Do I need to plumb the steam ports on an LS swap?
Yes. On most LS engines the thermostat sits low, on the water pump, instead of up top like older small- and big-blocks. GM added steam lines in the cylinder heads to vent trapped air and keep hot spots from forming at the top of the engine. Leave them open or capped and you risk air pockets and hot spots.
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Your options:
- An LS swap radiator with a steam port: most LS conversion radiators have one. Run the steam line to it.
- A universal or original radiator: use an adapter with a steam fitting. 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.
See the accessory drive guide for pump choices.
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