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Edelbrock 600 cfm Carb on a '56 322


1956century

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Hello,

I'm considering a new Edelbrock for my '56 Buick. Currently, the car is hard to start. I will fire up just fine, but it takes a minute or two of my foot tapping the throttle before it idles without immediately dying out. Also, the exhaust emits a very strong fume smell, which doesn't seem normal (running rich?). I have to leave the garage open after a drive, otherwise it stinks up the entire house. It is not leaking fuel anywhere. It has a fresh tune up with plugs, wires, points, condenser, cap and rotor. The compression varies a bit on a few cylinders, so it probably needs a valve job, but it runs fine.

I was looking at a 600 cfm carb with an electric choke. These can be had relatively cheap and I've read they're dead simple. I know I will lose the push gas start, but I will keep all of the old hardware for whenever I want to replace it.

I'm guessing the mechanical fuel pump went because the previous owner mounted a generic electrical fuel pump by the tank with a rubber line going all the way to the carb. It's loud as hell, but it works.

Also, the exhaust heat tube snapped at the manifold, so that is not connected.

I know the stock carb has a linkage set up for the transmission kickdown. Will I lose this with the Edelbrock?

Also, will the Edelbrock improve my fuel economy?

Lastly, is it worth upgrading or should I try to mess with the old carb?

Thanks for your help.

Edited by 1956century (see edit history)
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I cannot answer the question concerning linkage; but unless you are really good at tuning a carburetor, and have a machine shop to fabricate parts needed but unavailable, you will lose both driveability and fuel economy with this unit.

Also, it is doubtful that the clone will fit your intake without an adapter; and your original air cleaner will not fit.

WOT power on a dyno (easiest tuning on a carburetor) will probably be slightly higher; but you will lose everywhere else.

I would suggest worrying about the rubber fuel line first! The electric pump, if properly installed with constant power from an oil pressure switch, is fine, providing the pressure is correct for the application. Also, the pump should be as near the tank as possible. But the rubber line under the car is a fire hazard.

Once you get the rubber replaced with metal, I would suggest getting your choke operationable. Probably not too difficult to repair the original configuration; but it is pretty simple to fabricate a heat stove. Here is a link to an article for those who wish to use the original carb with an aftermarket manifold without heat provision. It will work just as well for you:

http://www.thecarburetorshop.com/Heatstovefabrication.htm

Jon.

Edited by carbking (see edit history)
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Agreed on the consensus here of fixing the stock choke and carb, steel fuel line and the heat stove.

Also,

I am suspecting that the combined choke inoperability and the electric fuel pump may be pouring gas into the motor; hence the strong gas smell.

You may wish to check the size and type of electric pump back there.....

If it's not right for your car, consider putting a stock fuel pump back in; before you fab up that new steel line.

Doesn't take much fuel pressure to please these old Buicks once everything

is set up right...

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When you had the tune-up done, did they do an idle mixture adjustment of the carburetor? Plus getting the base ignition timing set correrctly, to Buick specs? It's good that you have the new parts installed, but unless the carb and ignition timing adjustments were done, you could well end up with what you have.

"Choke stoves" are available at the auto supply, usually, in a "universal" configurtion that you can use to repair yours. Follow Jon's link.

The electric pump probably was installed as a local parts source probably didn't have a listing for a normal fuel pump any more . . . or he might have had some of the vapor lock issues which Old-Tank and 5563 have mentioned. Still, better to get a new factory-style pump and get it working than an electric pump which might be putting more fuel to the carb than the carb "likes".

MUCH better to fix what you've got rather than embark upon an easy-sounding project that'll unleash so many (EXPENSIVE) worms that you'll not believe it! Your existing carb should have worked well at one time, so it can again.

ALL of the Edelbrock AFBs are, as Jon has mentioned many times, calibrated for the most popular application-vehicles . . . the Chevy 350 V-8. To use one on a Buick AND get it to be as good as it should be, you'll need to recalibrate it on a chassis dyno (more $$$$) or via many hours of "driving time", as the Owner's Manual for the Edelbrock AFBs tells you how to do. But, when the AFB is "right", it works pretty darn well . . . but then your existing carb CAN do that too.

