Thread: Project Sebring GT Spyder

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All I can say is that it's very complex.
And very very clever.

I had to do quite a bit of catch up on your build. Your top is really impressive, I don't know if I'll ever have the talent or patience to do something like that. Your wiring is so incredibly well laid out and organized also. I get more impressed with it every time you show what you're doing and what you've done. It took me quite a few miles to get most of the bugs worked out at Rita as well, I think there will always be a list though lol

That electrical panel is impressive, beautiful work.

Time to move on to alignment. A quick recap. I couldn’t find anyone locally that will do it, so I had to do it myself. That’s not really my thing, but you do what you have to do.

My tools are pretty basic. Just an antique bubble type caster/camber gauge, some rods and fishing line. 34_40 graciously offered to loan me a new digital gauge, which I really appreciate, but I thought I could get the old gauge to work OK if I could get it attached.

The problem with the magnetic gauge is that it is design to attach to an iron brake rotor or drum. Since there is no steel or iron on my front hubs to stick it to, I needed another way. I got around this on the initial setup during construction by temporarily fitting a cast iron rotor, but that would have been a real pain to do now. I doubt all that swapping would have given me a good reading, either.



I found a self-centering wheel clamp online that had a steel pad on it for this purpose. I can’t remember who made it, but that doesn’t matter because everyone that had them listed were sold out with no delivery date. That did get me to thinking though about the old wheel alignment machines that I had seen in the past. They all had similar clamps to hold their lights, lasers, mirrors or whatever in the center of the wheel. I did a little searching on EBAY and came up with a guy that had 2 old Hunter wheel clamps for sale for less than the price of the shiny new one that wasn’t available. It appeared to have a hole in the center, and I thought I might make that work. I took a chance and ordered them.

I was correct about the hole and made up a simple flange and spindle that just slips into the existing hole in the clamp. These were turned and faced in the lathe to insure they were square. They are made from a couple of old steel plates with 5/8 bolts for the spindle. The whole thing worked pretty well since the clamps are made for this. The old gauge seemed to work good too and the readings I was getting were repeatable. I actually didn’t need 2 of them, but it did make swapping sides easier and quicker.







I went through the whole alignment process before deciding that now was the time to get the car up on the scales and set the shocks and ride height. I know, I know…….that was a bad move. I should have done this first because it messed up the alignment and I had to go back and do it all over again.

The specs I started with was 6* positive caster on both sides, ½* of negative camber on both sides and 1/16” of toe-in. I wanted to take out some caster so I left the camber and toe the same, but lowered the caster to 3* positive. Actually, I have just between 2 ¾* and 3* on the right side (passenger) and a solid 3* on the left. I don’t know how this will drive yet, but it does have the positive effect of moving the wheels more to the center of the wheel well. That was one of those things that was bugging me.

The toe was set with fishing line strung between 2 square tubing bars supported by jack stands. Crude, but it must be effective, since both Formula 1 and NASCAR both use similar methods although with much more sophisticated setups. The rearend had been squared in the car during construction. I did a quick check and it was still square. Good thing too, since it would have been strange for it to have moved.





The front and rear bars were clamped together and the grooves were cut at the same time. That way the strings would always be parallel. Then it was just a matter of adjusting them to be true with the car and rearend.

I figured the actual measured amount of toe in a round-about way. I knew I wanted 1/16 toe in, but that is only 1/32 on each tire. Measuring that close to a tire is just about impossible, so I wanted to measure to the machined rim flange, but 1/32 at the rim flange would be more than that at the tire tread.

I found an online calculator that would convert toe in inches to degrees. Then I used another calculator that converted degrees to inches and simply input the diameter as 16.5 which is the outer diameter of the rim. This gave me about .019 at the rim flange. I’m sure I wound up with a little more than that, though. Very hard to measure that close to a fishing line! I’m sure I’ll have to tweak the steering wheel to center after I drive it. Still, it should be pretty close.

Good Job Mike. I have the "Salt Flat Special" wheels on mine. Uses the same or similar hub cap as yours. I made a flat plate of steel matching the bolt circle and installed them - I used that flat surface to attach the magnet mounted gauge. Just sayin'..

