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S197 3V Fabman's build; How did we get here? Build Thread

Fabman

Epic Contributor
3,299
2,376
Pleasanton: 1/2 way between Sonoma and Laguna Seca
W2W Racing
20+ Years
Took some creative dicking around but I managed to modify this tower brace to fit.
I lowered the motor till the pan just clears the rack and re arched the brace until it just clears the manifold. Solid mounts so movement should be at a minimum.
Any bets on what breaks first?

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Fabman

Epic Contributor
3,299
2,376
Pleasanton: 1/2 way between Sonoma and Laguna Seca
W2W Racing
20+ Years
Hmm. mine cleared with lots of space with lowered engine mounts.. I guess the electric rack takes up less space?

View attachment 62248
I'm not sure what's different. I checked and measured everything, the only difference I could guess at is that I used the s550 motor mount castings that bolt to the block. I compared them to the 3 valve mounts before I installed the engine and they looked exactly the same. It is possible that they may be a tad taller and I didn't notice it, but I did look for that exact thing and decided there was no difference. So, either I missed it or its something else entirely. Regardless, The motor is as low as it will go without cutting the pan and we are too far along to go back now so we are where we are. If that motor does come out for some reason I am going to check more closely but for now it is what it is. I am hearing from some respectable racers that the bar is not needed anyway, and its definitely not light, so it will most likely come off anyway.
 
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JDee

Ancient Racer
1,030
915
halfway between Mosport and Shannonville
W2W Racing
20+ Years
I'm not sure what's different. I checked and measured everything, the only difference I could guess at is that I used the s550 motor mount castings that bolt to the block. I compared them to the 3 valve mounts before I installed the engine and they looked exactly the same. It is possible that they may be a tad taller and I didn't notice it, but I did look for that exact thing and decided there was no difference. So, either I missed it or its something else entirely. Regardless, The motor is as low as it will go without cutting the pan and we are too far along to go back now so we are where we are. If that motor does come out for some reason I am going to check more closely but for now it is what it is. I am hearing form some respectable racers that the bar is not needed anyway, and its not light, so it will most likely come off anyway.
Back in the day the thinking was if you stitch welded the seams up front the bar was not needed, I would think that is still true? I have a picture on my desktop of the Mustang GT4 engine room and there is no bar in there.
 

Boone

TMO Race
300
344
Greensboro, NC
Let's get geeky for a sec... With the SLA suspension, are the attachment points for the spring more in the vertical plane compared to the stock struts or coilovers? If so, that would make the strut tower brace less useful. I would think the offset coilovers would also lower the need for the STB since the spring is more vertical where it attaches to the upper strut mount. First time I've really pondered this. 🤓
 

Boone

TMO Race
300
344
Greensboro, NC
Can't resist quoting the S197forum post from Norm... Kind of like Will Farrell in old school... "Brace" yourself.

Chassis torsional stiffness is a problem in 3 dimensions, and the best that any 2-point STB can do is close in the chassis structure at a single longitudinal location. You do see this stiffening effect gradually diminish over perhaps a few inches either side of the STB location, but it's still correct to consider this stiffening effect to be localized.

In other words, you're stiffening only a single vertical-transverse plane along the car's entire wheelbase, and if you're effectively stiffening, say, 6" of length out of a Mustang's 107" wheelbase, you're not increasing the stiffness of the other 101" at all. Adding a diagonal brace in that same vertical-transverse plane does make that plane stiffer, but still won't do anything for the other 101".

Both the Garage Time guy and the Engineering Explained guy note that when you tie the two towers together that you get to use both towers' stiffnesses. Which is true as far as it goes, but does not tell the whole story (or even the most useful part of it). I think I'm going to have to draw some pictures before it'll make sense, but it has to do with the fact that the inside and outside tires are not loaded equally and do not produce equal cornering forces.

Garage Time guy's measured results weren't the least bit surprising. A different kind of 3-point brace would most likely have shown considerably more improvement.


Back to the subjective part . . . one thing that even light-duty stiffeners can do is change the structural vibration picture. They can chase more noticeable vibration modes out of the picture completely, where you're left with less noticeable modeshapes. You have to be visualizing the car structure vibrating like a massively complex tuning fork here, that when you tie off a point that's vibrating a lot relative to another point to that other point you change that vibration shape completely. A little like grabbing the tips of a simple tuning fork between your fingers, actually.

Vibrations are a part of what you perceive as "chassis solidity", which isn't the same thing as chassis stiffness (though there is a loose relationship between the two). That's why it 'feels' better, the car doesn't feel as "loosey-goosey" as it might have before. This concept can and should be extended to many of the other add-on stiffening that's available.


