Reviving Dead Cobra

[C5GTO]

With the onset of the summer driving season and after more than a year sitting around the garage with a dead engine, I felt compelled to revive the Cobra with a new engine. For some history, I first built this Classic Roadsters Cobra in the mid-90’s and had actively driven it to over 50K miles since then. For the last 25K miles, the car has been outfitted with a Ford Performance X302 which is a roller cam crate motor outfitted with Ford aluminum heads and other go-fast goodies. It was advertised as having up to 340HP of which mine had most but not all of that.

Just over a year ago while doing some spirited driving, an ominous “clicking” sound emerged out of the engine bay. At first, I thought it was a header gasket that started leaking. After a bit more driving, it turned into a “clacking” sound like maybe a rocker arm had become loose. Long story short, I limped the car home and after some basic diagnostics (compression check, rocker arm check, etc.), I determined it was an issue somewhere in the bottom end which would require engine removal.

I didn’t have the enthusiasm or garage space for the tear down so I put a car cover over the car and left it to gather dust. A related issue is that the car really needed an overdrive type transmission like a Tremec as the Richmond Gear 4+1 transmission translated into high engine RPMs at driving speeds in the 70-mph range. So the price tag for the repairs was not only a fixed engine but also a new transmission.

Fast forward to this last winter while the snow was flying and I was starting to have some serious withdrawal symptoms from not having a Cobra to keep driving exciting. I now had a new detached garage so space was no longer an issue and I decided to pull the engine to see what the problem was.



Everything inside the engine looked beautiful except the rear piston on the passenger side which had tried to weld itself to the cylinder wall. Obviously, a lubrication breakdown of some sort had raised its ugly head.



I had been hoping it was a spun rod bearing or something that could be fixed with some parts replacement. This was worse in that it had not only damaged the piston but also the engine block. Not something impossible to overcome but certainly more involved to fix. After some cussing and swearing, I decided the Cobra didn’t have enough power with the old engine and what was really needed is a 347cid engine to go with a new Tremec TKX transmission. After all, what Cobra can’t use a little more punch

[Tommy]

For me, every engine failure was mainly an excuse to upgrade.

[C5GTO]

After shopping around, I decided the replacement engine would be a Prestige Motorsports 425HP 347cid longblock. I also frequent the GT40s.com forum and a lot of guys speak highly of motors from Prestige Motorsports. They build them to order and dyno test each engine to ensure it meets the advertised performance specs. This way I could reuse the Canton oil pan and EFI setup from the old engine. They also offered a 440HP version of this engine which is basically a more aggressive camshaft. I opted for the 425 version as that extra horsepower is way up in the RPM range where it virtually would never get used on the street.

The build took a few weeks and they provided pictures while all the parts were coming together.







Yes, every setback and failed engine is a great excuse for an upgrade.

[eschaider]

Unless your engine failure was caused by an overheating problem, it was a tune problem. You will need to get your EFI retuned for your new engine, or it will suffer a similar but more extreme version of the failure you are currently repairing because of the increased power levels.

[C5GTO]

Originally Posted by eschaider

Unless your engine failure was caused by an overheating problem, it was a tune problem. You will need to get your EFI retuned for your new engine, or it will suffer a similar but more extreme version of the failure you are currently repairing because of the increased power levels.

It wasn't a coolant system overheat problem as the coolant temps at the gauge sensor didn't exceed 195 degrees prior to the failure. It might have been a localized overheat issue around that cylinder but I have no way of knowing that.

It could be a tune issue as the EFI system is a 30 year old EEC IV setup. The EFI was dyno tuned about 10 years ago but that was done much closer to sea level. The engine failure occurred at about 7,000 ft elevation. Yes, the ECU should have adjusted for the elevation change but you never know.

I am looking into a new EFI for this engine at this point. Another reason is driving this but I'm also concerned that the existing 30 year old EFI tech is a shaky foundation to build on and my trust level with it is low.

[Snake2998]

With EFI you could easily get one injector not working properly and that cylinder running over lean or one injector leaking and fuel washing away the lubrication of that cylinder. If you reuse the injectors have them checked.

