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Thermactor/Smog Pump Rebuild

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85lebaront2

Re: Thermactor/Smog Pump Rebuild

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Gary, depending on the application, the Thermactor pump was used to inject air into the exhaust stream to help eliminate unburned hydrocarbons. The first systems did just that, and if the air gulp or diverter valves malfunctioned could create one heck of a load backfire. The valves were even referred to as anti-backfire valves.

Gary has seen the plumbers nightmare the last of the carbureted 460s had, two air pumps, one feeding 6 of the eight exhaust ports (the crossover ports were not fed so as not to interfere with the EGR system) the other fed all eight exhaust ports at the manifolds. Dual air pumps, dual diverter valves, three check valves, a lot of vacuum lines and some very nicely made air piping and a ton of hose clamps.

Once catalytic converters were introduced it was found that due to the complexity of the exhaust makeup and the need to (a) complete oxidation of some components and (b) reduce other components the two part catalyst was used, the first part or first converter is a reducing converter and works in low oxygen conditions, the second catalyst or portion is the oxidizing part and needs a surplus of oxygen to function properly.

Ford's systems on the trucks, particularly the EFI models, use air into the exhaust ports with the engine cold to (a) burn off the excess fuel in warm up mode and (b) help "light off" the converter. Once a temperature threshold is passed, the system changes the air delivery into the center of the dual bed converter.

The oddball in the group is the EFI 460, early versions only used the pump to feed the center of the catalyst, later (1993-97) have air fed into the exhaust ports like the smaller engines, then to the center of the catalytic converter.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Gary Lewis

Re: Thermactor/Smog Pump Rebuild

Administrator

Yes, Bill, I forgot about the air injected into the ports. And that varied by the engine type, which is one of the reasons I didn't want to go into the details w/o knowing what he has. 351M's & 400's had air injected into the intake manifold, of all places. Windsors had the manifold between the backs of the heads, and they frequently corroded off. Then there was the 460:

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

ArdWrknTrk

Re: Thermactor/Smog Pump Rebuild

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Looks all too familiar.

I'm glad none of it is required in my state anymore.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Thermactor/Smog Pump Rebuild

Administrator

Nor in my state.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: Thermactor/Smog Pump Rebuild

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In reply to this post by Gary Lewis

Gary, the 351C, M & 400 had dry intake manifolds, the ends of the heads where the water passages would be on a Windsor, FE or 385 series were available, so Ford in their somewhat normal let's save a few bucks, used these areas for the air injection. Saved a lot of external plumbing.

Had a good friend who built a 1967 Shelby GT350 for SCCA racing (car is still around, a fellow named Greg Reynolds has it now) he wanted to use a Boss 302, cheapest way to build one due to the rarity is to use 351C 4V heads on a 302 short block. Air ports on the heads line up with the water passages in the Boss 302 intake. He had drilled the heads for the water passage into the intake, one on each head, so they couldn't be switched around.

I got a frantic call on a Thursday afternoon before the first race, water was pouring out of the exhaust header on one bank. After some examination, plugs looked great, I said let's not run it, fill it up and see what happens, sure enough water starts running out of the header. Pulled those plugs to be safe and took off the intake, when I showed him where the gasket sat on the heads, it was one of those duh! moments. A couple of pipe plugs and open the other end of each head for water so they were interchangeable and he was off to Summit Point to race.

Bill AKA "LOBO" Profile

85lebaront2

Re: Thermactor/Smog Pump Rebuild

Administrator

In reply to this post by ArdWrknTrk

Nor on an EFI conversion, VA has an update backdate law on engine changes, if you go with a newer engine, it only has to meet the year of the vehicle.

Bill AKA "LOBO" Profile

Gary Lewis

Re: Thermactor/Smog Pump Rebuild

Administrator

In reply to this post by 85lebaront2

Fun story, Bill. Did he win?

Yes, the intake on the Clevelands/M-Blocks were dry, so Ford did plumb the thermactor input there. When I first started working on Dad's truck the pump was long gone and there was a pipe plug in the intake manifold there. I'd never noticed that the air was plumbed in there, so I didn't know what it was. And there was a spitting noise when the engine was running. Sure enough, the pipe plug was leaking exhaust - out of the intake manifold.

Gary, AKA "Gary fellow": Profile

delco1946

Re: Thermactor/Smog Pump Rebuild

Dumb question but How do you know if your pump is/ isn’t working?

Christopher in Portland Or. 1981 F250 Ranger XLT 4x4 trailer special 351M, and auto C6

Gary Lewis

Re: Thermactor/Smog Pump Rebuild

Administrator

You can pull the output hose and tell that it is moving air.

Gary, AKA "Gary fellow": Profile