Getting the car up on scales was an eye opener, to say the least. On that front, there is good and bad news depending on how you look at it.

Right out of the gate, I’ll say that compared to other cars of this type, this one is an outright porker! It tipped the scales at 3250 lbs wet!!! I knew I had added some extra weight during construction, but I was a little surprised by just how much. To put this into perspective, a typical Cobra (original or replica) runs around 2400 lbs depending on engine and the original Sebring sales brochure says my car should be around 2550. So, I had added 700 lbs to the car without my fat butt even being in it!

I had kind of been expecting this (while hoping it might not be this bad), but it does make complete sense when you break everything down. I added a lot of metal to the structure of the car, most of it in the under cowl framework and the roll hoops and roll hoop support frame. Then there was the new metal firewall which is mostly 16 gauge steel. I had also beefed up the lower control arm mounts when I went to tubular control arms. All of this just made the chassis stiffer, so I consider that an acceptable trade off.

I also know I have a tendency to over-build things, but I’ll give myself a pass there too given the all of the custom parts in the car. If a critical custom part fails 500 miles from home, it might as well be made of unobtanium, ‘cause I ain’t likely gettin’ it replaced unless I happen to be in the parking lot of a well-equipped custom rod shop that wants to help. And, then I doubt I could afford it! The rear 3 link comes to mind. It has components that are many, many times stronger than needed, but unfortunately many, many times heavier than needed, too. The Watts link is also heavier than a simple panhard bar.

The stuff that didn’t make the performance or reliability better are things like a big AC unit, multi-speaker and multi-amp sound system, sound deadening, air suspension and larger seats. There is no telling how much was added by the over-done electrical system, alone. These things just make driving the car more enjoyable for me, especially on long trips. The seats are probably 3 or 4 times heavier than what was originally in the car, but without them, I wouldn’t be able to drive very far.

The T56 wasn’t necessary, but I like the double overdrive. I find shifting fun, most of the time. It is probably twice as heavy as the light duty T5 that was in the car but a lot stronger. The 9” rear axle is about 75-100 lbs heavier than the 8” that was in the car, but I like knowing that I can beat on it without much fear of breaking it. There is an old racers adage that says, “Worry about the ounces and the pounds will take care of themselves.” Unfortunately, that works both ways and my extra ounces made a lot of pounds.

The front/rear split was 46% front and 54% rear with me in the car. That officially makes this car a front-mid engine and helps explain why it seems to hook up so well. The 3-link helps there, too.

The weight also explains why the car rides so good once I got the shocks sorted out. A buddy that owns a 69 Camaro commented that it rode better than his car. The air suspension along with the extra weight is most likely the reason.

The main downside will be increased acceleration times. No way around that except to bump up the HP and I’m afraid that would negatively impact drivability. Right now, it drives like a stocker. No drama and no worrying about what gear you’re in (within reason). It’ll hit the 6500 rev limit very quickly (almost too quick in first), but will also lope along at 1700 in 6th gear. It also has a nice progressive throttle feel. No sudden surges in power. Just right for a car that is driven hard in corners. I would hate to change any of that.

A supercharger would be the only thing I would consider at this point. A Whipple screw type blower would add another 100 HP or more and would have that ultra-cool supercharger whine. Might even be able to adapt my big oval air cleaner to that. Something to think about although I would have a hard time slipping that kind of expense past the wife now that the car is “finished” in her eyes. And, I doubt Whipple makes a kit for the Holley accessory drive I have, so most of that “kit” would be on me to build. Sounds a lot like I’m trying to talk myself out of it, don’t it, but it DOES sound intriguing. Still, the engine is probably making an honest 400 or so HP at the crank as it sits, so I have to wonder if any more is really needed. Except for bragging rights that is. BTW – I’m making plans to get it up on a chassis dyno in the future. I would like to see what it’s doing, just for curiosity’s sake.

