food for thought. You could swap your headers for manifolds and go the Stock Appearing route...or...you could leave the car alone and run in the newly founded "MP" class. Basically "stock" cars with headers (closed) and a couple of other little mods allowed, kinda like back in the day. And coincidently, the Supercar Reunion is hosting an MP event along with our normal Supercar festivities at Gateway International! And since you're just up the road, I fully expect to see that Poncho picking on some poor unsuspecting Mopars! https://www.yenko.net/ubbthreads/imag...iggthumpup.gif Oh, here's the rules.

Re: Ram Air IV versus 455 HO
 

Thanks for posting the info on the MP class.That's really good news.

Re: Ram Air IV versus 455 HO
 

[ 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. https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

Re: Ram Air IV versus 455 HO
 

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.

Re: Ram Air IV versus 455 HO
 

I think you will find that the Pontiac 10 bolt has the cone type posi as well. Our Oshawa built '72 455 Lemans Sport has the Chevy 12 bolt rearend.

Re: Ram Air IV versus 455 HO
 

HI, I know of the Glasgo 70 TA, It was an orig. RAIII car, converted to a RAIV. Very low mile, super nice car.

Re: Ram Air IV versus 455 HO
 

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.

Re: Ram Air IV versus 455 HO
 

The 71/72 455HO Trans Am's and Formulas were always legit mid 14 second cars straight off the showroom floor, without any tinkering, and with the factory wheels and tires in place. All the 71/72 Formulas and Trans Am's had large 15" wheels and some pretty fat F60-15 rubber underneath, and the limited choices of rear gear selection made these cars pretty consistent from one example to another. Very impressive for a 3800+ lb. car running on regular gas.

The 69/70 RAIV cars were a bit more finnicky. The 3.90 gears were standard with the RAIV, and a/c was not available. With F70-14 tires, it was all up to the driver and their launch technique to determine whether a RAIV car was a mid 14 second car or a high 13 second car. In reality, most 69/70 RAIV cars WERE low 14 second cars straight off the showroom floor (as were most every other Musclecar in TOTAL showroom trim), and just like the others, a little traction put a RAIV car in the mid 13's. The 69 Firebird RAIV weighed in around 3500 lbs, while the 69/70 GTO was around 3650 lbs.

The 73/74 SD455 Formulas and Trans Am's were also legit low 14 second cars straight off the showroom floor, but in my opinion, they were the most impressive of all the factory Pontiac performance cars. The SD455's had a horrible, highly restrictive exhaust system, an EGR manifold, 3.42 or 3.08 gears (with or without a/c), they ran on regular gas, and didn't even have the benefit of a cold air induction system, or even an aluminum intake manifold. With the scoop opened up, these cars were touching the 13's, and raising the compression ratio a couple points from a pathetic 8 to 1 to a more reasonable 10 to 1, and removing the restrictive exhaust system (PMD claimed 50 hp reduction through the pipes and the factory crossflow muffler) to put the car in a "1970 era" mode, these cars were solid mid 13's on factory rubber.

Re: Ram Air IV versus 455 HO
 

"Pontiac dropped the ball in 1970 by not having a 455 RAIV ready" This is correct/ Pontiac 455 HO motors were made after compression ratios had already dropped to 8.2 to one.
Even at this rating 455HO's are strong motors. The 1970 455's were not high performance motors. Pontiac of course got in one more shot in 1973 with the 455 Super Duty, which is the ultimate Pontiac 455 motor. And could run with any muscle car ever built. The exhaust manifolds on SD cars are quite good, among the best Pontiac ever produced, however the pipes went back to a crossflow muffler in front of the gas tank, that REALLY added alot of backpressure to the excellent 455SD heads trying to breathe. Similar to big block chevy muscle cars....un cork the exhaust and you made ALOT more power. 50HP is very accurate.

As for RAIV's 400's, They were mid 13 second cars straight off the showroom floor, if you knew how to re-curve the distributor, and reset the timing correctly. If you removed the cleverly designed factory removeable pre-heater crossover and used block off plates you got another 10th out of em'......How do I know?? I have 2 of them now, and run them frequently in pure stock condition on radial tires and they run low 13's to 13.00's depending upon track temperture. I regularly beat my LS6 70' Chevelle. Weight has alot to do with that though. Go look up any pure stock/factory stock drag results and you will see these cars all running close to 13.00's on bias ply tires!!

I am also the organizer of this years Northeast Factory Stock and FAST Drag race. www.musclecarrace.com
Come out an see RAIV's as well as LS6's and HEMI's and alll the heavyweights do battle.

Anyone who has even looked at a set of Pontiac heads/intake and exhaust and compared RAIV parts and standard Pontiac performance parts would see an OBVIOUS difference.

