Technical Tips

I hope to fill the following sections of our web site with little tidbits of technical how-to that we've picked up over the years.  If you happen to spot something that is dead nuts wrong, drop me an email so that I can get it corrected.  Likewise, if you have something you would like to have added, let me know and I'll see what I can do.
 

Spark Plug Selection
Roller Rocker Adjustment
Normal Rotation Water Pump
Setting Pinion Angle
Installing a High-Torque Mini Starter

Fuel Pump Circuit Override

SPARK PLUGS FOR E7TE, GT-40 and GT-40P HEADS

Typical cast-iron Ford heads for the Mustang use a 14mm spark plug.  The E7TE heads use a short (0.460") reach plug while the GT-40 and GT-40P heads use a long (0.708") reach plug.  Both types are a tapered seat (no washer needed) plug with a 5/8" hex.  I would typically run either a Motorcraft or Autolite plug.  I try to stay away from Champion and your 'rob you blind' plugs such as the S%itfire plugs.  For the Motorcraft and Autolite plugs, it basically holds true that the lower the number in a family of plugs, the colder the plug.  Colder plugs are good for high performance applications as they wick the heat away from the electrode quicker.  Hotter plugs are better for everyday driving and fuel economy. The colder plugs resist pre-ignition and electrode erosion better.
  

Autolite recommends installing the plugs approximately 1/16th turn past finger tight or 7 to 15 ft-lbs.  Autolite plugs come with full-thread or part-thread.  The 10x series is full-thread while the 76x and 5xxx series are part-thread.  Either will work with the Ford heads.

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ADJUSTING ROLLER ROCKERS

Roller rockers are a simple bolt-on modification that will give your Mustang a boost in performance.  Many people have problems getting the proper lifter preload when making the switch however.  Here's an easy way to set the proper preload.
 

Slowly tighten the pedestal bolt while gently rolling the pushrod between your thumb and fore-finger.  At the first signs of drag on the spinning pushrod, stop tightening the pedestal bolt.  This is the 'zero lash' position.  Put your torque wrench on the bolt and note the wrench position (e.g. 12 o'clock, etc.).  Now begin to torque the pedestal bolt.  You should reach 18 ft-lbs of torque somewhere between one-quarter and three-quarters of a turn of the wrench (e.g. 3 o'clock to 9 o'clock if 12 o'clock was your starting point).  This should give you about 0.040" to 0.060" preload in the lifter.
 

If you didn't reach the specified torque by the time that you passed three-quarters of a turn, then the rocker needs to be shimmed.  Start with a thin shim and work progressively thicker until your torquing fall in the range.

If you reached the full torque in less than one-quarter turn, then the rocker needs to have shimming removed.  If no shims were removed, then the rocker pedestal needs to have some material removed from the bottom surface.  This can be done on a mill, or if you're careful, with a Dremel tool.  The pedestal surface must be flat and square when you're finished though.

 

For stud-mounted rockers, you're basically performing the same steps except that there is no shimming involved; after reaching zero lash, note the wrench position and continue tightening the 1/4 to 3/4 turn.  Then lock down the poly-lock by holding the adjusting nut while heavily torquing the inner set screw. Stud-mounted rockers allow nearly infinite adjustment without the hassles of shimming.

I tried to set my preload consistently between one-quarter and one-half turn. This helps keep the valve from hanging open too much when the lifter pumps up.  I usually run the valves by rotating the engine clockwise until the exhaust lifter raises (exhaust valve opening) about 1/8th inch, then adjust the intake rocker.  Then I continue rotating the engine until the intake valve opens and when it is within about 1/8th inch of being closed adjust the exhaust rocker.  This process insures that the lifters are on the base circle of the cam when the rockers are adjusted.
 

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NORMAL ROTATION WATER PUMP

If you've been bitten by the 5.0 performance bug, you've probably looked at that forty-two foot long serpentine belt hanging off the front of the engine and said to yourself "Gawd that's a lot of parasitic drag on the motor.  I bet I can free up 40 horsepower if I got rid of all those pulleys."  Well, it may not amount to 40 ponies, but the parasitic drag of the air pump, A/C compressor and power steering pump do add up.  Most people that are into serious racing have already gotten rid of these luxury items, but after doing so you're left with one minor problem.  How do you route the belt? The first thing you've got to remember is that late model Mustangs with serpentine drive belts actually have the water pump spinning the opposite direction as 'normal' pumps (and crankshaft).  So if you've removed the accessories, being left with the crank, W/P and alternator, you've got to make sure you're spinning the pump in the right direction or you're bound to have overheating problems.  Two possible solutions are shown below:

For the routing shown on the right, you'll have to disassemble your tensioner and reverse the spring operation in it so that its actually pulling UP on the belt.  The thing I don't like about this option for a street-driven car is that it leaves a pretty small portion of the belt actually touching the water pump pulley which could cause slippage at high RPM or high load conditions.  The preferred routing for a street car is shown on the left.  The stock water pump is replaced with a water pump from a 1983 Mercury Cougar with a 302.  This pump has the same exact dimensions as the stock pump, but has a normal rotation impeller to it.  The pump cost about $18.95 at the local parts store without a core.  With this arrangement, the tensioner doesn't need to be changed at all and still functions as designed by Ford.  One thing to consider with this technique though is that the water pump pulley now rides on the ribbed side of the belt where it had previously ridden on the smooth side of the belt.  This doesn't really cause a problem, but ASP does offer a grooved water pump pulley with their pulley sets that will keep the belt riding straight and true over all pulleys.  I use this grooved pulley with my combination. My belt length with the ASP Race Pulley set was about 42.5 inches long.

