Vintage Mustang Forums banner
1 - 3 of 3 Posts

Discussion Starter · #1 ·
The dashpot on my holley 4150C got stuck open yesterday leaving my secondaries wide open! I manually fiddled with the dashpot arm (vertical arm coming out of bottom of dashpot) and they closed. I sprayed carb cleaner on the arm and manually played with the plunger, but it seemed to be okay. I then tried to unscrew the top of the dashpot to take a closer look, but I noticed this rubber gasket type thing moving as I unscrewed . . .so I screwed them back in, tried playing with the plunger again and saw bubbles coming from the gasket (leftover carb cleaner making the bubbles). What's up?

10,588 Posts
Probably the diaphragm on the secondary pod is toast...

Those can be tricky to mess with and I spent much time and energy coming up with a way to tune the secondaries at the track without messing with the pod lid and diaphragm....the two piece lid that Holley sells is similar to the solution I found....

Get a new diaphram and go through the entire secondary linkage to ensure smooth operation. There should be a link on the other side connecting to the primaries which ensures the secondaries close when you let off the throttle. Verify its operation and the smooth operation of the secondary throttle shaft (you can disconnect the dashpot arm to do that E-clip...*G*)

Post back what you find and if you need any further assistance....installing a new diaphragm is mostly a matter of trial and error until you figure out what works best for you...just be sure not to rip the diaphragm near the screw holes and get the vacuum port hole lined up right....

1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.