As a side note. Both my 69 RAIV GTO's weigh 3700lbs
My 69 400 Firebird weighs 3450 lbs.

A 69' RAIV 400 Firebird or T/A properly tuned is a top performer. There is one that runs in pure stock classes running 12.70's again on bias ply tires.

Re: Ram Air IV versus 455 HO
 

Supergonzo, I think your quote "I regularly beat my LS6 70 Chevelle" would stir up a few people here.

https://www.yenko.net/ubbthreads/imag...mlins/haha.gif

Not sure about the weights. I've seen the weights on several early Birds and GTO's on NHRA digital scales (this was at Route 66 Raceway, the state of the art NHRA track). I have yet to see a 69 Firebird 400 under 3500 lbs. I weighed mine on the scales several times, and it weighed 3520 lbs without me. It's a 69 Firebird 400, TH400, P/S, PDB, no a/c, and on lightweight side, I had aluminum heads (66 lbs. lighter than #62 steel heads), aluminum water pump (4 lbs lighter than stock), aluminum intake (24 lbs. lighter than a cast iron), headers (6 lbs. lighter than standard manifolds), and a Reactor battery (21 lbs. lighter thand a Delco 1000 amp). In original form, it was 3641 lbs. Only thing that may get this under 3500 lbs. would be a 4-speed, manual brakes, and manual steering but even that would be close I think.

My friend weighed his 69 Firebird 400 ragtop, TH400, P/S, PDB, no a/c. It weighed a staggering 3950 lbs (without driver) on the NHRA scales. I simply could not believe it.
https://www.yenko.net/ubbthreads/imag...s/confused.gif

My brother's 68 GTO, TH400, P/S, PDB, hideaway headlights, 455 HO heads, 455HO exhaust manifolds, aluminum intake, weighed 3710 lbs. without driver.

The 67/68 Firebird were about 3450 lbs for the hardtops. My friend had his to 3350 lbs. with an aluminum intake and headers, manual steering and brakes, and a transplanted TH350.

Those dern Camaros always seemed to be lighter. https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

Re: Ram Air IV versus 455 HO
 

"Those dern Camaros always seemed to be lighter" Actually my own 69' Yenko clone weighs 3600 lbs, weighed it 4X times.
But I think its a little heavy for some reason.

I have to admit my 69' firebird has a fiberglass hood, 4spd, aluminum radiator,manual brakes. I would say 3520lbs would be more accurate for a typical model. Your right the earlier years are lighter.

I am certain the 68-69 goats all weigh close to 3700 lbs, I have 4 of them now, and have owned about 20 others. The 64-67 goats all weigh close to 3600lbs, depending upon options.
I was actually surprised the Firebird / Camaro's weighed that much.
---------------------------------
If Pontiac would have made a high compression 455HO in 1970 instead of a low compression motor in 1971.They would rank right up there with LS6's and Buick 455 Stage 1's as one of the baddest of all times. As it is in todays world , where most people build for near 10 to 1 compression for pump gas, they are very tough street machines to beat,as now the field has been equalized.
-----------------------------

Re: Ram Air IV versus 455 HO
 

As far as the LS6 goes... Chevy has the best heads for breathing period.
Problem 1 is the 70' LS6 weighs 3850 lbs, that doesn't help
Problem 2 is the intake manifold and the exhaust manifolds are choking the engine's breathing capabilities.
In other words they s*ck.

Chevy knew people were going to take their cars racing, and throw away the intakes for better ones and throw away the exhaust for headers. Once you do that to a BBC, you got a whole different animal. A car that most brands would have a very difficult time beating.

Pontiac GTO on the other hand, was a super cool image street machine. Pontiac was selling boatloads of GTO's while others were selling 1/3 as much most of the time. Chevrolet had 3X the dealer network and 4X the advertising budget as Pontiac and still couldn't out sell them!

Pontiac built good heads, excellent intakes, good exhaust manifolds, topped with great responsive Q-jets. And very little work was required to turn a showroom car into a "street cleaner". On the street they were tough to beat, but were never meant to be all out drag strip racing engines.

Ok, thats enough of a rant.

Re: Ram Air IV versus 455 HO
 

[ QUOTE ]
"Those dern Camaros always seemed to be lighter" Actually my own 69' Yenko clone weighs 3600 lbs, weighed it 4X times. But I think its a little heavy for some reason.


[/ QUOTE ]

Sounds about right. Our Y-Camaro is anywhere from 3700-3800+ with me in the seat and a tank of fuel...and I weigh a LOT less than the NHRA's 175-pound driver allowance. I wish we could shed a little weight, but I don't think dad would see the humor in gutting the car!

