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Underdrive Pulley Installation: 4.0 SOHC Motor

aldive

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To further press forward my pursuit of the greatest possible gas mileage in my Explorer, I decided to install an underdrive crankshaft pulley ( UDP ) on my 4.0 SOHC. The additional horsepower will be a most pleasant windfall.

UDPs for other applications have been around for about a decade. UDPs allow a motor to net more horsepower by freeing up power lost to parasitic drag. For dollar value, many think UDPs are one of the best mods for HP gain on the market today.

Nevertheless, with every mod there are the pros and the cons; this UDP mod is no exception. The advantages are stated above. Some potential disadvantages can be (1) diminished alternator charging and/or (2) reduced coolant flow at slow speed. and/or (3) increased steering effort at low speed and/or substandard AC performance at slow speed. Since I have a 130 amp alternator ( http://www.explorerforum.com/forums/showthread.php?t=139789&highlight=alternator ) and a Optima Yellow Top ( deep cycle ) battery ( Dead Link Removed ) I don’t feel the charging will be an issue. Only time will tell if the coolant flow, AC and steering are a fret.

On the 4.0 SOHC motor, the crankshaft pulley was integrated with the harmonic balancer into a single unit making “going underdrive” considerably more expensive and complicated than simply replacing a pulley.

Recently an UDP/harmonic balancer has become available from ASP ( Dead Link Removed - their website is out of date and they are horrendous at returning e mail; regrettably, they are the only manufacturer to data ) for the Ford 4.0 SOHC motor ( it will also fit the 4.0 OHV motor ).

ASP claims ( and posts a dyno chart ) 12.3 RWHP and 16.2 ft/lbs torque on a 2005 4.0 ‘stang. Nonetheless, after talking with my friend, Doug Studdard of Bama Chips ( http://www.bamachips.com ), he told me he installed the ASP UDP on a Mustang 4.0 and only netted 4.0 RWHP and was somewhat disappointed with the results. Nobody has reported gas mileage data.

Undaunted, I was determined to proceed with the project ( my goal was gas mileage not really HP ) and got my underdrive pulley/harmonic balancer from Doug at Bama Chips.

The ASP underdrive pulley/harmonic balancer is extremely well made out of billet steel. It’s a 25% underdrive device.

The installation was straightforward and relatively uncomplicated. The only necessary tool that might not be found in a DIYer’s inventory is a harmonic balancer puller and one can be obtained from Auto Zone “loan a tool program” ( $15 deposit ) if you don’t want to purchase one.

The first step was to remove my Mac intake (http://www.explorerforum.com/forums/showthread.php?t=130982&highlight=mac+intake ). Since I have an electric cooling fan ( http://www.explorerforum.com/forums/showthread.php?t=140251&highlight=electric+fan ), I removed the entire fan ( a 5 minute at the most job ). After removing the 19 mm center bolt ( too bad my air impact wrench wouldn’t fit in the area between the radiator and the pulley ) with a ½” breaker bar wedged against the frame while I bumped the motor over ( one bump was all that was needed. The bolt was then removed ( with my 3/8” air ratchet ) after which the battery was disconnected. The old bolt was discarded ( because it was a TTY bolt - a torque to yield bolt ( see http://www.explorerforum.com/forums/showthread.php?p=1368379#post1368379 ); a new one ( Ford # E7RY6A340B - $4.73 from Fast Parts Network [ http://www.fordpartsnetwork.com/ ] ) was used for the reinstallation. Then the serpentine belt was removed after rotating the drive belt tensioner counterclockwise with a breaker bar. The stock pulley/harmonic balancer was removed using my harmonic balancer puller, which turned out to be a major problem since none of the bolts in my puller kit were long enough and all the hardware stores were closed; the project was on hold until the next day when I purchased several length 8 mm x 1.25 bolts for the puller. Further the puller center bolt had to be cut to allow removal because of the restricted space caused by the radiator.

The new UDP/harmonic balancer was prepped for installation by attaching the plastic oil slinger ( Ford # FOTZ6K344BA, $57.35 if needed ) that had been carefully removed from the old unit. RTV was applied to the keyway and new oil ( Amsoil Series 2000 0W30 ) was applied to the sealing surfaces. The new UDP/harmonic balancer was inserted and the longer bolt included with the kit was screwed in about half way to seat the new UDP/harmonic balancer. This bolt was then removed and the new Ford bolt ( Loctite 371 Red was applied to the threads ) inserted and tightened with the air ratchet and then torqued to 44 ft/lbs, then tightened more by rotating it 90 degrees. After that a new serpentine belt ( a smaller than stock belt was required; I used a Goodyear Gatorback 4060850, $25.00 at Advanced Auto Parts. NOTE: I had to change the belt to a 4060840 - http://www.explorerforum.com/forums/showthread.php?p=1842893#post1842893 ] ) was attached followed by reinstallation of the electric fan and Mac intake. Finally, the battery was reconnected.

The motor was started, allowed to come up to operating temperature and observed for any maladies; none were present.

The installation, at a leisurely pace, took about 2 hours ( if the pulley remover hadn’t been such a PITA, it would be an hour or less job ). The cost of this project was a little over $300.

