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1973 GTS - Street/Track

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Post Options Post Options   Thanks (0) Thanks(0)   Quote BackInBlack Quote  Post ReplyReply Direct Link To This Post Posted: 28-October-2017 at 7:33AM
I haven't noticed any drone yet.  I reduced the pipe size from 3" to 2.5" which helped.  Mind you I'm not testing  at 70-80+ mph :-P

Casual freeway driving, keeping up with traffic around 55-60 tops.   I have hte interior completely out and it sounds quieter than the magnaflow.  I doubt it completely eliminates all drone.   It will just shift the drone frequency.  I haven't found it yet.

The old exhaust; I had a really bad drone around 60-65 mph.   Mind you its a stock 351C with 3:70 rear which put the revs around 2800-3000rpm.  I have a 5speed now and I control hte shift points which helps as well.


20/20 hindsight...my only regret with the exhaust work is; I would rather use an H pipe than an X pipe.  For street...no difference in performance but it would allow me to tuck the H pipe up behind the transmission keeping it up high and out of the way.   I think its more important to keep the exhaust up high to keep from scraping than getting 1 hp more at 7000 rpm.


Edited by BackInBlack - 29-October-2017 at 5:38AM
-John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Don V. Quote  Post ReplyReply Direct Link To This Post Posted: 29-October-2017 at 4:50AM
Originally posted by BackInBlack BackInBlack wrote:

Yes coil spring rear but replace control arms with tubular arms with spherical ends.   Works great.   Checked the new arms length to the stock ones that I pulled off the car.   Everything is exactly stock in dimensions and settings.  

Tremec tailshaft location looks like stock position; can't really verify that other than it fits with all the stock mounting.   Trans mount is the exact same height at the original I removed.   I found other references saying the same thing regarding setting ford 9" around 2 degrees.

The TKO tailshaft housing was shorter than the C6 that came out of the car.  It basically needed to be lengthened about 2.5" .  None of this should have changed the pinion angle.  The most likely candidate I think may be the new drive shaft may not be balanced well enough.


""Pinion angles can make the difference between a smooth ride, or a noisy and shaking ride down the freeway. Correct pinion angles are also very important to the life of your U-joints. Over time, the angles can change and become
incorrect due to loose factory tolerances, body and frame alignment, and changes in spring rates due to wear. You should check and correct pinion angles any time you change the ride height or modify the rear suspension.""

Putting larger tires on the rear changes the angle also. Changing the length of the driveshaft changes the angle also.

I don't know if the shaft balance is the problem you experience but you have said you have done things to the car that have changed the angle.

Also, what is discussed as the pinion angle (PA) isn't actually the pinion angle. PA is an adjustment that has co-opted what was a driveline datum or variable if you like. True pinion angle (TPA) has replaced PA to differentiate between the two. TPA is driveshaft angle minus PA. The relationship between TPA and what's called the Phase Angle, another datum, is critical to chassis development.

My suggestion to check your rear suspension wasn't about the individual pieces of the suspension. It was a suggestion to inspect positioning. Get under the car with a tape measure. If you have the shop manuals for your car there are various Fig.'s for the suspension and frame with what dimensions are spec'd at. Your car is over 40 years old and things change.

When Gurney and Elliot were driving Torinos' and Cyclones' they cut off the first 19 inches of the chassis, shortened the wheelbase and then moved the wheelbase. To a suspension, a frame is a number of permutations of a lever with a number of permutations of four pivot points on the ground. The rules for optimizing for comfort and performance are very different and PA is part of those rules. Tracking down why they did what they did is a good read and may help.

I'm out of suggestions except maybe if you are serious about coilovers, if they don't utilize a nitrogen or hydraulic reservoir I'd save the money and go with some quality adjustable Mcpherson Struts.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72FordGTS Quote  Post ReplyReply Direct Link To This Post Posted: 29-October-2017 at 5:34AM
I was able to get Canuck to host your video of your Borla mufflers.  So for anyone interested in hearing John's car, here is the link:
 
 
 
Vince

1972 Ford GTS Sportsroof - Survivor, One Family car
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BackInBlack Quote  Post ReplyReply Direct Link To This Post Posted: 29-October-2017 at 5:43AM
Originally posted by Don V. Don V. wrote:

the difference between a smooth ride, or a noisy and shaking ride down the freeway. Correct pinion angles are also very important to the life of your U-joints. Over time, the angles can change and become
incorrect due to loose factory tolerances, body and frame alignment, and changes in spring rates due to wear. You should check and correct pinion angles any time you change the ride height or modify the rear suspension.""

Putting larger tires on the rear changes the angle also. Changing the length of the driveshaft changes the angle also.

I don't know if the shaft balance is the problem you experience but you have said you have done things to the car that have changed the angle.


Thanks for the info.   Its all helpful.   I will check the PA.  I figured in the end it would shift and I would have to adjust it.   I just didn't think it would change enough until I actually lowered the car.  I plan to drop it 2".