Regards,

NTX5467

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Seems like the Edelbrock is a no go.

I would much rather have a functioning mechanical pump than this crappy electric one. Also, it is currently powered by the ignition/ACC line at the fuse box (straight connection, no relay), so if the ignition is in the ON position, it's continuously pumping. The original fuel pump is still attached with the fuel part blocked off. The vacuum part still functions, but I'm not sure how well. The wipers work, but they only move about half way up. Not sure what's at fault here.

I found a spare fuel pump in the trunk. I believe it came out of a junkyard car. Any way to tell if it still works without installing it?

The original fuel line is still in the car. Would it be wise to try to blow it out with compressed air and use it, or should I replace it?

NTX5467, when I did the tune-up, I checked the timing and it was spot on. I did not adjust the carburetor.

If it is running rich (which I'm not sure it is yet) because of the inoperable choke at start up, would it still be rich once it has warmed up? I'm trying to decipher what may be causing the smell.

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The carburetor is designed to function with the choke butterfly in the wide-open (vertical) position) once the engine is warm (5~15 minutes depending on ambient and engine speed during the warm-up). If the butterfly is not in the vertical position once warm, the carburetor will most assuredly deliver a very rich mixture.

Jon.

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If it is running rich (which I'm not sure it is yet) because of the inoperable choke at start up, would it still be rich once it has warmed up? I'm trying to decipher what may be causing the smell.

Maybe I missed it but, is the gas smell when the engine is warm and operating? Or when it is warmed up and then turned off?

If the latter (off), then it might be the gas in the carb cooking from manifold heat and vaporizing through the vent to the airhorn of the carb. I'm no expert in this but it seems the gas today, especially with the ethanol, kicks up a lot of fumes after the engines are turned off. The vent is there to allow the fumes to escape to the atmosphere.

If it's smelling like gas while it's running I would check for a sticky float. I recently had this problem on my 56, and have not had to take my carb apart yet, but I may do so in the spring.

In the meanwhile, I have found by lightly rapping on the front and rear of the carb with the plastic end of a screwdriver, before running the car, and adding some Marvel Mystery oil in the gas( for whatever lubricating properties it could introduce, the float is no longer sticking.

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  • 2 weeks later...

On the orig carb . . .

To get the choke blade to be vertical, loosen the three hold-down screws on the choke thermostat . . . but not remove them, although that might be needed. BUT make sure the choke blade will move first. If spring pressure returns it to the illustrated position, then an adjustment can be done.

On the top of the black phenolic thermostat housing, there is a "mark". You can see how it relates to the other index marks on the carb body. Once the three hold-down screws are loose, then you should be able to rotate the phenolic choke thermostat spring's housing on the carb body to allow the choke blade to be vertical rather than tilted. Once you get the phenolic housing rotated a few index notches and the choke blade is vertical, then you can re-snug the choke thermostat's three hold-down screws. That should take care of that part of the situation.

The other part is to get the idle mixture and speed adjustments done with the engine completely warmed up . . . like after driving it about 10 miles on the highway, or so, so that everything is up to operating temperature . . . letting it idle will not completely do it and might take 30 minutes or so.

Before starting these adjustments, make sure the ignition dwell is "to spec", then the ignition base timing . . . in that order. Then the base idle speed. After doing that, then you can tweak the idle mixture screws to get the highest idle rpm without having touched the idle speed screw on the carb. Once you have the highest idle speed at the existing idle speed screw setting, adjust the base idle speed screw to get the spec'd idle speed. Then tweak the idle mixture setting again, to make sure it's "right". From that point, you might further lean the mixture about 1/8th turn for good measure, adjusting the idle speed upward just a "schoosch" if needed.

