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Old 07-13-2011, 09:22 AM
ramairformula74 ramairformula74 is offline
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Default Core Support Bars question

I have a set of core support bars from a 1974. I know they are the same as 1975. The question is, are they the same for 1973 or are they shorter or longer? I've seen the repros in catalogs and they fit 73-75. I'm sure some will think this is a stupid question but a possible sale of my original GM bars is why I ask. The potential buyer thinks that 1973 are different. Any help would be great. Thanks in advance.

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Old 07-13-2011, 10:56 AM
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They are shorter than the '73s. 1973 has a large rubber bushing at the top that the bar bolts to.

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Old 07-14-2011, 12:49 AM
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How about the 76? Were they like the 75 or like the 78 & 79?
Thanks

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Old 07-14-2011, 07:00 AM
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The 76 cars that had these bars were like the 74-75 bars. Later cars did not have any bars at all.

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Old 07-14-2011, 12:08 PM
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Quote:
Originally Posted by superdutybob View Post
The 76 cars that had these bars were like the 74-75 bars. Later cars did not have any bars at all.
I thought 76 had no bars at all and 77-81 had the thiner flimsy bars.
I had 2 76 parts cars and neither had any evidence of a bar being screwed to the core support.

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Old 07-14-2011, 01:33 PM
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Quote:
Originally Posted by Rack776 View Post
I thought 76 had no bars at all and 77-81 had the thiner flimsy bars.
I had 2 76 parts cars and neither had any evidence of a bar being screwed to the core support.
That's what I said!

76 cars that had bars had them like the 74-75 bars. Later 76 cars got no bars at all, like you saw on your parts cars. After 76, all cars got the thin bars.

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Old 07-14-2011, 02:16 PM
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Quote:
Originally Posted by superdutybob View Post
That's what I said!

76 cars that had bars had them like the 74-75 bars. Later 76 cars got no bars at all, like you saw on your parts cars. After 76, all cars got the thin bars.
Aghhhh!, no need to shout!
I missed the "Late & Early" part of 1976 cars.

Thanks for the correction!

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Old 07-14-2011, 07:41 PM
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i have found several different bars over the years. in 73 there were 2 bars, both long but thinner bars on the formulas and firebirds. same for the 74-76 with bars. the Trans Am's had thicker bars with the formula's having thinner ones. even then i think the 75 was thinner than the 74?? it has been awhile since i looked at a set side by side. i know the 73-74 were thicker as the plastic air duct piece had a wider bracket to fit it.

just a guess, but i think the formula's ordered with the TA suspenion probably got the thicker bars??

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Old 07-19-2011, 12:17 PM
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71 Warbird, can you advise any more detail on the Thick vs Thin Bars for
73 and 74. My 73 has what i think are the originals, but would like to
confirm. Also my car does have the factory Trans-Am (Y99) suspension.

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Old 07-20-2011, 08:22 AM
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I fabbed a few sets of those bars from bars stock aluminum. I used the '74 bars as a pattern. I think i have a couple of sets if someone wants to buy for a trick look or paint them for stock appearance.
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Old 07-20-2011, 03:35 PM
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Quote:
Originally Posted by dadsformula View Post
71 Warbird, can you advise any more detail on the Thick vs Thin Bars for
73 and 74. My 73 has what i think are the originals, but would like to
confirm. Also my car does have the factory Trans-Am (Y99) suspension.
i hope someone else jumps in here. i'm not at home to take any pictures of the ones i have, and memory being what it is can't give exact sizes.

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Old 07-21-2011, 07:18 AM
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I believe that the 73-74 bars are the same thickness, with the 73 bars being a tad longer to reach out to the forward bushing. The 75 bars were thinned down versions of the 74 bars.

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Old 07-21-2011, 09:35 AM
ramairformula74 ramairformula74 is offline
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I see that the bars are reproduced and say they'll fit 73 to 75. Do you think they were made with extra holes to fit all three years?

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Old 07-21-2011, 01:08 PM
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73 is the only year for the longer Bars with the big hole for the Top bushing
mount. Not an easy part to find if missing. Ask me how i know. I have
not heard that different Bars were used based on engine size.

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Old 07-21-2011, 09:07 PM
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My findings...
1973 Formula (Mar), .316" thick
1974 Formula (Oct), .253" thick
1974 Formula (Nov), .310" thick (not pictured)
1974 Formula (Feb), .195" thick
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Old 07-22-2011, 05:07 PM
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Quote:
Originally Posted by Held for Ransom View Post
My findings...
1973 Formula (Mar), .316" thick
1974 Formula (Oct), .253" thick
1974 Formula (Nov), .310" thick (not pictured)
1974 Formula (Feb), .195" thick
On a lark, I measured mine for a '73 T/A and got .316 or 5/16th too.

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Old 07-22-2011, 07:31 PM
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According to the assembly manuals,
1973 PNs were 489182 and 489183.
1974 PNs were 493457 and 493358. And was changed to 496803 and 496358 on 10/12/73. Who knows when stock was depleted (or pulled) and new bars started to be used.

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Old 07-27-2011, 12:13 PM
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The thicker bars might have been part of the 73 crash standards they had to meet,
once the 75-75 bumper was used they might have used a thinner bars to save some weight/cost.

The 74-75 front "battering ram" ....I mean bumper is stronger than the 73 set up so the fender bars were less important in a crash and the extra weight went into the bumper bar.

Just my opinion. Good catch on the different thickness bars.

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Old 07-28-2011, 12:25 PM
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74/75 "Battering Ram" (nice description) i have no doupt is stronger, because
it was a full redesign. The 73 front end was revised to meet the 5mph requirement
but it sure is heavy. I will say one thing, the Bars beings attached to the upper
front bushings on 73's did make the front of the Car very riggid. This is a good
thing, but the 74 redesign (like it or not) is a much lighter design in addition
to being stronger.

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