Edelbrock Electric Choke Issue

[Clem Z.]

Re: Edelbrock Electric Choke Issue

if the screw comes out the screw and the cover can end up in the engine or worse it could jam the throttle open at a bad time. my suggestion unless you can do the repairs yourself buy a new smaller carb

i forgot you have a 350 cu in engine so a 750 CFM should work fine.

[Jim T.]

Re: Edelbrock Electric Choke Issue

Roger I have successfully repaired stripped threads on my Holly using a Heli-Coil product. The original hole is drilled larger, the Heli-Coil tap is used to thread the newly enlarged drilled hole, then the stainless steel threads are inserted/installed and you are ready to install the original screw. My fuel bowl screws were Heli-Coiled many years ago. I did another Heli-Coil on a screw hole for attaching the base plate to the body 6 months ago.

The heat riser vavle is located where your exhaust pipe connects to the exhaust manifold on the passenger side of your engine. With your installed engine the valve should be wired open 100% of the time since the intended function cannot be accomplished with the GM crate engine you have that does not use a exhaust crossover from one side of the intake manifold to the other side.

One the engine stamp pad at the front of the engine what information is stamped on your pad?

[Timothy B.]

Re: Edelbrock Electric Choke Issue

Roger,

Be very careful handling the screw, Clem is right that if the screw falls in the engine you will be in for alot of work. Don't ask me how I know.. Cover the venturi holes anytime you work on the carburetor or take it off the engine.

If a longer screw will work then try that or heli-core the hole. It's a simple repair that will work here. There is no gasoline leak at this location but if the cover is removed with the engine running the spring will pop the piston and rod up and out of the main jet so it's got to be fixed. Just snug these screws..

Sounds like the choke coil will hold the plate tight if moved in the rich direction so on a day when the air temp is approx 68-70* turn the cover to just close the choke and you will know it's adjusted correctly.

Looking at the pics of your engine set up I think it's a nice neat installation. Before you go tearing into the carburetor give more details like how the engine is timed, vacuum advance specs etc. Engine timing needs to be correct before any carburetor work, your issue sounds like a simple tuning problem. Finding the right person to fix it may be another issue.

[Roger P.]

Re: Edelbrock Electric Choke Issue

Good morning,
I got up this morning and took care of the stripped screw hole that secures the metering rod cover. After taping over the entire top of the carb only leaving the cover exposed, I removed the cover & screw. There was a fair amount of metal filings mixed with gas -- especially down in the screw hole. I found a longer screw with a similar gold finish in my toolbox and cut it down to slightly longer than the original screw. After cleaning out the hole, I snugged down the cover with the new screw (got lucky). Since it was about 68 degrees this morning, I also re-adjusted the choke as suggested. This task was a success, but I still have the original stumble issue to address. I don't know any of the timing or vacuum specs, so this is what I plan on doing. I will bring the car to my mechanic this week and have him replace the fuel line and filter (steel line from the carb to the fuel pump), as well as the base & airhorn gaskets (to ensure there are no leaks). While it is there, I will have him give me the timing and vacuum specs as they are currently. Once I have this information, I will report back to you guys for additional suggestions. It might take a week or so since I know this week will be busy for me returning to my business after taking time off during the holidays, but I will get it done.

I don't see any numbers or a pad on the front of my engine, but when I purchased the car, the shop that inspected the car for me reported that the engine number was V0328ZZZ with a 224 fuel pump. Is it common to have a fair amount of black oil/grease build-up on the back of the engine below the distributor where it connects to the bell housing? My engine is very clean overall, but not in that location.

Thanks to all,
Roger (50141)

[Stuart F.]

Re: Edelbrock Electric Choke Issue

Roger;

By any chance are you planning to come up here (Orlando) for the winter meet later this month?

If yes, please send me an email or pm with your cell number and day(s) you expect to be here. Would like to meet you and discuss your Vette in person.

Stu Fox

[Roger P.]

