# Frame stiffening



## Pennsylvania Amish Goat (Dec 18, 2020)

Need some opinions. Getting the frame of my 68 GTO blasted and powder coated. I was wondering if boxing the frame is really necessary. It will have a Butler 461 stroker motor. I won't be racing it. Is it a waste of time and money? I was looking at the summit kit. TIA


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## Jim K (Nov 17, 2020)

Everyone will have their own thoughts on this, but I would say unless your putting 700+ HP and 700+ Ft lbs of torque in the motor and planning on wanting to run 1/4 miles drags all the time, I would not bother with that. Now having said that, I would also do a close inspection after blasting for any weak areas where rust may have eaten at the metal through the years or possible incomplete welded areas from the factory and make sure all those areas are repaired.


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## armyadarkness (Dec 7, 2020)

I agree with @Jim K However! I DO recommend the frame supports at the rear upper control arms. They help out a lot with handling and traction.









GTO, Grand Prix, Lemans, and Tempest 1964-1967 Rear Frame Support # TS-47


<center><iframe width="360" height="315" src="https://www.youtube.com/embed/-GMOlrtcDU0?rel=0" frameborder="0" allowfullscreen></iframe></center> Now you can add support between the upper frame cross-member and lower arms pivot point on any A-Body (such as GTO, Grand Prix, Lemans, and Tempest...



www.globalwest.net


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## PontiacJim (Dec 29, 2012)

Since you are not planning on really beating on it, you should be OK.

As pointed out, the welding may not be the best job and could use a little attention. I found a few area that only had minimal welds and I completed them. Also make sure the lower section of the C-channel of the center sections between the back of the front fender and to the rear quarter (the frame under the door) is not all bent up from people putting a lift or hydraulic jack under the frame to lift the car. This will bend that lower metal of the C-channel. I had a couple places I had to straighten out on my '68 frame.

I on the other hand plan on abusing my car. I did far more frame stiffening than a Sherman tank would need, but I wanted to do my frame only once and not break anything with the Ford 9" 3.89 posi gears, 12" wide tires, and good traction. That combo should put a lot of pull on the chassis in more than just one place - so I added an aftermarket plate that was cut/designed for boxing the C-channel rail, but instead of plating on the outside to "box" the C-channel, I fitted it inside the C-channel to create more of an "I-beam" support and tack welded it in. 

I also have the upper/lower control arm supports as *Army *pointed out. This should be a minimum add-on which adds strength to the rear frame section.


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## goat671 (Apr 13, 2019)

I just received this kit from Hellwig along with a Gforce crossmember and transmission mount.
This kit duplicates the convertible frame plus and additional body brace per side.


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## GTO Yeah (Dec 6, 2021)

Anybody have thoughts on this frame kit from Summit? I'm seriously considering adding them to my car. We've already boxed the frame, but this little bit of insurance is enticing.

I change my mind everyday but based on what I plan to do at the moment, the Engine Analyzer program is telling me I'll be around 680hp at the motor. I'm toying with the idea of doing some autocross once I'm done with the car, and I'm wondering if these will help.


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## PontiacJim (Dec 29, 2012)

GTO Yeah said:


> Anybody have thoughts on this frame kit from Summit? I'm seriously considering adding them to my car. We've already boxed the frame, but this little bit of insurance is enticing.
> 
> I change my mind everyday but based on what I plan to do at the moment, the Engine Analyzer program is telling me I'll be around 680hp at the motor. I'm toying with the idea of doing some autocross once I'm done with the car, and I'm wondering if these will help.
> 
> View attachment 157849


You better re-boot your engine analyzer because it may have a virus.

I would* NOT *be autocrossing that car with the frame that is under the car. It is pretty rusty/thin in some areas and your steering box area was very weak. It would not hold up to 680HP and a couple of hard turns with sticky tires is probably going to crack/break the frame or rip out that steering box.

That said, I would not install that kit. You start adding strength to one area, and it will transmit stresses to another part of the frame. If anything, a roll cage is what will be needed to stiffen up the car/frame.

Just my opinion, but don't want to see you get injured either.


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## GTO Yeah (Dec 6, 2021)

PontiacJim said:


> You better re-boot your engine analyzer because it may have a virus.
> 
> I would* NOT *be autocrossing that car with the frame that is under the car. It is pretty rusty/thin in some areas and your steering box area was very weak. It would not hold up to 680HP and a couple of hard turns with sticky tires is probably going to crack/break the frame or rip out that steering box.
> 
> ...


