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There are two ways in which one can overcome the limitations of the stock engines:
1. Excessive power: anything over 300HP is not recommended, as the stock powdered metal rods simply cannot withstand the load presented. When we intentionally drove engines to destruction to uncover these answers back in 1998, the goal was to understand what we could safely sell the public without having them find out first!
Our test engine was equipped with a fuel system capable of supporting about 400HP. We began to see stress cracks form in the con rods at 310 HP. At 350 HP, a con rod failure completed the testing.
In this case, HP, not detonation (covered below) caused the failure. Of course, a set of billet rods cures this Achille's heel.
2. Detonation: Usually caused by a lean fuel mixture, inadequate octane, over-advanced timing, or some combination of the above. It is quite possible to fail a stock engine at well below 300HP if detonation occurs. The shock loads presented are enormous as compared to normal combustion, and will crack piston ring lands easily while also stressing the rods. Severe detonation can also shatter a rod.
Important note: these stock rods can be damaged from a detonation episode and not show it, even if Magnaflux inspected. Avoid the temptation to re-use the rods and replace the pistons: it can lead to a nightmare should the rod fail later.
I know all this engine stuff costs lotsa $$, but consider: invest the cash and have an engine you can then run at hi HP levels for years. Frankly, if $2000 worth of parts and labor hurts too bad, then don't roll the dice with your motor: keep that boost down. In the overall picture, these engines are actually inexpensive to build. Whether or not you need to build one is entirely up to you, based on your system choices, caliber of installation, intelligent boost level vs. fuel system capability, and ongoing maintenance. Don't play if you can't pay!
Bill Hahn Jr.
98 RS Turbo: 10.87 @ 136 MPH
HRC Stage V with N20
Nation's Fastest Street FWD 2G DSM
www.turbosystem.com
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