2F Carb Gurus Assemmmmmble!

[swamp-thing]

Hey gang — I purchased an Aisin 1979 2F carb from a mud member a couple years ago — it’s a 9b 27 carb ( feb 79 )
I want to swap it out with the carb currently on my truck, 9N 7 (November 79) for trouble shooting reasons.

The carbs look pretty similarish in most ways, HOWEVER, the Feb carb has this threaded port next to the main fuel inlet that my November carb has sealed up.

Pointing to it in the pic with screwdriver:
Question, What goes there? Can it be blocked off? If so do I just run to my local hardware store to see if I can find a plug or is it a specialty thing?

Thanks in advance!


~Swamp

 

[swamp-thing]

 

[Skreddy]

Fuel return. Does your fuel pump have the return? If so, fine to block that port. Might be BSPP thread.

 

[swamp-thing]

Thank you Skreddy — my fuel pump is a mechanical 3 port, i believe yes it has a return.

 

[swamp-thing]

Would it be odd for another 79 era carb ( only 9 months off my stamped date ) to have the return line port open when mine is closed?

 

[charliemeyer007]

At some point things change by date or serial number. Look at the application data at places like SOR.com.

Next it's a half decade year old rig - with previous owners that did whatever.

 

[65swb45]

The early’79 carburetors continued to have the threaded return line even though the fuel pump had changed to the three hose type with the return at the pump.

Why?

Just spitballing here. There are examples of other times where Toyota made changes while keeping one foot in ‘the past’, hedging their bets so to speak.

When they introduced the internal oil galley for the rocker arms on the ‘74 engine they made the head bolts an inch longer, presumably because they weren’t sure if the existing design was sufficient to handle the new internal pressure. They went back to the original head bolt length/depth 15 months later.

When they introduced the 2F carb in ‘75, they added an AAP circuit to the carb. Why? In case the standard circuits couldn’t deliver enough fuel for the 20cid larger engine. AAP was back ‘out’ in less than two years.

So that’s my guess why they drilled and then capped the early’79 carbs: they just weren’t sure if the ’new’ design of fuel pump would handle the return, so once again they hedged their bets.