Hm, maybe I'll have to dial back on some of the motor stuff. It just needs to go faster than my wife's car which has a 0-60 of 4.7sec. If I build a car slower than her SUV, I'll never live it down. 

Do most folks who do high horsepower builds only do so on an aftermarket tubular frame? I was surprised at how thin the frame is at some spots and I wouldn't even begin to know what a healthy limit would be powerwise.

I'd love a roll cage, but I'd want to daily the car as well. I wouldn't feel safe not wearing a helmet with a roll cage.


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## GTO Yeah (Dec 6, 2021)

PontiacJim said:


> You better re-boot your engine analyzer because it may have a virus.
> 
> I would* NOT *be autocrossing that car with the frame that is under the car. It is pretty rusty/thin in some areas and your steering box area was very weak. It would not hold up to 680HP and a couple of hard turns with sticky tires is probably going to crack/break the frame or rip out that steering box.
> 
> ...


I think you might be right about the virus. I ran it through the ole "Optimizer" overnight and I'm at 833hp @6500RPM! (with a few minor tweaks of course)


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## PontiacJim (Dec 29, 2012)

GTO Yeah said:


> Hm, maybe I'll have to dial back on some of the motor stuff. It just needs to go faster than my wife's car which has a 0-60 of 4.7sec. If I build a car slower than her SUV, I'll never live it down.
> 
> Do most folks who do high horsepower builds only do so on an aftermarket tubular frame? I was surprised at how thin the frame is at some spots and I wouldn't even begin to know what a healthy limit would be powerwise.
> 
> I'd love a roll cage, but I'd want to daily the car as well. I wouldn't feel safe not wearing a helmet with a roll cage.


You could have a high HP engine and use the stock frame with much modification to stiffen it. In both drag racing and any typ autocross, especially with an engine having a lot of torque, a robust suspension, and wide tires that'll grip, you will have flex and torsional twist.

Being honest, your frame was/is in poor condition in a few places and should be kept for cruising and/or easy driving. The car body of course will be adding some stiffness to the frame, but it has been known that a car having a lot of HP and good traction can buckle quarter panels and even buckle a roof. So boxing in the frame side rails adds stiffness and why convertibles had a boxed frame AND the boxed convertible frame was offered as an Heavy Duty frame option for those who intended to race their cars. Then adding a roll bar/cage further stiffens the overall chassis and car.

If it were me with regards to your build, I would have opted for another frame versus using the one that came with the car. This would have provided a more solid frame to work with and know it had good metal throughout. The other option for serious HP and serious autocross racing would have been the new aftermarket frame with all its stiffeners. But, not inexpensive.

Next, 680 HP could be had, but HP costs. 680 HP is also pushing the limits of the engine block and it's possible at that power level to crack/break/split the block as they were not designed/engineered to handle that kind of HP - this is why they DID incorporate all the additional strength into the SD455 block as it was aimed more for racing and racing abuse. With high HP levels, you want to go with motor plates, not the factory side engine mounts. The torque of high HP pulls/twists the block at the engine mount, and the block will flex, and this is what can cause the main crank saddles to distort and you wipe out bearings or split the block. The SD 455 engine was engineered to be much thicker along the pan rail in an effort to prevent this - among other improvements. This kind of HP really requires and available $$aftermarket block that incorporates the additional strength points to survive.

The transmission would also require to be built to handle that kind of HP/Torque or you will be picking up pieces in a bucket. So in building more HP/TQ, you have to consider the drivetrain behind the engine and then the suspension/frame requirements to handle the increased power.

Throw the engine analyzer out the window! LOL I'd like to have 680HP with a 270 duration cam and .456" lift.


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## GTO Yeah (Dec 6, 2021)

I appreciate the write-up. This gives me a lot to think about. 

This will be my first car without any sort of traction control, etc. Taking it to autocross was my way of learning the limits of the car without wrapping it around a tree.

I think I'm trying to have my cake and eat it too (keeping it as original as possible while still making it a high performance build). But that's probably not in the cards for this build.