Sketches are going to take some time. Maybe I'll include a sketch suggesting the possible benefit of running a 2-point STB specifically for hard braking . . . and I have at least one thought related to stiffnesses in general.


I've been down this road before (a number of times, on various forums). As a structural analyst/engineer, this kind of stuff is very much in my wheelhouse. I'm retired these days, but I didn't suddenly forget everything I knew about the concepts.


Norm
 

Fabman

Epic Contributor
3,299
2,376
Pleasanton: 1/2 way between Sonoma and Laguna Seca
W2W Racing
20+ Years
Can't resist quoting the S197forum post from Norm... Kind of like Will Farrell in old school... "Brace" yourself.

Chassis torsional stiffness is a problem in 3 dimensions, and the best that any 2-point STB can do is close in the chassis structure at a single longitudinal location. You do see this stiffening effect gradually diminish over perhaps a few inches either side of the STB location, but it's still correct to consider this stiffening effect to be localized.

In other words, you're stiffening only a single vertical-transverse plane along the car's entire wheelbase, and if you're effectively stiffening, say, 6" of length out of a Mustang's 107" wheelbase, you're not increasing the stiffness of the other 101" at all. Adding a diagonal brace in that same vertical-transverse plane does make that plane stiffer, but still won't do anything for the other 101".

Both the Garage Time guy and the Engineering Explained guy note that when you tie the two towers together that you get to use both towers' stiffnesses. Which is true as far as it goes, but does not tell the whole story (or even the most useful part of it). I think I'm going to have to draw some pictures before it'll make sense, but it has to do with the fact that the inside and outside tires are not loaded equally and do not produce equal cornering forces.

Garage Time guy's measured results weren't the least bit surprising. A different kind of 3-point brace would most likely have shown considerably more improvement.


Back to the subjective part . . . one thing that even light-duty stiffeners can do is change the structural vibration picture. They can chase more noticeable vibration modes out of the picture completely, where you're left with less noticeable modeshapes. You have to be visualizing the car structure vibrating like a massively complex tuning fork here, that when you tie off a point that's vibrating a lot relative to another point to that other point you change that vibration shape completely. A little like grabbing the tips of a simple tuning fork between your fingers, actually.

Vibrations are a part of what you perceive as "chassis solidity", which isn't the same thing as chassis stiffness (though there is a loose relationship between the two). That's why it 'feels' better, the car doesn't feel as "loosey-goosey" as it might have before. This concept can and should be extended to many of the other add-on stiffening that's available.


Sketches are going to take some time. Maybe I'll include a sketch suggesting the possible benefit of running a 2-point STB specifically for hard braking . . . and I have at least one thought related to stiffnesses in general.


I've been down this road before (a number of times, on various forums). As a structural analyst/engineer, this kind of stuff is very much in my wheelhouse. I'm retired these days, but I didn't suddenly forget everything I knew about the concepts.


Norm
I've long been a tube chassis guy and I have the inside of the car built like a brick poophouse but I didn't go through the firewall because at the time there was a blown 3 valve in the way. Now I am looking at the flimsy framework up there and kicking myself in the butt for not doing it when I had the chance, nor did I seam weld it. I am doubling the spring rate (wheel rate is around 60% of that) so the forces fed into those towers is doubled, so any stiffness is good stiffness was my thought.
If I could triangulate it to the firewall that would be helpful but as you know these cars have no real strength there either.
I'm going to pull the bar off and send it.
 

Fabman

Epic Contributor
3,299
2,376
Pleasanton: 1/2 way between Sonoma and Laguna Seca
W2W Racing
20+ Years
First quart in the new motor.

I like the way that the Coyote has the oil cap tucked into the valve cover at an angle but its not optimum for filling.
Enter the 3 valve adapter. Screws right into the Coyote cover and holds the funnel nice and flat.
Afterwards I'll just toss it in the race box and leave that clean 'Yote look on the car until the next oil change.
Nice addition if you have one lying around. ;)


IMG_1295.jpg





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Fabman

Epic Contributor
3,299
2,376
Pleasanton: 1/2 way between Sonoma and Laguna Seca
W2W Racing
20+ Years

Fabman

Epic Contributor
3,299
2,376
Pleasanton: 1/2 way between Sonoma and Laguna Seca
W2W Racing
20+ Years
Final assembly has begun. All suspension components carefully measured and fit including mic’ing all slots and machining shims/spacers for each location for a perfect fitment. All threads cleaned, anti seized and measured for proper thread depth, rod length and angle then logged for future reference. Motor is 100% plumbed and full of fluids and fuel. We are dangerously close to starting this thing up. Been a long time coming but we are so close I can taste it.

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