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Old 03-28-2020, 10:43 PM
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Default Subframe connectors for T-Top strengthening.

My only experience with subframe connectors is a one time restoration of a old retired 1970 Challenger Pro Stock car left in the hot salty FL. air for 40 years. We spent 2 years restoring it to run the Super Gas class and made our own weld in connectors for going in a straight line. My thoughts are for extra strength lost in the cutting of two big holes in the top of a 2nd Gen Bird. We all know what the TA was built for and even though many of them and some very famous have made it to the drag strips around the country they are road race course cars. I have no clue as to how the car would handle with a good quality of bolt on connectors say the PTFB or CP connectors. I'm really looking to add back the lost structure from cutting the top out of these cars, I mean surely they have to lose some body/chassis strength. On the other hand I still want the car to handle but don't want to modify the whole suspension because I've added the connectors. The reason I'm wanting to go with bolt in is because everything I do to this TA I want to be removable to be put back to stock trim easily. Anyone been the subframe connector rout and if so why and what was the outcome good or bad thanks.

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Old 03-28-2020, 11:01 PM
694.1 694.1 is offline
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Bolted 'em on an almost new '89 GTA with T tops. I can highly recommend them.

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Old 03-28-2020, 11:20 PM
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Originally Posted by 694.1 View Post
Bolted 'em on an almost new '89 GTA with T tops. I can highly recommend them.
Thank you 694 and what brand did you end up going with?

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Old 03-29-2020, 12:38 AM
Aus78Formula Aus78Formula is offline
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Absolutely. A T-top car flexes like jelly, even hardtops crack at the pillar corner. Add them to protect your paint and bodywork, if not for the improved ride and handling. PTFB here, bolted on and forgotten about. If you jack up one corner of the car an inch, the wheel at the other end will be off the ground the same height. There are no mods that you have to do in order to use these, but obviously new body mounts can assist, poly is better and if welding then you need solid. But I don't recommend welding and no need. I've already had mine on and off the car several times for different reasons, made impossible if welded.

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Old 03-29-2020, 01:20 AM
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If it's a factory T-top car, they added extra reinforcing to the body to compensate for the added flex from cutting the roof, but it was a crutch designed to get the car past the warranty period.

If those are aftermarket, the body has REALLY been compromised, but subframe connectors will help correct it.

Don't even waste your time with bolt-on connectors, get the ones that require welding.

The style I had on my '79 T/A were box shaped, from Comp. Eng. I believe. The forward ends had a U-shaped "sleeve" that slid over and around the car's front subframe and the rearward ends curved upwards to meet the floor pan just in front of and inside the front leaf spring mount. Because of their large and boxed construction they we kind of "low" which may create clearance problems, but given I had Cal-Trac traction bars and 3-1/2" header collectors it wasn't a major concern for me on ground clearance issues.

I would also advise prior to welding in any subframe connectors to replace the front subframe body mounts, as I'm sure they're worn out, and they're rubber. You'll want to replace them with solid mounts. That combined with the subframe connectors will stiffen the body up enough that you'll think you need a kidney belt to drive the car over even moderate bumps LOL. Add a roll bar and forget about it, body twist will be a long gone memory.

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Old 03-29-2020, 01:26 AM
Aus78Formula Aus78Formula is offline
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No, it's not necessary to go all out unless you race the car. Definitely not a waste of time to have bolt ons, far an improvement over nothing. If you have a harsh ride the connectors are only helping realise your suspension setup, and not creating it.


Last edited by Aus78Formula; 03-29-2020 at 01:34 AM.
  #7  
Old 03-29-2020, 11:03 AM
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‘78 with C&C tops, even tho they added a reinforcing plate the tops still rattled etc. Added CE bolt in connectors & it stopped a lot of squeaks & rattles!

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Old 03-29-2020, 11:35 AM
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My 78 had little cracks at the back of the door-window-C pillar. Thin coat of filler. Just pulling it in and out of the body shop started cracking. Pulled out all the factory lead there, There were only 3 spot welds holding the back of the top to the C pillar! Solid weld and no cracks even after alot of autocrossing and low 11 high 10 drag strip passes. I did add the old Moroso subframe connectors. They hang down lower than most of the options now.