As a final check, with your foot firmly on the brake, put the trans in "D" and see how it goes into gear and how the engine idles in that situation. It should be very smooth rather than be shaky from being too slow. Also, with your foot still on the brake, pat the throttle and see how it responds . . . it should respond quickly with no hesitation. Move the gear selector from "D" to "R" and see how that acts. In many automatics, going into "R" will be a little harsher than into "D", which is normal, even at the same idle speed . . . just firmer and maybe a little quicker. If you need to adjust the idle speed upward, do it in about 1/8th turn increments . . . not big changes each time as you're trying to hit that "sweet spot" of sorts.

End result should be that it starts quickly and easily when hot. Turns off without trying to keep running. Basically "no smell" from the exhaust pipes, too.

Several years ago, I basically deactivated the electric choke on my 4175 Holley on my '77 Camaro. Even with the electric choke, it would not come off with a warm engine, so I adjusted the choke thermostat to be vertical all of the time. I was surprised how well it worked in cold weather . . . but the aluminum heads I have on that 355 might be a factor.

In a "no choke" condition when the engine might otherwise need some "choke", having an ignition system that is at least as good as "stock" would be good . . . even a Pertronix conversion to electronic ignition would be good, but a points system in good condition can work too.

One trick I've found to help the spark plugs fire easier AND provide better performance is to basically "J-gap" (a Champion Spark Plug nomenclature from the early 1960s) a normal spark plug. End result is that the ground electrode extends only 1/2 the way over the center electrode, allowing more of the spark kernel to be exposed to the fuel/air mixture in the combustion chamber . . . very similar to what the NGK V-Power plugs do.

In the early days, after I found out about the J-Gap situation, I'd spend a Sunday afternoon with a point file and a gap gauge. Nothing else better to do in those high-school years on Sunday afternoons. I'd get the gaps "just right" and that would show on the Sunn scope at the dealership. The J-gap procedure seemed to make for sharper throttle response, too. Decades later, I found the NGK V-Power and used them instead. BUT you can replicate that whole situation on normal plugs by simply rotating the ground electrode with a pair of pliers to cover ONLY 1/2 of the center electrode rather than having the ground electrode be centered directly over the center electrode . . . as it seemed to be intended to do for ages. After the "rotation procedure", recheck the gap. If the gap isn't already at .030" rather than .035", using the slightly closer gap with a stock points ignition system might help a little.

Anyway . . . with "no automatic choke", you'll have to keep the engine idled-up for a few minutes until it's warmed enough to run reliably at the slower idle speed the inactive fast idle mechanism would compensate for. NOT higher rpms, just about 1000rpm or so. With the learner mixture, you might also need to adjust the accel pump to the richer position.

One other thing which might help is to used multi-weight oil that will flow easier at cooler temperatures. A 5W or 10W-30 viscosity rating, for example, rather than a straight-weight oil. The lower viscosity at start-up will put less load on the oil pump and also get oil moving in the motor sooner, which should work better in the "no choke" orientation.

Until it gets warm enough for the heater to work, NO heavy acceleration as this might cause "spit-backs" or "flame-outs" . . . not good . . . due to the generally leaner no-choke mixture. Normal accel should be ok, though.

I'm not going to say it'll be "perfect", but it is "doable" and you'll have to learn how to keep it running, in gear, until it gets warmed up . . . might even need to learn to use both feet, one on for the brake, one for the accel pedal, in this situation.

Key thing is to first get the choke thermostat adjusted and then make sure everything else is working as well as it can.

Happy Holidays!

NTX5467

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Thanks for all the help guys. I tried to adjust the choke (removed black housing) but the blade will not move from it's position. What's keeping it there?

photodec24114049pm.jpg

Also, where is the base idle speed screw? I can see the two mixture screws, but not this third screw. My manual also mentions it.

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Guest Jim_Edwards
Thanks for all the help guys. I tried to adjust the choke (removed black housing) but the blade will not move from it's position. What's keeping it there?

photodec24114049pm.jpg

Also, where is the base idle speed screw? I can see the two mixture screws, but not this third screw. My manual also mentions it.