Your mention of the Chevrolet heads is interesting. When I went through the Certified Stock tech for the Pure Stock Drags, there was our L-72, a Stage 1 Buick, a 440-6, and a Hemi all torn down in the same shop, so we all got to see the goods on each others combo. The comment that kept coming up was at how SERIOUS the Chevy heads looked, even though they were bone stock. Everything from the ports to the valves to the chamber...pretty impressive. Of course the hemi chamber was high-tech, but the Chevrolet was impressive in it's own right. I wish there had been a Poncho and a 427 Ford there to check out as well, but it was still neat nonetheless. https://www.yenko.net/ubbthreads/imag...ns/worship.gif

Re: Ram Air IV versus 455 HO
 

Okay, leave the 70 455HO with it's smaller D-port heads out of the question of this thread. Compare the 70 400RAIV with round port heads, and 71 455HO with round port heads. I notice the factory rating on each as: 70 400RAIV 370HP/5500RPM versus 71 455HO 335HP/4400RPM. Would it be true that the 71 HP is peaked out at 4400RPM. That's at 1100RPM under the RAIV rating, which seems to be very low RPM to rate its maximum HP. That is how the L88's were rated less than L71's in the Vettes.

Re: Ram Air IV versus 455 HO
 

These engines all used the same intakes and exhaust, the 70-71 were in heavier cars.
However:
The best breathing heads were 70 400 RAIV's
Followed by 69 400 RAIV's
Next would be 71 455 HO heads, slightly less flow on intake
Finally would be 72 455 HO heads, even slightly less flow in exhaust area. Pontiac engineers knew at this time, compression ratios were falling, and were trying to get as much torque as they could out of the heads, and not worry about upper RPM air flow, as the 400 RAIV's were built. The 455 HO's also did NOT use a RAIV cam although the heads were similar they used the earlier MUCH milder 068 (tripower) cam. Again due to emissions and better low rpm cylinder fill with low compression on those heads.

A 455HO does have a lower rpm peak than a 400.However
The 400 RAIV's were underated, as several magazine dyno test have been done (even recently) and showed in stock form they produced 400-420HP.
The 455 HO with its emission friendly cam has had dyno test in the neighbor hood of 360-370HP, if I remember correctly. The 4400 peak HP rating is definitely too low, and probably rated that way on purpose, to satisfy then very restrictive insurance rules.

Re: Ram Air IV versus 455 HO
 

However the 73 455 SD was the best of all of these. Even though rated at 310(290) net HP.

The 73 455 Sd intake was cast iron, by emission necessity. So it was fair in performance.
The 73 455SD heads out flow any other Pontiac heads made, other than RAV Tunnel ports. I have 2 sets of these and one going on a 73'T/A I'm building. At the time were said to out flow even HEMI heads! Although this is not true. What is true is that the heads were meticuously cast. Meaning most factory heads (any brand)have large casting differences among them, even within years. Depending upon the casting machine you could get a good LS6 head or a fair LS6 head. One that is clean and one that has casting imperfections in the passages, or even half closed passages alltogether. This is true of all brands.

The 73 455SD heads were all made very well. I have never seen a crappy one. They used slightly bigger Ram Air type exhaust manifolds than even the RAIV /455HO's.
As mike said: Today a 455SD with the original planned RAIV cam in it, and uncorked exhaust, 10 to 1 compression.. is a bad ass. One that is capable of staying with anything ever built in the muscle car era. Even in 1973 HotRod magazine tested one with 3.42 gears at [email protected] you read the article they mentioned that they had the air conditioning on while track testing it!! Other tests by other mamagzines were similar.

As a side bonus if you have ever driven a 70-74 Trans AM, they make any 60's muscle car feel like you are driving a school bus. They handle virtually like today's cars.

Re: Ram Air IV versus 455 HO
 

The SD455 head is truly the best head from a performance standpoint, but the huge chamber on the head, required to maintain low compression, was a killer.

On the topic of port comparisons and port flow, the SD455 stands alone. The Pontiac Engineers hogged the SD455 head intake runner out so much that they broke through the pushrod bulge (the main airflow obstruction on a Pontiac head) within the runners. They remedied this by inserting special pushrod tubes in those runners. They also raised the port roof so high that they broke through the valve cover bolt holes. Tuners soon found out about this, as many Pontiac people replaced the factory rocker arm lock nuts with adjustable versions for a few more rpms on the SD455. With the engine idling, setting the adjustable polylocks proved to be difficult. The engine is idling, the valve cover is off, and you're wondering why the engine is dying? On the SD455 cars, removing the valve cover bolts over those runners caused a massive vacuum leak. https://www.yenko.net/ubbthreads/imag...ins/tongue.gif You had to replace the necessary bolts if you idled the car with the valve covers off.

Seems a little extreme for 1973, but the SD455 was the Pontiac bad boy that made it to the party too late.

