[formulamedic]

Howdy folks! I am in possession of my 73 Formula Ram Air and have a question before I throw down for a manifold. There are two numbers listed for a correct intake manifold for that year non SD 455. Which one is for a ram air car and does it make a difference? the numbers are 492744 and 494282.

[Held for Ransom]

I believe there were three 4-bbl intakes for '73 and it depended on date built, not useage.

[1971455HO]

Welcome to Performance Years Forum formulamedic. I see no one has responded tour your question yet. I took a quick look in my Master Parts Catalogue and see no reference specifically for a "Ram Air" manifold for your '73 Formula. I have a '71 T/A and am not that familiar with Formulas. Is you car a 350...400...or a 455 Formula? I am assuming it is 4bbl because your asking about a ram air manifold. The non SD intake number I see (and this includes ALL) is 496295 All/4BBL/

[1971455HO]

Was this the site you used? http://www.pontiacpower.net/numbers/...s/#prettyPhoto

I think you got a couple of numbers switched, it's easy to do. In the 1973 section there are only three 4-bbl intakes to choose from 491244...494744...494282. Hopefully some of the Formula owners that know their stuff will jump in here and help you.

[formulamedic]

Awesome feedback. It is a 455 and I think the correct one is the 494282. My car is a ram air and I was not sure that there was a difference. This is my first Pontiac so I am learning on the go. Now I just need to source one-the car has a period edelbrock with the edelbrock carb on it. Runs great, but I want to put it back to original, at least externally.

[formulamedic]

Weird, I have yet to see the 496295 number for a 73 Formula 455. I think that either one will fit, but I have to source one to start with! As well as the right carb, then get it set up for my 8000 ft altitude. My car is a CA car, but my buddy in Aptos, has that sorted out with one of the national Rochester builders. I just cannot WAIT to start getting the car set up correctly and enjoying it! I know it may be a faux pas, but I have always been a Ford guy. That and a BMW nut of course, dont even get me started on Defenders...

Again all, thanks for the info, I am sure I will be asking many more questions!

[Held for Ransom]

Let me try this again.

What is the build date of the vehicle?
If your engine is the original one, what is the 2 character code stamped on the passenger side of block, just below the head?

The reason you don't see the PN 496295 as a cast number, is because there were things included on it, making it an assembly thus needing a different number.

And the middle manifold is casting number 492744.

[John V.]

I have a '73 Trans Am. I originally owned it from '78-'80, at that time it had the original 455 bottom end with an Edelbrock intake. I managed to put the carb stud thru the engine, cracking the block, swapped in a j'yard 455 out of a '72 GP. So even then, not much was original for the engine.

I bought the car back about 18 months ago with the goal of returning it to about what it was in '78. The previous owner bought it in the '90s with a 403 Olds in it. He told me the guy he bought it from told him he had yanked the Pontiac engine that was "junk" and installed the 403. I will be yanking the 403 and putting a proper 455 in it.

I have been following this thread because I also was curious about the '73 intakes.

I am aware of the (3) p/ns as listed by 1971455HO except he wrote 494744 which should be 492744.

Same intakes were used across the entire Pontiac line for 4 bbl applications, they were not Firebird specific.

The SD was an exception, it got its own specific intakes.

My understanding is that the 491244 casting was only cast very early in '73 production (possibly August only?) and would only be found on engines assembled very early with very low Engine Unit Nos.

I have never heard how the very early 491244 casting differed from the 492744 which followed it.

My own TA was built in January and undoubtedly would have had the 492744 casting.

The 494282 came about on or about March 15, 1973 (earliest cast dates would likely be somewhat before March 15). PMD was forced to redesign the EGR system. Required a different intake. New Engine Manifest Codes were issued and to distinguish the newly certified engine design, PMD painted them a different color. This change affected all Engine Unit Nos. starting with 532727.

About 700 engines already assembled engines were reworked and repainted. So some engines prior to 532727 would also have the 492744 intake.

Not only is 496295 a Service p/n for an assembly but I'm pretty sure used the '74 intake casting p/n 495106. This p/n would have serviced a '73 with the redesigned EGR system. I believe the 1st design EGR system would have been serviced with a different casting, possibly continued to use the 492744.

As HFR is indicating, you likely will know which intake casting was original to your engine by knowing the Engine Manifest Code on the block and the Engine Unit No. If it was built very early, it might have had the 491244.

HFR, do you have info on when the 491244 was cast? Are there observable physical differences between it and the 492744? Any idea why they came out with the 492744?

[Formulabruce]

formulamedic , please post a pic of the cowl tag, and or get the info on the block by the distributor ( date code ) Im sure other or myself can help you with a correct intake.

[wwilder9]

I have a first week of February 73 build trans am with and intake with 492144 intake number dated k272 with YA block 485428 H012 and en # of 332723, heads 4X-1H L152 & L122.

[John V.]

wwilder9, please recheck. I believe you mis-posted your intake p/n.

I am all but certain your intake is p/n 492744.

Note the 4th digit "7", not "1" as you posted.

[wwilder9]

I'm just trying to help.....Here you go.

[John V.]

Thanks, just wanted to be sure that the date code matched to a 492744 and not possibly the very early 491244.

I can see how you would read that as a "1", but it is truly a "7".

For comparison, robbed the attached pic of the very early 491244 intake from a thread here.