To answer the question "what's keeping it there?" It's crud! Actually varnish restricting the shaft and/or linkage movement. I'd give that puppy a severe hosing down with a can of Carburetor cleaning focusing on where the butterfly shaft goes through the air horn and all linkages involved. Working it as you spray. Basically the problem may not go away until the carburetor is removed given a proper bath in a bucket of Berryman's and rebuilt with a fresh kit.

Jim

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When you are hosing things with carb cleaner, spray some in the piston inside the choke housing. That would be my guess as far as where the actual stickage is.

The base idle screw is on the drivers side of the carb. It's the one with a spring on it.

Then follow NTX's post and if that doesn't work, then Jim E's rebuild suggestion.

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  • 1 month later...

Hi all,

I found a manual choke at my local parts store for $10. I'd be happy to use it, but as previously stated, my choke is stuck. It nudges back and forth, but no amount of carb cleaner is going to get it free. I believe this thing needs a rebuild.

Seeing as how I've never rebuilt one before, I'm assuming it's going to take me a while, and I'd rather tackle it myself than send it out. However, if I do need to send it out, I know who to send it to (thanks carbking ;)).

In the meantime, my friend offered me his working Edelbrock or Quadrajet to use. I'd like to bolt one of them up temporarily to keep my car on the road.

Does anyone know what adapter I need? I've read that the '56 manifold is square bore, and I've read that the Edelbrock is square bore, however, I know that they do not bolt up.

Thanks

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A significant issue will be the bolt pattern on the manifold vs. what the carb has on it. Both lateral width and longitudinal length between the mounting studs/bolt holes. If the Edlebrock has two sets of mounting holes, front and back, on the baseplate, then it might come closer to at least bolting up. It would be best if you could use the carb without an adapter, but sometimes that's not possible.

If the "Quadrajet" is the spreadbore, probably not a good adapter so it'd work very well, plus the mounting bolt pattern, too. But the main issue would be running on the primaries so an adapter might work reasonably well if you can find one . . . but if you need the secondaries, unless they are well-modulated for the engine size, they could allow too much airflow for the engine size (think "bog").

As 5563 mentioned, what assists the automatic choke coil is the piston in the carb's main body which opens when manifold vacuum is present. Kind of like an internal "vacuum break" or "choke pull-off". I suspect it can have accumulated carbon build-up somewhere "in there" which would keep the piston from easily being free-up. There might be some carb cleaner/spray which might help to get it freed-up enough to at least start to get it moving, once the accumulated varnish and other deposits are cleaned up. Ultimately, it could well need a complete soak/cleaning and rebuild. The rebuild kits should come with instructions. To me, they're not that complicated and should be rebuildable with common tools (pliers, screwdrivers, needle-nose pliers, etc.).

As keeping the vehicle on the road is important, I'd first try the Edlebrock (electric choke or manual choke) to see what it would take to get it on the engine and operational. Let us know how it all turns out, please.

NTX5467

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Century - 2 things:

(1) Please do not send your unit to carbking for restoration. His backlog is currently more than 18 months, and he is not currently accepting additional units for restoration. You may, however, call about parts ;).

(2) As mentioned by others, the probable reason that your choke butterfly will not move is that the choke piston is stuck. The piston is attached to a link on the shaft where it comes into the choke housing. Please observe the bottom of the choke housing at the lower extremity of the well housing the piston. Do you see the welch plug covering the well? Take a small drift punch and with a hammer, drive a small hole in the center of the welch plug from underneath. Now place a clean rag beneath the cylinder. Now insert the punch in the hole, and pry out the welch plug. Now add some penatrating oil in the top of the cylinder (on top of the piston) some will probably bypass the piston and leak through. Find a wooden dowel rod just smaller that the cylinder, and will a small hammer, TAP the rod against the piston. You can drive the piston up, and then force it down until it moves freely. SAVE THE WELCH PLUG. Take the plug to your local parts house and acquire a new plug and install it. With the choke moving, you can attach the manual choke kit and get the car running. When you are ready, acquire a rebuilding kit for the carburetor, and rebuild it. You will have to install the welch plug prior to starting the car even with the manual choke, or you will have a vacuum leak.

