stumbling on secondaries

[Shane22696]

Hey guys, for the past couple days when I hit the gas and the secondaries open up, the truck bucks and surges real hard until I let back off. I'm thinking I have trash stuck in the secondaries. I know it's not the ignition because I just did a full tune up with cap, rotor, module, plugs and plug wires. Is there any way to clean out the secondary passages without taking the carb apart? I know the trick for cleaning the primaries where you rev it and close the choke, but I wasn't sure if there was a way to do this on the secondaries. This is my daily driver so any help is greatly appreciated!

[ProStreet83C10]

my truck was doing same thing and i changed fuel filter in front of carb and added a bottle of lucas complete fuel system cleaner and all is well so far

[Shane22696]

Will do that tomorrow, thanks!

[Shane22696]

Ok, so I changed the fuel filter, but now it's doing it worse and when I hit the throttle it backfires real loud and tries to shut down. It actually did shut off once, but I got it back going. It runs great as long as I don't give it too much throttle. This is really starting to get on my nerves. We just rebuilt the carb 2 weeks ago.

Edit: it's an edelbrock 1406

[beamn7]

Quadrajet? Check the secondary air valves (top plates) for sticking / binding, check the adjustment of the air valves (not too loose) and also check the choke pull off. One of it's jobs is to allow the secondaries to open slowly.... You can also remove the secondary hanger and rods very easily and inspect. What hanger and rods are you running? (indentification letter on the hanger and 2 letters on the rods)

[Shane22696]

It's an edelbrock 1406

[INSIDIOUS '86]

Find another edelbrock on Craigslist for 75$ instead of wasting hours on this one. If it still does it with a new one you know your prob lies somewhere else
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[beamn7]

Ah, AKA Carter AFB. Good carb. Much better than a Holley! (anyone that knows carbs knows that)
Been years since I monkeyed with a AFB but if I recall you could also set the tension on the secondary air valves.
Check the tension on the secondaries. If they open too fast you'll get a momentary lean condition (similar to a quardrajet) causing a bog and possible backfire....

[beamn7]

Originally Posted by INSIDIOUS '86

Find another edelbrock on Craigslist for 75$ instead of wasting hours on this one. If it still does it with a new one you know your prob lies somewhere else
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No offense but that is half the problem with technicians nowadays. Replace the parts until it's fixed rather than diagnose is properly.
I work with 300+ dealerships across the country and see it almost daily....

[Shane22696]

It was running fine for the first week or so though, what would make that change?

[grs]

Originally Posted by Shane22696

Hey guys, for the past couple days when I hit the gas and the secondaries open up, the truck bucks and surges real hard until I let back off. I'm thinking I have trash stuck in the secondaries. I know it's not the ignition because I just did a full tune up with cap, rotor, module, plugs and plug wires. Is there any way to clean out the secondary passages without taking the carb apart? I know the trick for cleaning the primaries where you rev it and close the choke, but I wasn't sure if there was a way to do this on the secondaries. This is my daily driver so any help is greatly appreciated!

Did you have the problem before you tuned it up?

[beamn7]

Could be a piece of garbage in one of the jets, vaccum leak, timing (advance may be sticking), loose timing chain, weak valve springs, etc. Slap a gauge on it and see what you have. Should be approx 15-20in-hg and steady. Check the weights / advance....

[Shane22696]

Yes, I just tuned it up because it had started missing on #8 and it hadn't been tuned up since I got it.

[burnout2614]

My Edelbrock HATES ethanol gas, The needles clog often and the carb stumbles badly. peace

[gchemist]

Originally Posted by Shane22696

It's an edelbrock 1406

Edelbrocks have that problem due to design. The carbs put too much fuel into the intake before the engine is ready. It's reason vacuum secondaries on a qjet have a huge advantage. Fuel is not supplied until vacuum is high enough for fuel. You can probably tune to reduce it, but the WOT stumble will always be there.

[INSIDIOUS '86]

Originally Posted by beamn7

No offense but that is half the problem with technicians nowadays. Replace the parts until it's fixed rather than diagnose is properly.
I work with 300+ dealerships across the country and see it almost daily....

Difference between slapping things on seing what works rather than keeping sanity trying to get an edelbrock to tune ( do they really tune?)

Sounds like it has a nasty lean surge when the secs open I it was to rich it would feel like low power at wot and get gradually stronger as airflow increases. Take it apart and spray carb cleaner into all the passages and check your float needle valves
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