The Stovebolt Site Forums The Shop Area Engine Shop Edlebrock 4bbl Carb Adjustment

Stock 350, no hot cam, lifters stock, no special rods or pistons. Only mod besides the carb is exhaust headers. Back in the day I considered myself a fair tuner and could adjust about any carb. So the engine is running rich. I screwed the air mixture screws in and was able to close them all the way without the engine stumbling at all. Is that normal for today's carbs or do I have another issue? Burb starts and runs good just seemed to be on the rich side.

You have either a high float level or a too-high idle speed. If the engine is running fast enough to draw fuel through the venturis, the idle mixture screws will have little effect on the idle. If the fuel level is high enough to allow gas to drip from the venturis, it will be necessary to raise the idle speed to keep the engine from stalling. You should not be able to see any fuel flow from the venturi stack at idle speed.
Jerry

Starts and runs good is the same as if it ain't broke don't fix it. Those are good carbs. If the level and drop are correct they will run nice. They don't like more than 5-6 psi.

I have the 1405 600cfm Edelbrock carb on my Pontiac engine in my truck. It was running way rich esp at low speeds. I had 10.5 lbs fuel pressure. I put in a regulator and now have about 5-6 lbs pressure. I also hooked up a pcv valve and now the truck runs much better and idle is consistant. Before the idle would hunt between 500 to 800 rpm. Mileage around town went from 11 to 14.5...

You were definately over powering the needle and seat. 7 psi is the max.

650 RPM idle and a stock mechanical fuel pump. Has a crankcase breather. As many who read the forum regularly know I'm not a big fan of Edlebrock carbs but I'm trying to give it the benefit of help from the collective minds of the Stovebolt. If I can get it right I'll keep it. If I can't get it right I'll switch it out for a Holly later.

As you know it's an AFB, two piece "Carter". At least that's what I have had with Edlebrock logo's. Simple, reliable, carbs. For some reason, I was thinking Rochester Quadrajet at first.

My pump is a stock looking mechanical pump also, but it was putting out way too much pressure. I got a pressure gauge and plumbed it into the system, and discovered the high pressure. And I believe these carbs are designed to draw air thru the pcv system and that is part of the reason mine was running rich, I had the pcv inlet plugged.

Groan!

Jon.

Jon, what part of that makes you groan? It would be nice to have a comment other than that unknown reply. If I have said something wrong, I would like to know.

Cap'n, I run the hose to the carb on the drivers side and have a breather on the cover of my passenger side. On the front carb I have a bolt in some fuel line as a plug.

Horsin, what size carb are you running?

Carbking, do you tune your carbs with a wideband 02 setup? Mine are dyno tuned, I'm not worried about mpg as I get gpm with my driving style. Just curious is all. I'm not trying to ruffle feathers.

Bart - the groan was from the comparison of an e-clone to a Carter AFB. But I guess they can be compared; they both have 4 barrels. Likewise a Yugo can be compared to a Rolls-Royce; they both have 4 wheels.

Hollow65 - no, however have used other types of exhaust gas analysers. These days, too busy with the manufacture of carb kits to tune on carbs.

Jon.

I've never heard anything good about the eddies.

Nice idle, how much vacuum do you have at idle?
If the idle richness screws are sun in and seated it is getting fuel from elsewhere. If too great a pressure it is hard to see, unlike a holley. Look into the secondaries, the wells adjacent to the venturii where the counterweights if the airdoor rotate in, if the pressure is too great excess fuel will accumulate in those wells and you'll have either raw fuel or a collection of dried fuel in them.
Fuel boils easily in the edelbrock, get a 1/2" phonelic spacer under it - it might be boiling inside pushing fuel out as well. I use the RPC R9139 spacer, dirt cheap.

600 cfm electric choke model. Don't know how much vacuum, I don't have a gauge. It has the 1/2 inch spacer under it. Some good things to check, please keep um coming.

Wood or a resin spacer is a popular choice also, 4 hole or just a big one is optional.

Understood Jon, thanks. I am only saying that the info I have read says that Edelbrock acquired the rights to Carter AFB. Early on, some were manufactured by Weber for them. They have since redesigned some areas of the carb. The Performer Series is patterned after a Carter AFB.
I have had Edelbrock carbs and they run good for me. Carb brand loyalty is like Chevy-Ford. There are good ones and bad ones. Bad experiences and good experiences. People seem to hate a whole brand because of one bad experience or their uncle said...
There are as many Holley haters as Rochester and so on. Many engines are running on Edelbrock. Being a carb builder, I know you are able to quantify various brands and their failures. Carter has had some bad carbs (thermoquad). I like Rochester and Carter carbs. Carters seem to be easier to rebuild and run nice. I do respect your opinion and advice.
As far as both being 4 bbl, here is a quote from a carb building company. "As most good mechanics know the AFB Carter carburetor is the same basic carburetor as the Edelbrock carburetor and the Edelbrock is copied from the AFB Carter..We use the same exact parts inside both the AFB Carters and Edelbrocks."
Summit Carb kit Part no. AED-4190 "Carburetor Rebuild Kit, Carter, Edelbrock, AFB, Performer, Kit"

Bart - if you would like more history, give me a call some time. I have the beginnings of carpal tunnel, and don't like to type too much at once.