[C5GTO]

While waiting for the engine to be built and given the anticipated additional 125 HP, I decided to check out the brakes and rear end. After pulling the front calipers, I found the pads to be wearing crooked and thin. This Cobra has Mustang II front suspension and when first built was outfitted with the larger Granada rotors and GM “mid-size” single piston calipers (I believe D52 is the official GM designation). After further inspection, the cause of the angled/crooked pad wear is that the caliper brackets weren’t holding the calipers square to the rotor. Whoever made these aftermarket brackets did a poor job of designing/fabricating them and so off to the scrap bin for them.

Ok, so at a minimum a new set of caliper brackets and pads were required. The brakes had functioned adequately for the 50K miles on the car but as is the emerging theme here, every part failure is an opportunity to upgrade! So I decided to go with the Wilwood D52 bolt-on replacement calipers.



These units provide an upgrade to a double piston caliper and are made from aluminum for less unsprung weight. The piston surface area is about the same as what they are replacing so they won’t clamp any harder but should apply the pressure more evenly over the pads surface. With a new set of properly aligned caliper brackets, these should work very nicely. And yes, they do look better what little you can see of them through the Halibrand style rims.

On to the rear axle which is a 9 inch outfitted with Lincoln Versailles disks. The pads here showed very little wear which tells me I should look at adjusting the brake bias so rear brakes are used more. Now to test the posi differential to see if it is functioning properly. I blocked one tire from turning and spun the driveshaft yoke. The other tire turned just like an open differential works. No resistance was felt at all like you should feel with a minimally working posi unit.

Ok, so the rear axle needs to come apart. It had a slow drip leak from the pumpkin gasket that had been bothering me for many years. Now I had adequate reason to tear it down and fix that as well. After pulling the 9 inch pumpkin, I discovered it had a Ford Traction-lok clutch style posi.





I looked into rebuild kits for this unit, which are available, but the Traction-lok is 50 year old technology and the popular opinion is that the clutch disks wear fairly fast (even with friction modifiers) leaving little to no posi function sooner than preferable. So you guessed it, every part failure is an opportunity to upgrade!

I decided to replace the differential with an Eaton Detroit Trutrac unit (which contrary to its name, is made in Taiwan) that uses helical gears instead of clutches to provide its limited-slip function. Popular opinion on these is that they work great and don’t wear out like the clutch-based units. The ring and pinion looked fine so after replacing the differential roller cups/bearings, I proceeded to reassemble and setup the rear end. I used a LubeLocker brand gasket and so far no leaks or seepage has occurred so hopefully one less oil puddle to wipe up on the garage floor.

Well, if I keep this up, all the major mechanicals in my Cobra will get an upgrade! My pocket book says, “Ouch!” but hopefully it will all be worth it once I get the car back on the road.

[twobjshelbys]

Originally Posted by C5GTO

It wasn't a coolant system overheat problem as the coolant temps at the gauge sensor didn't exceed 195 degrees prior to the failure. It might have been a localized overheat issue around that cylinder but I have no way of knowing that.

It could be a tune issue as the EFI system is a 30 year old EEC IV setup. The EFI was dyno tuned about 10 years ago but that was done much closer to sea level. The engine failure occurred at about 7,000 ft elevation. Yes, the ECU should have adjusted for the elevation change but you never know.

I am looking into a new EFI for this engine at this point. Another reason is driving this but I'm also concerned that the existing 30 year old EFI tech is a shaky foundation to build on and my trust level with it is low.

The old EFI system probably doesn't do altitude compensation, but going up in altitude causes a rich condition. Did it backfire? Engine overheating from fueling is usually caused by a lean condition.

You should get a new EFI system, but at the cost these days, and if you don't need the benefits - ie, automatic altitude compensation - and unless you use a MAF based system which does compensate for altitude and other conditions, then you're just as well off with a well tuned carb(s). There are many topics on this subject here so I won't repeat any more other than to say that in most cases an EFI system operates as a very expensive carb.

[C5GTO]

Now on to my current Cobra revival dilemma, the EFI/ECU system, should I stay with existing or upgrade to newer technology? I was anticipating getting the new long block motor, dropping it in the Cobra, topping it off with the old EFI unit and having it on the road already. I’ve had the new engine in my possession for about a week now, I’ve been busy “preparing” it for install and no rumble from the side pipes yet.