Pic isn't great but you might be able to see that the top "bar" of the "1" is much smaller than the top "bar" on your "7".

[Burgess]

John V. wrote:
''The 494282 came about on or about March 15, 1973 (earliest cast dates would likely be somewhat before March 15). PMD was forced to redesign the EGR system. Required a different intake. New Engine Manifest Codes were issued and to distinguish the newly certified engine design, PMD painted them a different color. This change affected all Engine Unit Nos. starting with 532727.

About 700 engines already assembled engines were reworked and repainted. So some engines prior to 532727 would also have the 492744 intake."



I never paid very much attention to the intake on my 73 T/A, until I read through this thread, so I checked out what is on mine.

02D build, and it has the 494282 intake, casted B193. Heads both B193, Block B093, EUN 505456.

So, the later redesigned intake was used before the emission change.

[John V.]

Burgess, very interesting.

I see I made an mistake in that post. Should have said 700 engines prior to EUN 532727 got the 494282 intake (assuming 4 bbl), they could not have used the 492744..

I had become aware that the 494282 was being cast in Feb. '73 while searching for pictures of them. But I had not seen any previous evidence that this intake was in use as early as yours.

Your EUN 505456 would have been assembled I estimate about 2 weeks before EUN 532727, the "official" earliest EUN with the revised EGR except for the 700 or so "converted" engines, converted I assume because they had not yet been installed in a build prior to 3/15/73 so had to be converted to conform with the Memorandum of Understanding PMD had agreed to with EPA in order to be used rather than thrown away.

Your 02D Time Built code also would seem to suggest your car went thru final assembly well before 3/15/73.

If you have the PHS invoice record, what does it show for the Date Shipped?

Was your engine painted the later darker blue?

If so, was there evidence that it was originally painted the early blue?

When you say the 494282 was used BEFORE the emission change, did your TA get built with the early EGR?

If I understand correctly, the 494282 has a 2nd drilled and threaded boss, for the later EGR design. Used for a 2nd thermoswitch IIRC, not included with the original EGR system.

Does your intake have this 2nd tapped hole or is it not drilled, just the blank boss?

I'm not surprised that they released and began producing and installing the 494282 intake prior to 3/15/73.

Just curious as to how much before the "official" date did they start changing over to the new EGR design.

Your TA represents a fascinating data point. Depending what else you can tell us about your engine, would offer a very good clue as to how early the 494282 intake began to get installed on engine assemblies in place of the 492744.

[Burgess]

Here are some pics of the intake manifold, showing the drilled boss on the water crossover with a plug in it, and the single vacuum hose fitting with an adaptor bushing to fit a larger threaded hole (for a thermoswitch.) So apparently it has been machined for the second design, but still equipped with the early setup.

This intake has been off of the engine since the early eighties, luckily it was saved. Very little of the original paint remains, but it seems to be the lighter blue, matching the earlier system. The rest of the engine was repainted long ago.

I do not have the PHS for this T/A, but now I'm curious enough to buy it. I'll follow up with the shipping date when I get it.

[John V.]

Exactly as I would have guessed. Your engine built up to early EGR specs but using the late EGR intake. From evidence, looks like they started casting the 494282 some time between A113 (example on ebay) and your B193. And prior to March 15, '73 looks like PMD continued to assemble engines with the early EGR, just had to install a plug in the added tapped hole when using the 494282.

I've been comparing pix of all 3 intakes.

Curiously, ALL of them include the extra boss but only the 494282 was drilled and tapped.

I can find no differences between 491244 and 492744 at all except for the p/n. I haven't seen pix showing the bottom of many, but what I've seen looks identical between these two on the underside also.

Given the similarity in these two p/ns, I'm wondering if the 491244 was simply a foundry casting error, perhaps the p/n was 492744 all along but a mildly dyslexic foundry mold maker may have screwed up the p/n in the mold.

I haven't bothered to log examples of the 491244 previously but it seems to me that every one I've ever noticed always had an August '72 cast date.

If it was just a mold error, could be it was discovered pretty quickly and the mold corrected, with only a few days of casting production involved.

To get the ball rolling, I found a 491244 cast H092 for sale at Frank's and a pic of another cast H102. Another on ebay, cast H142.

Will be interesting to discover what other cast dates turn up.

The only differences I spotted on your 494282 was the drilled and tapped 2nd thermoswitch boss plus a large "X" cast to the right of the cast date. There is no such marking that I have noticed on either the 491244 or the 492744 intakes.

Another thing to watch for, since the 492744 had the necessary boss, it is possible that PMD could have reworked any remaining inventory of 492744 intakes so that they could be used with the late EGR. This might not have been necessary since they probably used up all remaining inventory of the 492744 before beginning to use the 494282 (as they did with your Feb assembled engine), but in case such a thing turns up, figured I would mention the possibility here.

[Held for Ransom]

Re: 491244. G182 and G312.

[John V.]

Looks like the 491244 was cast for at least 4 weeks in July-Aug '72. Still think it could have been a foundry error but no matter, this will help establish the time frame for when they were cast. Wonder what the earliest cast date is for the 492744, anybody have a very early one?

To compile the 491244 dates id'd so far:

G182
G312
H092
H102
H142

[formulamedic]

Awesome info guys! The car was shipped on 7.12.1973. I dont see the build date in my paperwork.