Fuel System: Another Edelbrock Question

[Michael J Hawk]

Been researching and can't find an answer so maybe one of you guys can help. Recently installed an Edelbrock 1403 on a 289. Fires up, idles great and has good power until I try to use the secondary system. There doesn't seem to be enough air flow to force the air valves open against the counter weights. The result is the engine just bogs down. Distributor is advancing normally and car has duel exhaust. It's not a Studebaker problem but I know this carb has been used by a lot of you.

[Bullet]

Dumb question on my part, since I have done this. Did you make sure your manifold has 4 holes of equal size? I know when I test fitted mine before I bored out the secondary holes on the manifold the secondaries only partially opened.

Mark

[karterfred88]

Been researching and can't find an answer so maybe one of you guys can help. Recently installed an Edelbrock 1403 on a 289. Fires up, idles great and has good power until I try to use the secondary system. There doesn't seem to be enough air flow to force the air valves open against the counter weights. The result is the engine just bogs down. Distributor is advancing normally and car has duel exhaust. It's not a Studebaker problem but I know this carb has been used by a lot of you.

It has to be a late model intake or modified --the bores are bigger than a WCFB. If not they won't open. If its the right manifold then double check your base gasket isn't on backwards--rears larger than fronts, both will keep the secondaries from opening enough to trigger the air valve

[Mike Van Veghten]

This COULD (probably) be an opening too fast / soon also..!
A "bog" is normally the lack of fuel. If there is no airflow, there will be no "excess" fuel.

In either case, as the others have noted, make sure all four butterflys open properly and do not hit anything.

Next thing to try is to increase the rear jetting by 4 sizes. See what happens.
Do you have the Edelbrock tuning book ? Lotsa helpfull hints in there also.

Mike

[Chucks Stude]

Instead of drilling, I installed a heat absorbing carb gasket from Jegs. It is made of layers of gasket material, and aluminum, and lifts the carb up enough to clear. Also, found out that you need to bend or cut off the heat riser tubes that were part of the old carb system, they interfere with the secondary mechanism on the Edelbrock.

[Michael J Hawk]

The secondary throttle bores are opening ok with no restriction. The guy I got the manifold from had opened the bores already. I have a .500 composite spacer also. It sounds like it's starving for fuel so I'll try rejetting. I was hoping for a plug and play with this thing. I'll take some time to study that tuning book. Thanks for the advice.

[Dick Steinkamp]

A 1403 out of the box should run a 289 or 259 just fine. There MAY be some fine tuning involved, but not a noticeable problem like you are experiencing. Was the carb new or did you get it used? If used, it may have been rejetted by the prior owner. Before you start changing jets, see if yours are the default ones that came with the carb (main jets, secondary jets, metering rods and step up springs). Check page 19 of this...

http://www.edelbrock.com/automotive/...404_manual.pdf

If they are the default jets/metering rods/step up springs, rejetting is not the solution.

If the carb is a used one, the secondary air valves may have been installed upside down. Make sure the are fully closed with the car not running and that you can easily open them with your finger.

[karterfred88]

Is this a stock 289? Year and original configuration? Might help to know what we are starting with. Is the 1403 new or used? It seems a stock new 1403 on a stock 289 would be plenty rich on the secondary side stock. Check for any vacuum leaks first, especially the intake as it is a replacement, and any vacuum hoses like the brake booster and any pcv valve. Also be sure the vacuum advance is hooked up to the right nipple on the carb and everything else that's not being used has the requisite plug in it, before tearing into jet replacements. The carb if stock and new should work well enough to only need minor changes by examining plugs after test runs. I think you maybe jumping the gun to tear into it right away if it is brand new.
You may need some of these not included with the carb new:

http://www.oreillyauto.com/site/c/detail/DAG0/47396/N1167.oap?ck=Search_N1167_-1_-1&pt=N1167&ppt=N1171

Available at most FLAPS since its a Dorman HELP item

[Michael J Hawk]

Thanks for this great info. The carb wasn't new when I bought it but looked new. I'm going to disassemble it and try to find the problem. I'm pulling 20# vacuum at idle and am sure about the hookups but the air valves are not shut all the way with the engine off. When I was a young man in the seventies I used to love to mess with carbs. This is the first for awhile.

[karterfred88]

Best of luck-when you find it, I'm sure you will happy with the performance. If nothing else, based on my experiences only: Take the carb off the car, remove the metering rod retaining covers and remove the rods, FIRST. Then teardown as far as you wish. After total reassembly, put the rods and springs back in, test they go up and down smoothly, put the retainers and screws back in--then put it back in the car. These d**## rods bend easily, stick easily going into the jets and will cause you no end of grief if they don't suck down when you start the engine. And you don't ever want to lose those tiny retaining plate screws into the carb--on the car!!

