Could someone explain returnless systems?

[70bird]

Voodoo indeed! If it was an interference problem, it seems to me it wouldn't matter if the motor is running or not. Is there a stepper motor of some kind on the pass. side? Probably not. How about the TPS possibly hanging up?



Maybe try this, shut the motor off when this happens and see if the secondaries close by themselves. If not you can rule out a vacuum related issue, and get back to looking for a mech. interference. Maybe you could disconnect the new linkage, start the motor and rev it while opening the secondaries manualy to see if the same problem occurs. If the problem persists, you can rule out a problem with the linkage. At the same time you could check (with the motor off) the movement of the secondaries independently to feel for any sticking points.

You stated that when this happens you have to close the secondaries by hand. Do you mean that you are pushing on the secondary shaft to do this? Or can you just push on the primary shaft to do the same thing?

As Andrew said, sounds like you have a defective throttle body.
Hopefuly you can exchange it!
Good luck

[demonpixel]

yes, i'm pushing on the secondary shaft to close them. i can't just push on the primary shaft to do the same thing.

right now i'm going to disconnect the new linkage and when the car is at running temp, i'm going to open the secondaries and see if they stick. if they're still open, i think you might be on to something relating to vacuum keeping them open...

i'll post yet another update in a few minutes. thanks mark!

[demonpixel]

well, sure enough, when the engine is on with the new linkage off and the secondaries stuck open, when i turn off the car, the secondaries come right back down!!

i'll double check my vacuum connections, but i didn't have this issue when i first installed the system a few months ago, so i'm pretty sure i connected my vacuum correctly. maybe something is loose??

here's a screenshot of the software's vacuum gauge when it's at idle. when the rpms are 1600-2200, the vacuum gauge says -20. then the secondaries slowwwly come back down to normal.

[andrewb70]

Vacuum is not keeping them open. It's a butterfly, not a flapper. There is equal suction on either side of the butterfly. Your barking up the wrong tree.

Disconnect the link between the primaries and secondaries. Then with your hand feel the action of both the primary and secondary shafts. Do they move smoothly? Do they stick, or bind in any way? Both of the throttle shafts should have very smooth motion and should take very little force to rotate by hand.

Andrew

[amx2334]

Can you post a good picture of the linkage? It sounds like the secondary return spring isn't hooked up.

[demonpixel]

amx, here is a pic of the old linkage.

andrew, i took the linkage out and did as you suggested. they BOTH move freely and do not bind up.

now here's something my buddy did just a little bit ago. From the MAP sensor, there is a vacuum hose that goes into a T. from the T, one vac line goes to the throttle body, and the other line goes to the (automatic) transmission (as the manual says to do). (i'm running no vac advance on my distributor.) now what my buddy did was he disconnected the vac line going to the transmission and put his thumb over the hole. engine on, secondaries stuck. then he made a vacuum leak with his thumb, only covering HALF OF THE VACUUM HOSE HOLE. THE SECONDARIES CAME BACK DOWN NORMALLY. we did this over and over, no matter what the linkage was (old or new).

andrew, i know you said it's probably not vacuum, but this definitely makes me think that it's vacuum related. my bud thinks that the MAP sensor might be bad.

you guys are great for helping me out; can't believe you've helped me along this much. i can't thank you guys enough.

if anyone's interested, here's the manual: http://www.demonpixel.com/AUTOMOTIVE...ion_manual.pdf

another friend of mine suggested that i may have a leak in my intake manifold. since the manifold is the stock one and it's cast iron, there may possibly be a crack in it if it's from 1972. what do you guys think of this as a possibility?

[Hammered]

Maybe the spring on your secondaries is too weak to hold them shut under high vacuum?

[andrewb70]

I certainly been wrong before, it just seems odd. Keep us updated.

I still don't understand why the vendor is not more supportive. Did they not bolt these things to an engine before they started selling them? If this is a known issue, you would think that they would have a solution already in place.

