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#1061587 - 04/19/19 10:33 PM Radiator Support To Firewall Brace  
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Frazier85 Offline
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Does anyone know where to find or who makes the long rod braces that run from the radiator support to the firewall for a 1985 SS? I have searched and searched but only can find the radiator support to fender braces which I already have and I have checked all of the local junk yards in my area with no luck. Any help on this would be much appreciated and thank you.

Last edited by Frazier85; 04/19/19 10:34 PM.

JAMES NSDQ
#1061588 - 04/19/19 10:46 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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I've never seen them unless you are referring to the Grand Prix fender braces.
Sounds like something you can fab pretty easily.


86 MCSS Notchback coupe, LS3, 4L65E, QP 9", Eaton Truetrac, 4 wheel disc, column shift, Dakota Digital, silver with maroon bench interior

#1061589 - 04/19/19 10:58 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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MattsMonte Online content
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The 73 monte carlo had those braces. The hood was very long.


http://www.dailyturismo.com/2016/07/1973-chevrolet-monte-carlo-s.html

the grand prix from our generation has a curved brace that works in ours

https://gbodyforum.com/threads/1981-grand-prix.56462/#lg=post-476978&slide=1


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1988 MCSS T-Tops. Frame off restoration, 330HP 350 crate engine, 700R4 transmission.
#1061591 - 04/19/19 11:00 PM Re: Radiator Support To Firewall Brace [Re: upflying]  
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No not those I already have those that run from the fender to the radiator core support. These run from the radiator core support on the outer edge by the fender across the top of engine and mount to the middle of the firewall. I saw them on a GN in a pic and found an article about them but no luck actually finding them to buy. I would make but currently can’t due to location.


JAMES NSDQ
#1061592 - 04/19/19 11:06 PM Re: Radiator Support To Firewall Brace [Re: MattsMonte]  
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Yes those would work as well. These are the ones I saw. I either way they seem to be a unicorn item to find.

https://buickturboregal.com/underhood-upper-support-braces/


JAMES NSDQ
#1061595 - 04/19/19 11:52 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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My guess is it is an adaptation of a second gen brace.


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1988 MCSS T-Tops. Frame off restoration, 330HP 350 crate engine, 700R4 transmission.
#1061596 - 04/20/19 12:05 AM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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Sounds like 78-80 Monte braces.


Jeff J
I believe.....guns don't kill people.....husbands that come home early do! Larry The Cable Guy
#1061597 - 04/20/19 12:16 AM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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78-79 on some G-bodies.
Pic of them here. Scroll down to the engine pic.
http://builttodrive.com/1979-monte-carlo-project/

GM used two different wall thickness of 3/4" OD tube for underhood braces, a .042" and a thicker .060".
3/4" EMT is .925" OD with a .060" wall.
1/2" EMT is .700" with a .045" wall.
EMT can be had anywhere selling electrical.
EMT would need to have the plating removed to hold paint well.
Bob

#1061599 - 04/20/19 01:31 AM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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Sc and c made some. Not sure if they still do.


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#1061600 - 04/20/19 01:42 AM Re: Radiator Support To Firewall Brace [Re: mmc427ss]  
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Thank you for the info. That is a big help. I will be looking into purchasing it very shortly.


JAMES NSDQ
#1061601 - 04/20/19 01:43 AM Re: Radiator Support To Firewall Brace [Re: 345HP87SSAC]  
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Thank you. I will look and see.


JAMES NSDQ
#1061602 - 04/20/19 01:44 AM Re: Radiator Support To Firewall Brace [Re: speeddemon]  
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Yeah I thought the old ones had them on some models but never saw it on our generation until I saw a GN with them.


JAMES NSDQ
#1061603 - 04/20/19 01:46 AM Re: Radiator Support To Firewall Brace [Re: MattsMonte]  
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Maybe or custom. Just something I want to do to keep everything nice and tight.


