[bluecomet]

I have been restoring a 72 trans am for years and needed a HO intake for the car because it was stripped. I ran into a man who said he had one. I eventually bought it off the man. Everything seemed in order but then I ran the numbers off the intake. According to Pontiac musclecar performance written by Pete McCarthy, the numbers match a aluminum super Duty intake. It says it was non production. Does anyone no what this is? The serial numbers on the intake are 485640. Is this rare or some type of aftermarket piece made by GM. Or is it a proto type that was meant for the 73 Super Duty. Any information on this piece would be greatly appreciated. Thanks.

[Rocky Rotella]

Do you have a picture of it? Does it have a separte cast iron heat crossover? Does it have an EGR valve?

Some SD manifolds supposedly made it to the public but I've never seen one. Not sure if it's a prototype but it's rare. How desirable is the question.

Sounds like something I'd want!

[Robert Williams]

That intake is very rare, it's a lab rat. The 73 AND 74 455 SD engines when designed were to have an aluminum intake manifold and that is what you have. The factory brass didn't even want the 73-74 SD engine. The production 73-74 SD engines were assembled with cast iron intakes. The aluminum SD intake was scraped because the brass was putting the heat on the engineering staff. I guess they did make a few but they never made production. You have a very rare intake manifold.

[bluecomet]

Thanks for the input guys. I knew when I was buying the manifold it was unique. It is on my 72 HO engine right now. It does have a heat riser with it. I had the engine balanced and blue printed. It runs well. I wish I had a picture of it before I had it installed on the car. It would be interesting to see this intake on a Super duty T/A. It is very light and I am sure it would make a big difference in the performance. I wonder if there is a way to find out how many of these were produced. Any ideas?

[NW S/D]

turbo, I know this is old, but do you still have this? and are you willing to sell? I want it for my 73 SD T/A, car is an early build date car. Thankx JF email @ [email protected]

[x-bird2]

when he first posted, i e-mail, he wasn't interested in selling. i e-mailed him again a few weeks ago to see if he could send a pic for an article, haven't gotten a reply.

[NW S/D]

May/June PE has Mitchells 72/73 SD show car in it, Has that # intake.

[Lloyd-TX]

Wrong!

Here is the intake manifold applications page from the December 1971 Pontiac MPC. Being from the Dec '71 MPC, this clearly indicates that initial production '72 455HO's were equipped with the 485640 intake manifold.

[Lloyd-TX]

and . . . here is a scan from the June 1977 MPC, showing the that the 488945 manifold superceded the 485640 piece.

I have been speaking with Rocky Rotella about this information. Rocky has archived several pictures of BOTH '72 455HO intake manifold castings, and they appear identical.

My theory is that the casting was altered, however slightly, when the 7F6 cylinder head casting was changed from the "scalloped" intake manifold gasket interface to the non-scalloped design.

Whatcha think?

[TA_Thomas]

That is the number on my intake "485640" snd it is the original intake.

[soupman]

I also have a early 72 T/a, and that is the number on the manifold also.

[Northern Goat]

I know this is an old topic, but I just bought this intake for my 73 SD motor. Does anyone have any new information on whether this was an experimental intake for the SD motor or not?

[Lloyd-TX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Northern Goat:
I know this is an old topic, but I just bought this intake for my 73 SD motor. Does anyone have any new information on whether this was an experimental intake for the SD motor or not? </div></BLOCKQUOTE>

The 485640 intake manifold is CLEARLY NOT any kind of "experimental" piece!!!!! See above scans I posted out of OLD Pontiac Master Parts Catalogs.

Once again - the Dec. '71 MPC scan shows the 485640 PN, and the June '77 MPC shows the 485640 being replaced by the 488945.

My Nov. '71 build date '72 GTO WW5 455HO car has the original 485640 casting intake on it.

There is NO DOUBT that the 485640 SD intake being an experimental SD piece is PURE MYTH!

[a73formula]

I don't know about the myth thing it just sounds like the engineers were thinking of using the 455 ho intakes on the sd cars and then backed away from the idea. As long as you keep the original intake a 455 ho intake would be a great add on to a sd car and you can have what pontiac probably initially intended for the sd cars.

[turbo]

Hi, I thought I would chime in on this. I have not checked the forum for awhile and was surprised you were talking about my old intake. Yes I just sold the intake to my friend from Canada. I put it on ebay and got many emails that were quite similar to the recent posts. One man claims he had the same intake and had documentation stating the intake was used on Super duties for off road purposes. I asked for the information but did not receive it. I have seen in some books that they mention this intake and that GM wanted to cut costs at the last minute and went with the iron one. I have gone by pete mcCarthy's book. I don't know where Pete got his information. The intake looks similar to a 72 HO. I have the cross over on my 72 trans am. I sold the intake when I found the matching number intake according to McCarthy's book. I tend to agree with the last post that the intake was probably meant for the super duty but never made it and was put on some 72's. The date on the underside was from 71. I am sure pontiac was thinking about the super duty in 71 and this is what they wanted for the motor. The intake ran very well on my car.

