Which Edelbrock carb? for 401

[63Electra]

My 63' Electra is in need of a new carb. I get coupons from pep boys and the like for new edelbrock carbs. What CFM whould you suggest for a stock engine, auto trans. how much modifiying will I have to do to the linkage to get the transmission to work? Anyone put an edelbrock on their nailhead before? How do they work?

[ol' yeller]

My experience with Edelbrock carbs isn't good. My experience is with a '65 Skylark 300 and a '69 Riviera. The linkage has to be cobbled together and both had to have work done to get them to run smoothly. The floats sometimes stick as well when shipped. I have found Daytona Auto Parts in Datona FL to do an excellent job of rebuilding my carbs to like new specs. They run right out of the box and look terrific. They completely rebuild the carb including new shaft bushings if required. They are on the web but I don't have their website address handy. I'm sure a quick Google search would locate their web address. They aren't cheap (neither is the Edelbrock) and turn-around time can be long in show season but they deliver what they say when they say they will. I have recommended them to several Buick buddies and they all were very pleased with them. I think this would make you happier in the long run. I'm sure Edelbrock carbs are fine for some cars (Chevy's ?) but Buicks need OEM. JMHO

[NTX5467]

Just because the Edelbrock AFBs LOOK like the OEM AFBs does not mean they are completely "right" for what you have. Lots of internal differences plus the jetting is not "Buick-spec" either.

Generally, the Carter AFBs and AVSs were very reliable carburetors. They are easy to rebuild, or "kit".

Why do you feel your existing carb needs replacing? Just curious . . .

As for cfm issues, I suspect the 550 cfm (or something near that) would be more than what you now have, or pretty close. You'll be limited by the existing intake manifold throttle bores more than anything else. If your intake manifold has the "heat track" in front of the primary throttle bores, you'll need a new intake manifold to use the Edelbock carbs (greatly suspected!!).

I've noticed a few "noted" carb shops that specialize in certain carburetors. Seems like there's a guy in the BCA Forums that goes by "Carb King" that has posted why the Edelbrock carbs are not good "out of the box" on Buick V-8s.

Of necessity, the Edelbrock AFB and AVS carbs are more oriented toward Chevrolet engines (throttle hookups and fuel calibrations). Getting them to work on anything else can be a lot of time and related expenses--even if you do it yourself. If you go to the Edelbrock website, you can download the approx 50 page Tuning Manual on the AFBs, to see what all's involved.

I do believe this is a situation where rebuilding (or having it done at a reputable business) is better than putting on a "universal fit" part and then trying to make it work as it should.

Just some thoughts,

NTX5467

[frydfsh]

I am running an Edelbrock 800 cfm on my 401 that has a mild TA performance cam, mildly ported and otherwise stock engine. It has an electric choke and AVS style secondary's. The engine starts great and runs very well with no stumble and good throtle response. I am satisfied with the performance of this carb. Only drawback so far is gas mileage, which on a recent trip averaged about 14 mpg. Carb is at present time being run right out of the box, some tuning is upcoming. I think that this carb deserves a fair shake, its not that different from the original AVS and is every bit as tunable.

[Go Poly]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: frydfsh</div><div class="ubbcode-body">I am running an Edelbrock 800 cfm on my 401 that has a mild TA performance cam, mildly ported and otherwise stock engine. It has an electric choke and AVS style secondary's. The engine starts great and runs very well with no stumble and good throtle response. I am satisfied with the performance of this carb. Only drawback so far is gas mileage, which on a recent trip averaged about 14 mpg. Carb is at present time being run right out of the box, some tuning is upcoming. I think that this carb deserves a fair shake, its not that different from the original AVS and is every bit as tunable. </div></div>

I have a 750 CFM Carter AFB (new, or at least it was 8 years ago prior to Edelbrock buying them). It has a terrible off idle stumble. Did you have to do much tuning?

[imported_buick5563]

Hey Frydfsh,

Were you able to get the trans kickdown linkage hooked up? If you did, can you post a picture. That is the main reason I didn't do what you did. Also, 14 mpg is still better than the 12 I was getting with my OEM carb.

Thanks,

Mike

[NTX5467]

The difference between the 625cfm and 750cfm AFBs is the size of the primary throttle bores (625cfm >> 1.56", 750cfm >> 1.69), with the sizing of the secondaries being the same (1.69"). If you use the industry standard calculation for carb sizing, the 625cfm should be plenty big for a 400cid V-8 to make a good bit of horsepower. Maybe not 500 horsepower, but probably a good, solid 350-375 horsepower. The 750cfm would take it over 400 flywheel horsepower, though.

I suspect that when you "over carb" and engine that's reasonably stock, you end up with the primary throttle plates closed too far to get the idle speed down to where it needs to be to not "slam" into gear from Park or Neutral into Reverse or Drive. If the throttle plates are closed too far, it can cause such a flatspot or hesitation when moving from curb idle speed to driving speed--especially if you're in a hurry.

