#1  
Old 07-13-2021, 07:01 AM
LM93 LM93 is offline
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Question How strong can you make a t-top firebird?

Hey, we're having a discussion in the boost forum about how much power I can have in my t-top bird without twisting up the body on a road course. The car is going to spend most of the time on the road so a roll cage is just too impractical. But there is a racetrack nearby that does public track days, so If I take the car there and push the car to its limits it's going to need some help. I have the basics planned out: Re-welded every seam on the subframe, used Lab-14 products to reinforce the control arm mounting points, welded steel tubing to the rear LCA bracket, g-braces, subframe connectors, and a sway bar brace. Does anyone have some suggestions for more?

Aftermarket chassis look really slick but are really expensive for a street car so would one be worth it? Prevention is cheaper than cure, sure, and if the body bends and stays bent, I don't know how you would bend it back. They're just a lot of money.

Another thing about new chassis, all the ones I've found online are set up for front and rear coilovers. Which is good for a racecar, bu since I'm not going to be adjusting the suspension every week for a new racetrack I think regular springs will be fine. Are there any rear frame setups that improve over stock and use leaf springs or should I ask the body shop to fabricate some new frame rails with heavy gauge rectangle tubing?

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Old 07-14-2021, 10:49 AM
autobahn autobahn is offline
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I'm a little surprised that they will let you run a convert or T top without a full cage

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Old 07-14-2021, 11:19 AM
autobahn autobahn is offline
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I'm a little surprised that they will let you run a convert or T top without a full cage

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  #4  
Old 07-14-2021, 03:58 PM
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Look at Global West and F Body Pro touring products . Subframe connectors and the front firewall to upper A arm bolt braces will help(I think F body calls them G braces Herb Adams first made them. Autocrossed mine pretty hard then drag raced in the 10.90s and no issues. Good suspension bushings, stiffer front springs and good shocks will make a world to difference. And to ave a really fun time get some extra wheels and buy some used road race slicks!

Be aware the top on T top cars only has 3 spot welds each side. Repainting mine and repairing the crack just pulling it in and out of the paint shop it recracked. Pulled all the factory lead out to se the 3 spot welds and welded it solid.

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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #5  
Old 07-14-2021, 04:21 PM
LM93 LM93 is offline
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Quote:
Originally Posted by Skip Fix View Post
Be aware the top on T top cars only has 3 spot welds each side. Repainting mine and repairing the crack just pulling it in and out of the paint shop it recracked. Pulled all the factory lead out to se the 3 spot welds and welded it solid.
There's spot welds every three inches around the gasket channels on my car. Are you talking about somewhere else?

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Old 07-14-2021, 05:18 PM
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Sounds like he may be talking about the sail panel joint. I melted the lead filler from mine and welded it solid as well. Common spot for a crack to show up when you start twisting the body with power.

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Old 07-14-2021, 06:25 PM
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Yes sail panel joint right at the top/rear of the door window where the T top is.

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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #8  
Old 07-14-2021, 09:37 PM
RamblerRacer RamblerRacer is offline
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My $.02.

No way any track should be letting anybody run sub 11.00s without a 6-point bar or more.

Second is if you go to the track and want to install a 5 point harness >>> do not fix the shoulder straps to the floor below the rear of the seat.
A frontal crash will crush your spine good.
The must ne connected to a bar behind the seat back

JT

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Old 07-15-2021, 06:09 AM
LM93 LM93 is offline
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Quote:
Originally Posted by RamblerRacer View Post
My $.02.

No way any track should be letting anybody run sub 11.00s without a 6-point bar or more.

Second is if you go to the track and want to install a 5 point harness >>> do not fix the shoulder straps to the floor below the rear of the seat.
A frontal crash will crush your spine good.
The must ne connected to a bar behind the seat back

JT
The car isn't going to be winning any awards for weight savings, I'll be happy if I can get under 13s. If I weld 1/4" steel plates to the package tray, could I mount the shoulder straps from there?

I didn't know about the sail panel seam. I'll have to make sure it gets a 100% welded.

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Old 07-16-2021, 07:10 AM
LM93 LM93 is offline
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Has anyone had the chance to compare subframe connectors from Pro Touring F Body and Detroit Speed? Those two are my top choices.