[Michael J Hawk]

I think I found the problem thanks to the picture you posted earlier pointing out the correct vacuum port for the distributor. It didn't make sense to me to hook it up to manifold vacuum but it runs better now. I've gotten confused in the past about that. It doesn't hesitate now when I punch it but I notice a lot of backfire through the exhaust on de-acceleration that I didn't have before. If I retard the timing a bit it diminishes but affect my power. I'm playing around with it so I can find the sweet compromise. I want to drive it to the meet in STL next month.

[karterfred88]

Put the timing back in, and add 2 more degrees, your not burning all the fuel now and then try next weaker rod springs so it leans out on deceleration and cruise quicker when you let off and vacuum pulls the rods down. Then you'll need to work on the secondary jets, probably need to lean them a little at a time. If it accelerates smoothly and runs nice at constant throttle just drive it that way for awhile till the plugs get some miles on them so you can get a real reading on them. Unless you have an exhaust analyzer and a dyno, trial and error is the only way to do it from here on. Glad you caught the port thing--lots of others miss it, so don't feel bad. It's on the opposite side from an AFB so gets mixed up all the time when substituting an Edelbrock for an AFB.

[Dick Steinkamp]

I think I found the problem thanks to the picture you posted earlier pointing out the correct vacuum port for the distributor. It didn't make sense to me to hook it up to manifold vacuum but it runs better now. I've gotten confused in the past about that. It doesn't hesitate now when I punch it but I notice a lot of backfire through the exhaust on de-acceleration that I didn't have before. If I retard the timing a bit it diminishes but affect my power. I'm playing around with it so I can find the sweet compromise. I want to drive it to the meet in STL next month.

This is a little confusing.

The original reported problem was that the secondary air valves were not opening. Where you pick up vacuum for the distributor would have nothing to do with this problem. The ONLY difference between manifold and ported vacuum is that the dizzy will see vacuum at idle with manifold vacuum and the throttle plates will have to be slightly open for it to see vacuum with ported vacuum. Once the throttle plates start to open, ported and manifold vacuum are identical. Of course vacuum goes away when you throttle up quickly and get into the 4 barrel no matter which you were hooked to.

If this statement is correct..

"Fires up, idles great and has good power until I try to use the secondary system. There doesn't seem to be enough air flow to force the air valves open against the counter weights."

...then it is not a manifold vs ported vacuum problem. When you floor it to get into the secondaries, there is no engine vacuum to effect dizzy advance.

Again, I would not mess with jets, rods or step up springs until you "baseline" the carb with the default parts. The engine should run fine with the carb at baseline. It is super easy to go down a rabbit hole with the almost infinite number of combinations of jets, rods and springs available.

BTW, I have tried both ported and manifold vacuum on various cars. The idle speed will increase with manifold vacuum and have to be set down to spec. Once off idle, no difference in drive-ability between the two...logically since with the throttle plates cracked ported and manifold vaccum are identical.

On deceleration, the engine vacuum is at its greatest and will pull down ANY step up springs available. Changing springs will not cause a leaner condition under deceleration. The rods are all the way down at this point no matter what springs are in there.

Same with secondary jets. The secondary jets are not operating under deceleration. Changing these jets will not eliminate backfire under deceleration.

It's tough to diagnose a drive-ability problem without being there. If the air valves are truly not opening, there is most likely a mechanical problem in the carb preventing this. The drive-ability problems you report in your later post could be a dirty carb, wrong ignition timing, bad mechanical advance, valve adjustment too tight, burned or sticking valves, mixture too rich (wrong main jet/metering rod combination), vacuum leak. More information would be needed.

[karterfred88]

Dick,
"Assuming the first diagnosis was correct." "There doesn't seem to be enough air flow to force the air valves open against the counter weights." I always assume the problem description is more important than the questioner's diagnosis. So I started with basics. It now runs okay so there might be problems other than the carb to cause "backfires" in the exhaust. My first impulse is to set the timing further ahead to try and extend the burn period till getting pinging and back off. The rest of the diagnosis may be carb or timing or ??. I suggested softer springs which is what Edelbrock seems to imply with their re-jetting calibration dialogue. May work only in theory. The rods may be hanging up on the edge of the jets and not pulling down all the way, but enough to get a good idle. It's surprising how rich the idle can be and still be smooth, I'm on my lean plus 2 and still too rich, but idles great, accelerates well, no lean surge, but I don't have combos to go even leaner yet. Plugs still in the dark brown stage ( with 170 lbs. compression on a R2 and one step hotter plugs, advanced plus 2 and no pinging on 93 octane crapahol 10%). I still agree with you on vacuum leaks though, as that was my first thought since the manifold was changed. As you know this is a convoluted path to a final resolution, all we can do from here is hope to suggest something that works.

[Michael J Hawk]

My mention of the throttle valves not opening was from observing them why working the throttle in the driveway. I figured it had something to do with the problem. Changing the port used help with drivability issue as I can now use the secondary without bogging down. The air valves still struggle to open however. It's almost like the counterweights are too heavy. Appreciated the dialogue. I'm learning a lot. I remember putting this carb (or something similar) on a 289 in my '57 Transtar I had in the seventies and never had any problems with it.