[Lloyd-TX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by turbo:
Hi, I thought I would chime in on this. I have not checked the forum for awhile and was surprised you were talking about my old intake. Yes I just sold the intake to my friend from Canada. I put it on ebay and got many emails that were quite similar to the recent posts. One man claims he had the same intake and had documentation stating the intake was used on Super duties for off road purposes. I asked for the information but did not receive it. I have seen in some books that they mention this intake and that GM wanted to cut costs at the last minute and went with the iron one. I have gone by pete mcCarthy's book. I don't know where Pete got his information. The intake looks similar to a 72 HO. I have the cross over on my 72 trans am. I sold the intake when I found the matching number intake according to McCarthy's book. I tend to agree with the last post that the intake was probably meant for the super duty but never made it and was put on some 72's. The date on the underside was from 71. I am sure pontiac was thinking about the super duty in 71 and this is what they wanted for the motor. The intake ran very well on my car. </div></BLOCKQUOTE>

All wishful thinking, speculation and heresay.

No disrespect to Pete McCarthy, but there have been other errors in his books as well. I would have to see this supposed documentation myself to be persuaded otherwise. Once again, the FACTS are that several of us have the 640 intake on our documented early build date '72 HO engines, and there can be no disputing the MPC information!

My best guess is that an early 455SD engineering prototype engine MAY have been equipped with this documented '72 455HO intake, but the simple fact remains the NO production 455SD engines were OEM equipped with ANY aluminum intake manifold. Methinks cold start emissions (and most likely cost concerns as well) ruled out an aluminum piece from being certified for the SD engine program. Also, it is a well-known fact that since the plenum floor had to be raised slightly to provide clearance for the cast iron exhaust crossover, that the earlier iron 4V intakes flow slightly better than the RA IV/HO inatkes anyway. In addition, since the SD engine had to be equipped with an EGR system, there was simply NO room for a separate crossover!

[turbo]

Pete McCarthy book states the intake was a non production intake. In another book I have read, the book makes mention to the intake having cold start issues. When pontiac was conceiving this engine in 71 the emissions were not as restrictive. I have a 72 trans am. It was a transitional year and even at that my car would not pass 73 emission and bumper regulations. That is why so many cars had to be scrapped after the 72 strike. No one is saying this intake came on any super duty production car. It may be one of the few they were trying on the prototype engines and when the higher ups said no because of cost concerns they did not want to throw them away so they probably put them on early 72 T/A's. When this intake warmed up after a couple of minutes it was awesome with the 455. If you were going to make an all out race engine like the super duty do you think if the engineers had there way they would have preferred an aluminum intake which is considerably lighter,more than likely. They had success with the 71 HO intake. I have had guys email me and said they remember being able to buy this intake from the GM parts dept. There are too many people out there that seem to have knowledge about this intake to simply dismiss it. It's just like the turn signal lens on the 72 trans am. My car is an early one and has clear lights. The car was made in 71. Cars made in 72 seem to have the amber lens. Looking at my data tag, my car started as a base firebird and was used in building a trans am. It is an early Trans am. Things changed quickly back then and people made the best with the cards they were dealt with. Who is to say for sure who is right. I think it is an interesting subject. We should all keep an open mind.

[Rocky Rotella]

Turbo, I have spent a great amount of time (years) researching the development of the SD-455. I have read many different stories from when these engines were new all the way to what’s published today. The most disappointing part of it all is how widely varied the stories are and the general inaccuracy amongst many of them. Next time I speak with Pete, I’ll make it a point to ask him where he found that information. Other than his book, I’ve never seen the 485640 listed as anything other than a ’72 HO application.

I have had the opportunity to speak with two of the key engineers who were responsible for the development and production of the SD-455. I specifically asked Skip McCully about the SD-455 aluminum manifold and was told that preliminary SD-455 dyno testing included a standard production RAIV aluminum manifold that was modified to accept both a Holley and QJ carburetors and pair of ported #614 RAIV heads. Once they started casting pre-production parts that were very close to the final production pieces, he said the aluminum manifold was canceled and a cast iron unit went in its place because of poor cold-start emissions and drivability and the fact that EGR had to be plumbed back into it. Another engineer validated those points on a different occasion.

That being said, we know that no production SD parts were cast earlier than mid-calendar year 1972. The most conclusive point in my eyes is that not a handful of these manifolds exist, there are several out there and they all have July and August ’71 cast dates (so far). I’ve got a 488945 right here with a Dec 1971 cast date. Even if these pieces were intended to be used on the SD-455, they cast several of them early in the ’72 model year—well before the heads or blocks, which just doesn’t make sense.

You said that people recall knowing this was available from the Pontiac parts counter. I’ve never heard this story from anyone nor do any of the parts manuals list the 485640 as anything other than the ’72 455 HO. I am convinced that it is nothing more than a early-72 model year 455 HO intake. I’ve never had one side-by-side to a 488945 but looking at several pictures I’ve archived, there is nothing much different between the two. Something had to change for the PN to change, but what?! Research continues…

[Lloyd-TX]

Well said as always, Rocky.

Having information directly from two of the SD455 program engineers kind of puts an end to this myth, now doesn't it?

Could this little tidbit of SD engine folklore be the seed for part of another HPP article, Rocky?

[turbo]

Hi Rocky, this is Jim from Jessup Pa. You were kind enough to send me some articles on how to tune my 72 Trans am about a year ago. I read your article in HPP about the Super Duty engine. It was well done. You bring up an interesting point of what could have happened to change the production number. I think Lloyd as a good idea on maybe you can find the answer and write an article about it. I am sure many people would be interested. You are correct when you say there is little to any difference in the intakes. I hope you can speak to Mr. McCarthy about where he got his information from. If I can find any answers on my end I will pass them on in the forum. I will see if I can contact the man who said he had information about the intake. Maybe he will respond and shed some more light on the subject.