pix
FORDMUSCLE.com FordMuscle Nav
Page
3
 
From page 2

Pistons - Cast, Hypereutectic, or Forged?
Most shops will reach for OEM cast replacement pistons when assemblying a stock bottom end. There is nothing wrong with cast, unless you plan to add a power


TRW/Sterling Pistons have huge valve reliefs for 2.02" valves, but the head volume is a gapping 8cc!
adder or high compression. We like to step up to hypereutectic simply because it offers more strength than cast, and they experience less thermal expansion than cast, meaning you can run a tighter piston to wall clearance for better oil control and less scuffing. Ultimately this translates to more power due to higher cylinder pressure.

Many people scoff at cast or hypereutectic and immediatley ask for forged aluminum pistons, without considering the draw backs. While forged is undoubtedly the strongest of the three pistons, that does not mean you will make more power. First of all forged pistons are very heavy - the Federal Mogul forged replacment piston for 5.0L engines weighs 80 grams more than its cast or hyper counterpart. The greater the reciprocating weight, the more power the engine needs to turn over the crank. Secondly, as detailed above, forged pistons have larger than stock valve reliefs. This increases the head volume and lower compression ratio. So unless you absoutely need a forged slug (forced induction, high compresion, etc) you will save money and increase power with a lighter hypereutectic piston.

Balancing Act
We called four reputable engine rebuilders and machine shops in the Northern California area to inquire about their beliefs on engine balancing. Suprisingly, none of them included balancing as part of a standard engine rebuild. They all charged between $175-$250 extra to balance a rotating assembly, and in fact most of the shops did not even do balancing in-house, they sent it out to another shop if you opted for it.

Most rebuilders assume that because they are using OEM replacement parts, that balancing will be within factory tolerances. (Afterall, they tell you, Ford doesn't balance each individual engine off its assembly line.) Take our word, this is not a safe assumption -always pay the extra $150-$200 to get an engine professionally balanced. If it comes down to spending a couple hundred dollars on balancing, or something questionable like torque plate honing the cylinders, you will do more for horsepower and life of the engine by balancing it.

We observed as much as a 30 gram difference between the Silvolite replacment pistons and the stock pistons that came out of our engine. According to Bay Area Balancing guru Tom Benoit, this is more than enough to cause a noticiable vibration, and accelerate bearing wear. Furthermore, machining the crank and rods, installing a new replacement damper and flywheel, and even a new clutch, are all things that can drastically effect engine balance.

This is state of the art balancing - a Hines HC500 micro-computer balancer. Before the rotating assembly is spun, the piston and rods are
weighed and equalize to the lightest one in the set. The weights are recorded, and then bobweights matching the total rotating weight of the piston, rod, rings, bearings, and even the weight of the oil, are attached to the crank main journals. Finally the harmonic balancer and flywheel (plus pressure plate) are attached to the crank. The "replica" rotating assembly is spun by the computer at several hundred rpm, while it records the amount of out-of-balance and the angle it is located at. The specialist then either removes or adds weight by either drilling holes or welding metal in the counter weights. Our balance shop (Bay Area Balancing) shoots for less than 1 gram total out of balance -in contrast, Ford specifications are abut 6 grams.

Completed Shortblock
Eventhough it took a couple weeks, and two attempts at assemblying the motor, in the end we got exactly what we wanted. The final short block assembly had the correct H3101 hypereutectic pistons, sitting at virtually zero-deck (measured at 0.003" under). With 60cc aluminum heads we will have a pump-gas friendly 9.55:1 compression ratio.

Page
3





Build a 5.0L Series
Part 1: The Shortblock
Part 2: The Longblock
Part 3: Install and Track Testing





5.0L Short-Block Specifications
Bore 4.020"
Stroke 3.000"
Compression Ratio 9.55:1
Piston to Deck height 0.003" below
Piston to wall clearance 0.015"
Piston top-ring end gap 0.025"
Piston 2nd-ring end gap 0.018"
Main Bearing clearance 0.0015"
Rod Bearing clearance 0.002"
Rod side clearance 0.018"
Main Bearing Journals 0.010" undersize
Rod Bearing Journals 0.010" oversize
Crank endplay 0.003"
 
5.0L Short Block Part No's
Piston 4.020" Silvolite H3101
Rings Hastings 2M 5504
Bearings Federal Mogul
Block/Crank/Rods 1989 5.0L
 
5.0L Short Block Costs:
Standard rebuild $795.00
Machine for Zero Deck $100
Balancing $200
Tax $101
(core charge) ($400)
Total Short Block $1196
 

pixblue
pixblue
Tech Archives Project Cars Readers Cars Feature Cars