1970 vs 1973 Primary Slow Jet

[algeeba]

Hello there.

I have a 1973 carburetor that I want to put on my FJ40 and, after cleaning it up, it looks like the accelerator pump housing has some pitting but I am not sure if it is still good enough to use or not. The 1970 carburetor accelerator pump housing that I have looks good so I started rebuilding my '73 with the '70 main housing.

After finishing rebuilding the '73 carb I began to reassemble the '70 to put it away and that is where all progress stopped. The '73 has a size 60 primary slow jet (short) and a size 80 secondary slow jet (long) whereas the '70 has size 50 for both jets and both long.

Investigating further, the '70 main body is bored 1/4" deeper where the primary slow jet goes as compared to the '73. No problem installing the '73 slow jet onto the '72 body but that is where my question is.

Will this set up where a short slow jet is installed onto a longer bore cause any problems? I believe it will not, but can any carb guru out there please reassure me.

Thanks.

 

[91 4runner]

Ya I started to play with emulsion tube sizes, there's really not much info on playing with the "guts" on these things,

Between the two carbs did you happen to see if the primaries and secondary main jets were the same?

I


...

 

[FJ40Jim]

Will this set up where a short slow jet is installed onto a longer bore cause any problems?

No problem. All that matters is the end of the jet is 'underwater'.

 

[largeone]

Thanks for this answer...I had the same question

No problem. All that matters is the end of the jet is 'underwater'.

Sorry to revive an old thread, but my subject is the same...I am rebuilding an 04/72 carburetor and the slow jet on the primary side is short. It is marked 55, but it looks the same size bore as the 80 (long) jet on the secondary side. Maybe it was bored out?

For now, I am reusing the 55 (or 80 or whatever size it actually is) in the primary side because it is the only short slow jet I have. I took apart a spare '71 carb I have, and it has long slow jets on both sides. My Keyster K11-358A kit only had one slow jet and it was a LONG 50.

So, now for the questions:

1) What will the unknown sized primary slow jet effect on my carb performance? It is obviously way bigger than the 50 long one I installed on the secondary side.

2) Where can I get/purchase a size 50 SHORT slow jet? (I live at 5300')

 

[FJ40Jim]

At 5000' altitude a 50 would be about right. A significantly larger slow jet will overfuel above idle. The actual idle mix is trimmed with idle mix screw, but as the idle speed increases above 600rpm the mix screw loses effectiveness. The slow jet is the mix control device at 1000rpm.

SOR might have jets for sale?

 

[largeone]

Thank you for taking the time to respond, Jim! I appreciate it.

Based on the year of the OP's carb, I took a gamble and ordered a Keyster kit for a later model carb...the kit was K11-364A (9/73 - 9/75 carb). This kit comes with all of the jets listed in the picture below, and the primary slow jet is SHORT, but it is a 60!!! Yippee.

 

[Spike Strip]

The above kit is a K11-364A CA emissions

For people who might be researching this in the future, the k11-362a Federal spec kit (same carb year coverage), contains these size Jets: