[RamAirBirds]

I should have done this in the first place. I dug out my Pontiac PMI manual with the Engineering drawings for the assembly line. Luckily i have an original that you can actually read unlike the reprints.
As you can see the engineers changed the springs from small #3848272 to LARGE #3907626 on 06/26/70.
So assuming they most likely "used up" some remaining springs they had wouldn't it be a safe bet to say the springs went LARGE in mid to end of JULY?
For sure they most likely used up old small springs but these were on every model Camaro and Firebird so stock depletion would have happened quickly.
It would seem to make sense that many of the RAIV cars then would have the LARGE spring since they were built/shipped July and August?

[RamAirBirds]

From the NASTYZ28 Forums.
I know this is a lot of information but just trying to make sure what a 07D Trans Am would get.

[unruhjonny]

Ok, so I looked into this.

The attached picture is of my car's original hinges and one extra).

I was able to clean them up, and find the paint marks, as well as the 524 & 525 stampings;
Finding the paint markings was a genuine surprise for me...

My car was built the first week of June, and the coils on these hinges (middle and right) are the small (28 count) coils.

The extra "1970" hinge in my collection is stamped with the number;
It comes from a pair that was repainted black, but with a little cleaning I was able to find trace blue paint;
This hinge has the larger 25 coil springs.

[unruhjonny]

wait, do early Firebirds and Camaros use the same hinge?

If so, this is new to me.

I had a couple pairs of camaro hinges in the past, and seem to recall they were different (the camaro ones would note work on a Firebird).

The assembly notes in post #21 shows a full part number for a 1970 Firebird, and that hinge assembly number is the same as one of the numbers on the 1970 Camaro service bulletin in post #22.

Since I had understood that all 70-81 Camaro hoods interchange, I had assumed that there was never interchange between Camaros and Firebird hinges during the second generation.

[RLEngland]

Good information. Leave it to the Camaro guys to have that service bulletin. I wish I had clearer drawings like that. You should reproduce it. Id' buy a better copy. Now if we only figure out the 524/525 vs. the XXXXXX stamping.

[unruhjonny]

I decided to dig a bit further into this just now;
Post #21 (link to follow) seems to suggest that for at least 1970 the hinges were the same between the Camaro and Firbird;
Post #30 seems to offer a clear suggestion as to why some hinges have the "XXXX" stamping":

THE 3966881 & 3966882 1ST DESIGN HOOD HINDGES ON 1970 CAMAROS WERE NOT STAMPED WITH A GM PART NUMBER AND
WERE USED IN PRODUCTION THRU THE 3RD WEEK OF FEBRUARY 1970

THE 1ST DESIGN HINDGE WAS WEAK AND HAD BINDING OR FLEXING PROBLEMS AND WERE REPLACED WITH IMPROVED SPRINGS
DURING PRODUCTION ON MONDAY FEBRUARY 23 1970 AT VAN NUYS AND NORWOOD ASSEBMLY PLANTS

THE FIRST BATCH OF IMPROVED REPLACEMENT SPRINGS WERE STAMPED WITH THE XXXXXXXX AND SOLD UNDER
GM PART NUMBER 3990431 & 3990432

MOST 2ND DESIGN HOOD HINDGES ARE JUST STAMPED WITH THE XXXXXXXX WITHOUT ANY OTHER NUMBERS STAMPED OVER THE X'S

SOMETIME AROUND APRIL OR MAY 1970 THE 9790524 AND 9790525 HOOD HINDGES REPLACED THE XXXXXXXX STAMPED HINDGES

IN REVIEW GM USED THREE DIFFERENT PART NUMBERS AND HOOD HINDGE ASSEMBLIES DURING ASSEMBLY LINE PRODUCTION
FOR THE 1970 CAMARO

LINK to NastyZ28.com hinge thread

I may reach out for clarification, but if anyone has a larger scan of that service bulletin, could they message me, or offer a link to anyone reading this(?).

[RamAirBirds]

Not to add confusion. Well, YES, to add confusion here is a set of hinges I had restored. Just the one side but you can clearly see the Part #479738 in what i would see as stamped OVER the XXXXXX Marking.
What does everyone think about that?

[RamAirBirds]

https://nastyz28.com/threads/correct....152274/page-5

[Formulabruce]

I have owned a 1970 " SS" 396, 05C car big springs, and a 1970 RS ( 307 2bbl PG) which was 06A. Big springs.
Based on sub assembly and the need for speed, I always assumed hinges were same across F body .
Spring changes, if both work, could easily be explained by PCPO. at sub assembly.

[unruhjonny]

PCPO?
Were both Norwood cars?
I ask, because if you have two Norwood cars with 524/525-big spring hinges with the same build date, or just before my car (06A), then that makes me curious about the smaller springs on my hinges;
It reads like the smaller springs were earlier, and phased out during the 524/525 run.
Maybe it was just chance that hinges with the smaller springs were on my car(?);
The assemblers were grabbing from the bottom of the bin when my car came down the line(?) - LOL.

This has been an an interesting discussion, I have learned some new stuff through this.

[Ramairnacho]

My passenger side is stamped xxxxx but my drivers side is blank and mine are original to my car. Why is one blank? I'll take pics of springs tomorrow. This is interesting.