A couple of comments on your last post:

On the Carter AFB parts vs e-clone parts: Carter produced 505 different AFB's. Within this group, there are THREE DIFFERENT STYLES of main jets and NINETEEN DIFFERENT styles of metering rods. There are also 10 different airhorn gaskets.

So you have the following odds on the e-clone parts working in a genuine AFB:

Airhorn gasket - 1 in 10
Main metering jet - 1 in 3
Step-up (or metering) rods - 1 in 19

Other major differences include: accelerator pumps, primary and secondary throttle shafts, and MAIN BODIES!

EDIT: Just to prove a point, I just checked. We make 111 DIFFERENT kits to service the various genuine Carter AFB carbs!

There are more Dr. Goodpliers than there are Mr. Goodwrenches!

As far as the comment on the Carter TQ: I have more than 150,000 carbs in my inventory, and the Carburetor of my choice on my own very high performance GTO is a thermoquad.

Carter has had some bad carbs (AS, RBS) but the TQ is not one of them. The TQ does have a poor reputation due to the ignorance of some who attempted to work on them without looking at instructions.

Jon.

I do my homework before I post. I know all these comments from other builders are one man's opinion. Just letting you know there are opposite opinions. Many carb kits are sold with enough parts to cover variances in models. The Summit kit covers 10 Carters and 9 Edelbrocks.
Even with you trying to overwhelm me with numbers like 150,000 carbs, The fact is the Edelbrock is a Carter AFB, that's all I am saying originally.(when I got the groan)
Mr. Goodwrench is just Mr. Goodpliers who thinks you need to "tune" a carb to be cool. Just clean it, put in the kit and start the motor. Most of us are not drag racers or performance crazy, but we can rebuild a carb., we can read and follow instructions. Don't look down on us regular guys. I haven't worried about gas mileage in 30 years.
Common Problems with TQ:
Cracked/Warped Main Bodies - The plastic construction of the Thermoquad main-body means older Thermoquads are prone to cracking or warping of the main-body, resulting in major fuel leaks. The best solution to this problem is to simply replace the main-body, although repair may be possible in some cases. This problem, and the associated cost of rectification, is no doubt one explanation for the proliferation of Holley carburettors now fitted to vehicles which were originally fitted with Thermoquads. Purchasing and rebuilding a good second-hand Thermoquad will cost roughly the same as fitting a new or rebuilt Holley carburettor.

Flooding/Sunken-floats - Most floats fitted to Thermoquads are made of a lightweight porous resin. With time (many years) the floats can become saturated with fuel and sink, causing the needle and seat to remain open, resulting in severe flooding of the carburettor. The only solution is to replace the floats, which are readily available and cost something around $50.

Stuck Choke - The Thermoquad choke is activated by a bi-metallic spring enclosed in the black bakelite housing on the side of the carburettor. When the engine is cold, the spring contracts, closing the choke. When the engine is running, the spring is heated by a 7 volt electric current, usually taken directly from a terminal on the vehicle's alternator. As the spring is heated, it releases and allows the choke to open. Incorporated into the top of the spring housing is a thermatic switch which controls the flow of current to the spring. This switch is comprised of a bi-metallic disc which is heated by a flow of air from the exhaust manifold, which is drawn via a pipe between the spring housing and exhaust manifold, past the switch, and into the carburettor. Once the switch is heated, it closes and initiates the flow of current to the spring.

This thermatic switch often becomes inoperative with age, resulting in the choke remaining permanently closed. This results in extremly rich mixtures, fast idle speed, and excessive fuel consumption.

One solution to this problem is to bypass the switch as follows. The electrical connection to the spring housing is an extension of a metal cover plate riveted to the top of the spring housing. Drill out these rivets and remove the cover. The bi-metallic disc and it's own small retracting spring is located in a recess under the cover. Remove the disc and it's spring. In the bottom of the recess is a small terminal which supplies current via the switch to the main choke spring. Drill out the bottom of the recess, including this small terminal, to reveal the heavy metal base which the spring is mounted on. Solder a copper strap of at least 1amp rating between this base and the cover plate. Replace the cover plate and screw in place. The air-pipe to the exhaust manifold can now also be removed as it is not needed any longer. Block the fitting to the spring housing with a suitable nut or bolt to prevent the ingress of dirt. This procedure is simpler with the spring housing removed from the carburettor.

Be sure replace the housing in it's original orientation as rotation in either direction affects the choke adjustment. With the thermatic switch bypassed, the choke will begin to disengage as soon as the engine has started, becoming fully disengaged maybe five minutes after the engine is running. This won't be problematic in most cases. See the choke adjustment section below should poor cold-running become apparent after this modification and compensatory adjustment required.

OK - here goes my carpal tunnel

And Bart - absolutely no offense meant, but you have read some misleading information somewhere.

TQ cracked bodies - the thermoplastic bodies ARE prone to cracking WHEN Dr. Goodpliers neglects to remove the two body screws hidden beneath the choke butterfly and then uses a screwdriver as a prybar to separate the body castings! I have worked on thousands and have yet to see one that warped or cracked without help.