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## BearGFR (Aug 25, 2008)

I also have and use EA Pro. I found that it's pretty accurate AS LONG AS you tell it the truth on all the input parameters AND use the right "Running Conditions" setting. The very first time I built my engine and took it to a dyno for break in before putting it into the car, I was expecting 550 HP because that's what EA had predicted - and I had actual flow bench numbers for the heads. It made 500 and I was disappointed. However, when I changed the 'Running Conditions' in EA from 'Std Dyno' to 'SAE', it was dead on. 

Bear


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## armyadarkness (Dec 7, 2020)

GTO Yeah said:


> I think I'm trying to have my cake and eat it too (keeping it as original as possible while still making it a high performance build).


Yeah, and I would abandon that idea. My car looks stock, AFAIC... but the suspension is full tube, the trans is a 5 speed Tremec, the engine is a roller. Stock interior and stock wheels with modest tires, keep it looking all original.

Anyone can go to the dragstrip or Friday night cruise, and see a GTO. Few people ever see one driving down the parkway, but that's where the WOW factor/ head turning takes place. 

Trying to make a GTO able to compete with a modern muscle car, would be a huge step in the wrong direction. Stick to 400hp and enjoy your car!


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## Baaad65 (Aug 29, 2019)

Speaking of frame stiffening and crossmembers my original had the ends rusted off and someone did a hack job of fixing it so I re did the ends with stiffer material and I riveted onto where the member was solid. How important is that member with a high torque/horse power motors, will it just twist in the rubber mounts ( which are new) I also have a poly trans mount and going with upgraded torque lock motor mounts from Ames this winter. So far everything looks tight but I guess I'll see at the track with better traction. I've thought about upgrading the member but that entails dropping the exhaust, and if it is recommended which brand does everyone like? Thanks, I'll hang up and listen.


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## armyadarkness (Dec 7, 2020)

A solid transmission cross member is critical, even for a stock build. I would never drive a car that didn't have a 100% reliable one.

As for what to buy... there are tons of them, including stock replacements.


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## armyadarkness (Dec 7, 2020)

I like the Hurst... but they're all very cool








Hurst Transmission Crossmember for 1964-1967 GTO, Tempest & Le Mans Convertibles Stock Replacement / Tremec TKX, TKO 5-speed – Hanlon Motorsports


Hurst Transmission Crossmember for 1964-1967 GTO, Tempest & Le Mans Convertibles Stock Replacement / Tremec TKX, TKO 5 speeds




www.hanlonmotorsports.com


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## armyadarkness (Dec 7, 2020)

The dougs one is sweet, too


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## GTO Yeah (Dec 6, 2021)

BearGFR said:


> I also have and use EA Pro. I found that it's pretty accurate AS LONG AS you tell it the truth on all the input parameters AND use the right "Running Conditions" setting. The very first time I built my engine and took it to a dyno for break in before putting it into the car, I was expecting 550 HP because that's what EA had predicted - and I had actual flow bench numbers for the heads. It made 500 and I was disappointed. However, when I changed the 'Running Conditions' in EA from 'Std Dyno' to 'SAE', it was dead on.
> 
> Bear


It's certainly a fun program to tinker around with.


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> The dougs one is sweet, too
> View attachment 157927


 Found this one.1964-1967 & 1968-1972 A-Body Hardtop Crossmember Next Gen | RCAE-NG-BLK


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## Baaad65 (Aug 29, 2019)

Summit has a replica of the G Force for 319.00 and I happen to have a 50.00 gift certificate now and they have a 20.00 promo code going.


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## GTO Yeah (Dec 6, 2021)

Baaad65 said:


> Summit has a replica of the G Force for 319.00 and I happen to have a 50.00 gift certificate now and they have a 20.00 promo code going.


It's fate!


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## armyadarkness (Dec 7, 2020)

Baaad65 said:


> Found this one.1964-1967 & 1968-1972 A-Body Hardtop Crossmember Next Gen | RCAE-NG-BLK


As I said, there are dozens of them. And it's not like asking about dizzy's or carbs... You couldnt swing a dead cat without hitting an upgraded crossmember for an A Body.. and the only easier way to find them than swinging dead cats, is Google.


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## Baaad65 (Aug 29, 2019)

armyadarkness said:


> As I said, there are dozens of them. And it's not like asking about dizzy's or carbs... You couldnt swing a dead cat without hitting an upgraded crossmember for an A Body.. and the only easier way to find them than swinging dead cats, is Google.