 

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SETTING PINION ANGLE

Need more traction out of your Steed?  Try adjusting your pinion angle.  As suspension gurus tell us, pinion angle is critical under hard launching conditions.  The action/reaction tendencies of the Mustang's pseudo four-link suspension creates a pretty significant amount of axle rotation under hard launches.  As the tires bite, the pinion's reaction is to rotate upwards towards the pinion snubber.  This tends to unload the tires and create wheel hop.  The optimum power transfer would be if you could get your transmission, driveshaft and pinion to form a perfectly straight line as shown in the top figure.  Unfortunately, with articulating suspension, varying ride heights and other geometric considerations its highly unlikely that you'll ever wind up with that perfect alignment.  When I'd measure my geometry with Megabite Jrs. lower control arms and stock upper control arms, my car had the pinion pointing upwards 2.5 degrees and the driveshaft pointing upwards 1.5 degrees (both running uphill when looking from the back of the car forward). I've tried to show this in the middle drawing.  Under hard launches, the pinion will have a tendency to rotate 3 to 4 degrees upwards which was leaving my pinion pointing to the sky (well almost).  I tried to limit this somewhat with a Competition Engineering adjustable pinion snubber (see photo here) but the initial upward orientation still wasn't what I needed. So then I installed a set of Unlimited Performance's double-adjustable uppers (see photo here). The adjustable uppers allow you to shorten (or lengthen) the upper control arm, which changes the initial pinion angle.  By shortening the UCA length, I was able to get the pinion pointing about 2.0 degrees downward with the driveshaft following it to about 2.0 upward.  This provides a total difference between the two of about 4.0 degrees downward (negative) pinion angle.  Under hard launches, if the pinion rotates 3 to 4 degrees upward, it should just about straighten the driveline for maximum bite and power transfer.

So how do you measure the angles?  I built four wood blocks of 2-by-12 lumber, two pieces thick by about 15 inches long.  This way I can get the car far enough up in the air to crawl under and make the measurements and adjustments while still maintaining the normal ride height, weight distribution and driveline geometry.  I bought a simple angle finder at Sears for about $10 that gives angles to the nearest 1/2 degree.  To measure the driveshaft angle, simply place the angle finder on a straight and smooth portion of the driveshaft.  To measure the pinion angle, I measure off the side of the pinion companion flange.  There's enough flatness to the edge that if you're careful you can get a good read off the angle finder.  Click here for an exploded view of the pinion and driveshaft measurement.

If you have converted your rear suspension to all spherical bearings instead of rubber or poly bushings, the deflection under load is going to be much, much less.  In this situation, you want to set your pinion angle as neutral as possible with the car at its normal ride height.

 

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Installing a High-Torque Mini Starter

Stuck with that huge early 90's starter on your small block Ford?  Ever wondered if you could use the newer, smaller high-torque mini starters?  Here's your answer to taking almost seven (7) pounds off your car, giving it easier starting, and giving yourself more clearance for that aftermarket exhaust system.  Ford sells a high-torque mini starter that came on the 94 & up Mustangs (and 93 Cobra).  This smaller diameter, higher torque starter usually runs around $139 plus about another $39 for the cable retrofit kit.  The cable kit is needed since the mini starter is a two-wire starter versus the old one-wire system. I don't know about you, but I about gagged at the cost.  So I went to a local parts store and picked up a remanufactured starter for about $89....half the cost.  To handle the one-wire to two-wire transformation, just make the following changes.

1. Move the large primary cable from the switched side of the solenoid to the 'always hot' side of the solenoid.  In other words, the large cable running from the solenoid on the fender well to the starter should be place on the same pole of the solenoid as the large cable running to the batter.

2. Make up a lighter gauge (I used 14 gauge) wire to run from the switched side of the solenoid down to the small terminal pole on the starter.  Use a ring terminal at the solenoid end of the wire and what ever type of terminal is required at the starter end of the wire.  MAKE SURE THAT THE TERMINAL ON THE STARTER END DOES NOT CONTACT THE PRIMARY CABLE OR TERMINAL. FAILURE TO DO SO WILL RESULT IN STARTER 'RUN ON' AND WILL RUIN BOTH THE STARTER AND THE FLYWHEEL/FLEXPLATE.

3. Secure the new small wire to the primary cable with zip-ties, tape, or wire sheathing to protect it from moving parts and foreign object damage.

And away you go.  Three simples steps to a better starter for your SBF.

 

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Fuel Pump Circuit Override

Ever have the need to have the fuel pump run without the engine running?  We all know that the fuel pump will run momentarily when the ignition key is first turned to the "ON" position, but sometimes you need or want to have the fuel pump run continuously for things like looking for leaks or draining the tank. The momentary circuit can be easily over-ridden to allow for continuous fuel pump operation by simply grounding one of the plugs in the EEC Test connector. The EEC Test connector is shown below [for my '90GT, the EEC Test connector is located on the driver's side shock tower between the shock tower and firewall].  

 

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