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Old 03-29-2020, 12:00 PM
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Quote:
Originally Posted by Brian Baker View Post
If it's a factory T-top car, they added extra reinforcing to the body to compensate for the added flex from cutting the roof, but it was a crutch designed to get the car past the warranty period.

If those are aftermarket, the body has REALLY been compromised, but subframe connectors will help correct it.

Don't even waste your time with bolt-on connectors, get the ones that require welding.

The style I had on my '79 T/A were box shaped, from Comp. Eng. I believe. The forward ends had a U-shaped "sleeve" that slid over and around the car's front subframe and the rearward ends curved upwards to meet the floor pan just in front of and inside the front leaf spring mount. Because of their large and boxed construction they we kind of "low" which may create clearance problems, but given I had Cal-Trac traction bars and 3-1/2" header collectors it wasn't a major concern for me on ground clearance issues.

I would also advise prior to welding in any subframe connectors to replace the front subframe body mounts, as I'm sure they're worn out, and they're rubber. You'll want to replace them with solid mounts. That combined with the subframe connectors will stiffen the body up enough that you'll think you need a kidney belt to drive the car over even moderate bumps LOL. Add a roll bar and forget about it, body twist will be a long gone memory.
Mine are the Hurst Hatches my paperwork is telling me my car wasn't dropped shipped from the factory to Hurst. I also don't have a bill of sale from the dealership showing they sent the car over to Hurst for the conversion for a customer. So was it done by a pro or in a garage I'll never know, but what I do know is all the body panels and doors line up and close and open nicely. I'm not planning any kind of racing just want to add some of the integrity back to the car for a cruiser so I'm going to stay with the bolt in connectors. Thanks for the input Brian

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Old 03-29-2020, 12:06 PM
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Quote:
Originally Posted by highway star View Post
‘78 with C&C tops, even tho they added a reinforcing plate the tops still rattled etc. Added CE bolt in connectors & it stopped a lot of squeaks & rattles!
What should I look for as far as plating is it in the roof or chassis? I do see yours are the C&C tops so Hurst may have a different reinforcement. Isn't the C&C tops the ones that meet in the middle without showing a T-bar until the tops are removed? Thanks

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Old 03-29-2020, 12:12 PM
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You are correct on the look of the c n c tops. They are very similar in styling and construction to 3 gen t tops. I have them in my car and the sub-structure is pretty substantial. I dont race, just cruise around moderately and have not noticed any 'body movement'. Overall car feels solid. One day if I get my other project done and have a couple of spare dollars lying around I may put them on. But I dont feel that it is a necessity at this point. The fisher tops were designed and built into the car from the factory so I would believe they offer a bit more strength than the hurst tops.

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Old 03-29-2020, 01:51 PM
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Quote:
Originally Posted by Gen2guy View Post
What should I look for as far as plating is it in the roof or chassis? I do see yours are the C&C tops so Hurst may have a different reinforcement. Isn't the C&C tops the ones that meet in the middle without showing a T-bar until the tops are removed? Thanks
A plate at the front T section & a plate at the rear T section. I first noticed them when I redid the headliner.

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Old 03-29-2020, 06:29 PM
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https://www.summitracing.com/parts/c...rd?prefilter=1


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Old 03-29-2020, 07:44 PM
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Installed bolt-in Comp Engineering sub connectors on my modded '80 Turbo SE early in '83. That was right before installed Herb's bars, alum subframe bushings, rear mounted battery, & koni shocks. Ended up tearing the outer skin of the Fisher Top t-bar within a year. This was aprox 6" from the back of the t-bar. V-eed out the crack, MIG welded up the crack, then refinished the roof. Result it cracked again within 6 months. This was on a under 30k mile car I ordered new.

