Quick TQ pull-off question

[midnight340]

I've got my Thermoquad dialed in really nicely, great A/F #s all around, plugs are good. Timing curve is good. Yesterday I removed the air cleaner and watched the secondary air door open when blipping throttle quickly and the vacuum dropped.

Today, the pull-off is preventing the door opening. The air door is adjusted properly. Not running, I can easily push down on the door and it feels right. Running at idle it is getting vacuum and pulls on the air door. But when I pull the carb open quickly there is no vacuum drop at the pull-off and the air door stays tightly shut.

What am I missing here???

 

[midnight340]

The only changes from yesterday are that I quickened the timing curve slightly with a spring change in the MSD and it's 20* cooler out. Messing with it more the door will open a small amount with revving the engine, yesterday it would open most of the way for a split second.

The real problem is that I am retired and have time to try to figure this out. Previously I would have been happy with, "Oh, it runs pretty good."

 

[RustyRatRod]

You had to be wailin on it hard to open the secondaries with no load. Load is what makes the secondaries really open.

 

[Bewy]

Congrats on a really smart move using the TQ.
The AV dashpots fail over time. The rubber diaphragm goes stiff & doesn't release. Push the plunger in with your finger & let go. Should release quickly. If not, or releases slowly, time for a new one. I like the #407 dashpot, used on 440s & has slightly stronger spring than others.

 

[Bewy]

Another thought....
The secondary throttle blades need to be open for the AV to open. If the choke is not completely off, I think it can keep the blades closed. Not 100% sure on this, as I remove the choke & fast idle linkage on my TQs.

 

[RustyRatRod]

Another thought....
The secondary throttle blades need to be open for the AV to open. If the choke is not completely off, I think it can keep the blades closed. Not 100% sure on this, as I remove the choke & fast idle linkage on my TQs.

You got it right. The choke has to be off before the secondaries can open, unless that feature has been defeated.

 

[midnight340]

Thanks guys, I'll take another look at things today.

 

[midnight340]

Congrats on a really smart move using the TQ.
The AV dashpots fail over time. The rubber diaphragm goes stiff & doesn't release. Push the plunger in with your finger & let go. Should release quickly. If not, or releases slowly, time for a new one. I like the #407 dashpot, used on 440s & has slightly stronger spring than others.

I'll check mine.
Yes, absolutely happy with the move to the Thermoquad. Granted there is a learning curve in regards to tuning! This the single reason people don't like them. Once you get it down they are easy to tweak, and the metering is so much better, A/F #s more stable, and less affected by variables so very trouble free.

Another thought....
The secondary throttle blades need to be open for the AV to open. If the choke is not completely off, I think it can keep the blades closed. Not 100% sure on this, as I remove the choke & fast idle linkage on my TQs.

I did remove the choke and disabled fast idle linkage, so no issue there. (Parked in a heated shop so do not miss the choke at all.)