JAMES NSDQ
#1061617 - 04/21/19 03:34 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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Nice and tight is good


84ss current restoration
86 ss gone
85 ss new
85 z28 tpi
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#1061659 - 04/25/19 01:14 AM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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MAP Offline
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Hi Folks,

With the hood open, it seems obvious that braces of that kind would increase stiffness in a way that would keep the fenders squarer to the firewall. But with the hood closed, I can't see how they would make much difference, since the hood itself makes an outstanding brace, even allowing that the rubber perimeter snubbers permit some relative motion. My guess is that the factory added the braces to try to improve crashworthiness, because in a front-end collision, the hood folds almost immediately into an inverted V. The fenders tend fold at that location too, which is why those braces could be useful to increase initial vehicle deceleration. This video shows what I mean: https://www.youtube.com/watch?v=kuHQcq38E1c

If you watch the video frame by frame, initial vehicle deceleration upon impact is very low, but increases abruptly once the front wheels and engine slam into the firewall. Since peak acceleration is closely correlated with bodily injury, if they can smooth the deceleration profile by increasing initial deceleration, and those braces (allegedly) help to do that, then they can increase occupant survivability. But even the factory wasn't consistent, since some A/G body cars had them, and some didn't. After all, this was the era BC (Before Computers.) But I know that's not why we're reading here...

Really, the front end of the car is an amazingly loose, sloppy bowl of jelly as it responds to typical suspension motions. I believe those braces do very little to help in that regard. Today such looseness would never be tolerated, but then again, back in the day to keep people alive in crashes without airbags, you needed the front end to be a big, loose bowl of jelly.

Bottom line: I return to my belief that the hood accomplishes all the useful shear-mode rigidifying that one might desire.

Best,
MAP

Last edited by MAP; 04/25/19 03:35 AM.
#1061681 - 04/27/19 02:21 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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Very interesting video MAP. The 78 Monte in the video should have had the factory braces that we are discussing and it would appear that they didn't do much. I have had a 78 and I can say that the braces that the OP is asking about were very light weight, while they may stiffen the radiator support up a little, I feel they would do nothing in a crash like in the video.


1983 Monte Carlo SS Turnkey ZZ4/700R4, Dakota Digital Instrument Cluster, 77k mile car. Many more mods to come soon.
#1061684 - 04/27/19 07:38 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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MAP Offline
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Hi ss4ever,

I can definitely see that - who knows, maybe some GM engineers got similar results and came to the same conclusion, deleting them from most of the A/G bodies built thereafter. (One disclaimer: that video was surprisingly amateurish - for example, no high-speed frame rate. Let's hope that GM did internal research that was more rigorous than that.)

But aside from the question of those braces, there's no question at all that the front end could benefit from lots of stiffening. The only trouble is that in a front-end crash, stiffening usually means higher deceleration, and higher deceleration means higher bodily injury. Again - we're at a big disadvantage without airbags. But the deceleration profile seen in that crash video is laughably far from constant, so I would focus on stiffening in roughly the forward half of the engine compartment. I don't think that's particularly hard, but it would take surgery that's more invasive than just a pair of tubes connecting the firewall with the fenders.

Best,
MAP

Last edited by MAP; 04/27/19 07:40 PM.
#1061707 - 05/01/19 04:39 AM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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Supposedly GM deleted many of the G body bracing in the 80's to cut costs and reduce weight for meeting MPG requirements. Also each GM division at the time had their own design teams that came up with their own solutions to the weak points in the G platform. Such as the Monte front brace vs the GP front brace and even Buick's bizarre body bushing deletion. This is why each make of G bodies have their unique quirks.

Last edited by Buick Runner; 05/01/19 04:41 AM.

SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes, and Jmod.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1061761 - 05/06/19 09:30 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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MAP Offline
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Thanks Buick - that matches my recollection too. Interesting in the cutting cost versus cutting weight matter, that cutting cost took priority nearly 100% of the time. No surprise in that regard. Best - MAP

#1061823 - 05/10/19 12:06 AM Re: Radiator Support To Firewall Brace [Re: MAP]  
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The braces are for stiffening the rad support to fender (think improved connections) and subsequently improving NVH characteristics. They have nothing to do with crashworthiness at all. These vehicles did not even have a shotgun structure and they perform remarkably well. This is due to the frame - it's designed to absorb the majority of the energy in high speed crash events.


Mr. Engineer
#1061861 - 05/11/19 11:15 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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MAP Offline
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Greetings Mr. Engineer,

Interesting - being a senior engineer myself, how do you make these assertions? Please share your insights.

