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When to go forged, and what to look for

 
lakisha.2011
New User
Posts: 4
Joined: 11/11
Posted: 11/24/11 07:35 AM

Tech level: 4

Specifics pertain to modular platforms, general lessons for built shortblocks are more universal.

Making a lot more power than stock and worried about horror stories you've heard about thrown rods, spun rod bearings and cracked blocks? You should, thinking about the unthinkable is responsible. After all, the last thing you want to do after you've invested money in the engine compartment is to turn it into a large paper weight.

The limits:

Power limits are often measured in horsepower (to the wheel or engine). However, the agreed upon limits are much debated over. Below are general thresholds favoring caution.

1. 4.6 shortblock, 96-98, 99-04 GT
Cast iron block
Cast crank with 6 counterweights
Powdered-metal/cracked cap rods
Hypereutectic pistons (11cc dish before 98, 17cc after).

1.5. 4.6 shortblock, 2005+ GT
Aluminum block.
Cast crank with 6 counterweights
Powdered-metal/cracked cap rods
Hypereutectic pistons (6.5cc dish).

2. 4.6 shortblock, 96-98, 99/01 cobra
Aluminum block. Teksid brand in 96-98 and halfway through 99, WAP brand after.
Forged steel crank with 8 counterweights.
Powdered-metal/cracked cap rods
Hypereutectic pistons (3cc dish)

3. 4.6/5.4 shortblock, 03/04 Cobra and Lightning
Cast iron block.
Forged steel crank with 8 counterweights.
Forged Manley H-beam rods.
Forged 4032 alloy pistons

4. 5.4 shortblock, 05-10 GT500
Cast Iron block
Forged steel crank
Forged cracked I-Beams
Forged aluminum pistons

Main bolts/studs:
Stock equipped on all 4.6 blocks are 4 main bolts (except for Teksid which use 2 vertical and one side bolt per main side [6 total]). Stock bolts are TTY, or torque to yield, which means they stretch with torque to the correct spec upon installation and cannot be used again. This is one draw back. The main reason these are replaced with studs is to reduce or eliminate main cap walk and fretting. Also these allow you to utilize more accurate torque readings.
___Because studs dont stretch/twist, there is less being asked of the block's threads. For this reason, studs are recommended for aluminum blocks before they might on iron blocks. Also, studs allow for ease of bearing cap alignment. I would recomend considering main caps on an Iron block past power levels of 500-550+, above this power level it may be wise to consider aftermarket side bolts as well. Here are mine for comparison, ARP main studs and MMR side-bolts:

Picture17115580  
Parts for Mustangs

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