My preliminary impression ( albeit subjective ) after a short road trial, was that the motor revved quicker and acceleration was enhanced. The motor operating temperature at idle as determined by my OBD II scanner ( http://www.autoxray.com/default.htm ) was 192 F, which was unchanged from the stock pulley/harmonic balancer configuration. The charging voltage ( as monitored by a Dakota Digital [ http://dakotadigital.com ] digital voltmeter ) at idle was 13.0 volts ( prior to the install, the idle voltage was 13.4 ). I did not experience any steering difficulties and the AC functioned normally.

Even so, an extended road trip will be required to assess this project’s effect on gas mileage; data will be posted when available.

I feel that this UDP project was well worth the time and expense; recommended to anyone wanting “more” out of their 4.0 SOHC ( or OHV ).

NOTE: An underdrive water pump pulley is on order from Underdog Performance ( http://underdog-performance.com/id92.html ).and should be here in about 3 weeks. As soon as it arrives, I shall install it and evaluate performance and mileage.

Is an underdrive alternator pulley ( http://underdog-performance.com ) in my future? Yes it is; it’s currently sitting on the bench awaiting installation after running the UDP/harmonic balancer for a day or two.
 

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karl_burns

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Great write-up, as always....
(not being picky) So will roadtrips test each phase of "The Underdrive Project"? I mena, will you test highway gas mileage soon, then install the underdrive water pump, test gas mileage, then install the underdrive alternator....
Great job Al! Keep us posted.
Karl
 
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MONMIX

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Did you dyno it ? I want dyno numbers !!!!!!!!!! :p

Just messin' Al.

You mentioned " enhanced acceleration ", is it significant ? $300.00 is a decent amount of money, do you feel enhanced accleration warrents the cost ?

You know me Al, MPG's are pretty low on my list, and sh!t it and get it is rather high ;)
 
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aldive

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MONMIX said:
Did you dyno it ? I want dyno numbers !!!!!!!!!! :p

Just messin' Al.

You mentioned " enhanced acceleration ", is it significant ? $300.00 is a decent amount of money, do you feel enhanced accleration warrents the cost ?

You know me Al, MPG's are pretty low on my list, and sh!t it and get it is rather high ;)

Gee Kevin, I forgot to dyno it. Must be a worthless mod. :)

I am not sure about the enhanced acceleration and the cost of the mod, sorry.

I am pleased though.
 
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410Fortune

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Nice work and thanks for the detailed install.
I think every time a puller or press is involved you can plan on it taking longer then expected.
A friend of mine once showed me and its a great idea:
Whenever working near the radiator, cut a piece of cardboard about the size of the rad and use it to keep your hands/tools from denting the radiator fins if you should slip a bit.

Where is your Dakota gage reading the voltage from? 13.0 seems low to me at idle for your alternator, but maybe I am just used to my truck.
Is 13.0 acceptable? I expect it remains steady even when under full load (fan, headlights, AC)?
 
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aldive

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Driving impressions with the UDP/harmonic balancer installed ….

There was no decrease in the efficiency of the AC or the power steering when driving in traffic.

There appears to be a power boost over 3k RPMs.

My only concern is alternator output. I am installing the underdrive alternator pulley today and we shall see what happened then.

Overall, I am very pleased.
 
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zhanx

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aldive is a msd dis-4 next on your list? nice job on the write up.
 
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410Fortune

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MSD DIS is a waste of $$$$ for most even built V6's. The Ford DIS ignition is perfectly adequate and is actually quite good as far as OEM ignitions go.
Thank goodness, they needed to do something after the TFI module nightmare on the old dist systems...
 
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2drsrbtrrthn4

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410Fortune said:
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Thank goodness, they needed to do something after the TFI module nightmare on the old dist systems...


410 you just rekindled the memories of replacing the TFI modules in my 87 5.0 T-Bird and my 89 351W Bronco. Good stuff.
 
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410Fortune

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I kept a spare and the thumb wrench to change then on teh 2.9L in my glovebox, however I actually never had one fail on my truck, just everyone elses 5.0L cars that I worked on....
 
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aldive

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aldive said:
Driving impressions with the UDP/harmonic balancer installed ….

There was no decrease in the efficiency of the AC or the power steering when driving in traffic.

There appears to be a power boost over 3k RPMs.

My only concern is alternator output. I am installing the underdrive alternator pulley today and we shall see what happened then.

Overall, I am very pleased.

The serpentine belt that I used was somewhat of a comprise; it was about 1/4" too long and I started getting slipping and squealing.

The problem was solved by going a 1/4" too short. I replaced the 4060850 belt with a 4060845.

All is well.
 
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aldive

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First mileage data with the UDP installed is now available.

278 miles of all "in town" driving, 11 gallons of Amoco 93 gas used, special dyno tuned computer program ( Bama Chips ) - 25.27 MPG.

Several points are noteworthy:

(1) the tune was a performance tune, not a special economy tune

(2) this is the best mileage ever attained for "in town" driving

(3) can't wait for a highway run
 
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Buzzsaw

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I saw an electric water pump on the internet this week and I immediately thought of you aldive, it said you had to have an electric fan but you've already got that going for you. Have you thought of looking into that option?
 
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aldive

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Yes, I have definitely considered it. Problem is that I have yet to see one for my motor.

I think it would be a good mod.
 
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