[Michael Brand F/SA]

Hello,

I'm looking for information on the hoods that came on the 455 4X Formula Firebirds for 1973. Did any of them come with the flat or trans am hoods or did they only come with the formula hood?

Thanks so much,

Michael

[RicksGTO]

Just the Formula 455SD cars got the shaker so the standard 455 Formula would have come with the twin scoop Formula hood. No Formulas came with the flat hood regardless of engine option.

[unruhjonny]

The only reason why the 1973-1974 Formula Super Duty 455 cars came wit hthe shaker hood was because of emmisson's testing, as I recall reading, the certification was done with the shaker aircleaner, and to certify for the Formula air cleaner would have been another round of testing.

In summary:

all 1970-1975 Formulas, with the sole exception of the 1973-1974 SD-455 cars, came with the same "Formula" hood.

[Formulabruce]

Originally Posted by unruhjonny

The only reason why the 1973-1974 Formula Super Duty 455 cars came wit hthe shaker hood was because of emmisson's testing, as I recall reading, the certification was done with the shaker aircleaner, and to certify for the Formula air cleaner would have been another round of testing.

In summary:

all 1970-1975 Formulas, with the sole exception of the 1973-1974 SD-455 cars, came with the same "Formula" hood.

I read it was actually noise related certification...guess I need to do more research

[Norwood]

Originally Posted by Formulabruce

I read it was actually noise related certification...guess I need to do more research

That's why they put the block off plate on

[bird72]

one of the quirks of emerging by 73 "rules" and such..... one could get an open scooped proper Formula hood ram air D port Formula 455 in 1973, or a cool round port thumper with a stopped up shaker to confuse it's Formula identity and make it forever a WTH? car we are still discussing.

I understand the shaker was stopped up due to noise, which seems silly in itself. I take it the now stopped shaker SD engine was certified EPA for that exact air cleaner set up, and a Formula Ram Air pan'd SD would have required a seperate EPA certification. Probably to save a buck, or maybe even risk not passing the test (?) with a different set up caused a "ah, stick the shaker on the Formula" fix to the whole dilemna and it was definitely the cheapest out....

shakers with no other TA parts look funny on a bird to me, but I think I could live with that oddity if an SD was under it

[unruhjonny]

I too had understood that the shaker was closed off because of the noise level created under WOT;
I had also come to unerstand that the noise deal was under the blanket of emissions testing...
I was pretty certain that I read the air cleaner was a factor in certification at that time, and the for certification purposes the shaker was used...

I have been wrong before, and beofre I take my dirt-nap, I'm sure I'll be wrong a-pleanty-o-more times

[SD Formula]

Originally Posted by Michael Brand F/SA

Hello,

I'm looking for information on the hoods that came on the 455 4X Formula Firebirds for 1973. Did any of them come with the flat or trans am hoods or did they only come with the formula hood?

Thanks so much,

Michael

Michael, Here is some part number information I received years ago on Formula fiberglass hoods, I don't remember where I got it from, or if it is accurate. I also do not know if these numbers are stamped in the bottom of the hood or not. Hope this info. helps.
70-72 Formula non-ram air hood 480172 --- 70-72 Formula ram air hood 479677
73-75 Formula non-ram air hood 490660 --- 73-75 Formula ram air hood 490661
73-74 The 101, SD Formulas used the (73-76 Trans-Am) steel shaker hood 500154
Maybe others could chime in with additional information and clarity.

[firebirdbob70.5]

1970 Formula Hood Ram Air from the factory are the scoops back wall cut out completely or does it have seven evenly spaced holes per (HIGH PERFORMANCE PONTIAC MAGAZINE ) Feb 2004 issue page 69

[RAFormulas]

Originally Posted by firebirdbob70.5

1970 Formula Hood Ram Air from the factory are the scoops back wall cut out completely or does it have seven evenly spaced holes per (HIGH PERFORMANCE PONTIAC MAGAZINE ) Feb 2004 issue page 69

Ram air hoods and non-ram air hoods are identical except for the cut outs. The factory left a slight ridge when they cut out the ram air hoods. Many people make this smooth which is incorrect. There is no need to cut the 7 holes that you spoke of.

[Loffen]

Does anyone have a picture of a factory cut out ?

[The Boss]

Here you go...

[formula400]

70 formula hood is one year only. Looks the same but doesnt have the support riveted on like the others

[The Boss]

Originally Posted by formula400

70 formula hood is one year only. Looks the same but doesnt have the support riveted on like the others

The early ones are like this but some time before the new 71 models showed up the hoods with the straps started showing up. We've never had a big enough sample of original hood cars to narrow down a date.

[Loffen]

Originally Posted by The Boss

Here you go...

Great Thanks !!

So around 1/8" high edge maybe a little bit more ?

[The Boss]

Look at the inside of the scoop - it'll be real clear where the edge should be.

[Loffen]

I can see the edge man

I did just wonder if it is 2,3 or 4 mm high. (mm = millimeter ( 1/10 of 1 cm (cm = centimeter ( 1"= 2.54 cm or 25.4 mm ))))

[Brewster]

The Formula SD cars received the shakers due to that was the only set-up that had been approved by the feds. There wasn't enough time to submit any other options before production thus it was that or nutting.