Hisssssss!
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Postmaster
Joined: Mar 2005
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From: Earth
Hisssssss!
How does she leak vacuum? Let me count the ways...
There are finally no vacuum leaks left on the Bronco. I can't believe the thing was running as well as it did all things considered.
Vacuum was leaking through a shot vacuum advance diaphragm, which was killing performance at cruise without the advance beyond the leak.
Vacuum leaks in the A/C at the firewall plug/lines and in a control pot when the system is at "Off". Took a vacuum pump to find those...
Last but not least, the grommet on the brake booster.
Ya know, you preach checking for vacuum leaks but live your own life in denial. Physician, heal thyself!
I switched the vacuum advance to the manifold vacuum side of the carb, too. I've got this chambered pipe muffler on the thing that backraps like crazy. Used to backrap, anyway. That's gone along with what was left of the boggy/laziness. Let the debate begin, but if anyone's having trouble tuning that last little bit of sloppiness out of a carb I'd give it a go.
There's still some room to bump up the timing, I think, I'll find out this weekend. Then I should actually be able to get an accurate reading on an A/F meter. I don't think it needs to be tuned, but want to check the A/F at cruise and part-throttle just to be sure. Nuke the site from orbit, just to be sure. Lean kills.
Right now the only thing I've changed on the carb is the accelerator pump nozzle to the smallest one they have, IIRC .024" vs. .028" stock, and the pink springs. I almost pity the guys with Holley carbs. Edelbrocks are so easy. Bolt it on and go. At least once you get rid of all the cursed vacuum leaks.
There are finally no vacuum leaks left on the Bronco. I can't believe the thing was running as well as it did all things considered.
Vacuum was leaking through a shot vacuum advance diaphragm, which was killing performance at cruise without the advance beyond the leak.
Vacuum leaks in the A/C at the firewall plug/lines and in a control pot when the system is at "Off". Took a vacuum pump to find those...
Last but not least, the grommet on the brake booster.
Ya know, you preach checking for vacuum leaks but live your own life in denial. Physician, heal thyself!
I switched the vacuum advance to the manifold vacuum side of the carb, too. I've got this chambered pipe muffler on the thing that backraps like crazy. Used to backrap, anyway. That's gone along with what was left of the boggy/laziness. Let the debate begin, but if anyone's having trouble tuning that last little bit of sloppiness out of a carb I'd give it a go.
There's still some room to bump up the timing, I think, I'll find out this weekend. Then I should actually be able to get an accurate reading on an A/F meter. I don't think it needs to be tuned, but want to check the A/F at cruise and part-throttle just to be sure. Nuke the site from orbit, just to be sure. Lean kills.
Right now the only thing I've changed on the carb is the accelerator pump nozzle to the smallest one they have, IIRC .024" vs. .028" stock, and the pink springs. I almost pity the guys with Holley carbs. Edelbrocks are so easy. Bolt it on and go. At least once you get rid of all the cursed vacuum leaks.
Postmaster
Joined: Dec 2006
Posts: 3,603
Likes: 10
From: Spokane, WA
Vacuum leaks can be a PITA because of the places they can hide. Another place that is sometimes overlooked is a worn throttle shaft in a carburetor...something not routinely fixed by rebuilders.
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Postmaster
Joined: Mar 2005
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From: Earth
I had another Edelbrock carb that almost drove me crazy. I could not get the idle down even when the screw was 1/8" off the lever. Checked for vacuum everywhere, plugged off everything. It would not come down. Yanked the carb and the linkage on the choke side was binding. Slight bend, it was idling smoothly at 500rpm.
I always want to look past the simple, little things for some giant booger-man. In fact, just for funzies I'm going to hook up the old Jacobs Mileage Master ignition box I bought almost 20 years ago to fix what was, in retrospect, probably a vacuum leak. The multiple spark is nice, though.
I always want to look past the simple, little things for some giant booger-man. In fact, just for funzies I'm going to hook up the old Jacobs Mileage Master ignition box I bought almost 20 years ago to fix what was, in retrospect, probably a vacuum leak. The multiple spark is nice, though.