Re: Edelbrock Electric Choke Issue

Good evening,
As I mentioned last week, I was able to take my car to my mechanic the other day. He didn't have his vacuum gauge available , but he was able to check the timing; 10* at idle and 32* at about 3,000 rpm. He didn't have time to change the fuel line, fuel filter, or carburetor gaskets at this time. He told me that the timing was perfect, but that the vacuum line at the carb had to be moved from full-time vacuum to ported vacuum because the timing wasn't advancing. After switching to ported vacuum, the timing advanced properly. At my request, he tried to check for a vacuum leak using his smoke machine. However, he told me it wouldn't work on a carbureted engine since the smoke would exit the carb. I asked him to cover the top of the carb, but when he turned on the machine, gas started flowing out of the carb and onto the intake manifold . Although I was hopeful that he nailed the hesitation problem, the car stumbled at the first stop sign . Short of a vacuum leak at the base of the carb or the intake manifold, the issue has to be carburetor tuning. I am not a mechanic, but decided to buy an Edelbrock Carburetor Calibration Kit for my 1407 (750 CFM). I know another mechanic changed the jets to lean the carburetor about a year ago, so I figured that I would keep it simple and change out the metering rods and springs. I was going to richen the power mode and lean the cruise mode from the stock set-up, but then discovered that the rods currently installed were exactly the ones I was going to use! So I thought about it some more and decided to try leaning the power & cruise modes since I was getting some black smoke when accelerating in the driveway, and would always smell gas after shutdown. I don't think the cold engine stumble problem is 100% resolved, but it does seem much better. Does this make sense to you guys? I still have the maximum shot from the accelerator pump, but I will try the leaner settings on that, too, to see what happens. If I still have some hesitation, the carb gaskets will get replaced just to rule out a vacuum leak, and so I can check the inside of the carb. If I can't completely resolve it, I might have to live with a slight stumble until the engine is warmed up . I understand that this isn't uncommon with a performance cam as installed in my 350/345 ZZZ GM Performance engine.

Thank you all,
Roger (50141)

[Timothy B.]

Re: Edelbrock Electric Choke Issue

Roger,

I am sure your mechanic has the best intentions when working on your car. The vacuum advance should be fine with full manifold vacuum to the can so are you sure he took it from manifold to ported source on the carburetor. Without knowing the engine vacuum at idle there is no way to adjust the vacuum advance control to work properly.

Your car needs a good old mechanic willing to spend time to correct the problem. A vacuum gauge when working on these old cars is as important as a wrench!! I don't think this problem is A/F ratio so be careful when changing parts and write down notes on parts that were there so you can go back if needed.

I suggest adjusting the accelerator pump to the instructions given in the manual and consider larger squirters (nozzles) to give a larger shot of fuel earlier. The lever adjustment controls the volume but the discharge nozzle size will allow the volume to be discharged earlier into the engine. This will help cover a lean condition when going from idle to main circuits which may be the problem with the 750 cfm size carburetor.

Other than that I would not throw $$ but find a good mechanic willing to spend time to correct the condition and tune the engine.

[Roger P.]

Re: Edelbrock Electric Choke Issue

Tim,
I was told by the mechanic that the timing remained consistent and very high when it was on full manifold vacuum, but reacted properly when switched to ported vacuum (low at idle and high at WOT). Keep in mind that I had two other mechanics - one carburetor specialist and one Corvette specialist - work on tuning my engine with less than successful results. Granted, the engine runs great other than the hesitation problem, but that is the issue that I am trying to resolve. After reading dozens of threads on this website as well as several other websites, I realize that I am not alone in my frustration to correct this issue. Very few threads end with a resolution. I know it is very difficult to diagnose a problem without actually seeing the car, but I am trying because I don't want to give more money to mechanics for them to profit without results. The metering rods and springs are quick & easy to replace, so I decided that it was worth a shot. I kept the ones removed to the side, but why put them back just to perpetuate the problem? With the money I already spent with mechanics, I could have purchased a brand new carburetor - including installation. I assumed that someone would have experienced my exact cold off-idle hesitation problem and that would lead me to a solution. When I take her out for a test drive next weekend, I will see if my tinkering has made a significant improvement. If not, I will look into larger accelerator pump squirters or continue my search for a "good old mechanic" as you had suggested. I have one last question that no one was able to answer before... how can I check for a vacuum leak on a carbureted engine? Other than spraying carb cleaner, what other methods are available that won't remove my engine paint?

Your assistance is appreciated,
Roger (50141)

[Michael W.]

Re: Edelbrock Electric Choke Issue

Tim,
I was told by the mechanic that the timing remained consistent and very high when it was on full manifold vacuum, but reacted properly when switched to ported vacuum (low at idle and high at WOT).

Roger,

The timing is supposed to remain consistent and very high (advanced) while on full manifold vacuum- that is the correct and desirable action. Ported vacuum is by and large an anti-pollution strategy that does not improve the drivability of the cars at all.

[John G.]

Re: Edelbrock Electric Choke Issue

I am also experiencing the same cold engine off-idle stumble. The carburetor on my engine (327) is similar - a 625 CFM electric choke AFB.

In my case the engine won't even idle (when cold) unless the choke butterfly stays in the closed (or almost so) position. I also noticed the choke butterfly seems to open a bit too fast on this carburetor when the engine is cold. Once the engine warms up the idle becomes fairly stable and the acceleration stumble goes away.

One thing I did do is install the FI spacer in place of the heat riser valve. Also, the intake manifold gasket heat riser passage was semi-blocked off with the metal tabs that come with the intake gasket set. There's a small hole in the metal tab to let in a 'bit' of heat through the passage. The intake manifold is the cast iron 300hp '359'.

I suspect fuel atomization (or lack of) might be part of the problem with what's going on when the engine is cold. Even so, I don't recall having had this problem, this bad, before the engine was rebuilt.