Correct ! I wonder how much mine flexes and if it's that big of a deal on the street where it spends 99.9% of the time. Of course it does tie your frame together instead of the member just floating in a rubber grommet


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## Machinest-guy (Jul 19, 2019)

Hummm. Lots of opinions here. 

I ran a '65 convertible in H Production modified class SCCA in the 1970's with about 400 HP, 3.73 gears, and sticky Goodyear blue streak tires. Frame was OEM. Overall result was top ten or better in Western Region. I found the weak spots in the frame were in the front where the side rails meet the kick ups and forward from there and so on. And welding needed to be redone 100% not just tac on seams. I believe if I'd pushed the car much harder I would have needed rear frame reinforcement but Auto X doesn't shock load stuff as drags do. I had a single hoop roll bar with two back braces that I'm sure helped save the frame in back but from a suspension geometry perspective all the problems were in front. This weak front end limited the spring rate you could add to the front. If the springs were too stiff you just flexed the frame more instead of letting the control arms move to compensate for alignment angles changing as steering input changed. 

I ran this same front clip on an IMCA modified car for a decade. Same issues. The kick up area needed to be reinforced as much as possible. The IMCA car had a tube frame behind the front clip going to a Ford 9 inch etc, etc. 

I also ran this sort of frame in an entry level stock car in the Winston West series under NASCAR rules. On dirt the frame was beat up on a weekly basis and needed to be straightened at least once a month. Again it was a top ten car and finished 10th in the track championship out of more than 220 cars registered for the class. My frames had full roll cages and reinforcement. You just can't do enough to strengthen the front when on dirt and pounding potholes. The side rail kits are nice but worthless until you can move all the loads generated by tires into the front suspension mounts of the frame then back to the middle / rear where the roll bar can dissipate them. 

I've used Engine Analyzer software for decades. Currently have Pro version. It is only as good as the data inputs. You need to make some locked up tappets and mock together your valve train AT ADJUSTED LASH to get usable duration and timing numbers AT THE VALVE FACE. And you need to have actual air flow tested data to input for the head section. I've built nationally competitive road race engines using it. The dyno and the software were only a few HP / Ft lbs apart but you'll spend as much on measuring equipment to do your first engine as the engine costs. Then the software will pay big dividends in time and money saved by modeling first. 

Good luck, have fun. Think front. Ladd


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## GTO Yeah (Dec 6, 2021)

Machinest-guy said:


> Hummm. Lots of opinions here.
> 
> I ran a '65 convertible in H Production modified class SCCA in the 1970's with about 400 HP, 3.73 gears, and sticky Goodyear blue streak tires. Frame was OEM. Overall result was top ten or better in Western Region. I found the weak spots in the frame were in the front where the side rails meet the kick ups and forward from there and so on. And welding needed to be redone 100% not just tac on seams. I believe if I'd pushed the car much harder I would have needed rear frame reinforcement but Auto X doesn't shock load stuff as drags do. I had a single hoop roll bar with two back braces that I'm sure helped save the frame in back but from a suspension geometry perspective all the problems were in front. This weak front end limited the spring rate you could add to the front. If the springs were too stiff you just flexed the frame more instead of letting the control arms move to compensate for alignment angles changing as steering input changed.
> 
> ...


I don't think I'd try to competitively autocross it, but it's awesome that you did! Do you have any tips for driving a heavier, torquey car like the GTO? My point of reference is a 6th gen Mustang and Corvette that I was able to drive for a weekend (all nanny controls on!).

As PJ pointed out earlier, my frame was in rough shape when I got the car. Lots of rust. My dad did some repair work and redid some of the welds. He also welded a 1/4" plate on the inside of the horns to give the front frame brace something extra to hold on to. All the same, I think I might have to dial back my aspirations for the power I'll be putting through the frame. I was originally shooting for around 600 hp at the crank, but I'm rethinking my plans. 

I've read on the Chevelle forums that some people reinforce the rear upper and lower control arm mounts. There are some stories floating around over there of people seeing failures at those points. Have you hear of any of this? The metal is a little tweaked on mine, which leads me to think it might be a problem area worth reinforcing.