So the top things on my list to check is:
1. Check pinion angle, drive shaft angles as well.   I have rear adjustable control arms and boy I am glad I made the conversion because now it allows me to easily make these adjustments.
2.  Drive shaft balancing.   Just double check it...


-John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BackInBlack Quote  Post ReplyReply Direct Link To This Post Posted: 29-October-2017 at 5:46AM
Originally posted by 72FordGTS 72FordGTS wrote:

I was able to get Canuck to host your video of your Borla mufflers.  So for anyone interested in hearing John's car, here is the link:
 
 
 

Thanks!  Sounds pretty good to me Wink
Its much better in person.   The audio doesn't do it justice.   It has a nice low tone growl in person.  Even my wife heard it for the first time and said "that sounds so much better than before".

Passed the wifey test.
-John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 29-October-2017 at 6:55AM
yeah that does sound quiet, but a nice deep growl Big smile
JOHN
74 GRAN TORINO S&H CLONE
74 CORVETTE COUPE CUSTOM
90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
75 V8 MONZA SUPERCHARGED
79 COURIER VERT. SLAMMED
75 VEGA V6 5 SPD
70 CHEV C10 P/U
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Don V. Quote  Post ReplyReply Direct Link To This Post Posted: 30-October-2017 at 4:18AM
You did a lot for your car with getting rid of the U-channel control arms. I assume you deleted the post with the video link to the movie clip of the guy getting chased. Keep in mind what probably went on with the filming of the clip. What is seen in the clip probably has no relationship with the sequence of filming. It's actually obvious in the clip that the car is set up differently for different stunts. The car has made turns where the cross camber adjustment had to have been changed for some right and left hand turns. Most of the rear end sliding is the result of intentional positive camber on the rear tires. Negative camber would have done away with most of it with the added traction. You can also see steering angle changes in the body roll and how the front end dives that isn't consistent.

Here's Gurney and Parnelli Jones in 68 at riverside.

https://www.youtube.com/watch?v=b2rWMfF68R8

Your concerns about diminishing return as you invest in the car is reasonable but you're still working with 40+ years old technology. With modern tires though you can achieve much of what Gurney achieves with his car with not a whole lot of work or investment. There is no way around involving some work on your frame though. For performance, it's weak. Almost everything at the time was except for going straight. Our frames were intentionally twisted during manufacturing. No matter what you do with the suspension, it's not going to improve the platform it rides on, the frame. If that wasn't true, we'd still be driving on frames made of wood.

Lowering will help a lot with how the car looks but it's not going to improve performance. Lowering the center of gravity on a chassis designed to a ride height degrades suspension geometry. There's nothing new to this:

""Why, because the dynamic measurements – car loaded in a corner, body rolling 1 or more inches – will have the control arm in a different location than the non lowered car which will affect the dynamic camber.  For example, say a McPherson suspension set at 2.5 negative static camber at stock ride height has a dynamic camber in a 7 degree turn of  3.5 degrees negative.  The car is lowered so the front lower control arm now goes up from the cross member (frame mounting point) to the lower ball joint by the wheel; it went down slightly before lowering.  The static camber is re adjusted to the 2.5 negative setting, but the dynamic camber at the same 7 degree turn is now 2.5 degrees, not the more desirable 3.5 degrees.  There is less impact on dual control arm cars, but the same phenomenon occurs.""

Lowering ride height is not a substitute for down force which is what you are really after.

About your PA. The Lincolns' and I think Thunderbirds' at the time had shafts with Double Cardan Joints. If what you do exceeds adjustment limits they might be a good solution if cut or extended as needed.

Edited by Don V. - 30-October-2017 at 4:19AM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BackInBlack Quote  Post ReplyReply Direct Link To This Post Posted: 30-October-2017 at 5:54AM
"Your concerns about diminishing return as you invest in the car is reasonable but you're still working with 40+ years old technology. With modern tires though you can achieve much of what Gurney achieves with his car with not a whole lot of work or investment. There is no way around involving some work on your frame though. For performance, it's weak. Almost everything at the time was except for going straight. Our frames were intentionally twisted during manufacturing. No matter what you do with the suspension, it's not going to improve the platform it rides on, the frame. If that wasn't true, we'd still be driving on frames made of wood."

