Radiator Hoses 78 FJ40 5.7L Vortec Swap (1 Viewer)

Apr 23, 2017
Changed the waterpump on my 5.7L Vortec and decided to change hoses at the same time. Figured I'd share part numbers to make it more straight forward.

Truck has an aluminum radiator with 1 1/2 inlet and outlet.

Water pump inlet is 1 3/4

Thermostat is 1 1/4

Here's what you need hose wise.

GM bottom hose for the truck is straight forward. A Gates 21941 gets that done. This hose has a 1 3/4 inch end and a 1 1/2 inch end. Just need to trim the 1 1/2 end to fit the appropriate distance making sure to steer clear of the fan blade.

Upper hose was more of an issue.

Radiator side you want a Gates 23234. I believe this is a bottom hose for a Jeep. The bend is perfect. Just cut to fit.

Thermostat side is the tail end of the original GM upper hose as the bend to the stat housing is strange. For that I used a 71880.

To reduce the 1 1/2 radiator side to 1 1/4 stat side an AN627-21A billet reducer at $8 does the job.

The other heater hoses were the GM PNs.

See pics

Radiator Inlet 1_1.5.jpg

Thermostat 1_1.25.jpg

1.5_1.25 Splice.jpg

Reducer Coupling.jpg

Done deal.jpg
Jun 5, 2007
Brea, Calif.
All above info okie dokie, but as I recall, when Downey had aluminum radiators made for engine swaps, the top hose did not go to the top tank, the LS swaps used a radiator with vertical side tanks, and the top hose went to the top of the driver's vertical side tank.

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