Jon.

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Guest Jim_Edwards
Hi all,

I found a manual choke at my local parts store for $10. I'd be happy to use it, but as previously stated, my choke is stuck. It nudges back and forth, but no amount of carb cleaner is going to get it free. I believe this thing needs a rebuild.

Seeing as how I've never rebuilt one before, I'm assuming it's going to take me a while, and I'd rather tackle it myself than send it out. However, if I do need to send it out, I know who to send it to (thanks carbking ;)).

In the meantime, my friend offered me his working Edelbrock or Quadrajet to use. I'd like to bolt one of them up temporarily to keep my car on the road.

Does anyone know what adapter I need? I've read that the '56 manifold is square bore, and I've read that the Edelbrock is square bore, however, I know that they do not bolt up.

Thanks

Edlebrock and Holley both make replacement carbs that are square bore and spread bore. Virtually all new replacement carbs will need to be re-jetted with smaller jets to use on your engine. Though you can get an adapter to use a spread bore on a square bore manifold you may create hood clearance issues you don't want.

I'd take NTX5467's suggestion and try to free up that choke piston. I've done it many times with nothing but a few shots of spray carb cleaner and letting it sit for a while.

Jim

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carbking . . . thanks for that detailed "free-up" procedure of the internal choke pull-off assist piston.

NTX5467

My pleasure.

The welsh plug is a lot cheaper than the metal linkage piece attaching to the piston; which is the piece normally broken when someone attempts to "pry" out one of the pistons.

Jon.

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  • 3 months later...

Update:

I was able to free the choke up by soaking it in penetrating oil and prying on the linkage with a flat head screwdriver. I attached an electric choke from an Edelbrock only to find that it moves in the opposite direction and is therefore useless. I bought a manual choke at a local parts store (it's been sitting on the shelf for years) for $13 and hooked it up. I now have a fully functioning choke.

I have yet to test my extra mechanical fuel pump. In the mean time, I replaced the electric fuel pump with a new one. The one I bought is a flow through pump so I can use it inline. I mounted it in between the two rear springs on the cross member. I blew out the original hard line and connected it all up. The line is solid and clean (very happy about this).

I then proceeded to tune the carb. I found that when I unscrew the throttle stop screw all the way, it doesn't make a huge difference in the idle. The throttle linkage will not move back any further. My idle is currently just a few notches past the minimum possible idle, so it doesn't go all that low. kaycee mentioned the dash pot might be holding it back, so I threaded it in further and that's definitely not it.

Also, the exhaust still gives off a very strong smell. I'm using 87 octane, unleaded.

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It works good, although I have nothing to really compare to. I found a good deal on an Edelbrock and an adapter, so I have those in case I need them.

The car starts up on the first time, every time, which is nice. The manual choke interferes with the air cleaner, so I'll have to figure something out there.

Still have a strong exhaust smell, but I don't know if the carburetor is to blame for that.

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Well, good luck. Keep us posted. You're getting a lot of good advice, (better than I can offer), I can add, however; Mine runs very well with the original type carburetor and choke. But, not before; it is well warmed up. I would; exhaust every effort, on the original type carburetor, and choke. A different type Carburetor (IMHO) would, introduce; more gremlins to chase away.:)

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I had a 1956 Olds 88 with a 4GC carb. I went to a junk yard and picked up a 1974-ish electric choke element. It looks just like yours and has a wire connector.

I bought a GB terminal and ran the wire to the hot side of the coil. When the key was on the heater in the choke element is energized. It worked great.

There are two versions of heater, a 4 minute and a 6 minute. they are not marked and it really doesn't make a difference.

Bernie

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