One potential benefit of the extra weight is that I may be able to use the easier-to-get 15 inch Cooper Cobra tires. The Cobra guys all seem to like the stickier tires for the extra traction with the lighter cars. Most of them consider that to be a safety issue given how hard it apparently is to get a Cobra to hook with something with the high wear rating of the Coopers. This car is now getting into the weight range that the Coopers were most likely made for. That being a typical American muscle car. It’s almost as heavy my buddy’s 69 Camaro!

Time to drive the snot out of it! Nice work! Enjoy!

Stovens, I'm doing the best I can and enjoying every minute

I also had a couple of issues with the air suspension.

The first was with the auto-leveling portion. I used the same circuit on this car that I had on my T-bucket. That system worked perfectly, but for some reason the same setup on the Healey refused to work right when adding air to the bags.

My system uses a combination GM sensor/control unit that was used on high end GM cars (mostly Cadillacs) from the late 60’s to the 90’s, maybe longer.



I combined that with a few relays, some small industrial valves and a small aftermarket compressor. The air bags have their own valves hard piped directly to the top of each bag. This makes each bag a separate spring and a leak in one won’t affect the other. When the system needs to add air, the control unit hits a relay that opens the valves on the bags and another relay starts the air compressor. When the sensor is satisfied, the compressor shuts off and the bag valves close. Going down, the bag valves open and a separate down valve opens. No matter which direction you are going, the bag valves must open. I solved this on the T-bucket by using opposing diodes in the relay circuit of the bag valves. Simple and cheap, worked perfectly on the T, but not on the Healey. Tried my spare controller, same thing. With the diode in place on the “up” circuit, the compressor relay refused to close. Pull the diode and the compressor started instantly. I even pulled the rear electric panel and carefully traced the circuit to see if I had made an error. Nope, just wouldn’t work the same way.

There have been many different versions of the GM controller in all the time that it has been used. They all look pretty much exactly the same on the outside. The ones I have are from the 90’s, while the one on the T was from the 80’s. It may have been some internal change to the newer controller was causing the issue. Since both controllers behaved the same, the problem had to lie somewhere in the internal controller circuits, unless both controllers have failed exactly the same way. Possible but not likely. So, what to do about it?

I removed the diode from the circuit and used a separate relay to trigger the bag valves that is now operated by the compressor relay and not the controller itself. The controller only “sees” the compressor relay now and seems perfectly happy to operate it. Luckily, I had left a couple of spare relay sockets in the rear and this mod only took about a day to pull the rear panel and rewire. The control system works perfectly now.

If I had to hazard a guess on what caused this, I would say that the output of the controller must be very limited in the amount of current it can send to the relay circuit. Having two relays on the output was dragging the current down so far that there wasn’t enough to do the job. When I pulled the diode, the circuit was able to trigger the single compressor relay. Funny though, that it worked on the down side of the circuit and was able to trigger two relays, but that circuit uses two micro relays and the up circuit uses a regular size power relay and a micro relay. Must have been right on the ragged edge of the controller output.

Not much to show picture wise here, but this is a shot of the rear electrical panel. I separated this from the under-dash panel for two reasons, lack of room under the dash and the possibility that some of this could change in the future. The air suspension control might have to be changed or the sound system may go out. Eventually, all this will be hidden behind a removable panel. There are also several relay and fuse slots for future upgrades. All of the connections can be separated quickly so the panel can be removed, and the panel is fed by it’s own 4 gauge feed from the main power disconnect as well as a 4 gauge ground that runs to a 5/16” stainless bolt welded to the chassis.





The radio is a Clarion Marine head unit with a wired remote control. There is no CD/DVD player since everything I listen to is either on a thumb drive or my phone. I 3D printed a holder for the radio remote that is mated to a Ram mount arm. This is temporary because I have an addition to the console planned that will incorporate this and the 3.5 screen for the Holley fuel injection. That’ll come later.







The amps are Audio Control compact units rated at 300 watts each. One for the four 6 ½ mid/tweet coaxial combos and the other for the subs. I didn’t have space for a true sub-woofer, so I had to use two 6x9 dedicated free-air woofers. Seems to work fine given the horrible acoustics in an open top car and there is enough volume for my half deaf ears to hear…..most of the time.