TQ sunken float - the earlier TQ's used brass floats, not the poly-nitrophyll foam. Later TQ's did use the foam float, like everyone else, and yes there is a problem with the foam floats. I use the brass ones.

Stuck choke - the electric choke you mention was, to the best of my knowledge, used only on the 4 aftermarket TQ's (9800, 9801, 9810, 9811). Same electric element used by everyone else; and occasionally, one did fail. If one was used on an original equipment TQ, I am unaware of it. Most of the chokes were divorced units, with a rod up to the choke shaft. Some were equiped with manual choke, which is my preference.

And I was not attempting to overwhelm you with numbers; simply letting you know that with all those to choose from, the TQ is my carburetor of choice.

There is another issue of leaking IF the rebuilder uses the cheap FLAPS repair kits that contain O-rings rather than the more expensive X-Rings.

The major reason why the TQ's were replaced by Holleys is that for the most part, the original equipment TQ's were on Chrysler engines, which were strong polluters. After 1974, the standard TQ's were calibrated at an A/F ratio of 16.8:1; while the lean-burn TQ's were calibrated at an A/F ratio of 18.2:1. These A/F ratios were required so the Chrysler engines would pass California/Federal smog emissions requirements. After replacement with the Holleys, the vehicles would no longer pass smog emission tests. Lots of performance TQ's were produced for export, especially for Ford.

Jon.

Now I have carpel tunnel from this post. Thanks Jon. For the info I mean.

Back to the original problem. Purchased a fuel pressure regulator today. Will install tomorrow and set to 5-6psi. Hope that is the problem. If so, cheap fix.

Sorry I opened the barn door about one brand vs another. Just voicing my opinion, wasn't looking to start a long debate.

Keep the good advice coming!

And my apologies for the post that got us off-target. Hope you have fixed your problem.

Jon.

I don't know why a stock mechanical pump for a 350 carb motor would need a regulator?

The replacement stock fuel pumps I've dealt with are all over the board with the pressure they put out.

You guys are correct. Some pumps seem to be 9psi, some say 7.5-9. The Edelbrock 1403 is 6 max and if you have a reg, set to 5.5.
In trying to figure out why I never need a reg..... I think I always get a pump for a sixties or seventies SBC because they have only one in and one out, in doing so, they are 4.5psi.(M16080) That's what Qjet wants and probably your Edelbrock. Some SBC have a bolt inline with pump rod so as to hold it while installing pump. You probably know this already.

If you have access to a fuel pressure gauge, install it with the regulator to check the regulator. You can remove the gauge when you get the pressure where you want. Just because you adjust the regulator to 6 psi doesn't make it so!

Have had best results with the $34.95 FLAPS dial-type regulator in throwing them at rabbbits, rather than installing them on engines. They also make decent paperweights, but too light for doorstops.

The more expensive Holley regulators available at speed shops seem to work well.

Jon.

AirTex 40725/40254 has one in, one out and 5.25 To 6.5 psi. $17 at O'Reilly's. The 350's, up into the time TBI came in, used these pumps. All these pumps have the same mounting configuration but I'm not positive they have the same arm.(M16080)

Thanks guys. Didn't get to installing the regulator today, baby sitting grandson. Tomorrow looks promising. Could a vacuum leak cause the problem? I don't hear anything but been having issues with the power brakes.

What problem? Without sounding rude, you said "seems" to be running rich and "starts and runs good". I usually have way more "problems" than that. I think your life is good right now. Enjoy the Grandson.

Problem as stated before. Cannot adjust the carb smells like it is running rich. Screwed all the way in and it still runs. Years ago if you screwed the adj all the way in the motor would darn near if not completely die. Am I missing something that is normal now days?

I believe HRLincoln and Hollow gave the best possible. Wait till you control pressure and see. Too much pressure will do exactly what you say it's doing. If no change do the float level/high idle adjust as suggested. I think HRL is saying dripping will over ride the idle needles, which allow gas in with throttle plates near closed, and they become un-adjustable. What is the part number of your carb and pump? What year is your motor.

I believe the carb is a 1405, the pump and year of engine are unknown at this point. I'm doing the pressure regulator and then if necessary will go to the float levels. Will update as to results.

10-4

Well, as promised, here is what I found. Installed the pressure regulator between the fuel filter and the carb. Set it to 5 1/2 lbs. Fired her up and instantly ran better. Doesn't smell rich anymore. So, thanks guys for your help even if it was a long way around to get there.

What did you use for a fuel pressure regulator? I've been thinking of putting one on my '65.

Thanks

Mr Gasket has a kit that contains the regulator and 3 sets of fittings. $34.99 at O'Reilly's. Tops out at 6psi. Just cut your rubber fuel line put the right fittings on and 2 hose clamps (not included in the kit), there is an in and out side clearly marked, set the pressure and your on the road.

Thanks.

You may find it runs even better at 3 1/2 or 4. Its easy enough to find out. Glad you figured it out, sometimes the long road is the only way to get there.

Joe