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Why not have a Fox?
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Discussion Starter #1
... for a fox with an engine making approximately 600hp and 550ft-lbs. Assume the driveline is built to handle it and the car used sticky tires on the track every other weekend.

I read all the talk about weld-in subframe connectors but I don't know how much stiffening they actually provide? Would weld-in subframe connectors be sufficient for a car at that power/torque level or would the chassis need more to be safe?
 

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Resident Know-it-all
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Safe? You mean to keep from twisting the car? Weld in subframe connectors, not the full length ones work very well at stiffening up the chassis. With that power level and sticky tires, you need to get an upper and lower torquebox reinforcement kit and weld/bolt it in as well. Upr makes a nice kit. A rollbar stiffens the chassis up as well and adds to the safety factor.
 

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I would take it a step further and weld the torque boxes themselves, where they are spot welded to the unibody. Should you go with a rollbar, there are those with swing out side bars (for easier entry and exit), and those that are solid that you have to climb over somewhat. Unless the bars are low enough to run under the armrests entirely, they may interfere with the door armrest. Enough so that armrests have been removed altogether, or notched for the bar.

A strut tower brace will help stiffen the front end a bit. Bolt in braces or weld in. Weld in gets in the way should the engine, or even the intake, ever need pulled. Unless one uses a bolt in brace or goes carb, then its easy.
 

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Why not have a Fox?
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5,798 Posts
Discussion Starter #4
Safe? You mean to keep from twisting the car? Weld in subframe connectors, not the full length ones work very well at stiffening up the chassis. With that power level and sticky tires, you need to get an upper and lower torquebox reinforcement kit and weld/bolt it in as well. Upr makes a nice kit. A rollbar stiffens the chassis up as well and adds to the safety factor.
Correct, to keep from twisting the car. Basically I want to know what needs to be done to keep that power level and traction from tearing the car apart or cracking my windshield. It would be a street/strip build. I wouldn't be at the track every weekend, but when I would go I'd like to beat on it. I was planning on torque box reinforcement along with the subframes, just forgot to mention it. I didn't necessarily want to get a rollcage but I might eventually. Think the car would be OK without a rollcage?

I would take it a step further and weld the torque boxes themselves, where they are spot welded to the unibody. Should you go with a rollbar, there are those with swing out side bars (for easier entry and exit), and those that are solid that you have to climb over somewhat. Unless the bars are low enough to run under the armrests entirely, they may interfere with the door armrest. Enough so that armrests have been removed altogether, or notched for the bar.

A strut tower brace will help stiffen the front end a bit. Bolt in braces or weld in. Weld in gets in the way should the engine, or even the intake, ever need pulled. Unless one uses a bolt in brace or goes carb, then its easy.
Ah, I forgot about strut tower braces. Thanks for the notes on rollbars.
 

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600hp should get you in the 9's , a rollcage isn't really optional at that point, imo, or most strips. I would also run a panhard and torque bar setup .
 

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Rent Asunder!
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Weld-in subframe connectors and torque box reinforcement should be enough to keep it together. Though I will say with 600hp / 550tq, you'll be looking into the 9s which requires a whole new set of safety rules. You'll need a 10-point cage certified to 8.50 with sticker, IHRA/NHRA license, SFI certified balancer and flexplate/flywheel, window net, engine diaper, full protective clothing to include jacket, pants, shoes, gloves, helmet, and neck collar, aftermarket axles with C-clip eliminators, SFI bellhousing, harness, and a parachute if you exceed 150mph. (doubtful unless you're putting this in a dragster)

That 10-point cage would handle your rigidity needs plus the other safety requirements to keep the car together and you safe. It's something that you need to consider when building a drag car. Once you dip under that 9.99 ET, the cost to play goes way up.

BTW, what's your plan for the build to make those numbers. Considering the high torque number, I'm guessing either a big cube 408-460ci windsor with a lot of compression or a 351-408ci engine with something like an underdriven 6-71 blower. (which would look badass)

EDIT: Not trying to discourage you with that but just being realistic. If you go to any decent track and run a 9.99 or quicker (or 135mph or faster) without the necessary safety equipment, they'll usually give you a warning the first time and 2nd time give you the boot. You'll need at least a 6-point rollbar for 11.50 - 10.00 cert anyway. Just recommending that keeping your power level down a tad to around 525-550hp may allow you to keep from shelling out thousands in safety equipment, be able to abuse it at the track still being quicker than the majority of the people there on a fun run night, and still have more power than you can put to the ground on the street.
 