When you have a collection of aftermarket parts that make up your engine (the engine block is the only component sourced from a Ford factory), it’s most often more complicated in real life than in theory. Ford changed several things on these small block Windsor motors over the years that is most often the root cause behind complications. Things like drive belt pulley spacing, water pump hose inlet location, timing indicator/pointer location and an EFI intake that extends over the valve covers. So as I was working through preparations/adjustments, I decided to trial fit the intake manifold. I had made the assumption that if the intake fit over the existing valve covers and these same valve covers were used on the new engine, then the intake should also fit with no clearance issues on the new engine. Here’s a picture of the old EFI intake that has been on the car since original build.



So I went to great lengths to make sure the old valve covers would fit over the new engine valve train and thus I should avoid any complications there. That assumption proved false and my biggest complication so far. It turns out the new aluminum head castings are taller than the Ford X302 aluminum head castings that were in the old engine raising the valve covers upward by about ¼ inch. It’s no wonder why these heads flow better, they have more room for the passages and ports.

This wouldn’t normally be an issue but it is if you have a big, wide intake with minimal/no clearance between the intake plenum and valve cover top. I had to squeeze out all extra space way back when to fit the engine under the hood (even lowered the engine mounts by 1” as well). So even after grinding away about 1/8” of material on bottom of intake plenum, there’s still a gap in the upper and lower intake flange of about 1/16”. Any more grinding and there will be a hole into the intake, not good.

In trying to identify all possible resolutions, it occurred to me that an upgrade to a Weber style 8 stack EFI would work. In pricing it out, yikes, that’s an expensive option but boy, wouldn’t it like right at home in a Cobra.



I could also go down the path of buying a different long runner intake that has a shorter plenum, would fit over the top of the higher valve cover and still fit under the hood. A much cheaper alternative but just doesn’t have the same eye candy appeal of Weber throttle bodies.



If the 25 year old EEC IV system is left in place, it’s really a ticking time bomb and potentially the cause of the prior piston failure. Upgrading the ECU is a possibility but is doing that just a slippery slope to a new throttle body, distributor/ignition system, etc. etc. All this to just end up with an EFI intake that doesn’t really look right in a Cobra anyway. Those Weber ITBs sure have the right look but at 4X the cost, yikes!

Are there other viable alternatives I’m missing? I don’t really want to go a non-EFI option like carburetors. I’m told that the Borla ITBs are really the only non-junk ITB option out there.

I’d be interested in hearing your thoughts, options, etc.

[twobjshelbys]

Or like I said you could just use a $750 carb and an hour with a tuner and get the same results as a 3k-4k efi hardware and a day with a tuner.

To really understand why I claim the above just understand modern self-adjusting fuel injection systems in modern vehicles were a solution to the stricter emissions standards. Manufacturers could make a vehicle that would pass emissions and operate well under all conditions - mainly altitude. And static altitude at that. Probably less than 10% of the cars actually driven in the US actually benefit from the semi-automatic altitude compensation built into todays EFI systems. Most run the same drive back and forth to work every day for decades as I have. But Ford, Dodge and Honda got to build one car that operates at sea level (or near it) as well as at 8000 ft.

If you're looking for bling, then the faux 8-stack is eye candy. And I say the 8-stack+EFI solution is best if you want that look only because I wouldn't wish a real 8 cyl Weber on anyone. But the EFI systems that go with them are finicky and the adjustments needed to keep the throttle bodies synchronized are not for someone that isn't mechanically inclined and equipped with the proper tools.

Otherwise EFI will not really gain anything that a good carb will give you.

But it's your money

[Tom Wells]

two,

I agree with the points you make above :-)

As a survivor of two impossible carb misadventures I'd like to add another point: with today's gasoline, which it is in name only, there are vast differences in that fluid as currently produced compared with decades ago when carbs were king.

Short answer - boiling point of gasoline in 1960 was way higher than it is after 2000.

