Ram Air IV versus 455 HO

[supergonzo]

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.

[Charley Lillard]

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 ?

[StealthBird]

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)

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.

[Charley Lillard]

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 ?

[Steve_Hoog]

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

[Astock]

I have 100% orig. '65 GTO 389-6 at Glasgo's getting the Phase III blueprint that will put the car in the 12's with the skinnies and full exhaust. And,they swear by the Comp cam XE274H.

[Steve_Hoog]

If you can not run your best time with full exhaust these days, you best put it back on the trailer. These younger kids racing today have corrected my way of thinking. Don't get me wrong, I still love the sound of open headers but when they run down the track in a full exhausted 9 second car.... I have to rethink things.

Dude, I love that repo Magnum the Glasco's built. Very very nice. I would think any work they do for you will be top notch.

[supergonzo]

Yes I like that cam as well. 230/236 degrees duration and .488/.491 lift with stock 1.5 rockers. A good street cam. Especially for a 389/400.
The 455 SD can take a slight step up in camshaft without affecting idle quality noticeably.(particularily lift) But that one is ok.

[Chevy454]

[ 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...

[StealthBird]

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!