Ended up stripping the interior out of the car, including all the addition acoustic insulation & had a local chassis shop install custom weld-in sub frame connectors. Removed the complete headliner, t-top weatherstrips, & upon examination, several spotwelds between the inner & outer structure of the roof had torn & allowed the top panel to slightly twist, then tear. Ended up having a new GM roof skin put on the car. Also replaced one of the black framed Fisher tops as the thin alum on the edge where the rear plastic guide glued in, the alum frame was torn in that area. The whole experience majorly irked me, & in late '87 I mothballed the '80 with little over 45k miles. Very solid car w a butt load of perfect interior parts & NOS. It will be the last 2nd Gen T/A I repaint & reassemble. Whether when that days comes, I add PTFB subs & a minimum of a 6 point chrome moly roll bar, or take it totally back to stock, is still up in the air, have bigger fish to fry with other ongoing projects.

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Old 03-29-2020, 08:40 PM
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Quote:
Originally Posted by 'ol Pinion head View Post
Installed bolt-in Comp Engineering sub connectors on my modded '80 Turbo SE early in '83. That was right before installed Herb's bars, alum subframe bushings, rear mounted battery, & koni shocks. Ended up tearing the outer skin of the Fisher Top t-bar within a year. This was aprox 6" from the back of the t-bar. V-eed out the crack, MIG welded up the crack, then refinished the roof. Result it cracked again within 6 months. This was on a under 30k mile car I ordered new.

Ended up stripping the interior out of the car, including all the addition acoustic insulation & had a local chassis shop install custom weld-in sub frame connectors. Removed the complete headliner, t-top weatherstrips, & upon examination, several spotwelds between the inner & outer structure of the roof had torn & allowed the top panel to slightly twist, then tear. Ended up having a new GM roof skin put on the car. Also replaced one of the black framed Fisher tops as the thin alum on the edge where the rear plastic guide glued in, the alum frame was torn in that area. The whole experience majorly irked me, & in late '87 I mothballed the '80 with little over 45k miles. Very solid car w a butt load of perfect interior parts & NOS. It will be the last 2nd Gen T/A I repaint & reassemble. Whether when that days comes, I add PTFB subs & a minimum of a 6 point chrome moly roll bar, or take it totally back to stock, is still up in the air, have bigger fish to fry with other ongoing projects.
Now that is quite a story and some good info thanks Pinion

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Old 03-29-2020, 09:36 PM
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Quote:
Originally Posted by highway star View Post
A plate at the front T section & a plate at the rear T section. I first noticed them when I redid the headliner.
So of course I go out to look at my Hurst roof and no such braces now I'm kinda of worried maybe it was done in a garage lol. So I got on the inner-web and found a article at firebirdtransamparts.com called "Hurst Hacked" How Hurst Hatches fit and work written by a former installer. The only braces they used were a U shaped flat steel piece of metal a 1/4" thick sandwiched in between the 2 layers of the roof metal and mine has that. It also mention how they really just hacked into the roofs and there were a couple of Vee shaped cuts they made at the back of the hatches mine has those cuts also. I also found out mine is the 1st Hurst Hatch run, a great article.

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Old 03-30-2020, 12:09 AM
Aus78Formula Aus78Formula is offline
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Even more a perfect time to add some SFC's. I have seen T-top inner roof bracing for sale on ebay etc, from time to time, most likely from wrecked cars, not sure if something that can be added easily, or how they did it back then. It possibly says in the Pontiac Roof Hatch manual, grab one if you haven't already.

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Old 03-30-2020, 12:34 AM
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As my '79 W72 car's body shell will eventually make its way on the rotiseree, am going to run either an epoxy primer or a P0R-15 like product in the Fisher top cavity while the shell is fully braced & upside down. Next, my plan is to shoot a low expansion rate foam product in the cavity to fill it with a close cell foam which will add considerable strength. First witnessed a body shop in Dallas using an expanding foam product for this exact procedure on a Fisher top T/A in the late 90's.

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Old 03-30-2020, 12:42 AM
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POR-15 is only suitable if already rusted and even then for mediocre results.

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Old 03-30-2020, 12:47 AM
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POR-15 is only suitable if already rusted and even then for mediocre results.
Understand the limitations of POR-15. Am not a big fan it, but it works well when ran down in clean gutted doors. Some type of product will need to go on the inside of the partiallly bare metal in the roof cavity before the foam product is applied.

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