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Discussion Starter #1
I’m hoping somebody has run into this issue before and can help out. A year ago I bought my brother-in-laws 62 impala SS. It has a mid 70’s 350 with a mild cam (very mild I put that in this winter) , Edelbrock EPS intake manifold and a 1406 carb. He explained when I bought it that when the secondary’s open the car basically dies. Get off the gas and vrrrooom off it goes. He attributed it to a bent gas tank pick up that he bent during an attempt to repair the gas gauge. Sounded reasonable, I’ve seen his work before; he’s not the best at repairs and is more concerned about fixing it fast as opposed to correctly.
So I figured no big deal,I’ll take care of this over the winter and finish driving it to cruise nights for the rest of the season. The tank is old so I’ll replace the pickup, gas tank, fuel pump and lines. All the items were readily available, inexpensive and fairly easy to replace. Besides all of it was 46 years old, the tank had quite a bit of sediment in it anyway.

So over the winter I replaced the Tank, fuel lines, Edelbrock pump(around 5psi), fuel filter, spark plugs, spark plug wires ,cap , rotor ,air filter and heads (don’t ask lol). Even after that it still dies when the secondary’s open! So I read up that it could be the small needle valves in the carb, Edelbrock makes a larger valve for this purpose. I ordered the larger valves, installed them and same problem!..

This occurs when the car is hot/cold cool or hot days, doesn’t matter. Nothing seems to affect how it runs. On the primaries it runs fine. I’m about to order a new (rebuilt) Quadrajet to replace it.

Is this carb just a piece of cr*p or am I missing something? Oh I replaced the gas cap too!
It is definitely a fuel starvation issue. As long as it’s on the primaries it runs fine, open it up and within 2 seconds bam just like it ran out of gas. Let up ,off it goes(when the bowl fills back up).

Oh and the fuel lines are far away from any heat source.
I popsted this on another forum , buts rather slow there. Its still a chevy small block!

STUMPED!
Any help would be greatly appreciated!
 

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Of course , you've checked for vacuum leaks and anything else giving this effect.

Might bump up initial timing to as much as 10°-12° BTDC before condemning the carb.
Could it be the secondary air valve opening too quickly? The top plate on the secondaries?
Does it really run out of gas?
Can you borrow or buy a salvage Q-jet before laying out the money for a rebuilt unit?

Overall, reads like a nice car. I wish I still had my '64 Impala, not an SS, but 2-dr hardtop and I liked it better than an SS.
 

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Any rubber hose in the fuel system ?

If so, you may want to replace them (cracked and sucking air, or collapsing)
 

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Discussion Starter #4
ya it really seems like it just flat runs out of gas. If I keep it matted, it will do the funky misfiring like your getting dribbles of gas into the carb. the bang,,bang ,,pop,,vrrroorm ,,pop,,bang .bang,, vrroom. etc...let off the gas and in a second or 2 carb fills back up and off ya go.
i dont think they are opening too soon, it pretty well up in the rpms before they start coming in.
Thats the odd thing , the timing can be advanced like 20+ degrees (or it seems that way) I think the damper is from an engine that has the timing mark at the 12 oclock location, as opossed to the 2 oclock location. engine runs much better when timed so its at the 12 oclock location.
Yes I do have a quadrajet on my firebird that im going to try this weekend.
Think it could be ignition related?
It really acts like its running out of gas or a bad fuel pump that cant keep up with demand.

ALL hoses and lines replaced from tank to carb!
Bob
 

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I would verify you have fuel on the sec side of the carb. Then make sure the sec jetting is ok and that nothing on the sec side of the carb is plugged up.

The way this carb works the sec's are designed to start opening when the pri side is 65% open and both hit wot at the same time. The sec air valve is there to override this if there isn't enough airflow through the carb to use the additional fuel. From what you describe it sounds like the sec air valve is opening, the sec throttle is opening and you are just not getting fuel.

This might help you if you don't have a copy already...

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf
 

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Discussion Starter #6
Thanks I do have the manual , i'm going to pull the carb off this weekend, Hopefully something is blocking fuel supply to the secondary jets. Its the last thing it could possibly be. like I said everything else is brand new from the tank to carb!