[Formulabruce]

Originally Posted by unruhjonny

PCPO?
Were both Norwood cars?
I ask, because if you have two Norwood cars with 524/525-big spring hinges with the same build date, or just before my car (06A), then that makes me curious about the smaller springs on my hinges;
It reads like the smaller springs were earlier, and phased out during the 524/525 run.
Maybe it was just chance that hinges with the smaller springs were on my car(?);
The assemblers were grabbing from the bottom of the bin when my car came down the line(?) - LOL.

This has been an an interesting discussion, I have learned some new stuff through this.

PCPO. is a parts change pick order.
Both my 1970 Camaros were Norwood cars.
FIFO.. If you ever worked around food or items with an expiration date, FIFO. is mandatory. FIFO = First in, First out. So, " grabbing from the bottom of the bin" didn't happen, BUT Its easy to assume that a crate of hinge springs got pushed back as more came in, and
was grabbed as a PCPO came in unless it had a engineering manufacturing directive on top.
Picture a room the size of a huge Wallmart with just " parts" for sub assemblies, and hardware.
Now picture a room the size of a football field with " Finished" sub assemblies. Few folks on fork trucks filling PCPO' S, replenishments and a couple in charge of getting designated parts to a drive line sub assembly ( let's use an M-13) then another grabbing the correct 12 bolt ( paper tag on brake drum) and getting it staged for same car.
Not always was logic used as GM wanted" faster, faster"
And workers didn't want to move at the speed of 1 F body every 45 seconds out the door..
Deviations in what we see as Normal are more common than people think.
Like 2 different brands of screws holding the nose together on the same car...

[johnta1]

Back to top!

[F Body Freak]

Thank you, sir


Rod

[F Body Freak]

Originally Posted by RamAirBirds

Would it be correct that the 70 Trans Am used the smaller springs on the Hood Hinge? Same as the earlier Firebirds and GTO's? Then switched to the larger Diameter Spring in 1971?
1970 Parts Book calls for #3848272
1971-75 calls for #3907626
I have a set of Original 1970 ONLY Hinges here that have the larger Diameter Spring. Wondering if they switched to LARGE spring at some point later in the 70 model year due to the "Hinge Issues" they were having in 1970.
Also as we know the 70 ONLY hinge has the small welded on reinforcement piece due to the problems they were having. Question: Was this change made DURING the model year or was the "problem" discovered and changed BEFORE Production Started?
Any Thoughts from the 70 Trans Am experts on this Forum are appreciated.
RA

Originally Posted by RLEngland

I think the correct part number for 70 hood hinge springs is 546325. 69-70 546325 have 29 coils, 1 7/16 (1.34" - 1.43") outside diameter, 1/4 inch rod size, and measure 9 1/2 inches.

I compared these measurements to a couple sets of 70 only hinge springs and they were the same.

Ames sells a set that is very close in measure with 30 coils (If I'm counting them correctly).

I think 3848272 is 1967-1969 camaro hinges 28 Coils 9 3/8" long.

In reference to these measurements, the hinges on my 70 Formula are only 7 inches long. 26 springs, about an inch & a quarter around.
The Camaro springs I have are 7 & 3/4 long. 25 springs, & about an inch & a half around. With no numbers on them. I checked 3 of them & found no numbers on any of them. One of them has the blue paint smear tho...
The plot thickens, I guess

[F Body Freak]

In this thread someone said thier hinge had either the 479737 or 479738 number on their hinge with XXXXXX over top of it, & 2 guys on the Nasty Z28 thread had the 737 & 738 numbers on their hinges, so I guess I'm the 4th person to have these numbered hinges on either a 70 Bird or Camaro, so who knows. 🤷
I've only owned my Formula for a year & a half, but as I've dug into it I've discovered it to be very original. Like I said in the other thread, I think. It has a 70 Formula hood without the bracing that they put on them to try & fix the warping & bow issues they were having.

[johnta1]

In the Z28 thread they said the hinges were 3990431 & 3990432, which Pontiac didn't use that range of part #'s - 3990 (I don't think anyway)

[F Body Freak]

Well the early Camaro ones were 3966881 & 3966882, but not stamped it says. 🤷
Then they went to the 524s & 525s.
From what I understand the 3990431 & 3990432s were the ones stamped with XXXXXX. So some different, & some the same. The guy on Nasty with the 737 & 738s said his was an 1100 mile car, & he had the blue paint smears, which mine dont.
Probably never figure it out for certain.
I just know that with what I've learned, I have concerns for my original unbraced hood, and with the smaller hinges.
I was careful with it previously, I've never been one to slam the hood on any vehicle, but now, EVEN MORE SO


Rod

[johnta1]

The blue paint smears is for the braced hinge.
Quick ID for workers to see it was the corrected hinge.
(probably welded that piece on stock hinges then swiped paint on it until they got more corrected hinges in)



With the new body style Bird there were a LOT of stuff having to be reworked I imagine.

Is your car like a 01C or 01D?

[TXSTARFIRE]

My 7-73 MPC shows 70-74 Firebird hinges as 3990431 and 432. Also in post #3 and #4 spring P/N 546325 is mentioned. My MPC shows this spring used on 69 Firebird with 400 4 B.C. only. This # was NLA 4-75. Anyone know why this spring would be different?