If you try to use a stock carb with a reasonably wild-spec cam (when it was designed and configured to work with the stock (or similar) cam, you have to drill holes in the primary throttle plates to allow enough extra air into the engine but still maintain the desired relationship between the throttle plates and the idle port and transition port slot in the carb's throttle body with respect to where the throttle plates are when curb idle speed is adjusted. The wilder cam needs more airflow into the motor, so you crank open the primary throttle plates to increase the idle speed.

Then, the throttle plates are openned TOO FAR for the idle port to work as designed and the transition slot is uncovered too far, so it doesn't work either. When you open the throttle from that point to accelerate, ONLY the accelerator pump really works to cover the transition from the "idle" and "run" modes of operation.

When you drill those holes, you allow the extra air in while also letting the throttle plates close to a position that's more in the "stock" configuration position. It sounds crazy, but that's what's been recommended (and it works!!!) for many years. You can find that procedure in most every Holley Carb book that's been printed (by S-A designes or HPBooks) for the past 30+years. You can probably peruse these books at one of the mall's chain bookstores, or Borders or Barnes&Noble.

Those same Holley carb books also have illustrations of what I'm talking about happens when the throttle plates are closed too far or open too far.

So, my theory is that with the larger carbs for the engines (which are more reasonably "stock" than not), the throttle plates are being closed too far (especially with the larger cfm models).

From the equation to determine carb sizing for a particular engine size, you can also consider that how much air the engine really uses can be an issue too. For example, a Chevy 396 might need more air to idle than a Buick 400 or the Nailhead 401. Key issues might be intake manifolding, combustion chamber/piston designs, amount of cam overlap, the efficiency of the exhaust port, and the exhaust manifold/system design and efficiency. These differences would also be the reason that a "one size fits all" carb will need to be fine tuned for the particular engine it's attached to rather than being universally "plug and play".

And that doesn't even come close to addressing the linkage configuration issues! Perhaps, the carb linkage issues might be aided by converting the vehicles to "cable throttle" from "rod throttle"?

Just some thoughts,

NTX5467

[NTX5467]

mlander . . . considering the poster lists location as California, I suspect the "Go Poly" handle would refer to a school as California Polytechnic (i.e., Cal Poly) or another school/university with "Polytechnic" in its name . . . rather than a reference to the Chrysler Polysperical Cylinder Head engine family (i.e., early "A", with the "LA" family being the later model 273, 318, 340, 360s). That's my interpretation of the situation.

I believe there are a few websites devoted to the Chrysler "A" engine, which you can probably find via Google or similar. Chrysler did use Carter AFBs as their choice of 4bbl carbs. I suspect that all 4bbls of that era would be doing good to flow 500cfm at the current industry standard pressure drop for 4bbls.

Prior to the decision to use cfm flow at ____" Hg pressure drop to rate carb air flow capabilities, they used "square inches of venturi area" as flow benches had not really come into popular use back then.

Respectfully,

NTX5467

[Go Poly]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: NTX5467</div><div class="ubbcode-body">mlander . . . considering the poster lists location as California, I suspect the "Go Poly" handle would refer to a school as California Polytechnic (i.e., Cal Poly) or another school/university with "Polytechnic" in its name . . . rather than a reference to the Chrysler Polysperical Cylinder Head engine family (i.e., early "A", with the "LA" family being the later model 273, 318, 340, 360s). That's my interpretation of the situation.

I believe there are a few websites devoted to the Chrysler "A" engine, which you can probably find via Google or similar. Chrysler did use Carter AFBs as their choice of 4bbl carbs. I suspect that all 4bbls of that era would be doing good to flow 500cfm at the current industry standard pressure drop for 4bbls.

Prior to the decision to use cfm flow at ____" Hg pressure drop to rate carb air flow capabilities, they used "square inches of venturi area" as flow benches had not really come into popular use back then.

Respectfully,

NTX5467 </div></div>

That would be correct. Cal Poly San Luis Obispo, my alma mater.

[carbking]

Go Poly - while not officially published as such by Carter, the 401 carbs were approximately 625 CFM (1.5 in Hg wet). This figure is obtained by comparing throttle bore AND venturi size to Carter carburetors which do have published CFM.

Often, a vehicle with an auto transmission will have an off-idle stumble due to too RICH an idle setting. (Read NTX5467's explanation of idle control).

Carter did not build "aftermarket" AFB's calibrated for Buick. There was absolutely no need. Carter had factory-calibrated single and dual quad carburetors for the Buick. Why confuse the customer when you already have a product that works, and there is no additional tooling costs?

Jon.

[FireballV8]

I have an Edelbrock AFB carb, which was on my 58 Century when I got it, I converted the car back to the stock carb, so if anyone is interested I have the carb for sale. It includes a new needle & jet kit as well as a modified original air cleaner to fit the carb, but look original when the hood is open.

Open to offers, email steveclassic@earthlink.net

Thanks