Best,
MAP

Last edited by MAP; 05/12/19 12:02 AM.
#1061864 - 05/12/19 06:03 AM Re: Radiator Support To Firewall Brace [Re: MAP]  
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Originally Posted by MAP
Thanks Buick - that matches my recollection too. Interesting in the cutting cost versus cutting weight matter, that cutting cost took priority nearly 100% of the time. No surprise in that regard. Best - MAP


There is a term for this called de-counting, basically manufactures will eliminate product features over the production span to adjust the profit margin. There is a lot of complex math that goes into these financial decisions, and production costs can easily and rapidly cut down profit margins. In business, reduced costs are considered cash inflows and worthwhile investments if the NPV is high enough.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes, and Jmod.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1061872 - 05/12/19 02:51 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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MAP - Assertions? Like in evidence, data? Look at the connections of the fender to the rad support, hinge pillar, and rad support to frame on a G body. Anything you can do to improve joint stiffness will increase frequency response. (Body mount stiffness, frame design are factors as well - You have to balance what you can work with). Take a look at new cars today, a large majority have some type of K-brace or tower to tower brace under the hood to improve NVH target characteristics.

As for frame design, it is the single most important factor for body on frame vehicles in energy management. Section properties, gauge, material are all driven by how much energy you must absorb for the multiple impact conditions.


Mr. Engineer
#1061883 - 05/12/19 10:33 PM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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MAP Offline
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I was hoping for a deeper discussion, but that's OK. Yes, most of the strain energy in a frontal crash in an A/G body undoubtedly resides in the frame, but the deceleration profile of the vehicle is strongly influenced by how the frame rails (think Euler column buckling criterion) bend and deform under impact. Sections of those long, spindly, thin-walled frame rails are fundamentally unstable under axial compression. Here, the various stiffnesses seen in the coupled structure ancillary to the frame can exert a significant influence on the strain-energy-rate profile of the frame front end as the car comes to a stop in roughly 60-100ms at about 30mph initial speed against a rigid barrier.

By having the hood and fenders fold-up almost immediately as the NHTSA videos show, we encourage frame bending under the #2 bushing location. By retarding or limiting fender folding a little by using a tube, we shift the center of the deceleration profile to occur a little earlier. This should help reduce peak deceleration.

The deceleration profile, more than the strain energy absorbed per se, correlates strongly with bodily injury.

Anyway, given that the factory seemed to use those braces haphazardly, it's easy to deduce that whatever function they ostensibly served, was of dubious or marginal value. As for NVH and specifically shear stiffness, I think the hood does a much better job than those braces, and especially given that the factory anchored the tubes to flexible members.

Buick - thanks for the further explanation. But this isn't just straightforward math, because at some point in the process, someone has to make an equivalency between the value of saved cost and weight, versus the cost of lost something else: presumably NVH and crashworthiness.

Best,
MAP


Last edited by MAP; 05/13/19 12:05 AM.
#1061886 - 05/13/19 03:33 AM Re: Radiator Support To Firewall Brace [Re: Frazier85]  
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Hi Map, it really depends on the type of business ethics GM used at the time, both the parent company as well as within each division. Managers often must weigh the interests of the stock holders which are generally their primary concern, thd managers' own interests ( the agenecy problem), as well as the interests of other stake holders such as consumers, employees, suppliers, government, etc.

Anytime management decides to take on an investment, such as a new product, product improvements, cost reduction, etc, they perform a net profit value analysis. A NPV is the initial cashflow 0 (generally a negative number as they are usually an outflow into the investment) plus the expected cash inflows generated by the investment from each year, discounted by a weighted average cost of capital to the power of the year. For example, the fist year cash inflow is discounted by the WACC to the power of 1, second year is discounted to the power of 2, and so on. Now in large corporations with several divisions, each division will determine their own discount rate, and often divisional managers will push for low discount rates in order to more easily justify their pet projects and make them appear more profitable than they really are. This is one of the disadvantages of not using a single standardized WACC, however, there are disadvantages to using a single standard WACC too which are even worse. This discounting is done to account for the cost of rasing capital and the effects of inflation reducing the buying power of money over time. However, in cases like government mandates, managers don't have much of a choice such as meeting minimum gas mileage standards set by the EPA which are racheted up each year.

Last edited by Buick Runner; 05/13/19 03:41 AM.

SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes, and Jmod.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
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