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## bignuk1 (8 mo ago)

I like insurance and at $700 seemed like a no-brainer for my 67s. I have recently installed the summit kits in both my hardtop and convertible project frames. Required a bit of modification. I also strengthened the rear coil pad with a plate on the back side. The hardtop frame I bought had some gusetts welded in so I left them. I added front and rear coil over suspension and a new ford 9in. I have a 500 hp stroked 400 on order from Len Williams and still in search of another 500 hp powerplant. Cant say if it was required, however, has worked out well on other cars and trucks I have had to box and strengthen the frame before adding 500hp. And I just plain like fabrication! I also plan on using tremec TKX 5 spds. Will post pics when all done. Waiting on bolt on cross bar from global west after some solid advice on the forum!


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## Machinest-guy (Jul 19, 2019)

Well there is no doubt you're into it now. Whew. I never had a frame table to align stuff when it was off the frame machine so fabrication at this scale never happened on my cars. (upon re-thinking that comment I realize on the IMCA car we built our frames off OEM clips on a special slab 8ft by 20ft of cement that was dead level and flat +/- 1/8 inch anywhere to anywhere) Although I did spend about eight years doing nothing but Corvette service and restoration. When a frame was as bad as some of the areas here we'd change the frame and scrap what was left - our watch word was you can't weld to rust. And welds are stronger than the frame so the frame will just re-crack or tear. But that isn't to say it can't be done. I fixed a lot of truck frames when I did HD for a lumber and supply outfit in the '70's with gusset plates and braces. It all worked but wasn't pretty. 

I'm looking at the frame photo just above this post where the full frame is shown on cinder blocks with the brace tubes added. 
Hummmm. Those tubes are not very effective, in my opinion. Let's start at the back and work forward. 

The rear control arms attach to the frame behind the added bars. Forces from the axle want to lift the frame putting it into a cantilever droop. Those forces want to twist the axle mount cross member which looks braced enough but when those forces come forward from the brace into the OEM frame it will bend there unless a superstructure is added bridging from the cross member to in front of the rear mid body mounting pad. Weakness in this area is the root cause of buckling rear quarter panels. 

I can see how forces will travel up the OEM frame rails and tubes without much deformity but that is not a problem area because the body (with solid mounts) forms the superstructure resisting droop. So why put tube in the way of your mufflers?

Those forces are all reintroduced to the OEM frame at the front kick up which isn't strengthened at all that I can see. This is the area to work on. It generally requires cutting out body metal and adding tubing to move the droop forces forward to tie into the front suspension spring pocket area (and hence the front engine mount attachment points). 

A note on the driveshaft hoop. It seems to me if you break a rear U-joint you want the shaft to exit the car as quickly as possible by falling out of the transmission onto the ground. This minimizes damage to your car. From this perspective the hoop in installed upside down. But track safety officials want the driveshaft to stay in the car so insist it be done as you have mounted it. That way it can beat the hell out of your car, then fall on the ground. May I suggest if you are going to run a rear driveshaft hoop it be totally around the shaft. And then put one in the front to hold the shaft within the front driveshaft sheet metal tunnel. The front of the driveshaft needs to be controlled. That is where the real issues start to threaten your safety.

In this case the transmission cross member and the rear driveshaft hoop count for zero anti droop reinforcement. 
Anything in front of the front cross member is just metal holding the radiator and front fenders on. Except for the steering box loads which are pretty minor. Remember: steering box loads go into the drag link, center link, and idler arm. Suspension loads - the major forces - go into the ball joints, control arms and then the frame. Two separate issues with two separate solutions.

It is pretty easy to get a car built with enough power to bend these frames / bodies. In 1975 I had a 1970 SS 396 El Camino with a T400 transmission. It had a bunch of Corvette 427 stuff in it but only had 425 or so HP. On the street it would hook up hard enough with BFG tires to bend the frame enough the body would flex turning on the dome light as it hit second gear. 