There is a pile of stuff in the forum regarding these ideas.  As for myself I have changed my mind on a few things as I learn more.   In general, I agree with your statements.   However, I do think there is alot of potential in these cars to perform better without massively cutting and replacing suspension systems.  As on previous discussions threads what I trying to fix are as follows in priority:
1.  Tire/wheels; sticky big rubber maximizing contact patch.   My goal later to is migrate to Michelin Pilots.  Currently running 285/40R18 in rear and 255/45R18 in front with Conti DWs.
2.  AFter working on the car lately Ive been coming to the conclusion that the frame is pretty flexible and twists as you mentioned.  I ran some of my own tests in my garage and measured a few inches of flex.  The weakest point that I found appears to be the front torque boxes which is somewhat expected.   This is probably the second biggest weakness I see to improving handling with this car.  I looked into roll bars but I dont want to cut holes in the body to weld the roll bar to the frame.  To much butchering of the car.   I'm looking into how I may weld in a X-brace support to stiffen the frame from underneath. 
3.  Suspension tweaking tuning...changing springs, sway bars etc to meet the driving goals.   Lowering the car will help some, but it isn't drastic as some might think.  I agree with that.   One common problem of the era was the camber curves.  Lots of suspension travel to float over obstacles.  Same problem with the Chevelle and other cars of that era; with short spindle height putting the upper a-arm in a downward pointing position at rest.   High roll centers, etc.  In the end its the whole combination of parts that make it work which includes changing the suspension to a degree.

"Lowering will help a lot with how the car looks but it's not going to improve performance. Lowering the center of gravity on a chassis designed to a ride height degrades suspension geometry. There's nothing new to this:"

I'm lowering and changing the geometry, adjusting to stay withing similar tolerances.  Its mostly for looks.  I'm also looking at it regarding weight balance.  Currently I have over 1.5" rake front to back with stock springs and I want to reduce that some while lowering it.  I'm targeting a ride height over 6" as measured by the side frame rail.  2" drop should not be a problem, I still have more measurements to take.  Right now my car is 9.5" from the floor of the garage to the bottom of the frame rail in front of the rear tire.   Granted its a long wheel base and the ride height is set to clear average street obstacles( like speed bumps, man hole covers, etc), but seriously this is a truck. 


I like discussions presented as a trade study.   There is no right or wrong answer, simply a trade-off in results based on design choices.   The trick is to understand the original design requirements and reasons for them.  People bash OEM designs but dont often realize the difficult requirements imposed on the engineer with the pressures from upper management to keep stock holders happy.

As you said in another post these cars were designed as a family car with cushy suspension with a lot of under-steer.   I'm changing those design goals to a street performance oriented design.  I'm learning and making mistakes as a go and I correct them based on test results.  I do what I can to make informed changes and appreciate advice, info, design support, etc. to help reach those goals.  

I may bounce around a bit some ideas like using coil-overs, etc, etc. because I'm trying to weigh the trades with these metrics in mind: difficulty, cost, reliability, and performance value proposition.   I'm willing the sacrifice boat floaty cushy ride to get the performance.  I'll sit on a pillow if it meets the  performance goals.

Cool video...btw






Edited by BackInBlack - 30-October-2017 at 6:53AM
-John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72FordGTS Quote  Post ReplyReply Direct Link To This Post Posted: 30-October-2017 at 12:53PM
You're not kidding about the frame flex.  I have noticed it even when my car is on jack stands.  The doors don't close as nice as when the car's on the ground. Ford engineered these chassis to have flex in them from the factory.  There idea was to have a somewhat flexible frame but a stiffer body structure when they switch to perimeter frames. 
 
In the end I know John you are going for track performance, whereas I am purely street.  I have a lot of seat time in modern high performance cars. I can say the Torino's handling with CVPI springs, new bushings, Addco bars, spherical strut rod bearings and Bilsteins shocks is night and day from factory.  It's definitely a good handler for a big old car, and based on seat of the pants performance it feels better than a late model CVPI (definitely less understeer).  But, on the rough stuff, you definitely notice the flexing of the chassis and the lack of composure compared to modern high performance stuff.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BackInBlack Quote  Post ReplyReply Direct Link To This Post Posted: 30-October-2017 at 3:42PM
I dont know what the answers are...I'm not trying to redesign the car.   I'm not going for some extreme build (eg Chip Foose)  with custom chassis and cut/replaced suspension.   I had visions of grandeur and mistitled my project thread.   I'm really probably reaching for a little beyond your typical street build.   Not extreme...seems like there are some simple things that may be done to improve the frame.   

Gussets, cutting into the torque box and reinforcing it, X-brace ...I can see any of these options might be enough.   I just dont know.   For now...I'm just taking your advice, BillyC, and others and get teh car back on the road with the CVPI springs, etc.  and test it some more.   Figure out what the next improvement might be... 

I have the parts for the front suspension,  reworking the geometry just a little (ala shelby), and plan  to drop it 2 inches max.   I've got to get the paint and body finished now.  then finish the suspension and brakes.  I'll keep looking and learning regarding what I want ot do with the frame.   I definitely want to keep it streetable.

Edit: I was also looking for any reference material regarding the perimeter frame design.  What I noticed is that it flexes like a truck with the except of the front torque boxes.  They seem pivot at that point.   Try putting the jack stand under the torque boxes and watch the door gap.  


Edited by BackInBlack - 30-October-2017 at 11:06PM
-John
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