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1988-1990 TOWN CAR 5.0HO CONVERSION
Submitted by pro-five-oh / 07-28-04

Thanks to Four Eyed Stangs and EricCoolCats for their advice and experimentation to their cars!
    Please check out Eric's website at Cool Cats for more information on the HO swap.


  


Stock 5.0


HO 5.0

  

Introduction

As you may have noticed, modern day cars (especially those pesky 4 cylinder imports) have become seriously fast, and can leave your 150-155hp TC in the dust. Using junkyard or leftover Ford parts from a Mustang or Mark VII owner, the HO conversion will net you over 1000rpm for your powerband and more than 50 horsepower! And once you get tired of 200-225hp, the sky is the limit when you have the same powertrain as a 1987-93 Mustang 5.0

Keep in mind that this article assumes you have knowledge of how to disassemble a motor down to the cylinder heads, to perform a camshaft swap, have correct tools and have access to a shop manual (Ford, Helms, Haynes, Chiltons) that discusses 5.0s in reasonable detail if you get stuck along the way. If you are unsure of any of these things, you may wish to have a mechanic perform the HO conversion.

Parts Required

HO Cylinder Heads (free to $200)
  • The correct heads for this swap have an E7TE casting number for the first 4 digits. You will find these heads on 1987-up Mustang 5.0s, 1986-up Ford F-150 5.0, 1988-1992 Mark VII and 1991-1993 Thunderbird and Cougar. If you are buying these heads from a car with high mileage, having them rebuilt with new valve springs and such is recommended. Also taking a grinding tool to the bumps in the exhaust ports will increase flow with no adverse side effects.
  • Aftermarket heads like GT-40/AFR heads cannot be used on a stock TC shortblock. This is because TCs have flat-top pistons that do not have valve reliefs. The only exception to the rule is the Trick Flow "Twisted Wedge" head. Its unique design works with flat top pistons PROVIDED you use the correct duration camshaft. Contact Trick Flow for more information if you are so inclined.
HO Computer ($20 $150)
  • Because Lincoln built-in the cruise control features starting in 1988, the 1988-1990 TCs require a specific computer. This computer is the 1988-1992 5.0HO Mark VII computer. Yes, you can put a Mustang computer in and the motor will run properly, but why would you when it will disable your cruise control? Spend the time and find a 1988-1992 Mark VII computer.
  • Once you have acquired the new computer, swapping it over is simple. The TC computer is under the dash, on the firewall, between the brake and E-brake pedals. The bolt that holds the computer in must be accessed from under the hood. It is between the brake booster and fender. Loosen the bolt until it freewheels in its place; do not try to pull it out!



Now from under the dashboard, you will see the metal box with the computer, pictured here on the right hand side.


With the bolt loosened, you can pull on the computer and pull it out!

  • You may wish to convert to mass-air metering for smoother idle and better drivability with future additions like a supercharger or a custom built motor with better cylinder heads bigger fuel injectors. In this case, a Mustang A9L computer will be needed and a conversion to Ford's stand alone cruise control will be necessary. Or you can purchase a Mark VII specific twEECer (www.tweecer.com) to tune your HO motor for any possible combination. It is your choice if you wish to take your horsepower more seriously.
HO Camshaft (free to $50)
  • The camshaft controls the unique firing order of the 5.0HO and is necessary for the conversion. You can find this part in 1986-up Mustang, or 1986-1992 Mark VIIs.
  • Aftermarket camshafts like Crane and Ford Motorsport Cams cannot be used on a stock TC shortblock. This is because TCs have flat-top pistons that do not have valve reliefs. Using a more aggressive cam with E7TE heads or most aftermarket heads will cause terminal engine damage! As previously mentioned, Trick Flow offers a specific cam for their cylinder heads that will clear flat top pistons.
HO Throttle Body and EGR Spacer: (free to $50)
  • Because the TC has a reverse mounted intake, the 60mm HO throttlebody and matching EGR spacer does not directly bolt in. Examine the differences in the two following diagrams:
  • Below is the (60mm) HO spacer: the red arrows point to the EGR valve studs and the blue arrows point to the throttle bracket mounting holes.


    Below is the (50mm) TC spacer: the red arrow points to the throttle plate mounting studs, they are not holes like the HO unit. The EGR is mounted to the opposite side. The throttle cable plate mount locations are opposite from the HO.


  • It is possible to modify the 60mm HO EGR spacer with tapped holes and studs to allow proper EGR placement and a different bolt pattern to attach the throttle bracket. But the 50mm unit can also be bored out to a larger diameter, making it comparable to a 60mm unit. Since this part is not the main restriction on a 5.0HO, a bored out TC unit is probably just fine. Its your call right here: my advice is to get friendly with a local machine shop!
HO Upper Intake: (free-$50)
  • This part may or may not include an EGR spacer mentioned above. The lower intake is the same as a TC, but the upper has less restrictive runners. This part can be found on 1987-up Mustang and on the 1988-1992 Mark VII.
  • This part may not be a direct bolt in; on the TC, the HO upper may hit the fuel rail. See the picture (below left), the yellow paint on the intake shows the trouble spot.



