Chase Bays Raised Inline Filler Neck



The Chase Bays Raised Inline Filler Neck offers a unique set of innovative features. It is designed to solve a major set of problems in an aesthetically pleasing and modular way. Originally we used these to raise the fill point for our Tucked Radiators since the radiator height was lowered, but once we opened the book we found many things to fix. Lets start at the most obvious feature...

Raised Fill Point

Many might not understand this yet but for other half; they're jumping for joy. This is a feature no other company is offering. A major issue with some engines (especially engine swaps) is the difficulty in bleeding the system. The fill point on the radiator is lower than the coolant passages in the cylinder head or the heater core. This causes unsolvable air bubbles that continue to accumulate as the system cycles. Even when you use coolant bleeding kits, it puts the cap and overflow point below those coolant passages. This causes the cap to overflow more fluid per second if the pressure level of your cap is exceeded. All in all, its an issue enthusiasts have been dealing with for decades.

Our filler neck raises the fill point 3.75" inches / 95.25mm from the center of lower fitting to where the cap seal ends (not the very top). The total height from bottom to top is 5.25" inches / 133.35mm. It installs by welding one of the adapters directly to the upper water neck. You can see example photos below. You can also butt the filler neck up to the water neck and use a short piece of hose to connect the two. That method will take up to 3" inches / 76.2mm more space, but in some scenarios space is not an issue.


We have made the inlet and outlet -20AN female ORB threads and we made adapters to cater to 99% of applications. This is another feature that no other company is offering. The adapters are offered in:
• 1.38" Normal hose connection (SR20DET, 1JZ-GTE/2JZ-GTE, all Honda, Subaru, Toyota)
• 1.5" Normal hose connection (RB20/25/26, GM LS V8, KA24DE)
• -16AN (1" inch inner diameter)
• -20AN (1.25" inch inner diameter)

We're offering one option as "Raw Aluminum Weld-On" and this will be used for those who are welding directly to their upper water necks. It is a normal hose connection that isn't anodized black and can be cut then welded like our example installed photos at the bottom of this page.

Side Ports

There are two 1/8 NPT ports on the filler neck, one on each side. These are in place for accessories you may need to plumb in. Water Temp Sensor, Fan Thermoswitch, Freeze Port, etc. If you don't need to add anything we provide matching black NPT plugs for a seamless dismissal.


It is machined out of 6061 billet aluminum, bead blasted, then anodized semi-gloss black. The Chase Bays logo is laser etched white on both sides. It uses a Type A Radiator Cap thats extremely common on imports. We sell one of our own as an option on this page. The overflow port is 1/8 NPT threads and has a 1/4 Hose Barb connection standard. If you want a -4AN male connection we sell those separately here:

Don't forget to add our matching Coolant Overflow Tank, available here: