RCM Cylinder 4 Cooling Mod Kit - Street Spec

Cylinder four runs hotter than the other three on Subaru's EJ engines. It is a design consequence, not a fault: the routing of the water passageways at the back of the block leaves coolant flow weakest around that cylinder, and on a tuned engine that is exactly where the extra heat is least welcome.

The Street Spec kit is RCM's budget answer to it. There is an unused port at the back of the block at cylinder four's location; the kit feeds that port and tees it into the water matrix pipe directly above, adding flow where the factory design left it short.

What is in this kit

• Billet fittings fixed onto quality coolant hose.
• Genuine Subaru water hose clamps.
• Tee piece with fittings for the connection into the water matrix pipe.
• Two supplied pipe lengths, so you can set the position and bend correctly for your car.

The billet barb is sized deliberately. Its internal diameter sets the flow rate around cylinder four high enough to cool it and no higher — the point is to even the engine out, not to overcool one cylinder.

Fitting note from RCM: the position of the metal water pipe the kit attaches to varies slightly between vehicles. Trim the supplied pipe if needed so the hose does not kink.

Street Spec or the full kit?

This kit uses quality coolant hose, Subaru clamps and pipe you cut to length. The full kit uses a pre-formed 90-degree Samco silicone hose with the billet fittings banded in place and stainless HiGrip fittings, so there is nothing to trim and no risk of a kink. Same barb sizing and same principle either way — the difference is hose quality, fittings and how much of the fitting work you do.

Fitting

No machining and no modification to the block — the port it uses is already there and unused from the factory. We fit these as part of engine builds at our Red Deer shop.

Not sure whether your engine has the port, or which kit suits your build? Send us the engine and we will confirm before you order. More RCM parts in our Roger Clark Motorsport range.