Author Topic: One-sided booster drip - Oldsmobile 7043250  (Read 191 times)

Offline Glutenfreecarbs

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One-sided booster drip - Oldsmobile 7043250
« on: June 20, 2021, 05:25:21 PM »
So here's a strange one: I just rebuilt my first Oldsmobile carb (using Cliff's SR kit), and it starts and idles beautifully, but the driver-side booster is visibly dripping.

The engine doesn't exhibit the usual symptoms of booster drip. I've got full control of the idle mixture screws, wideband reading is steady, and no stink from the tailpipe. The throttle blades are almost completely closed; the throttle linkage juuuuust barely rests on the idle speed screw.

The primary throttle blades have ~1/10" holes in them, which is kindof a wildcard to me. Maybe this idle recipe is just meant for big engines (455 ci?) that like bypass air, and not my relatively-small 350?

Is there anything "asymmetrical" about the idle circuits on these units that would cause a drip on just one side?
« Last Edit: June 20, 2021, 05:45:17 PM by Glutenfreecarbs »

Offline Cliff Ruggles

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Re: One-sided booster drip - Oldsmobile 7043250
« Reply #1 on: June 21, 2021, 04:00:01 AM »
Did you remove the idle tubes and size them?

Check the power piston hanger arms to make sure they exactly level and even.

What "recipe" is it using, idle tubes, DCR's, etc?

Is this for a "stock" 350 Olds?  Engine specs?.....

Offline Glutenfreecarbs

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Re: One-sided booster drip - Oldsmobile 7043250
« Reply #2 on: June 21, 2021, 04:25:31 PM »
Nevermind; an afternoon of errands, traffic, and a few good WOT pulls seem to have cleared out its sinuses, and this carb is really happy now.

Thanks for the reminder to verify the PP hanger arms are level. I'll check that in a few days when I open it up to change rods/jets. The weather here (NE Ohio) has been too unstable to make proper tuning decisions; I saw a corrected altitude of 3,500' at lunchtime today. Yuck.

This carb was a "barn find," and looked (and smelled) completely stock. I'm actually using it on a mild Chevy 350. I wanted to see if an older Q-jet with narrower primary venturii would a better fit than my usual  late-model SMAB units...more to come.







Offline Glutenfreecarbs

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Re: One-sided booster drip - Oldsmobile 7043250
« Reply #3 on: July 19, 2021, 04:58:28 PM »
So I finally found the root cause of this strange and intermittent one-sided drip! -one of the primary throttle blades was bent, resulting in the other blade being unable to fully close. Never seen that issue before...


Offline Cliff Ruggles

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Re: One-sided booster drip - Oldsmobile 7043250
« Reply #4 on: July 20, 2021, 03:47:09 AM »
The primary plates are delicate and the shafts easily twisted.

I spend a LOT of time in that area during a rebuild, and pretty common to find issues there.....