So far in your photos there has been little done to reinforce against torque twisting this frame. That is a major issue to consider because those forces bend your front cross member changing the alignment angles.... Thicker gauge metal in the cross member is a good answer but hard to do. I once raced against a guy who welded up all the holes in the front frame rails then filled the rails from front mount to side rail with lightweight concrete. It added about 300 lbs to his car but that frame didn't move a bit. 
Best regards to you for your ambitious project. Ladd


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## Baaad65 (Aug 29, 2019)

Machinest-guy said:


> Well there is no doubt you're into it now. Whew. I never had a frame table to align stuff when it was off the frame machine so fabrication at this scale never happened on my cars. (upon re-thinking that comment I realize on the IMCA car we built our frames off OEM clips on a special slab 8ft by 20ft of cement that was dead level and flat +/- 1/8 inch anywhere to anywhere) Although I did spend about eight years doing nothing but Corvette service and restoration. When a frame was as bad as some of the areas here we'd change the frame and scrap what was left - our watch word was you can't weld to rust. And welds are stronger than the frame so the frame will just re-crack or tear. But that isn't to say it can't be done. I fixed a lot of truck frames when I did HD for a lumber and supply outfit in the '70's with gusset plates and braces. It all worked but wasn't pretty.
> 
> I'm looking at the frame photo just above this post where the full frame is shown on cinder blocks with the brace tubes added.
> Hummmm. Those tubes are not very effective, in my opinion. Let's start at the back and work forward.
> ...


Speaking of driveshaft loops this is going in next weekend before I go racing, it has to go in about in the middle of the shaft because that's the only place it will fit. Also recieved these new toys today for more of my winter projects.


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## Sick467 (Oct 29, 2019)

A friend of mine who races old Pontiacs with his son just told me a story of a rogue driveshaft gone wrong...those loops may be the difference between having dinner with your loved ones or meeting you maker! @Baaad65 tell me more about where you got it and where it has to be mounted, please.

My friend's story had to do with a 9.6 second quarter mile firebird that let go of the driveshaft that nearly caught him in the main vein after coming through the floorboard.... All's well that ends well!


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## Baaad65 (Aug 29, 2019)

I'm sure there's some videos of cars losing the front joint and the shaft pole vaults the car...not a good situation to say the least. It's going on channel about in the middle of the car because my X pipe is in the way in the front. The rules at this strip say anything running slicks under 13.99 must have a loop so I talked to the manager about having drag radials and he said it should be ok..."should"? I'm not renting a trailer and driving an hour each way to then fail tech inspection. It was from a company on ebay and I'm sure made in China. I'll post pix when it's installed you know me 😉


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## GTO Yeah (Dec 6, 2021)

I posted some pics on my build thread as well, but we decided to replace the lower control arm mounts with something a little stronger. It's a good thing too, because the metal behind it was rotted out.


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## GTO Yeah (Dec 6, 2021)

And here's a sneak peak of the braces we're planning to weld near the shock towers.

The question I have is should these be welded right up against the shock towers to provide a little extra strength (like on the driver side)? Or should they be further down like on the passenger side? 

I was also thinking of redoing the welds on the shock tower metal where it touches the frame.

It's my understanding that the shock towers are another weak spot on the A-body frame design.


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## armyadarkness (Dec 7, 2020)

Seems overkill to me, that being said, I would weld them like the driverside


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## GTO Yeah (Dec 6, 2021)

armyadarkness said:


> Seems overkill to me, that being said, I would weld them like the driverside


I think maybe that should be the new name of my car once I finish her--Overkill.

It's a common argument my dad and I have. Me with zero experience scoring the internet for things to fix before they're broken and him with years of experience saying "you don't need that."


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## Baaad65 (Aug 29, 2019)

I've been thinking that too watching this thread, what kind of motor and trans are you planning I can't remember and are you going to drag race it regularly with big sticky tires? You and you're dad are doing a great job though, I drag raced last weekend and don't have half the suspension and frame strengthening you do with 461 4spd and 9.5 drag radials and only broke the rear end internals.


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## GTO Yeah (Dec 6, 2021)

Baaad65 said:


> I've been thinking that too watching this thread, what kind of motor and trans are you planning I can't remember and are you going to drag race it regularly with big sticky tires? You and you're dad are doing a great job though, I drag raced last weekend and don't have half the suspension and frame strengthening you do with 461 4spd and 9.5 drag radials and only broke the rear end internals.


Thanks! I keep thinking of the old adage "an ounce of prevention is worth a pound of cure." I figure I might as well overbuild everything I can while the body is off the frame.