EFI can deal with today's alcohol-laden gasoline substitute mostly because it operates well above atmospheric pressure. Something like 43 psi or more. This keeps the alcohol component from evaporating. When it does boil it can sometimes be spectacular.

When the carb's float bowls are above roughly 120 degrees F, if I stopped after a 10 to 100 mile run, the bowl vents looked like Old Faithful. This resulted in flooding the engine, leading to instant shutoff.

Tried insulators, heat shields, carb fuel return systems and more I don't recall at the moment; finally gave in to the the laws of physics and went to EFI which solved that problem. The only thing I didn't try was aiming an air conditioning vent at each float bowl LOL

The altitude compensation, cold starting and other items are lagniappe, not the main course for me. Have over 50K miles on two Holley EFI-equipped engines and wouldn't think of going back.

My 2 cents,

Tom

PS: The only other thing I'd like to have tried was no-alcohol gasoline. Sadly, it wasn't around enough years ago to be practical. If I had a carb today, that'd be the first thing I'd try!

[patrickt]

Tom brings up a good point. But, with 93 octane E85, an aluminum turkey pan and keeping the levels in the bowls just a bit lower than the 60 year old "to the sight hole" rule, my Holley 3310 can handle 165 degree bowl temps with no problems. Now, my turkey pan is removable and when I pull it off and go for a ride you can definitely tell the difference. Give me an ol' fashioned carb any day of the week, but you've got to be prepared to learn how to tweak it just right. And a carb is never going to go heavily lean/rich on one cylinder and result in a seize up.

[C5GTO]

So after looking into the Weber style 8 stack option for a couple of days, I’ve run into a potential show stopper timing issue. My number 1 motivation for reviving the Cobra was to have it drivable for this summer driving season. Well summer is here (in Arizona anyway) and the Cobra still has no rumbly sounds from its side pipes. Now I’m finding out there’s an 8 to 12 week lead time to have a Weber style 8 stack system ready to ship. Then I’d have to custom build an air filtration unit for it (the only purchasable option is screens that keep the large rocks out) because it’s dusty in the desert and I have a ¼ mile rock/dirt roadway to get to my house. Yes, I can build the air unit but not until I have the 8 stack in the same garage as the Cobra.

Hmmm, sounds like I’d be feeling the chills of autumn before I’d have the Cobra back on the road if I went that way.

So I’m looking at any and all alternatives that get the Cobra to a drivable state in the not too distant future at a reasonable cost. Given the posts above about carburetor versus EFI, 93 octane gas is not readily available in my area and I really don’t want to have gas boiling on a hot engine or gas fumes in the garage. So I’ll stick to EFI alternatives unless none play out.

The alternative I hadn’t looked into prior is using an old school 4 barrel intake manifold and a Holley carb style EFI system. It looks like a 4 barrel carb for an authentic Cobra look. Check. They are in stock at Summit for quick shipment. Check. The TerminatorX Stealth product is self learning but also connects to laptop for diagnostics and tuning. Check. The basic bits add up to about $3,400 but if that gets the Cobra driving again with the 91 octane gasoline available from the local stations then OK. My Cobra is already outfitted with the EFI basics like a high pressure fuel pump/filter and a gas return pipe to the tank. So potentially the Cobra could be back on the road in a couple of weeks. Check.

So for the people that have experience with the Holley carb style EFI, what’s your experience been like? I don’t expect to get more power than a 4 barrel carb but that’s not the point. It’s about drivability, no gas boil-overs, no gas smell in the garage and being able to fuel it with the garbage gas locally available. Were you able to get the Holley EFI systems installed and working with a reasonable amount of work? Have they been reliable with good drivability?

[twobjshelbys]

So it seems to me that you are a bait and switch participant and you've already made up your mind and are on a path and are dribbling our your path a little at a time. If so just say so and stop asking us to analyze it. So be it, but I'm done trying to give advice since you've already decided and like voting for president, it won't change your path or your mind. In the Cobra space there are no wrong or right solutions and you are free to solve the problem however you want.

At least half of the regular participants here are in the Phoenix valley. Ask them.

It's your money. But as far as EFI is concerned for me a fool and his money are soon parted unless you meet a very short list of requirements. A street car in the valley is not on the list.

