Hi All,

Sorry it is a 4.9L question, not a 4.6L (typo)


I have a 1989 F-150 with a 4.9L 5-speed 4X4. I currently need a new motor, and I have been asked a question that I'm not sure how to answer. Everywhere I call, they ask if it is the Air in Manifold, or Air in Head. Does anyone know how I determine this? I have my motor apart, because I was going to rebuild it but have found the machining is a little high for the truck. I am only planning to keeping the truck about another year and a half before it is replaced with a newer one.

If anyone could help, it would be greatly appreciated.

Thanks,
Adam

 

Their referring to 'thermactor air injection', flow driven by/through the smog pump.. 89 will have the thermactor fittings right along the manifold side of the head, between the manifold and the row of exposed head bolts.. 87-96 should have the integrated taps.. The cylinder head is drilled/tapped directly into the exhaust ports.. Early builds had no provision in the head directly, and had the thermactor manifold attached to the exhaust manifold itself..

 

So, this is the tube that has the "bell shaped" adapter and a tube running the length of the head?

 

Yes..

Many engines used to have the thermactor manifold (tube/s) as part of the exhaust manifold emmisions, and the manifold was drilled/tapped to accept the runner manifolds.. The smog pump air was injected into the exhaust manifolds up close to the head.. Later engines had provisions for the tubes with the fittings right in the exhaust port of the head..

 

Thanks man, that helps a ton.