I'd like to shoot for 500hp at the crank with a 461 stroker kit and aluminum heads (trying to decide between Butler's Speedmaster and Edelbrock heads). 600hp was my original goal, but some of the guys here with more experience than me warned me off it based on the original condition of my frame.

I've got a Currie 9in rear end with Twin Trac, 3.50 ratio, and 1350 yoke.

For trans, I really like the Tremec TKX, but I'm still unsure if wide or close ratio is right for me.

I'd reaaaaally like to cram as much rubber I can fit under the rear (without tubbing), but I might start with stock sizes for my first year with it.

I don't think I'll drag it regularly, but I love the idea of racing it every other month or so. I'd also love to autocross it at some point. I feel like that gives me a safe space the learn the limits of the car without hurting myself or others.

EDIT:
How do you find the fit of the 9.5 radials? Do you have any rubbing?


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## Baaad65 (Aug 29, 2019)

GTO Yeah said:


> Thanks! I keep thinking of the old adage "an ounce of prevention is worth a pound of cure." I figure I might as well overbuild everything I can while the body is off the frame.
> 
> I'd like to shoot for 500hp at the crank with a 461 stroker kit and aluminum heads (trying to decide between Butler's Speedmaster and Edelbrock heads). 600hp was my original goal, but some of the guys here with more experience than me warned me off it based on the original condition of my frame.
> 
> ...


I have a about 500hp with iron heads and it's pretty scary so getting 600 hp is a whole other ball game especially on our crap gas but Butler does them, if I did aluminum heads I'd go with Kauffman's just because everyone has Eddies. Now I think I'm going with a Strange Dana S60 diff with 3.54 gear. Ya you're better off doing all that you are doing if you're going to race it that much, I only got three passes before I broke down. Mine's a '65 so the wells might be different but I have 8" x 15" wheels with a 4.5 offset and 275/60 MT et street drag radials, I did trim the well edge and trim up to the screw heads and trimmed the bump out inside the outer well, they would only rub on decent bumps. I have an inch of clearance on the inside to the frame so I wish I could get a wheel like mine with a 5" offset but I would need 17" wheels then the tire selection gets scarce. You could do some trimming before paint in the well and get a wheel with a 5.47 offset which would allow a pretty big tire. Check out tiresize.com for fitment tools, a TKX will be nice and there are calculators and guys here that can help with your choice, mine is a M23Z with a 2.99 first gear and I had a 3.42 rear so it got out of the hole quick. Army has the wide ratio of 3.27 but a 3.36 rear and says it's like a dump truck in first.


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## GTO Yeah (Dec 6, 2021)

Baaad65 said:


> I have a about 500hp with iron heads and it's pretty scary so getting 600 hp is a whole other ball game especially on our crap gas but Butler does them, if I did aluminum heads I'd go with Kauffman's just because everyone has Eddies. Now I think I'm going with a Strange Dana S60 diff with 3.54 gear. Ya you're better off doing all that you are doing if you're going to race it that much, I only got three passes before I broke down. Mine's a '65 so the wells might be different but I have 8" x 15" wheels with a 4.5 offset and 275/60 MT et street drag radials, I did trim the well edge and trim up to the screw heads and trimmed the bump out inside the outer well, they would only rub on decent bumps. I have an inch of clearance on the inside to the frame so I wish I could get a wheel like mine with a 5" offset but I would need 17" wheels then the tire selection gets scarce. You could do some trimming before paint in the well and get a wheel with a 5.47 offset which would allow a pretty big tire. Check out tiresize.com for fitment tools, a TKX will be nice and there are calculators and guys here that can help with your choice, mine is a M23Z with a 2.99 first gear and I had a 3.42 rear so it got out of the hole quick. Army has the wide ratio of 3.27 but a 3.36 rear and says it's like a dump truck in first.


I just reread this thread from page 1 and I should probably start saving up for a tubular frame now so I'm ready once I break my rusted one. More than one person here has told me this should be a cruiser and it will probably be one of those "I told you so" moments when I'm back here in a couple years asking about aftermarket frames.

But I want this car to scare me a little bit. My motorcycle scares the CRAP out of me sometimes and I want to recreate that feeling on 4 wheels. I'm pretty good at exercising restraint, but I like knowing the power is there when I want it. I know I talk a lot about racing it, but who knows. Once it's done I'll probably baby the hell out of it and just cruise. There's a lot of time and effort put into restoring this car to risk destroying it. I also want it to be my daily driver (if there are still gas stations around by the time it's done).

