Necessary Hole in Carb Insulator Spacer?

[Rooster47]

I have a 1976 FJ40 with a 1978 2F and a Trollhole Carb.

Recently I had the carb off and noticed a hole (port, passageway?) in the bottom of the carb that did not have a matching hole in the carburetor insulator, and I wondered if it was necessary.

Using search, I found this same question asked, but not very well answered:

Carburetor Insulator Gasket

forum.ih8mud.com

It includes these pictures which do show an insulator with a matching hole.

The insulator that I have is like this one shown on Cruiser Outfitters, which has the large heat shield attached. Like mine, the one on Cruiser Outfitters does not have that hole:

And even more interesting is when I search google for images of the insulator, I see many that look like this, with a definite witness mark from that hole:

I apologize for not having actual pictures of my setup. But from these can anyone shed light on this?
My rig does not run very well, so I'm suspicious of everything that doesn't look right.

Thanks

 

[GA Architect]

FWIW - My '77 FJ40's 2F looks exactly like yours, hole in the carb base but no hole in the heat shield.

 

[saltydog20]

The hole is just an access to the screw that holds the carb to the base. it is not an "active" port.

 

[Rooster47]

Perfect. Thank you

That would explain it. Should have looked closer at it when I had it apart.

It does leave me curious about the insulator pictured above that does have a hole through it.

 

[65swb45]

If you look into the primary bore of the carburetor, you will see a hole drilled from the bore to that passage that provides constant vacuum to the hollow screw, which leads to...the power piston.

 

[fjwagon]

I remember working on a friends 78 fj40, it was not running right and ask me to look at it. I noticed the hole you are talking did not match the carb hole. I found by spraying carb cleaner and it went nowhere so removed the carb noticed the insulator was installed wrong. I reinstalled it to match the hole on the carb. The same carb had a missing grommet on acceleration mechanism. Gosh, this this was about 15 years ago.

 

[ceylonfj40nut]

If you look into the primary bore of the carburetor, you will see a hole drilled from the bore to that passage that provides constant vacuum to the hollow screw, which leads to...the power piston.

Reinitiating old thread. Have same insulator on 76 fj40. No hole in insulator or primary bore to hole in carb base for through hole bolt vacuum. So through bolt does not get vacuum from carb base. I have a vacuum port by the number 8 mark on the air horn. If I connect this to intake vacuum will it work? Or do I have to plug this vacuum port and drill a hole through my insulator?

 

[numby]

Does your hollow screw/power piston work off of manifold vacuum and does your number 8 vacuum port run internally to those?

 

[Grayscale]

The brass barb on the air horn, pulls on the power valve, using manifold vacuum. That delivers manifold vacuum, externally. No carb mods necessary.

 

[ceylonfj40nut]

Yep i blocked off base hole with finger and applied vacuum to air horn port and heard power piston click at 5psi vac