Andrew

[demonpixel]

ok that's like the fourth time someone's mentioned the secondaries spring being too weak so i'm starting to believe that's it lol...looking at it, a really strong spring could do the trick. i felt how tight it was around the black rod, and there is a little bit of slop. is there supposed to be? this is going to sound stupid but how do you tighten that spring, because i tried removing that Phillips head screw and that thing would NOT come off!!

how common is it for these holley double pumper styles to have weak secondary springs from the factory??

[70bird]

Jeez, what a PITA this thing is for you!
I assume it is not possible for you to return it???? Exchange???

It is not common for Holley (I repeat HOLLEY) carbs to have this problem. After 25 years of playing with Holley carbs and swaping carbs to and from different vehicles, I have never seen this happen. I don't know if there is a stiffer spring even available. When I suggested a vac. related problem, I truly didn't believe this would be the case and just kind of threw that in there as something to rule out. It makes no real sense to me either.
As Andrew mentioned, there is equal vac/force on both sides of the butterflies.

Assuming the secondary spring is indeed too light, and that you can get a stiffer one, You will need to remove the butterflies from the shaft and slide the shaft out of the throttle plate to change the spring. THIS WILL VOID ANY WARRANTY!!!!!!!

Did you puchase this new?
I would exhaust my options of trying to return/exchange this thing, before taking it apart.

[andrewb70]

There is a critical difference between this throttle body and a carburetor. The carburetor uses a ventury. I am sure that this throttle body has a straight bore. I don't know how this effects anything, but I al just throwing it out there.

Andrew

[amx2334]

When you remove the link between the primary and secondary how much effort does it take to open the secondaries? From an open position the throttle blades should "snap!" shut.Not just gently close but snap.
Can you get that same view of the throttle body as it sits on the car? Maybe we can compare the two. I am looking at the spring to see if maybe it came off the tang.If there is no spring action the throttle will tend to open by itself.Just start an engine up without the return spring on it to see what I mean.

[demonpixel]

amx, i'll try to get you some pics of it on the car tonight. the return spring is still on the tang. to answer your question, with the car off and no linkage on, the secondaries DO snap shut when i let go after opening them.

just got off the phone with retrotek. they said that my vacuum is holding my secondaries open, and they said they are sending me a stiffer return spring and a phillips screw, and to uninstall the one that's one the tb now i need to undo the driver side phillips screw. that thing is on there TIGHT. they said to just use any means necessary to get it off, brute force, vise grips, etc. in the pics i'll post to you tonight, you'll see that i've already stripped it some.

they also said if getting the screw off doesn't work, they'll send me a new throttle body.

i'll keep ya updated, as always...

[demonpixel]

here are the pics. i included a pic of the car in case you guys wanted to see that also. definitely a work in progress

[Hammered]

Zig,

That throttle cable looping under the secondary linkage doesn't look good. I would move it out and away from the linkage. I would attach it where the ball stud is now.

This realy sucks - I hope you get it fixed. Slop in the spring sounds like the problem maybe.

John

[demonpixel]

John, I took the throttle cable off the ball stud because I thought it'd be better to see the linkage when I took the above photos. Don't worry, that's where I connect it when I drive it!

[demonpixel]

Well, I came home yesterday, grabbed a set of pliers, and lo and behold, I wound the secondary return spring not once around the black rod, but TWICE. It was MUCH tighter after that.

I hooked up the Holley 1:1 linkage from Summit I got, and said f it, I'm going to drive it. Drove it around and got on it, no problems! That 1:1 linkage REALLY makes a difference too, there is no slop anymore (nice and snug) and accelerating from idle to cruise is really smooth. From cruise to a dead stop, the secondaries came down just fine.

I'm going to keep an eye on it and see how it does on highways but it seems like the car is ok for now.

Oh, another thing I did, was I chose a different profile setup (just to see what would happen). It was for a smaller cam and a little less torque than the profile I was using before, and it ran better. More accurately I should say, I like the way it runs better.

Thanks again guys for checking back and giving input, all of it definitely helped!

[70bird]

ALRIGHT!!!