My heads/cam LS1 is underperforming — I still have the stock LS1 intake and stock injectors. What's holding it back?
Likely both. Heads and cam only pay off when the whole airflow path and fuel system keep up:
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- Intake: an aftermarket intake paired with heads and cam "really wakes up" an LS1. The factory LS1 intake — and even the better LS6 or TBSS factory intakes — have limits. Also make sure the intake's port shape matches your heads (cathedral vs rectangle).
- Injectors: more airflow needs higher-flow injectors to match. Stock injectors can run out on a heads/cam combination. Size them with the fuel system calculator.
- Throttle body and exhaust: a suitably sized throttle body and headers/cat-back complete the airflow path.
- Tune: a custom tune for air/fuel and timing is essential after these changes.
The stock intake and injectors are choking the combo. We recommend a FAST 90/90 (used ones are cheap now that the 92/102 are out), 42 lb/hr injectors, since stock injectors can max out as low as 3000 rpm on a cammed car, and a proper dyno tune, because mail-order tunes can't accurately calibrate a custom engine. Once sorted, expect roughly 370 rwhp and about 114-115 mph traps.
Check this first:
- Log injector duty cycle to confirm the injectors are maxed
- Plan a dyno tune after the injector and intake change
Careful: Running out of injector on a cammed engine leans it out at higher rpm, which can damage the engine.
Based on what we've seen work across our own builds, our friends' builds and the wider LS community, reviewed by our lead shop tuner (over 20 years of LS and LT tuning experience). Every combination is different, so use at your own risk and check our safe tuning limits before any wide-open pass.
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Check this first
- Log injector duty cycle to confirm the injectors are maxed
- Plan a dyno tune after the injector and intake change
Try this, then this
- FAST 90/90 intake + 42 lb/hr injectors
- Dyno tune
- Check exhaust and heads if still underperforming
How you know it's fixed
- Duty cycle in a safe range, dyno tune dialed in, trap speeds up around 114-115 mph
Still not fixed?
- If it's still short, the tune or another restriction (exhaust, heads) is the next look
Time and cost: Used FAST 90/90s are cheap; injectors plus a dyno tune are the real cost