LocostUSA.com

Picked up the steel I needed. 3x2x11ga @ $7/foot along with cold rolled round that is nice to have on hand. 3/8=$0.65, 7/16=0.84, 1/2=1.10/foot.

The coilovers are the deal breaker on not cutting the floor. The original spit dampers have the upper end buried in the tunnel opening for a poor mounting angle that is slightly improved by the tbird upright being closer to the car CL, but there isn't enough room lengthwise to allow a decent mounting angle without the bottom of the coilover well below the LCA. I've considered trying to reuse the transverse leaf (too wide), torsion bars, pushrods, bellcranks, bike mono coilovers, race shocks for dwarfs, atv utv universals (which I already have), poured through oem damper/strut catalogs, and made a tech call to moog for some unlisted specs.

I found a pair of car replacement rear strut assemblies for under $100/pair. The spring rate is 180#, they have an extended length of 16.5 inches, and 5 inches of travel but the diameter is around 6 inches at the top (they taper) which would require widening the corrugated tunnel or some other creativity. They have an eye lower with a flanged upper hat mount about four inches down from the top.

I decided to raise the original cross tunnel 3 inches with the belt reels, leaving the pinch weld to the fender wells, then spot/stitch to the fender wells 3 inches higher, bend/slope/fill as needed with .050" in front and back, then paint and seam seal like the original. This should keep it looking close to original, clear the 8.8, clear the tbird UCA and spindle, allow the tbird diff mount to be used, provide more LCA clearance, and more room for the mufflers to tuck under the trunk. The tunnel body mounts are retained. The down side is the original fuel tank won't fit as-is but it is a bit too small anyway and mounted higher than necessary.

Put my plasma cutter together. It had no hose kit or hardware so I need to pick up some 3/8 braided vinyl. Organized the extra accessories I bought in a clear plastic tackle box. I use these boxes for mig parts and drill bit organizers.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Tacked my 2x3x31 rails into a U around the back of the 8.8 with a 1x3. I'm using the bulky oem tbird diff rear mount. I have everything I might need but 1/8x3 strip for building the diff mount frame side brkt so back to the metal shop.

Figured out how to fab my upper spring seats and ordered my rear struts for $45/pair plus $25 for the bump stops and bellows. For about $82 I could have the complete assemblies and had left over upper seats and springs I could use on something else. I already have the adjustable lower seats from the lowering kit I used for the triumph front dampers. Standard 2.5 id springs, extended length just under 15 inches with about 4.5 inches of travel, no strut mods so a standard replacement part. The kit came with short springs but they are way too stiff. I think they are about 450# if memory serves.

Roughed in first attempt. Rails will need to be narrowed another inch so the body mount holes between the seats are not directly over the outer wall of the tubing. The diff case where the cv cups enter should be equidistant to the car CL for equal length shafts but an offset pinion. Diff roughly placed back in to check distance to the diff and the precise angle and location is not set. Pinion will be offset, angle level to rails, height TBD and not ditated by the rail clearance since the rails below will be removable and shaped as needed for clearance. Looks like the tbird rear mount will need to be two inches above the rail. Since the cross tunnel is being raised, it may not be an issue since current rail-floor clearance in this area is about 1-3/4. Currently left 3 inches too long.

By bringing the rails in as far as possible, I can add about four inches to the LCAs.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Picked up 1/8x3/4 and 1/8x3 for $0.51/ft and $2/ft.

Had to do some maths...
NEEDED: minimum distance from rear rail mount hole to rear cross member forward face.
Dim 14 ifs turret mount to the rear most rail attachment, 68.1-68.22, 68.16 +/- 0.6
Dim 15 ifs turret mount to rear face of the upper body tunnel mount/damper mount; 86.93-87.19, 87.06 +/- 0.13
Dim 37, axle CL to rear face of upper body tunnel mount/damper mount; 4.06"
Tbird rear diff mount rear edge to tbird diff axle CL; 10.5"
Ifs to rail 68.16"
Ifs to shock 87.06"
Shock to axle 4.06"
87.06-68.16= 18.90"
18.90-4.06= 14.84" rear rail mount cl to axle cl, +/- 0.13.
14.84+10.5+0.13= rear rail mount to rear cross member minimum distance (rounded up) 25.5".
With this spec, after I finish building the irs in the body, I can weld the chassis back together and the axle and attachments should be in the correct position for setting the bonnet-door-cowl gaps.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Here is the rear diff mount design to use the original tbird mount under the spitfire trunk floor with no holes.
Also changing to a 3x2 xmember from a 1x3 due to the diff mount load.
A 2x6x1/8 strip with 7/16 nuts welded on will slip into the open sides of the 1x3 mount base.

A pic of the oem irs diff mount.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

MV8, that looks very overkill IMO. I would think since the 2 mounting bolts are only 1-1/2 off the edge of a 3x2 on edge, a simple 1/4" plate across the top of that 3x2 would be more than enough to transfer the torque to that 3x2. If a bit more strength is desired, adding two 1/8 " strips , in a position like the orange ones would be plenty. I think I would do that. Your build though.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Thanks! I hope you are right! I'm not sure how much upward force may occur over the open vee mount. The oem is really a half mount with a rubber pad on top to sit against am xmember that is about 3 inches thick if memory serves. I have only an inch or so to work with above the mount without cutting the floor since the mount flange is an inch above the rails that are two inches below the floor, so a third of the original cross section.