  • Using a grinder to make some clearance might fail and you may grind through to the intake port. It all depends on how much metal you take out! (see picture below)


    The smarter alternative is to get an intake spacer designed for the 1987-93 5.0 Mustang. It is used to increase the runner length of the intake by ½" for more low-end torque production. But for the TC, it has an added benefit of clearing the fuel rail! The Ford Motorsport part number for this is: FMS-M9486A51.


  • Aftermarket 5.0 intake manifolds (GT-40, Cobra, Edelbrock, Trick Flow, etc) are an interesting alternative, though they will only add a few horsepower and net very little gains in real world power. That, and they will cost significantly more than an HO upper intake. The question of EGR fitment and throttlebody connections is also unanswered, so this may not be a good idea for your TC.
HO Fuel Injectors: (free to $50)
  • The Town Car runs 14 lb/hr fuel injectors that have grey plastic tops on them. This size will not work with a stock HO computer. The HO computer requires 19 lb/hr injectors with an orange or tan colored plastic top. You can find these injectors on 1987-up Mustang 5.0s, 1988-1992 Mark VII, and 1992-1993 Thunderbird and Cougar.
  • If you want new injectors instead, Ford Motorsport also sells a set of new 19lb/hr injectors (FMS-M9593C302) for around $230.
HO Headers, Upgraded Exhaust System (Optional and Highly Recommended)
  • The stock TC exhaust is very restrictive and bulky. The stock TC exhaust manifolds weigh in at over 20lbs each, while the headers are about 5lbs. Switching to stock HO headers will help improve flow tremendously and give you a mild growl. Aftermarket shorty headers (1 1/2" diameter is preferred unless you run aftermarket heads) are also s omething to consider, especially if you can find a good deal on them. And yes, long tube headers are not known to fiton a TC!
  • 1990 TCs (and 1990-1991 Crown Vic/Grand Marquis) come factory equipped with tubular headers similar to the HO headers. Though not a true header like the Mustang parts, these would be ideal for an HO swap because of the O2 sensor location.
     

  • If 1990 TC headers are not in your future, the HO headers will also require you to relocate your oxygen sensors to the pipes just before the catalytic converters, so you will need to weld in a bung to the exhaust and lengthen the oxygen sensor wiring accordingly. This is not a big deal if you are going to an aftermarket exhaust.
  • Yes, you need to become friends with an exhaust shop! Doing a dual exhaust conversion can give you either a loud exhaust, or a fairly quiet one. It depends on what size pipe you pick (2" is perfect, 2.5" is great for future engine modifications) the mufflers, and if catalytic converters are being used. It has been said that Mustang and Mark VII H-pipes (stock or aftermarket) can be used with minimal modifications to fit. Odds are your TC's exhaust is very old and could use this anyway.
Miscellaneous Parts (As Needed)
  • New Gasket Set, Brass TV cable bushing (see TECH article for more info), Water pump, Fan clutch, EGR valve, Oxygen sensors, MAP sensor, Serpentine belt, Radiator, Thermostat, hoses, PCV valve, etc…
  • 1987-up Mustang or 1988-up Mark VII MAP sensor (optional, I never used it when I did the conversion, though others recommend it)
  • New Roller Lifters (recommended for high mileage motors)
  • 1.6" Roller Rockers (most will require a swap to HO valve covers due to clearance issues)
  • New Fuel Pump (higher flow units are available for similar prices to the HO and non-HO unit, but the pump in your TC is more than adequate for this conversion)

FINAL NOTES:

After all the parts are installed, you will need to move the spark plug wires to the HO firing order. The firing order is 1-3-7-2-6-5-4-8. The firing order of the fuel injectors changes, but the computer does that. You will NOT need to change any fuel injector wiring in your stock harness for this conversion.

HO engine timing is the same at 10 degrees BTDC. Once the car is running correctly, you can get some added power if you bump up the timing to 12 or 14 degrees. Try 1-degree increments at a time since every engine responds differently and back off if you hear any detonation (pinging). Also remember that if you do advance the timing, premium unleaded gasoline (93 octane or higher) is required. Your stock ignition system is more than adequate unless you plan on making 500hp or more in the near future.

Don't want to do a full HO conversion? Do not install the HO camshaft and the HO computer but do the rest. The E7TE cylinder heads are the heart of this transplant. You should still make an honest 180hp or more with a much stronger powerband. It is up to you. Just remember that the HO camshaft and computer MUST be installed together.

Well, this was a lot of content to digest, but this information should help you complete a 5.0HO conversion. As always, spending time finding the best used/new parts, methodically disassembling the engine, and having the right tools is always a plus. And remember: this had been done before and you can do it!

Best of luck!


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