REBUILD & RESTORATION
The objective of our process is to deliver a pump that looks and functions like a new or NOS unit. Most pumps we see installed on cars are well-used originals or “restored” pumps recreated from late 1970’s pumps, which are incorrect in appearance. These are low-price offerings and represent a demerit against a properly restored car – whether restored for a judged show or not.
Whether we start with a purchased core pump or a pump sent to us for work, the process is the same. Document it as received, disassemble, and clean (including ultrasonic cleaning of vanes/vane bearings/rear bearing). In most cases, the vane bearings and rear bearing can be re-used. In all cases, the front bearing is replaced.
The pump housing is bead blasted, tumbled and originally machined surfaces re-machined to obtain a new/NOS appearance. The housing is dated to suit the build date of the car or as specified by the customer. This dating is performed using custom-made letter and number stamps that exactly match the original date code fonts and a stamp holder to ensure perfect alignment.
The re-used bearings are repacked with long-life grease and the pump is assembled with new carbon seals, as required. Original replated fasteners are used in most cases. This includes new fasteners for the pulley. Pumps with a relief valve mounted on the side of the body receive either a new reproduction relief valve or a replated original. A correct reproduction filter/fan is included, though we do use original fans for rebuilds if the customer’s pump includes one which is acceptable. Ultrasonic cleaning is magical for many original fans.
Finally, the pump is run tested. This is primarily done to confirm there are no unusual (or embarrassing!) noises and that the pump runs properly and develops air pressure.
GENERAL INFO
Commonly referred to as a “smog pump”, Ford refers to it as an air pump and GM refers to it as an A.I.R. pump. Other terms are secondary air injection pump and air injection pump. Ford termed their early systems utilizing an air pump as Thermactor systems and GM called them A.I.R. systems.
Here is Ford’s description as to it’s purpose and function;
The Thermactor exhaust emission control system injects fresh air into the hot exhaust stream as it leaves the engine combustion chamber through the exhaust ports. At this point, the fresh air mixes with the hot exhaust gases and promotes further oxidation (burning) of both the hydrocarbons and carbon monoxide. This induced burning or oxidation lowers the concentration of hydrocarbons and carbon monoxide, converting some of them into harmless carbon dioxide and water.
The Thermactor system consists of the following major components:
§ Belt-driven air supply pump
§ Air bypass valve
§ Check valve(s)
§ Internal or external air manifold(s)
SMOG PUMP DETAILS
Interestingly, both the GM and Ford smog pumps of the 1968-1973 vintage were manufactured by Saginaw, a division of General Motors. There is a photo in the Gallery of the “S” Saginaw logo cast into the pump housing. However, they are not identical. The cast aluminum bodies differ due to differences in how the pumps are mounted to the engine. The internal parts, however, are identical.
These specific pumps are a 2-vane design and utilize a 3-bolt hub for pulley attachment. The 3-bolt hub is an identifying feature of these pumps, as it is one of the differences between these pumps and the earlier 1966-1967 design. Our service does not include these early pumps; they are a 3-vane design, have many more component parts and we do not have the spare parts to support their restoration and rebuild at this time.
The design of these pumps is termed “sliding vane”. The vanes ride on a shaft that is offset from the rotor centerline, which forces them to slide in and out of the rotor, following the contour of the internal surface of the housing. This action compresses the air until it reaches a “cutoff” bar where the flow is directed out of a hole in the back cover plate. The vanes slide on carbon seals; a horseshoe shaped seal on the ends of the vane slots and a long seal down each side. One of the long seals is spring loaded to permit some movement of the vane while retaining a seal.
Each vane contains two very small roller bearings where it rides on the offset shaft. The rear of the rotor contains a large diameter roller bearing which rides on a race in the back cover plate. At the front of the aluminum housing is a common ball bearing; actually the same bearing used in most alternators. It is VERY securely fixed in the housing with an injected plastic material. The location of this bearing in the housing bore determines the clearance of the rotor vanes between the inside faces of the housing and the back cover plate (axial clearance). This clearance is critical to smooth and quiet running of the pump, so positioning of the front bearing in the housing is also critical.
There is a hub pressed on the rotor shaft, which is the interface between the pump shaft and the drive pulley. There is also a plastic filter/fan pressed over the OD of this hub. Yes, it is actually a filter. The air inlet to the pump is in the front of the aluminum housing, behind the filter/fan. The “fan” functions as a mechanical separator to separate the larger dirt particles from the inlet air. The original filter/fan was an off-white/yellowish plastic, which changed to a black fan around 1971.
These pumps can be tricky to disassemble without breaking anything in the process. They can be even trickier to reassemble, due to the importance of getting the placement of the front bearing just right. Experience counts!
Amusingly, Ford acknowledges what they term “Noisy Thermactor Air Pump”. They site such issues as squealing, chirping, squeaking and knocking as normal during break-in. These are pumps, and do make pumping sounds, but we test each pump on a test rig to ensure that they don’t make such sounds which would be embarrassing to the car owner at a car show