Good luck and have fun.

[C5GTO]

Originally Posted by twobjshelbys

So it seems to me that you are a bait and switch participant and you've already made up your mind and are on a path and are dribbling our your path a little at a time. If so just say so and stop asking us to analyze it. So be it, but I'm done trying to give advice since you've already decided and like voting for president, it won't change your path or your mind. In the Cobra space there are no wrong or right solutions and you are free to solve the problem however you want.

At least half of the regular participants here are in the Phoenix valley. Ask them.

It's your money. But as far as EFI is concerned for me a fool and his money are soon parted unless you meet a very short list of requirements. A street car in the valley is not on the list.

Good luck and have fun.

Thanks for your input Tony.

If you are referring to a made up mind on carb versus EFI, then yes I want to go the EFI route. That wasn't the question being asked though. The question being asked, and I really have not made a decision on it yet, is which form/product choice of EFI.

My perception from being a car hobbyist over the last 30+ years is that the formulation of gasoline available at most local stations will follow governmental regulations and the needs/requirements of the vehicles consuming it. Since the vast majority of regularly driven cars have EFI these days, I can only assume the gasoline formulations will continue to be optimized for EFI and to minimize air pollution. My intuition tells me that gasoline formulations will continue to change and only get worse for carbureted engines. That's my opinion but I wanted to be transparent to encourage others to share their experience with aftermarket EFI products.

So please do speak up (yes, you who live in Phoenix area as well, this forum is my way to reach you) and provide your experience with the various EFI options for Cobras.

[twobjshelbys]

I learned all I wanted to know about retro-fit EFI systems with my Cobra which was equipped with a Accel system that did not self learn and after much time and money found that Roush had not populated the altitude compensation table.

I do not believe gasoline formulations are a first order effect of any driveability (ie steady state) issues with carb based engines. They are "tuned" out early leaving seasonal variations which are second order effects. Yes, today's fuel can be a contributor to vapor lock and other problems but first I never had it happen and second don't consider spending all the extra money to prevent a problem that I've never experienced. I was stuck with my system and the cost to get it working. The guys that drive their cars almost every weekend on some road trip can give feedback about the necessity.

Have at it though.

[sunman]

A friend of mine has a Terminator X on a LS motor in a 70 Chevy truck
He’s got the Dakota custom dash that fits the truck
It’s sweet and on my list of parts
Kinda would like to hear more feedback on the system if anyone is using one

[PDUB]

whatever you do, I encourage you not to put that awful, ugly Mustang efi stuff on there! That is just not Cobra material...

A short term option could be a 4v intake and carb as a temporary fix until the proper efi setup can be delivered. That would get you driving this summer and give you another project for next winter. Sell the intake and carb when you're done. You have the added advantage that if the carb works for you, you are done! If not, change it out for an efi...

[C5GTO]

Originally Posted by PDUB

whatever you do, I encourage you not to put that awful, ugly Mustang efi stuff on there! That is just not Cobra material... [

Yes, I'm in agreement the 90's Mustang style intakes don't look at home on a Cobra!

Here's the setup the guys from Prestige Motorsports are recommending. It's the Holley TerminatorX multi port EFI:





and maybe top it off with an oval Cobra air cleaner. If I added a turkey pan it would even cover up the EFI fuel rails.

I was at a dyno tuner today for a different car and the tuner highly recommended the Holley TerminatorX ECU and tuning software. Said in his experience it's one of the best available today.

In thinking about this further, if I go the multi port EFI route (versus Sniper or Stealth style) and I got the itch for a Weber style 8 stack later, then all that would need to be swapped out is the intake manifold and add Weber throttle bodies along with a new wiring pigtail for the imbedded injectors. The ECU, sensors, dist/ignition are all common/shared between the multi port and 8 stack systems.

Does anyone have experience with the Holley TerminatorX multi port EFI? Whether on a Cobra or other vehicle, I'd like to hear your experience, good or bad.

[PDUB]

Originally Posted by C5GTO

Yes, I'm in agreement the 90's Mustang style intakes don't look at home on a Cobra!

Good news! Now dispense with the serpentine belt and you are good to go!