The compressor and air manifold for the air suspension. The compressor is by Viar. The fittings are all brass DOT push to connect. Solenoid valve is the down control valve and it’s Chinese. More on that later.

I might be asking a dumb question, but just wondering if your newer relays are the type that have a diode in the energizing circuit? The ones like that that I have encountered will let voltage pass in one direction only.

Ken, not a dumb question at all. Yes, a few of the relays have internal diodes, but I did check the polarity. After a screw-up at my relay supplier that left me with some odd reverse polarity diode relays (that I had no idea was even a thing), I swapped over to relays with resisters. As far as I know, they don't protect against fly-back voltage quite as well as diodes, but don't have forced polarity either. That little reverse diode fiasco cost me a day and a half of troubleshooting, head scratching and research to figure out, not to mention about 5 or 6 burnt out relays. Talk about learning the hard way!

This was the first project I've done with a lot of sensitive electronics so I used the protected relays to keep electrical noise down. In the past, I've used relays with none. I suspect with your background in avionics, you already knew all this and a lot more than I do on the subject. I know just enough to be dangerous, as they say!

The second issue was a leak. Depending on load, it could leak down in a few seconds or a few hours. The way this system is built, the only real places for a leak to affect the ride height is if a bag has a hole or the bag valve is leaking. Turns out this “leak” was two issues in one.

The system on my T used two small 7076 air bags and worked perfectly for almost 10 years with these as the only springs. I knew the Healey would be a little heavier, so I upped these to slightly larger 7012 bags. But, the Healey is far heavier than I thought it would be and this forced the system to operate at a much higher pressure to hold up that weight. This was obvious the first time I fired the air suspension up, because it took a looooong time for the bags to air up. It was obvious that the small compressor was struggling to get the job done. The T never took more than about 30 seconds, even with the system empty.

The Chinese solenoid valves are rated for 100 psi and I thought that would be plenty, because that is what the American made valves on the T were rated for. I never thought the system would get anywhere close to that pressure. Of course, the Chinese valve is most likely over-rated, as has been my experience with most things from China. That 100-psi rating is probably better de-rated to about 80 psi to be on the safe side.

The higher bag pressure was causing the solenoid valves to leak by. The suspension would drift down slowly until the pressure in the bag was low enough for the valve to handle and then everything was fine.

To solve all of this, I replaced the bags with larger 110/70’s so that the system pressure would be lower and replaced the bag valves with USA made parts with a slightly higher pressure rating. This seems to have done the trick. It now only takes about the same time as the T did for the system to adjust, even from zero pressure, and I don’t think it’s leaking down much, if any, even after several days.

The new bags did present a problem in that they don’t mount like the old bags and they are shorter. The length wasn’t an issue because the old bags had way more travel than needed and the height difference was taken up by a couple of thick aluminum plates. The top plate was made with a center stud attachment similar to the old bags to serve as an adapter. The lower plate is just a spacer.

The old style bag is on the left, the new one is on the right and the new bag with adapter is in the middle.



Here are the new bags on the car. You can see the new valves piped to the top of the bags.





While I was at it, I also swapped out the standard coil over springs for progressively wound springs. These allow the air suspension to be the main support for a good ride but get progressively stiffer the further they are compressed. Air bags are progressive by nature, but not enough, IMO. The T would find the bump stops every now and then on big bumps. I’m hoping the progressive springs will keep this to a minimum on this car.



I think it’s all good now. Driving will tell. Hope to do that this weekend.

I’ve been fighting an oil leak on the valve covers since the car has been on the road and I think I have finally solved the problem. I replaced the gaskets a couple of times and replaced the bolts with a different style, but nothing seemed to work. The leak wasn’t terrible, but it was enough to drip oil down on the exhaust ever so often and stink. Also, there was an oil film on everything under the car. With all the O-ring style gaskets on an LS engine, this just didn’t seem right. I used to expect it with the old school cork gasket engines, but the new engines are supposed to be more oil tight.

