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Are there small holes (i.e. .030") drilled in the throttle plates on the secondary carbs from the factory? The carb tags are 7026055, 7026056, and 7026057. Oddly the carb tags look like they're dated in 67 - two have F6 67 and the third one has C F6 20.
We're in the process of rebuilding them and want to make sure everything is correct.
The secondary throttle plates do not have any .030 holes in them. The end carb plates have to be totally sealed with no light passing around them. The reason is the end carbs do not have idle circuits and if air is passing through or past the plates they will draw fuel and not idle. The most critical issue with these tri carbs is the secondary rod has to be adjusted absolutely correct. The adjustment is made by bending the rod. The rod has to fit the throttle arms perfectly. If the rod is too long it will push the rear carb plates open and if it's too short it will pull the front plates open and cause it to draw fuel. One of the end carb arms is slotted and the other one is round. This allows for the little play. Just bend the rod till it goes into the arms effortlessly. Your tags are June of 66 .
Last edited by 66-3X2 442; Jan 19, 2023 at 04:14 PM.
The factory put those tiny holes in the secondary throttle plates so a tiny bit of fuel would be drawn even when the secondaries were not used for an extended time. They did this so the fuel in the secondary bowls would not get stale.
The factory put those tiny holes in the secondary throttle plates so a tiny bit of fuel would be drawn even when the secondaries were not used for an extended time. They did this so the fuel in the secondary bowls would not get stale.
I meant .030 holes but you're correct there are some very small holes.
The secondary throttle plates do not have any holes in them. The end carb plates have to be totally sealed with no light passing around them. The reason is the end carbs do not idle circuits and if air is passing through or past the plates they will draw fuel and not idle. The most critical issue with these tri carbs is the secondary rod has to be adjusted absolutely correct. The adjustment is made by bending the rod. The rod has to fit the throttle arms perfectly. If the rod is too long it will push the rear carb plates open and if it's too short it will pull the front plates open and cause it to draw fuel. One of the end carb arms is slotted and the other one is round. This allows for the little play. Just bend the rod till it goes into the arms effortlessly. Your tags are June of 66 .
So F6 is the date, correct? What's the 67 and 20?
I was reading this on the Pontiac site about the holes in the secondary carbs and the reasoning. The carbs we have do have the small holes in the throttle plates on both of the end carbs thus the question. https://forums.maxperformanceinc.com...NAhhgzIUxZqyyU
Basically the car is a friend's 55 Olds that has a 66 425 with the tri power on it. My understanding is the tri powers were originally only on the 400s, is that correct? If so, I assume the jetting should be close enough to work on the 425.
FWIW - I'm more of a chevy guy so working on an Olds it a bit new to me. I'm just trying to help a fellow old car guy out.
I was reading this on the Pontiac site about the holes in the secondary carbs and the reasoning. The carbs we have do have the small holes in the throttle plates on both of the end carbs thus the question. https://forums.maxperformanceinc.com...NAhhgzIUxZqyyU
The tags have F6 which is June being F and the 6 is 1966. The other numbers are inspector codes. What I meant was the end carbs do not have a .030 hole but a very small hole. Let me correct that. They could very well be .030 holes as I have never checked them. I was busy with something else when I first replied. Sorry for the bad info.
Last edited by 66-3X2 442; Jan 19, 2023 at 07:16 PM.
Basically the car is a friend's 55 Olds that has a 66 425 with the tri power on it. My understanding is the tri powers were originally only on the 400s, is that correct? If so, I assume the jetting should be close enough to work on the 425.
FWIW - I'm more of a chevy guy so working on an Olds it a bit new to me. I'm just trying to help a fellow old car guy out.
The tri carbs have 63 jets in the center carb and 68 in the end carbs. They should work fine on a 425 but you can always jet them up a coupls of thou.