I've also got a bit of sleuthing to do to try and nail this one down. You're not alone!

[Michael W.]

Re: Edelbrock Electric Choke Issue

I am also experiencing the same cold engine off-idle stumble.

One thing I did do is install the FI spacer in place of the heat riser valve.

I've also got a bit of sleuthing to do to try and nail this one down. You're not alone!

I could suggest a good place to start.........

[Timothy B.]

Re: Edelbrock Electric Choke Issue

Roger,

It's like Michael said about the timing, your mechanic is probably used to working on cars of the 70's-up where the ported vacuum advance timing is used for emissions reasons. Do some reading in the archives about manifold vacuum and ported vacuum for a good explaination of how these cars were set up in the 60's.

Engine timing is something that should be correct before carburetor work. Many times the carburetor is blamed but problems could be elsewhere like ignition timing.


If you install a vacuum gauge and observe the needle, it will be steady no matter what vacuum the engine draws. If you have a Chiltons book, in the tune up section there will be pictures of vacuum gauge fluctuations showing different engine conditions, (vacuum leak, late timing, etc.). This will give a indication of how the gauge should look on a warmed up engine.

I think it was Clem that mentioned manifold heat or lack of it on the engine, this could be a big factor in the problem. The heat helps gas (vaporize) the atomized A/F mixture while the engine warms.

My thoughts are the choke is opening to fast, lack of heat under the plenum and possible lack of sufficent accelerator pump shot at the proper time. The size of the venturies on the 750 may require more signal for the main circuit to start flow hence the need for heavier accelerator pump shot to cover this lean condition when you open the primaries.


John,

If you have the cast manifold start by removing the restriction in the gasket for manifold heat and install a heat riser valve.

[Paul Y.]

Re: Edelbrock Electric Choke Issue

Roger,

I am sure your mechanic has the best intentions when working on your car. The vacuum advance should be fine with full manifold vacuum to the can so are you sure he took it from manifold to ported source on the carburetor. Without knowing the engine vacuum at idle there is no way to adjust the vacuum advance control to work properly.

Your car needs a good old mechanic willing to spend time to correct the problem. A vacuum gauge when working on these old cars is as important as a wrench!! I don't think this problem is A/F ratio so be careful when changing parts and write down notes on parts that were there so you can go back if needed.

I suggest adjusting the accelerator pump to the instructions given in the manual and consider larger squirters (nozzles) to give a larger shot of fuel earlier. The lever adjustment controls the volume but the discharge nozzle size will allow the volume to be discharged earlier into the engine. This will help cover a lean condition when going from idle to main circuits which may be the problem with the 750 cfm size carburetor.

Other than that I would not throw $$ but find a good mechanic willing to spend time to correct the condition and tune the engine.

Tim, I think you meant the opposite. The squirter size controls the volume and the rod position controls the time of start of the accelarator pump.

[Paul Y.]

Re: Edelbrock Electric Choke Issue

I am running a 750 Edelbrock at mile high altitude in a first generation El Camino with a ZZ2 motor and was told the same thing about the bog or flat spot. I know that it was over carbed but I wanted to work with what I had. I found that the choke needed to be enriched quite a bit. Enough so that it runs on the fast idle when started cold. I leaned the carburator down with jet changes and rod and spring changes and got the advance map correct and it still had a slight flat spot until I went to the next size up on the squirter. Like others have said, make sure the ignition is correct and then go to the carburator. I also found that to open the idle jet screws a half turn more than needed for optimum idle seemed to help. A flat spot can be terribly frustrating but I just wanted you to know that it could be remedied. Good luck.

[Stuart F.]

Re: Edelbrock Electric Choke Issue

The issues discussed about hesitation and stumble are complex and can differ from one car to another based on, as we see here; the engine, the set up, and the accessories used, etc.. I wouldn't begin to say I have all the answers just because I have solved my problems, but there have been a lot of good suggestions put forth here for Roger that should give him a good start. First of all, he has an odd combination w/o any manifold heat and a generic carb that is possibly ill suited for it. The Edelbrock electric choke, by it's design, is certainly good enough to get it started, but does not provide for good warm up characteristics.

One final point, you have been very worried about the possibilty of vacuum leaks. I can state for one, every vacuum leak I've encountered over the past 50 years has been very obvious - be it a hose or leaking base gasket, etc.. Generally, the engine will not idle down properly - certainly not with the usual amount of throttle opening. It may act, when accelerated (by hand with air filter off), like it has no accelerator pump at all and do a big bog down. Besides this, the gas mileage will be horrible. These are just a few examples. Like Tim said, find agood chart of typical vacuum gauge readings and needle movements for an example of what they mean. From what I've read in your postings, you don't have a vacuum leak so save your "gaskets for the sake of gaskets" money.

Hope you can make it to the winter meet.

Stu Fox