Bob
 

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A lot of times ignition issues are misdiagnosed as a carb issue. I had a 1406 at one time and 1st let me say that those carbs are designed to be an economy carb, not a performance carb. The 1405 is the performance version. That being said, the 1406 doesn't have a secondary air valve. The secondary barrels are open. The Performer series carbs are not like the AVS series. If you are 100% positive that you are not dealing with an ignition issue, then try pulling the 8 screws that hold the top of the carb onto the main body and inspect the secondary jets. You may also want to make sure you pump is maintaining 5psi under WOT conditions. Just because it says it at idle doesn't mean it's holding it under WOT. Just a thought.
 

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had the same problem with that same carb...tried to verify fuel into the bowls all good...switched carbs..with another edelbrock temp...problem went away...
 

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Discussion Starter #9
I have taken the carb apart , i actually thought it was a jetting change . So I bought the tuning kit for the 1406. Tried all sorts of cominations from lean to rich, no change. maybe the port that supplies the seconday fuel is plugged.
I'm going to pick up a quadrajet to square flange adapter tomorrow. i have a known good qjet on my bird that i'll try out. See what happens then. I really dont think its an ignition issue , but i could be wrong of course..I was suspect of the ignition system , so i bought a pertronix point elimination kit for the old point style distributor. I'll drop that in first before swapping the carb off my bird, right now its a GM HEI

thznks for the sugestions, i'll let you know what i find..

Bob
 

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I have a similair prob. with the 1406, ill keep an eye on this topic.. my left eye that is...
 

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....i dont think they are opening too soon, it pretty well up in the rpms before they start coming in.
they're mechanical secondaries, they'll "come in" as soon as your foot is about 70% into the pedal. RPM's don't matter. there is a counterweighted "air valve" over the secondaries that will open up once the secondaries start pulling air. but the butterflies themselves snap open with your foot.

as was already mentioned, pull off the top of the carb and check around inside the bowls. squirt some carb cleaner into the secondary jets, make sure you're getting a nice spray out the secondary venturies. when i rebuilt my edelbrock, those suckers (venturies) were FULL of crud.

you mentioned "needle valves" in your first post. are you talking about the needle and seats in the float bowls?
 

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the secondary has an adjustment on it for the top barrel to open. it may be opening too soon. have some one step on gas and you turn back screw for it tighter. top barrel is opening up to quick for you.adjustment is on drivers side of carb.
 

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Discussion Starter #13
Thanks I'll look at that this weekend. Work has kept me too busy to do anything in the evening. Where is the adjustment screw located?
Yes I am refering to the needle and seat for the floats. They are marginally larger that the stock set.

Bob
 

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There is NO adjustment to the secondaries on an ede.
They are exactly as Aaron described.
There are only 2 float bowls, on each side, each feeding both a primary and a secondary, so if she runs on the primary's, she's not running out of fuel.
The secondary passages could very well be plugged up.
 

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A note on the adapter for the Q-Jet. If the Q-Jet does indeed solve the issue, DO NOT run the car using that adapter. For testing purposes, it's fine, but it will restrict air/fuel flow. If you decide to keep the Q-Jet, you will have to get a new manifold that accepts a spreadbore carb.
 

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Discussion Starter #16
I'll dis-assemble the 1406 again and look at the secondary jet fuel passages and be sure they are clear of any debris.
The reason I say it seems like it runs out of fuel is it does run for just a few seconds as the secondary’s open , but runs "dry" shortly after. Just like the fuel demand outstrips the supply. I can drive all day without issue if I don’t get on it. I can’t imagine that this 350 would be too much for the carb. Like I said it’s a 1975 or so low compression block/heads with a very mild cam.
I have tried both mashing the pedal to the floor and slowly advancing the throttle to just where the secondary’s come in, and either case when the secondary’s open with a few seconds it will "run out of fuel" . It sounds just like I’m running out of gas or it goes extremely lean. But as long as I keep my foot in it,, it will backfire ,, drop rpm and basically die.
Let off the gas and within a few seconds, off you go. Which I attribute to the fuel bowls filling back up as demand for lots of fuel has dropped off.
So I’ll tear it down tomorrow afternoon. I was hoping this car would be more "turn key " than it has been. It takes too much time from my 69 bird!

Thanks for all the help though! I appreciate it
 
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