Vented Carb Screw Question (1 Viewer)

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Anyone know how long the vented screw that goes up from the thottle body to the carb is supposed to be?

I'm rebuilding a non-USA 1977 carb (H3660 tag) and am missing the vented screw which I think is PN 21824-38010 Screw, Set, No.2(For Carburetor Body Set) and from what I can tell, is a standard part for a bunch of models and was the same on US and general market carbs. I managed to track down a used one, but it is too short and ends right at top of the insulator block. I'm trying to figure out if the screw I bought is broken off, or if I need a different part number for a longer screw.

My non-EGR insulator is 20mm thick and the screw I have is 43mm long and has 13 threads on it. Anyone have any idea either how long this screw should be on a 1975-80 carb, or how thick the insulator block is on a USA spec carb (to see if my problem is that the non-EGR insulator is thicker)? This screw is still available in Japan, but before I pay for shipping, I'd like to make sure it's the right screw. I know I don't have the pre-1975 shorter screw as I previously bought one of those, which is way too short.

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Alternatively, does anyone know how important this screw actually is? My carb was missing it before, it it didn't seem to have any negative effects.
 
Alternatively, does anyone know how important this screw actually is? My carb was missing it before, it it didn't seem to have any negative effects.
I would think that with it missing, you'd be prone to an air leak, due to the fact the other two bolts would pull on the other side unequally.
 
this ^

And the actual use of the vent on the screw is to activate the power valve when there is enough vaccum in your intake. The power valve will unlock extra fuel flow in the 1st main jet.
If you put a screw without vent, I guess you would be missing some power for the transition between the use of the 1st and secondary body. Maybe even running lean in some acceleration conditions?
If you don't put the screw you may have leak and a carb not seated perfectly correct.

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The previous replies are correct: the venting performs the essential function of providing the internal vacuum signal for the power valve.

There are four different lengths of that screw: 70-73/4, 74 Cali spec (just a hair longer than an FJ60, 75-80 &81-up. The one you need is the longest of the 4. I’ve never bothered to measure one, so I can’t offer you that info.

I suppose if I ever have need of one, I will get some shouldered 6mm bolts of appropriate length and pay to have them gun-drilled, then grind the head into a round dome and use a hacksaw to cut a slot across it. Form follows function.
 

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