The 60K story, unabridged.
FOREWARD: Do you have an automatic or manual transmission? It makes a difference of 40,000 miles on the frequency of the front end engine work (timing belt).
THE STORY:
CHAPTER ONE: THE TOP END
The 60K, as it is known, is a preventative maintenance activity to ensure that the SHO engine lives a long and powerful life. The Yamaha heads have a direct acting mechanical bucket (DAMB, Ford's words, not mine) valve train that requires periodic adjustment to keep the gap between the cam lobe and the shim mounted on the tappet at the optimal spacing for maximum performance and engine longevity. Wear of the shims and metal creep of the heads themselves conspire to change the gaps over time. Too large and the lobes impact the shims hard enough to cause accelerated wear and maybe damage to the cam lobes. Too small and the different rates of thermal expansion may cause the valve not to seat completely and allow hot exhaust gasses to erode the valve seating area. This would require an old fashioned valve job, with the heads removed, to correct.
The double platinum spark plugs also were designed for a 60,000 mile lifetime and are scheduled to be replaced every 60K. The use of "standard" single platinum plugs will have you changing them at much more frequent intervals.
Those two services constitute the basis for the upper engine portion of the 60K. At longer intervals (usually 120,000 miles) or when necessary due to their failure, other wearable components are replaced as necessary. These include the valve cover seals and the spark plug well seals. These respectively keep the oil off the exterior of the engine and out of the spark plug wells where it can look bad or cause spark leaks.
Also along those spark leakage lines, the spark plug wires are usually good for about 120,000 miles before the heat under the hood and age deteriorate their inslation. The idle air bypass valve (IAB) is also easily accessed for cleaning when the intake is removed. A thorough cleaning of the intake's internal and external surfaces is also a good thing to take care of at this time.
CHAPTER TWO: THE FRONT END
The front of the engine (timing belt end) is where there is a service interval difference between the manual transaxle (MTX) and automatic transaxle (ATX) SHOs. The 60K interval applies only to the MTX's 3.0L engine. Due to the manually set tensioners for the timing belt and the accessory belts, the MTX requires that these belts be changed every 60,000 miles. The superior gas piston tensioners on the newer designed ATX's 3.2L engine allow 100,000 miles between replacements.
The required front end services during the 60/100K maintenances on the MTX and ATX SHOs are the timing belt replacement and the accessory belt replacement. There are a few other parts that are accessible only while the timing belt has been removed so it is during this service that these parts are also attended to.
You don't need to replace these other parts unless they fail, but most of the same engine disassembly as required to get to the timing belt is required for all of them. These other parts are the water pump, the crankshaft position sensor (CPS) and the front main crankshaft oil seal. With the 60,000 mile service interval of the MTX, it can be decided to schedule these additional replacements every other 60K service, or every 120,000 miles. With the longer 100,000 mile interval of the ATX, it is usually a prudent choice to replace them each at timing belt change.
CONCLUSION
The 60/100K services are preventative maintenance activities that are intended to keep the rather high power density SHO engines running at their best for as long as possible. Failure to do the services per the maintenance schedule won't stop the car in its tracks, but it may slow you down and lessen your enjoyment of the car. You will find that many SHOs have changed hands when the 60/100K service interval comes due just because the owners don't want to deal with the complexity or the expense of it. This is one of the details that makes the SHO owners a tighter knit group. Few shops know what the SHO is. Even fewer know what the 60K really means. It is not a tune-up. It is a new lease on life.
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Scott
1991, 252K miles, glass hood, police grill, SVO shifter, Catz fogs,
K&N, 73mm MAF, Superchip, PP Y-pipe, Borla cat-back, 190 lph pump
Eibach/Tokico/polyurethane, SHO Shop front & rear strut braces,
16x7.5" Moda R1, 225/55ZR16 Bridgestone RE730, -1 deg camber x 4,
Class II hitch, Silver award at the SHOklahoma Car Show
[This message has been edited by sdpatt (edited 10-26-2001).]