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Hi Flow Sending Units
Pontiac V8 Hi Flow Sending Units
The Restriction Nobody Looks At — Hi Flow Sending Units for Pontiac V8s
A hi flow sending unit replaces the factory tank sender with one that flows enough to feed a real fuel system. Factory Pontiac senders use 5/16" or 3/8" tubes and a restrictive in-tank sock, which is exactly the wrong thing on the suction side of an electric pump. This is also how you add a return line without cutting the tank.
Butler stocks Rob Mc Performance 1/2" outlet and return sending units for GTO, LeMans, Tempest and Firebird applications, plus Tanks Inc five-hole GM-type senders in both 0-30 and 0-90 ohm ranges for cars using factory gauges.
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More About Hi Flow Sending Units
1. Who actually needs one
This is not a dress-up part. Rob Mc gives two clear triggers, and most Pontiac builds that hit either one have a sender problem they have not found yet.
| Over 450 horsepower | The 1/2" units are recommended for cars with engines over 450 hp, where a 5/16" or 3/8" factory pickup becomes the limit. |
| Any electric pump with a bypass regulator | Recommended for all cars running an electric pump and a return or bypass style regulator, because that fuel has to go back in the tank somewhere. The 1/2" return tube does it without modifying the tank or switching to a cell, and caps off if you do not run a return. |
| Drop-in | These replace the factory 5/16" or 3/8" senders directly, and Rob Mc positions them as a budget alternative to a fuel cell or a welded-on sump. |
2. Finding your application
The Rob Mc units are chassis and year specific, and one carries a clearance warning worth reading twice.
| A-body | Separate units for 1964-67 and 1968-72 GTO, LeMans and Tempest, for use in stock tanks with an optional AN fitting upgrade. |
| Firebird | 1967-69, 1970-73 and 1974-79 versions. The 1970-73 Firebird and Trans Am unit will not clear a cross-flow muffler that mounts behind the rear axle, so check your exhaust first. |
| No strainer provision | All of the Rob Mc units are listed as having no provision for a strainer. That is deliberate, and it leads into the next section. |
3. Ohm range, filtration and materials
Get the ohm range wrong and your fuel gauge lies to you for as long as you own the car.
| Ohm range | Tanks Inc lists their GM five-hole sender in 0-30 ohms for cars up to 1964 and 0-90 ohms for 1965 and up. The Rob Mc units use a stainless 0-90 ohm sender that works with OEM gauges. |
| Tanks Inc detail | Five mounting screws, fits tanks 6 to 24 inches deep by cutting to length, reads resistance to ground so it works on 6 to 24 volt positive or negative ground systems, and has no fuel pickup tube built in. |
| Filtration | The Rob Mc units eliminate the restrictive in-tank sock filter, and Rob Mc specifies their inline prefilter in its place. Never run an electric pump with nothing filtering the suction side. |
| Materials | Billet aluminum base with anodized tubes, listed for gasoline or alcohol, made in the USA. |
If you are adding a bypass regulator, this is what gives the bypassed fuel somewhere to go. Order the sender, the regulator and the prefilter together so the tank only comes out once.
Not sure what your Pontiac needs?
Call our tech team at 866-762-7527. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.