I like Strange, but I found Currie to be cheaper in the end. I also liked the idea of being able to swap out the third member if I changed my mind on gear ratios. Hence the 9 inch, but it sounds like you're only swapping out the internals? Either way, I'm sure it'll be awesome.


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## PontiacJim (Dec 29, 2012)

GTO Yeah said:


> I just reread this thread from page 1 and I should probably start saving up for a tubular frame now so I'm ready once I break my rusted one. More than one person here has told me this should be a cruiser and it will probably be one of those "I told you so" moments when I'm back here in a couple years asking about aftermarket frames.
> 
> But I want this car to scare me a little bit. My motorcycle scares the CRAP out of me sometimes and I want to recreate that feeling on 4 wheels. I'm pretty good at exercising restraint, but I like knowing the power is there when I want it. I know I talk a lot about racing it, but who knows. Once it's done I'll probably baby the hell out of it and just cruise. There's a lot of time and effort put into restoring this car to risk destroying it. I also want it to be my daily driver (if there are still gas stations around by the time it's done).
> 
> I like Strange, but I found Currie to be cheaper in the end. I also liked the idea of being able to swap out the third member if I changed my mind on gear ratios. Hence the 9 inch, but it sounds like you're only swapping out the internals? Either way, I'm sure it'll be awesome.




If you want a scary ride, just get married. If you want a scary ride that has a higher probability of a near death experience, get divorced. 

Agree with *Army*, a bit overkill and I don't see any advantage to those plates on the frame rail sides in front of the control arm crossmember.

I added a plate I fitted/shaped and bolted to the control arm crossmember. Not being a structural engineer by any means, it made sense to strengthen the crossmember because it is what the rear-end was going to pull hard on with wide tires and posi. I created a "design" that also added more strength to the attachment points of both the upper and lower control arms. Added plating to strengthen the "ears"on the control arm side.

I also beefed up the shock supports - nothing fancy, but simply more support by adding some plating.

Plated/beefed up the lower control arm attachment points at the frame, but you have that covered, so no photos posted.

I think if I dropped a top fuel engine in the car, I wouldn't have to worry about pulling the rear-end out of the car.


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## Baaad65 (Aug 29, 2019)

GTO Yeah said:


> I just reread this thread from page 1 and I should probably start saving up for a tubular frame now so I'm ready once I break my rusted one. More than one person here has told me this should be a cruiser and it will probably be one of those "I told you so" moments when I'm back here in a couple years asking about aftermarket frames.
> 
> But I want this car to scare me a little bit. My motorcycle scares the CRAP out of me sometimes and I want to recreate that feeling on 4 wheels. I'm pretty good at exercising restraint, but I like knowing the power is there when I want it. I know I talk a lot about racing it, but who knows. Once it's done I'll probably baby the hell out of it and just cruise. There's a lot of time and effort put into restoring this car to risk destroying it. I also want it to be my daily driver (if there are still gas stations around by the time it's done).
> 
> I like Strange, but I found Currie to be cheaper in the end. I also liked the idea of being able to swap out the third member if I changed my mind on gear ratios. Hence the 9 inch, but it sounds like you're only swapping out the internals? Either way, I'm sure it'll be awesome.


I think you'll be fine unless you're going 700-800 hp with 12 inch slicks, you've done a lot to it and they were good steel thick full frames. I'm going with the whole rear instead of trusting myself to rebuild it and then still have a 56 yr old 12 bolt. And I'm not interested in changing gears, I can get the thing for around 3K.


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## Baaad65 (Aug 29, 2019)

1964-1972 A-Body Bolt-In Rear End | Strange S60 With 35 Spline Alloy Axles & Differential - Strange Engineering and I like that the upper arm mounts are raised from factory to eliminate wheel hop, the lower mount has multi locations too.


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## Baaad65 (Aug 29, 2019)

I'm asking for Summit gift cards for Christmas and Summit said today I can order through them using PayPal credit then pick up from Strange which is about 30 minutes from my office to save the freight charges 👍


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## GTO Yeah (Dec 6, 2021)

Continuing on the theme of overkill, we redid some of the welds in the rear and made some new control arm mounts. I'll post the rest of the process pics in my build thread.


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