What hose sizes and routing tips simplify LS radiator plumbing?
Sizes and sides:
Last updated
- Upper hose: LS upper hose is 1-1/4 in (smaller than SBC/BBC), though the upper hose connection on all LS pumps is also listed as 1-3/8 in; verify.
- Both hoses on the passenger side on most LS engines: Most LS water pumps have both inlet and outlet on the passenger side; LS swap radiators put both ports on the passenger-side tank.
- Thermostat low on the water pump, in the lower hose.
Routing tips:
- An adapter from the LS upper outlet to a 1-1/2 in radiator inlet lets you use common radiators and hoses. Speedway's LS swap radiator hose adapter (listed at $24.99) fixes both problems at once: a 1/4 in hose barb takes the steam line, and it adapts the LS water pump's 1-1/4 in upper outlet to the 1-1/2 in inlet on a typical radiator.
- A double-pass radiator puts the upper outlet on the correct side for an LS.
- Always plumb the steam line — LS thermostat sits low on the water pump, so a steam line is needed to purge trapped air; most LS swap radiators have a steam port, and adapters let universal radiators work.
- Check the accessory drive and pump you're running: pump outlets differ (see which water pump).
Related questions
- Best LS swap radiator
- LS steam vent: do I need it?
- My LS is overheating — what should I check first?
- Can I cool an LS swap with a stock-style radiator instead of an expensive LS conversion radiator?
- How should electric fans be wired with a Terminator X / LS swap ECU?
- Which water pump should I run for an LS swap: truck pump or Camaro pump?