Just rebuilt my 4180C factory Holley 4bbl on my 87 F150 with a 351W and C6 (no OD) auto transmission. I've got it pretty much sorted out having acid dipped everything and put a renew kit in it (needles, seats, drilling out curb idle adjust screws, etc.).

The truck runs 100% better, however I am having a slight problem. I believe that the dashpot (vacuum operated throttle kicker or VOTM) is going bad. When I attempt to make slow turns (especially right turns) I occasionally lose power and the motor stumbles, and occasionally stalls completely.

I have the float levels set properly, the mechanical fuel pump is fine, I have a clean fuel filter and every thing else appears to be set properly.

I have had to set the idle higher (above 900rpm) to keep the motor from stalling in these low-speed turns. The dashpot does not contact the throttle linkage at all now; but I can't remember if it did prior to my rebuild. The dashpot will extend and touch the linkage on cold startup and keep the revs high...then lower when warm. But I understand that it is supposed to extend itself on deceleration to keep the engine idle alive. I can push the dashpot in with my finger when it is extended on cold starts.

Does this sound like 1) dashpot is bad and needs replacing 2) dashpot is good, but I don't have it set properly?

Any help or ideas would be greatly appreciated. The problem does seem worse when temps are above 90 degrees and I've got the A/C on.

 

Hi Axel F,
On some applications, like my 85 bronco, 4180 's don't use a votm and have no similar problems. I've never seen one set to raise idle during deceleration but anything is possible. My guess would be it’s not the dashpot if it’s working your cold idle ok. Could be a lot of things- maybe something causing the float level to drop, like the needle sticking. Or maybe a vacuum leak or ERG related. Also make sure it gets some idle from all 4 idle screws not just the front 2. Hope this helps. Good Luck

 

hard to get those carbs to run right when they are old and rebuilt. best bet is to grab a good used edelbrock 600 and be done with it. when i had my probs on my old 85 lx ho i rebuilt it and it was worse. found a edelbrock and all was great. real easy to work on.

your obviously not looking for performance so get great driveability with an edel.