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  #11  
Old 07-17-2021, 10:04 AM
'ol Pinion head 'ol Pinion head is offline
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Quote:
Originally Posted by LM93 View Post
Has anyone had the chance to compare subframe connectors from Pro Touring F Body and Detroit Speed? Those two are my top choices.
To get to the level of body stability that a t-top 2nd Gen needs for anyything above spirited driving, I'd go straight to a very experience chassis builder & have a custom 8 pt, most likely a 10 point, rollbar installed with chassis shop fabbed subframe connectors. For what you are trying to do, there's little reason to purchase bolt-on subs. Years ago on my less that 25k mile modded '80 Turbo T/A, I installed bolt-in Comp subs & Adams VSE alum body bushings along with VSE bars, shackles, front spring eye mods. After a few months I cracked the center roof skin. I then took my '80 to a local competition chassis shop & had them install weld in subframe connectors. These pieces of rectangular steel did not hang down & required slotting the rear footwells. In prep of taking the T/A to Glen's, I stripped out all of the extra acoustic insulation & all of the tar based floor insulation other than front floor pans near the cowl. Considering my '80 was used for street driving, Glen's shops installation of the subs did induce some creaking & groaning under hard cornering & acceleration into the interior of the T/A. That issue could have been lessened by channeling a piece of formed sheetmetal over the subs where they came through the rear foot wells. Glen had simply performed what was a standard fare install, like he had on many 2nd Gens that we're run at the strip.

Read in your parallel topic your thoughts on 3 point seat belt attachment for rear passengers. Once the Bird is prepared with a propperly installed 8 or 10 point bar, it is going to be very hard for a passenger to access the rear seat. The main hoop & the rear down bars are not the issue. The diagonal lateral supports coming off the main hoop, as well the crossbar behind the front seats will make it a lot of fun to access the rear seat. I've observed custom installed 10 point roll bars on 2nd & 3rd Gens where the crossbar between the main hoop uprights was removable. Am not sure if such an installation would pass a highly scrutinized NHRA tech.

Below is link to earlier topic where I responded concerning the damage & repairs I did to my Fisher roof '80 Turbo SE. The separation of the inner & outer panels of the roof was a major eye opener, wish I'd caught it earlier.

https://forums.maxperformanceinc.com...d.php?t=839113


Special ordered the '80 new ('79 400 4spd orders had all been allocated). The best thing I ever did was mothball the '80 in 1987 & focus on chasing, purchasing, & restoring earlier performance Pontiacs. Have processed a ton of 2nd Gen Bird parts cars over the years & ran across quite a few slightly pooched in roof panels, torn B pillar joints, and torn rear T-bar roof sheet metal on several other late 70's TransAms. None of them had the handling mods or the power on tap that I was putting down in the '80 coming off the corners. That stated, the straightline performance of my modded '80 turbo on the bottle PALES in comparison to what can be done quite affordably today.

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Last edited by 'ol Pinion head; 07-17-2021 at 10:14 AM.
  #12  
Old 07-17-2021, 07:53 PM
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My 78 has the Comp Engineering or Moroso subframe connectors . Front slides under last subframe bushing-Had Global make a wider one to capture it better. Hit the floor so had to section to bolt the rear under the front spring perch then weld it back. Kin of ugly. The 81 and the 79 Camaro IA have a different type I think Pro Toruing sold them before he made his own rectangular tuning-maybe Chris Alston round tubing. Bolts to the outside of the front subframe and also to the rear subframe right beside the front leaf spring perch. Hard to use a lift on those as it has to go on them vs a flat tubing or subframe.and jack stand placement a little different since they are over the reer subframe. Some of the Detraoit Speed you have to cut into the flooring and weld into it-more of a job than I wanted to do.

FWIW my 78 autocrossed with road race slicks for a number of years and has been drag racing since then in the high 10s and no more cracks on the top.

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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #13  
Old 07-17-2021, 10:50 PM
'ol Pinion head 'ol Pinion head is offline
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Skip, thought your '78 T/A was a solid roof. My memory may be failing me, remember seeing you making rounds @ Enos back in early NMCA days.

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Old 07-18-2021, 08:41 AM
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Nope Fisher T tops. Just not an SE with the gold striping to accent them. Now I wish it was a solid roof car!

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Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #15  
Old 07-18-2021, 11:07 PM
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I looked under the 78 today about to swap rear springs and with the old CE/Moroso's you can not get to the inside of the front spring eye bolt so it can not be tightened under load.

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Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #16  
Old 07-23-2021, 01:03 PM
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The Cars & Concepts t-tops have a sturdy brace tacked in from front to back of roof line.
Mine is ample along with welded subframe connectors. High 7's 1/8th with slicks. Perhaps more substantial than Fisher, etc.?
Pic of rusty brace on web:
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Old 07-25-2021, 10:55 AM
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Just too bad the C&C tops are the worst looking ones of the bunch..

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  #18  
Old 07-25-2021, 09:19 PM
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Here is a picture of the Moroso/CE as it goes in the subframe on my 78. The darned humidity even in a shop has done all that surface rust undercarrriage was shown with mirrors 30 years ago!
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Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
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