Looking at the factory five, they maintain the cross section of the cover flange by tying the cover directly (no rubber) to what appears to be a 1x2 wide side up and a tubular x-brace. Too easy to damage the cover without a mount (and the partially threaded bolts to prevent overtightening) but it would make it much easier to fit and fab.

Pretty easy to make this with 1/8 strip and a handheld bandsaw. We'll see how it goes when it warms up enough for me to get out there.

Here is the diy coilover tops for my oem rear struts and lowering kit sleeves.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I think this is right. Somebody, please check my very amateur physics and math.

This mount shares the torque force with the forward mounts. For the ease of figurin', assume the engine can put out 200 Ft-Lbs of force, the diff is 4:1, the mounts are 1 ft from the axle center, and the tires will give infinite transfer to the pavement.

(200ftLbs *4) = 800 ft lbs of twist. Share that by two mounts at 1 ft from C/L and each mount will see 400# of twisting force. If the length from axle center to mounts are unequal, then the force they see is inversely proportional. 400# of force at 1.5" off the edge and 1" from the center of the 3X2, then (1.5+1)/12 = 0.21. 0.21 *400 = 83 ft-lbs of twist force on the 3x2. It still has ~400 lbs of beam force on that 3X2. There are various calculators online that will quantify the design, such as https://www.engineersedge.com/

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Thanks for that! I'll plug in some specifics. I didn't even consider calculating and just looked at the 4000lb tank it came out of.

I have several T5s for different applications that I could use. Worst case would be the worst T5 I have with a 4.03 first and the 2.8 tweaked to about 200 ft lbs, subtracting 20% parasitic for around 645 ft lbs to the 8.8 diff which is a 3.08 for 1986.6 ft lbs. The mounting CL from the axle CL is 7.5F/10R for 198.6 ft lbs down since the pinion tries to climb at 265ftlbs. I guess my concern was for reverse. Probably some dynamic worst case of suddenly getting traction, but yeah, sounds like overkill.

EDIT: my math was wrong as I didn't split the diff load between the mounts. Still close to your results. Think I will keep the orange flanges, yellow filler, and use a 1/8 base, then fit a floating 1/8 nut plate on top, leaving off the green and purple strips.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Found some time today to work on the rear coilovers.
Ground the shoulder of the oem spring seat so the threaded sleeves would seat properly. Traced a 2.5" id coil spring on to 1/8x4 strip and cut out the bases, drilled to clear the m10-1.25 strut stud, rolled 1/8x1/2 strip around the edge and tacked, then hung the coilover by the stud to locate the nut and protect the threads while welding the nut to the base.

I have a few sets of 2.5 id springs to pick from depending on the effective angle. Still need to fit the upper parts (tube/shell, maybe gussets), make a bush and sleeve, and pick up the jamb nuts.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Assembled my diy strut coilovers. I've not decided if I will add a tube top or flanges to the diy upper seats.

After considering eccentrics and threaded adjusters, I've decided to make removable lcap brkts that can be shimmed to adjust toe with 3/8" nut 3x3 plates on the rails and the flanges about 2" apart (left side drawing in pic). This way I can make new brackets off the car if not satisfied with the lcap location. Using an energy susp poly bush kit for the tbird knuckles. Lcaps are energy susp 8.3118r for toyota camry and avalon applications. Accept a 7/16 bolt and 1.5 inch pipe shells 1.5 wide.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Tbird rare pressed and riveted (most are cast iron) lca showing toe control link and lincoln aluminum lcas with single shear knuckles.

Final rev on the rear diff mount.

Compliant bushing kit for tbird knuckles, $65.

Finished the shells. Perfect fit to the toyota energy bushes. Cut all the lcap brkt flanges with a paper template, drilled the hole to 3/8 (will be 7/16), then fit a bolt to clamp the band sawed flanges together. Currently grinding the edge so they are all exactly the same size.

A pic of some of the atv type coilovers I was looking at before making hats for strut based.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Cut and drilled all the IRS lcap brkts and base plates for welding to the rails, providing toe and camber adjustment with the compliant poly bushes. Temp grade 2 hardware for fitting.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

This just in! A spy photo from deep within my state-of-the-art build lab. Fit the rails to the chassis and marked off to start fitting the diff and install lcaps on the bench, then finish in the shell before welding to the chassis. Still need to rework the rails around the T5 tail housing and mount the trans mount brkt. BFH on standby.

Difference between 7.5 front diff mounts and 8.8 with bonded washers and a inner crush sleeve. I cut some 0.75x2.5 1/4 wall dom to reuse the original tbird bolts but changed my mind.

The triangle cuts are to clear the original nut plates welded inside the frame that are in perfect shape and I didn't feel like trying grind out from the inside. The rail outer wall falls right on the hole cl.

Have most of the front mount done too with three 1/8 strips but I think I've done enough for today. The sun is blazing.

Some unusual builds I've seen on FB or craigs. Yes, I am being nice. To each his own. The beholder and all that....

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Those build are a little scary to me. As you say, to each his own.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

My thoughts exactly! I can only imagine the amount of twist in those frames!

_________________
Thom