Pete McCarthy did some serious flow work tests a while ago, and ran all the Pontiac heads through a Superflow. There was always some debate on what was truly the best street head.

Best performance head : 1970 Ram Air IV
Best intake port : 1969-70 Ram Air V
Best exhaust port : 1968 1/2 Ram Air II
Best D-port head : No.16, No.48, No.12 (tie)
Best low-compression D-port head : No.96(1971)
Best low-compression post-1972 head : No. 6X
Best balanced head (exhaust to intake) : 1963 421 SD
Best low-lift (under .400) head : 1967 No.670
Worst exhaust-to-intake port ratio : 1969-70 Ram Air V
Worst intake-to exhaust ratio : 1968 1/2 Ram Air II
Biggest surprise : Intake port, No.17 350 head
Biggest disappointment : 1969-70 RA V, 1973-74 455 SD (tie)
Biggest "sleeper" : 1975 No. 5C
Most undercammed : 1963 SD, 1971 455 HO, 1973-74 455 SD (tie)
Most underexhausted : 1964 GTO (No.9770716)
Most potential for porting : 1973-74 455 SD, 1968 1/2 RA II (tie)

Re: Ram Air IV versus 455 HO
 

I am rebuilding a 73 SD engine right now. Do you recommend 10-1 and a RAIV cam ? Solid or hyd ? Will it idle with AC ?

Re: Ram Air IV versus 455 HO
 

I agree with Mike 1000% A well prepped 455SD is one hauling mean machine. The block even had Dry Sump racing provisions built in!
----------------------------
Charley it depends on your budget, but I would recommend a Hyd roller possibly a Comp XR276HR or a XR288HR depending upon what you want to do with the car. A HYD roller with 230-240 degrees duration would make you very happy and it will idle just fine. 10 to 1 for pump gas would be fine. You need ROSS Pistons, they are the best and they are off the shelf most times. Throw in a set of aluminum rods if you have money to burn and that 455SD will rev like a small block.

Re: Ram Air IV versus 455 HO
 

The SD455 heads are so rare and valuable today that it's a shame to port or shave them in any way. The original SD455 was designed with the RAIV cam. The prototypes used the RAIV cam, but couldn't pass emissions (there's a whole story about that that's pretty cool) https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

The skies the limit if you want to build it with "secret" parts. Aluminum rods, lightweight pistons, hydraulic roller, it really depends what you want to do with it, and if sounding totally stock is a priority.

Re: Ram Air IV versus 455 HO
 

I don't need anything exotic as it will still not see much driving. If I wanna go fast I have other stuff. I know I need to bore it and put new pistons so I might as well go 10-1. The cam looks fine but if there is a good hyd cam that would compliment the 10-1 and still idle well I should go for it. I am told intake gaskets are hard to find and the repo ones fall apart, any suggestions ?

Re: Ram Air IV versus 455 HO
 

[ QUOTE ]
Even in 1973 HotRod magazine tested one with 3.42 gears at [email protected] you read the article they mentioned that they had the air conditioning on while track testing it!!

[/ QUOTE ]

Unfortunately, that wasn't with the production cam. Darn Feds...

Re: Ram Air IV versus 455 HO
 

Rob, that was true, but what was so impressive was that that SD455 ran that time with 8.4 compression, weighing 3800 lbs, a ridiculously 3.42 rear gear, emission equipment, and an EGR on a steel intake. Simply amazing in any era, not to mention 1973! https://www.yenko.net/ubbthreads/imag...ns/worship.gif

Re: Ram Air IV versus 455 HO
 

Charely

There are 10 and half dozen ways to build a Pontiac, but to think you won't go fast in it... that is a huge mistake. The majority of stock components adjust the compression with head cc and gasket crush. I believe you have a SD, if memory serves me correct. You will probably want to stick with the factory heads. TRW (Seal Power or whoever they are now) did make a shelf piston for those rods, it only had two valve reliefs. If you find some nice .015 crush gaskets, run a zero deck, and mill the heads accordingly to achieve your final compression ratio.... I think you will be happy. Running low 12's with a 9.5 455, is a piece of cake and you get to use pump gas. Then again maybe you will want a highway cruiser. Some of the old cross country racers use to order these SD's with the highway gears, and achieve some serious cruising speeds.

Steve

https://www.yenko.net/ubbthreads/imag...arleySucks.gif

Re: Ram Air IV versus 455 HO
 

For those non Pontiac people, basically any round port exhaust head Pontiac motor has real good potential. RAII/RAIV/RAV/455HO/455SD

"Running low 12's with a 9.5 455, is a piece of cake and you get to use pump gas." I agree no problem.

Don't cut the heads though, get the right pistons instead. Any HYD cam with 240 degrees duration and under .520 lift and you'll have a fast and reliable street cleaner, while enjoying 60 degree air temps inside the car in summer!