Case Study- composite carburetor (11 Viewers)

[65swb45]

It’s no secret that good cores are getting harder to come by. Gotta start with good bones and go from there, just like with the rigs. I bought this core a few weeks ago on the forum, advertised as a '71. It had the bellcrank for the early'70s that the cable hooks directly to. I could tell just from the pics that it was likely a composite carb (one that has parts from more than one year), but I thought the bones were good, so I pulled the trigger.

Got the core and sure enough the date code starts with a 1. Now that could be '71, '81 or '91. But that, along with the bellcrank would be enough for most to assume that it was a '71.

I started disassembling the carb, wondering why the throttle body had an idle speed screw only found on a Cali-spec 1974. Then I realized that the bellcrank wasn't shiny like most of the linkage; it was bare metal. wait a minute: so is the Throttle Positioner. And so is the cap screw above the needle and seat. And so is the accelerator pump lift rod!

One of the bolts that holds the fuel bowl to the throttle body is too short, and the other is missing. Flip the core over and release the hollow screw from the bottom and it is a complete screw, no shoulder. Finally the light bulb goes off: this IS a 1974 Cali-spec carb that someone has gone through the trouble to remove the EGR plate from and retrofitted to 1971 specs.

THAT would have required changing the screw. And the bolts. And the lift rod. And the throttle positioner. AND it would require removing the banjo line above the float seat. It's not an easy retrofit, but it obviously can be done, and was done.

I thought about returning it to Cali-spec, as I have all the parts on hand to do so. But there isn't a lot of call for 1974 Cali-spec carbs. So I decided to finish the retrofit, in a way only I can. I opened the unobtainium vault.

Locating the fuel bowl hardware was easy. Same for the Throttle Positioner. I looked in the box of cap screws and found that I still had a couple of NOS ones. I got a little stash of NOS belllcranks from the middle east recently, and I knew for sure that I had an NOS lift rod in the vault. So it was time to have some fun.

The lift rod has been in the vault since 1994!

 

[65swb45]

After a standard dip and cleaning, reassembly was a simple matter of swapping over the rest of the shiny yellow parts. The culprit in the carb, assuming that was the reason it wasn't still on the rig the retrofit had been done for, was a completely clogged slo-jet that neither the carb dip or welding tip files could budge. It happens. Last month I did a 2F carb from the Middle East where someone had pinched the end of the slo-jet tube closed! :rolleyes

 

[65swb45]

None of my pictures do this justice: it's REALLY shiny! (and for sale)

 

[charliemeyer007]

So I have been trying for days to get on your website - error too slow to respond is all I get

This site can’t be reached​

www.marksoffroad.net took too long to respond.

 

[aging fleet]

So I have been trying for days to get on your website - error too slow to respond is all I get

This site can’t be reached​

www.marksoffroad.net took too long to respond.

Mark, same experience for me. Carb looks really nice.

 

[liko]

He is real old school and busy. Phone only, and he prolly won’t answer, leave a message, he’ll call you. Nothing good is easy. Beautiful carb Mark, kudos

 

[65swb45]

I wasn’t planning to sideline a tech thread with my website problems, but the short answer is that my daughter built my website and is in charge of the website, and we are not currently speaking.

See if this works any better: Marks Off Road Home Page - https://marksoffroad.net/index2.html

 

[thatcabledude]

You turned a tech thread into a sale ad in the third post.

I wasn’t planning to sideline a tech thread with my website problems….

 

[65swb45]

One of the other interesting things about this particular composite carb is that it was made during the short timeframe where Aisan was using some sort of fuel-impervious green plastic to coat the primary throttle shaft. This started showing up in some of their carbs in the late ‘70s on production carburetors, but this marks the one and only time that I have ever seen it used on an F engine replacement carburetor. That greatly increases the likelihood in my mind that 1981 was the original production date. End of forensics lesson.

 

[Pighead]

Aisan was using some sort of fuel-impervious green plastic to coat the primary throttle shaft.

That explains why the green shaft then.

 

[73FJ40]

You turned a tech thread into a sale ad in the third post.

You don't have to be a Kevin.

 

[mattressking]

That explains why the green shaft then.

View attachment 4002936

Green shaft isn't Aisan specific, it was quite common on domestic carburetors as well, it is a PTFE coating.....one to look at is Henkel Acheson Colloid, Emralon

 

[peesalot]

Not speaking, again ? I thought you had made progress on that front ?
FWIW that pic looks more like a clock to me than a carb.

 

[65swb45]

Green shaft isn't Aisan specific, it was quite common on domestic carburetors as well, it is a PTFE coating.....one to look at is Henkel Acheson Colloid, Emralon

I wouldn’t know that Nate, as my mechanical universe is almost exclusively early Landcruiser. So I learned something new today. Thank you.

My WAG is that this came into use in the same timeframe as the switch to unleaded gas, and was used because of the concern at the time about insufficient lubrication.

 

[65swb45]

Not speaking, again ? I thought you had made progress on that front ?

If you’re referring to the troll, as I told @Spike Strip many years ago, defending yourself on the internet is like entering the Special Olympics: even if you win you feel retarded.

 

[peesalot]

Daughter silly, it happens doesnt it.

 

[Spike Strip]

Some great tech, here. Never knew why some of those throttle shafts were green.

Carb looks great! Belongs in your display case!

 

[mattressking]

I wouldn’t know that Nate, as my mechanical universe is almost exclusively early Landcruiser. So I learned something new today. Thank you.

My WAG is that this came into use in the same timeframe as the switch to unleaded gas, and was used because of the concern at the time about insufficient lubrication.

IIRC, the PTFE coating occurred at the same time when Aisan used pressed throttle bushings in the base. Once the brass bushings disappeared again (79/80?), so did the coating and back to cadmium or whatever was used at the time.