Just bought a '69 427/400 with the 3 deuces. It is all factory original. The secondarys do not seem to open up even with wot. Is there a temperature safety that will not allow the secondarys to open until engine is up to operating temp? The previous owner drilled the t'stat. With the temps around here in the 40s the engine doesn't fully warm up. Maybe only 150-160 degrees. thanks

:confused:

 

Secondaries are strictly vacuum controlled unless somebody messed with the hoses and/or the diaphragm springs.

If they are adjusted fairly close to factory correct, you will not feel them open like the old Q-Jets did.

They are designed for a smooth transition.




[Modified by Tom454, 7:55 PM 4/24/2002]

 

thanks Tom

 

I can attest to to Toms reply. Q jets give you a kick in the butt, Tri powers give a much smoother transition, but it still can be felt

 

If that car came with the 3X2 setup, it's probably a 427/435. The secondaries should open with engine vacuum. Get a photo or drawing of the complete setup and make sure all hoses are installed correctly. The linkage on the drivers side of the car should work freely and is adjustable. The rubber diaphragms should be replaced, even if they aren't torn. Make sure you put them and the springs in correctly. If all this is done, they will work and you'll get one helluva kick in the pants. I would also replace your thermostat with a 180 but that item shouldn't affect the secondaries. You might also check the baseplate gaskets on all the carbs, make sure there are no leaks and everything operates smoothly. Oops, one more thing....the float level is adjustable on all three carbs and should be adjusted to just barely leak out of the bottom of the sight plug while the car is idling. Keep us posted on how you make out.....

 

3x2 was 400 and 435.

George

 

I agree it can definitely be felt... I guess you can say it's a kick in the pants.
But if it is too much of a kick in the pants, then it has been modified, or it is not adjusted per factory.

I have been working on TriPower setups since 1965... Ford & GM. I bought my 70 454 with Trips at Carlisle (non-original).
Currently, I do Holley rebuilds including machine work such as (but not limited to) throttlebody repair. I have repaired carbs for a lot of Forum members, all over the country.

By selecting different springs for the diaphragms, you can modify the point where the secondaries kick in. The springs were tailored to the factory cam & heads. All of the ones that I have worked on that followed GM's "original" curve, provided a smooth transition, but it definitely could be noticed as an extremely strong pull (as MELVIN said). Since the system works on center carb venturi produced vacuum (not manifold vacuum), there is not a specific point where the carbs just slam open... it was designed to be a gradual process.... unless someone put very weak springs in the diaphragms. This is different than the Ford big block that I had with TriPower and mechanical secondaries. There is definitely a different feel to mechanical linkage. The factpry GM TriPower does not give the same kick as the Ford product... intentionally. GM tried to set it up so that the engine received only enough fuel that could be used. The mechanical linkage Ford setup, which also has 3 accelerator pumps unlike GM, just dumped in the fuel regardless of whether or not it could be used. This caused a momentary "bog", and then all hell broke loose... the proverbial "kick in the butt" feeling. This is the diff between the two systems. Q-Jets did the same thing when they were not adjusted correctly... bog... then boom. That's what I was hinting at.

As posted.. there is a 400 horse (oval port heads) and a 435 horse (rectangular port heads) version.

 

I think Tom has the description down pat, "an extremely hard pull."

I didnt know thats why they were designed that way (as far as cutting down on too much gas), but it makes sense.

Still teachin' me stuff, ay Tom?...

 

Hey , thanks for all the info. The car has brand new carbs on it. I've never driven in or ridden in a 3x2 car before so I don't know what it is supposed to feel like. I guess I will have to fiddle with it and see what I can do. The motor has been completely rebuilt less than 1000 miles ago so I don't know how hard I can beat on it yet. Sure looks awesome!

Thanks again.