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Why not have a Fox?
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5,798 Posts
Discussion Starter #7
Weld-in subframe connectors and torque box reinforcement should be enough to keep it together. Though I will say with 600hp / 550tq, you'll be looking into the 9s which requires a whole new set of safety rules. You'll need a 10-point cage certified to 8.50 with sticker, IHRA/NHRA license, SFI certified balancer and flexplate/flywheel, window net, engine diaper, full protective clothing to include jacket, pants, shoes, gloves, helmet, and neck collar, aftermarket axles with C-clip eliminators, SFI bellhousing, harness, and a parachute if you exceed 150mph. (doubtful unless you're putting this in a dragster)

That 10-point cage would handle your rigidity needs plus the other safety requirements to keep the car together and you safe. It's something that you need to consider when building a drag car. Once you dip under that 9.99 ET, the cost to play goes way up.

BTW, what's your plan for the build to make those numbers. Considering the high torque number, I'm guessing either a big cube 408-460ci windsor with a lot of compression or a 351-408ci engine with something like an underdriven 6-71 blower. (which would look badass)

EDIT: Not trying to discourage you with that but just being realistic. If you go to any decent track and run a 9.99 or quicker (or 135mph or faster) without the necessary safety equipment, they'll usually give you a warning the first time and 2nd time give you the boot. You'll need at least a 6-point rollbar for 11.50 - 10.00 cert anyway. Just recommending that keeping your power level down a tad to around 525-550hp may allow you to keep from shelling out thousands in safety equipment, be able to abuse it at the track still being quicker than the majority of the people there on a fun run night, and still have more power than you can put to the ground on the street.
Thanks for the info. I've got a big block I'd like to build eventually. N/A, aluminum heads and intake, efi, possibly stroked but I think that would be too much as the output I'm expecting with OE displacement will be too much for a fox anyways realistically. I don't plan on being competitive with the car. I'd just go to the track on fun nights and I would definitely sand-bag it if you guys think those numbers are capable of 9's (I know for a fact that even if the car was capable, I'm not as a driver). I'd be plenty happy with 11s.

Basically it comes down to my dream build engine and I'm trying to decide what to put it in. A fox might not be the best candidate but I'm familiar with them and they're fairly cheap which is why I'm toying with the idea. I want to be able to drive the car anywhere. I don't want a full-on racecar. I'm not totally against putting a cage in it, I just didn't think it would be necessary but it may be after all.
 

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Rent Asunder!
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Well if 11s is your goal, you don't need a big block. You can do that for cheap with a stock bottom end 302, a set of 170-185cc heads that flow in the 240-260 cfm range, a shelf hydraulic cam, and decent intake. Pair that with 3.73-4.10 gear and half of a driver mod, you'll run 11s all day long and have no need for the chassis reinforcement beyond subframe connectors.
 

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Why not have a Fox?
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Discussion Starter #9
I'm fully aware that a small block would be sufficient for 11s and cheaper than a big block. However my goal here is not a time slip. I just want to have fun building my dream engine how I want it and find something to put it in without tearing the car up if I took it to a track from time to time for fun. That's really all I want. If it turns out being capable of 9s, great. If all it'll run is 13s, great. I'm not concerned about the time slip because I don't ever plan on being competitive.

I appreciate the ideas though. I'm not going into this blind. I understand the cost associated with what I want to do and I know there are cheaper options but this is what I've wanted for so long and I'm finally getting to a point where I might be able to make it happen.
 

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So what motor are you planning to build to get this type of power? I would suspect a mild built 460 to end up around 450 in drivers form as you're describing.
 

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Rent Asunder!
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I'm fully aware that a small block would be sufficient for 11s and cheaper than a big block. However my goal here is not a time slip. I just want to have fun building my dream engine how I want it and find something to put it in without tearing the car up if I took it to a track from time to time for fun. That's really all I want. If it turns out being capable of 9s, great. If all it'll run is 13s, great. I'm not concerned about the time slip because I don't ever plan on being competitive.

I appreciate the ideas though. I'm not going into this blind. I understand the cost associated with what I want to do and I know there are cheaper options but this is what I've wanted for so long and I'm finally getting to a point where I might be able to make it happen.
Oh ok, that makes more sense now. There's a bunch of 550-600hp combos posted on 429-460.com.
 

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Why not have a Fox?
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Discussion Starter #12
So what motor are you planning to build to get this type of power? I would suspect a mild built 460 to end up around 450 in drivers form as you're describing.
It's not a Ford big block... If I can get the build started here within a year or so I'll definitely post more info.

Oh ok, that makes more sense now. There's a bunch of 550-600hp combos posted on 429-460.com.
I'll check that out just for fun. Like I mentioned above, it's not a Ford motor.
 

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... for a fox with an engine making approximately 600hp and 550ft-lbs. Assume the driveline is built to handle it and the car used sticky tires on the track every other weekend.

I read all the talk about weld-in subframe connectors but I don't know how much stiffening they actually provide? Would weld-in subframe connectors be sufficient for a car at that power/torque level or would the chassis need more to be safe?
I have built 331 stroker with over 550HP and do not have subframe connectors. Ran digs, rolls, 4K launches, unibody been holding on for over 7 years. I wanted to but shop wanted to keep my car for few weeks and I just never went back to it. But you will benefit a lot from having a subframe connectors.
 
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