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Discussion Starter · #1 ·
I am evaluating options to streangthen the chassis on my 68 1800. I will put in some sort of sub frame connector but I am not sure if there is anything commercially produced. I kind of doubt it but I thought I would ask. I have some plans I am considering that would tie into the rear suspension mounting points and connect to the front frame rails. If I build the connectors myself I would also tie them into the rockers. This boxing effect should add additional rigidity.

Has anyone built their own?
 

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I've never seen it done, and haven't found any particular need to do it. What I have done is to extend a roll cage through the firewall and tie that into the tops of the frame sections -- you could probably get a similar effect by adding some sort of gussets from the frame to the firewall and inboard of the wheel wells. The whole unibody is pretty darned stiff on its own, though.
 

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Nope. Can't say anyone has subframe units for the 1800. But I think if you are driving a car hard enough that the body is going to deform due to stress you will probably need a rollcage in it (since you are probably racing the car) which will make the car more rigid than a subframe connector would (If it is tied in correctly).

-Jon
 

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Discussion Starter · #4 ·
The car is going to be a street car but have more power than originally deigned for. I don't want to use a cage due to safety concerns of my passengers in the rear seat. Thanks for your ideas guys. It looks like I need to do a little more research before proceeding with my original plan.
 

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I have my CAD guy working on a Skeleton system that ties the front subframe in to the back 4 link arm connectors, and once he has the pieces finalized, I will show them.. It is basically a box sytem that acts like an exo-skeleton to the existing body frame work, and once it is installed, it will mimic the original set up of the car.. It has two flanges running down both sides of the cupping skeleton, that allows you to bolt the corresponding interior floor plate down on top of it, and that should really offer alot of additional support.. I hope that makes sense, because it is actually very simple.
 

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A quick question(s)-- I'm assuming that the reason for the additional support has to do with body-flex from adding additional horsepower? Also probably make handling more predictable too. Just suppositions, but further enlightenment is always welcome.
 

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Discussion Starter · #7 ·
That is exactly right Brian. I am in the process of preparing the car for a v8 conversion and want to add as much strength that is feasible without adding a roll cage to the car. It will have somewhere between 450-500 hp.

I have found that strengthening of the chassis also makes the handling more predictable. It is easier to plant the power to the ground and makes the curves easier to navigate.
 

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That is exactly right Brian. I am in the process of preparing the car for a v8 conversion and want to add as much strength that is feasible without adding a roll cage to the car. It will have somewhere between 450-500 hp.

I have found that strengthening of the chassis also makes the handling more predictable. It is easier to plant the power to the ground and makes the curves easier to navigate.
It is very unlikely that you will be able to apply any significant fraction of the 500 hp WHILE taking curves, so the "handling benefits" are unlikely. But even though these body shells are very rigid, it is conceivable that during drag racing you may have some more body flexing than one would want.
 

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Dimitri, you are correctly about the flex being potentially more than desired with full blown drag racing, but that is only if you are going to the extreme of over-size racing slicks, and trying to get the car to bite as hard as it can.. For enjoyable drag racing that doesnt put you in the time bracket for full chassis and extra safety features, there really shouldnt be a problem, because there will be alot of force let go with the tire slip.

You are also correct about only being able to apply a fraction of the 450-500 horsepower in the curves, but I think that is common knowledge, and you normally wouldnt apply full horsepower potential while entering or directly in the curve? And the fact that the determined amount of optimal horserpower usage in the corner, is actually dictated with your right foot, which is not constantly mashed to the floor.. LOL

It is this available horespower capability that will blow the conventional classic Volvo away, right after the curve and in the straight aways, because there is a good 250-300 horsepower more in reserve, than the tuned up B18/B20. I think the fact that the LS can run in the same lower power range as the lesser horsepower car is getting lost in the translation.. If you actually drive, you will find yourself metering the throttle in the lower ranges, with the increased potential in the higher ranges. The 375-600 horsepower LS is not some radical engine that is tempermentaly and tricky to find it smoother ranges, these things are smooth and steady all the way from the bottom idle on up to full redline, so they will be able to take a corner with just the same power range that you will think is optimum.
 

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Discussion Starter · #10 ·
I am by no way a chassis engineer and make no claims to such. I have read some books and have personal experience with high HP street cars. My research and experience shows me the more stable the chassis is the better the suspension will be able to handle it. Whey you start throwing in variables (chassis flex in this example) the suspension may not react the way you want it to. Adding subframe connectors may be a waste of time for the the average stock build but I would personally like to make sure the car is as stable as I can get it.

I agree with you Dimitri there is not a chance the car could hold 500 hp while taking curves. My thoughts were what Roberts was stating about exiting the corner. I hope to get the benefit of SFC's at that point. If they provide more traction while accelerating then great. In reality, I will likely lack traction at most points when the throttle is fully depressed. Adding them can't hurt and now is the time to do it for me.
 

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A stiffer chassis results in a better handling car, very simple fact. Why do you think everyone does strut braces, cross braces in the trunk, that sort of stuff is really really common and it does make a big difference.

Anyone who says otherwise truly doesn't understand a thing about cars.
 

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A stiffer chassis results in a better handling car, very simple fact. Why do you think everyone does strut braces, cross braces in the trunk, that sort of stuff is really really common and it does make a big difference.

Anyone who says otherwise truly doesn't understand a thing about cars.
Things are rarely as simple as they appear. Torsional stiffness can indeed be an issue for certain builds, especially when super lightweight is the name of the game. The Amazon/P1800 is not exactly a light construction car that suffers from excessive torsional deflections. I just wanted to clarify the connection between the braces and its connection to the potential improvement in handling, and I think that was accomplished.
 
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