The issue, I think, was the Holley valve covers. They were badly bowed and warped. This may be a generic problem with them since I have looked at two sets, bought at different times, and all 4 covers were almost exactly the same. All 4 were out of “flatness” by pretty much the same amount in the same places. I wanted to keep these because I like using the old SBC valve covers as coil covers.



The covers only have minimal finish machine work done on them from raw castings and this was for threaded holes. No finish machine work was done on the sealing surfaces. When checked on the seal side, they are low in the middle of the cover by almost .060 of an inch. That’s a 1/16! No matter how good the gaskets are, they can’t handle that much difference in the sealing surfaces, and since the covers are just hunks of thick cast aluminum, they are way too stiff to flex. The bow is present on the top side, too and caused some minor issues with the SBC covers.

The Z axis readout tells the tale. This particular cover was out .051 (inches). That’s .011 shy of 1/16”.



This shows how bad the top surface was. The straight edge is laying across from to top end to end. Look at that gap!



I fixed them by giving them a ride in the milling machine. This took them down to a flat surface, but it did create one problem. The LS valve cover gaskets have a rectangular projection on them that locks into a groove in the cover. This groove was now too shallow on the ends of the cover to allow the o-ring portion to seal. I had to trim the “tails” where needed and then resort to the old SBC trick of gluing them down with black 3M weatherstrip cement. Messy, but effective. There is still about half of the locking strip left so I’m not worried about them blowing out.

While doing the machine work, I discovered yet another issue with them. The covers that were on my car were powder coated when all the other parts were done on the car. In the interest of saving time, I machined an extra set I had that came from Holley already powder coated black. At least, I thought they were powder coated. While blowing the aluminum shavings off from machining them, I was pretty surprised to see the paint on the inside pealing off in big chunks. I couldn’t put them on like that and have all those paint chips get sucked into the oil system, so I had to bead blast them on the inside to clean them up.

The bottom cover had that much paint come off with nothing but a blow gun and shop air! You can see the new machined gasket surfaces.



After stripping the inside and gluing on the gaskets.



There is also another flaw in these covers. The lips cast into the cover that are supposed to hold them in place while starting the bolts are too short to work right. I could probably solve this with a couple of pressed in dowl pins, but instead as a quick fix, I made 2 headless bolts to serve as guides in the mounting holes. This worked, but I think the dowls would work better.



Sorry, but this is a pitiful reflection on Holley. I know they can build good stuff since the Holley mid-mount accessory drive I have on this engine was one of the best fitting aftermarket parts I’ve ever installed. It went on and functions like an OEM part. These valve covers may have been a neat idea, but the execution was pure crap.

I have about 40 miles on the car since the repair and I haven’t seen or smelled any evidence of a leak. Fingers crossed.

Speaking of oil. I changed the oil again. This time after about 3000 miles. I cut the filter apart and found nothing unusual, even in bright sunlight. This oil was an old-fashioned dino oil as was the new charge. Now that I think the oil leaks are fixed and everything should be broken in, I will be switching to some kind of synthetic going forward. If anybody wants to make recommendations as to brands they like, I’m listening. I may go with a semi-synthetic rather than a full-synthetic since I still like to change the oil in my toys every 3000 miles or so. Remember, I AM a 20th century Neanderthal after all, and the full-synthetic stuff is pretty pricey for that.

Sorry to hear about the valve covers. Shame really, they went out the door so poorly made. Not a good look for Holley I'd think. Oil? After a few trips I changed mine out and went with Mobil 1 10w30 for a few years. Lately I've been running Royal Purple 10w30 no real reason for the switch except it's what my parts store had in stock. But I do notice the oil pressure is consistently higher by 8 to 10 psi. fwiw..

I know of many that run Mobil1, but I'm hard headed and have stuck with Pennzoil. I run synthetic 5W-30 in the Dakota and 10W-40 High Mileage in the Vette along with some ZDDP additive. I don't use anything but Wix or K&N oil filters.
Mike, my background was in radar though electronics was just getting in to solid state but the theory is related except in a much smaller package.

Full synth at Walmart, Quaker State for 20 bucks a gallon, that's pretty cheap. I think I would've thrown those covers in the garbage, good save.