63 carb replacement
I have a 63 300hp A/C car. I have the 3621 afb and cars runs very poorly, also have a 3721 afb. I'm thinking of just getting an Edelbrock to make my life easier. Car is a 4 speed and has a 3:08 differential. Anybody have a suggestion about a carb to give good performance but also allow me to keep same air cleaner etc. Thanks, been messing with the 3621 for while, had bout enough, JOe
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Re: 63 carb replcacment
I don't know what a 3621 came from so I have no idea if the calibration is any where near correct for a 327/300, but a 3721S/SA/SB in good working order should work fine on any 300HP/manual trans. The original '63 300 HP w/manual trans model was a 3461S, which transistioned to the 3721S/SA/SB during '64-'65 production.
Any of these 3721 models should work fine if it's properly configured and bubba hasn't messed it up too bad over the years, but even if it has been butchered, it can probably be brought back to OE specification and performance.
Stu Fox has done a lot of work with AFBs. He will probably be along to comment. In the meantime you can search his many posts on the subject.
My recommendation is to get your 3721... into proper working order before you try an Edelbrock. In most cases, a properly repaired /configured OE carb is a better solution than trying to make a generic aftermarket replacement work.
The "Edelbrock AFB" has a lot of different configuration features - different fuel inlet location, different choke system, and I think it has a different diameter air horn, so it won't accept the OE air cleaner.
Duke -
Re: 63 carb replcacment
I mixed up the numbers, I have the 3461 on the car. I will have the 3721 rebuilt, thank you for you inputComment
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Re: 63 carb replcacment
If at all possible, stick with the 3461S if you can. Compared to the 3721S series, it is worth gold. If you just want to toss it, I'd be glad to take it off your hands, Ha! The 3461 has a number of very subtle and unique features which make it a better choice for performance, but on your L-75 engine w/a/c it probably wouldn't make much difference, and I'm sure you just want it to run good.
Like Duke said, any of the 3721 series carbs should do well for you, and I agree to stay away from the Edelbrock series. I saw a 63 SWC advertised as a 100% correct NOM car as part of a raffle and the picture they show with the hood open you can see the extended fuel line to the rear of an Edelbrock carb (a real turn off).
Perhaps you need to diagnose your poor running condition a little further to be certain it is the carburetor. There is only just so much that can be the fault of the carb and it usually can be corrected w/o having to replace it. If in fact it is completely worn out, i.e. severly worn primary throttle shaft bores in the body, that too can be repaired. And believe me, with the current value of a 3461S, it IS worth repairing. A common problem with any AFB with a stock clean air heated choke is a stuck choke pull off piston due to either white corrosion in the cylinder or warping. I too spent many frustrating maintenance hours trying to get the choke to work right. To solve it, for day to day operation, I chose to go with an electric choke similar to the Edelbrock, but different in that the unit I use (I bought many years ago) has a thermal sensor to control the amount of current to the choke heating element. It does a superior job of controlling the choke during the engine warm up cycle. Eliminating the hot air source did away with the piston sticking problem, and the possibility of the hot air tube putting stress on the choke housing.
Many of today's problems with any of our vintage Corvettes with carburetors can be traced to the Ethanol laced gas - and that's another whole big story. Perhaps if you described what problems you are experiencing, Duke, myself or a number of the TDB members could help you rectify them. But, what ever you do, don't give up or give away that 3461S too easy.
Stu FoxComment
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Re: 63 carb replcacment
thank you, the car starts from cold perfectly, the choke works and then kicks down to about 700 and idles well. Warm starting is horrible with excessive cranking needed and occasional back fire. Acceleration even when car is warmed up results in the car almost stalling then bucking and occasional backfire. I can prevent the hesitation and bucking by keeping rpms above 1500 for starting in first gear from a stop or shifting thru the other gears. If I'm at a red light with people behind me I have to rev car up to 1500 and slowly let out clutch to avoid bucking, bog down and near stall. On occasion the car will stall while idling. I hope this gives you some idea of what's happening. I would live to stay with the original carb. Thank you, JoeComment
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Re: 63 carb replcacment
It sounds like you have a severe percolation problem. Do you drive the car in stop and go traffic when it's over 80 outside and use the AC?
There are lots of solutions to percolation, and the cause is well known. Insulating the fuel lines is one step that should yield noticable improvement. An archive search should give you plenty to study on the cause and cures for percolation including a thread in the last few days.
In the meantime make sure the heat riser valve is not stuck, then move it to the full open position (weight pointing down) and wire it full open.
When was the last time your car got a full ignition system check - points/condenser, rotor, cap, and plug wire resistance check. If you don't know or can't remember...
Set the initial timing at about 12 degrees and make sure your VAC is functioning properly by adding 16 degrees to initial for a total idle timing of about 28 degrees at 500 RPM idling in Neutral with the A/C compressor engaged. If you have the original 201 15 VAC that doesn't work or something you can't ID, buy a NAPA VC1820, which has a stamped ID "B22" or cross reference the NAPA part number to a different brand, and it should be the same SMP manufactured "B22" VAC that provides full vacuum advance at 15". If idle vacuum is less than 17" with the A/C compressor engaged, use a 12" VC1765, which is stamped "B20" or "B26".
Once you check out the ignition system and set timing, go through the idle speed/mixture adjustment procedure explained in the 1963 Corvette Shop Manual.
One thing for sure based on your additional report on operating problems - installing some generic aftermarket carburetor will NOT solve your problems.
DukeLast edited by Duke W.; August 7, 2013, 08:58 PM.Comment
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Re: 63 carb replcacment
I agree with Duke in the above post just take your time and do a tune up, it's a word we don't use much anymore because of modern technology in today's car engines.
When you put the engine under load like starting off the mixture gets lean and if the secondary ignition system can't deliver the voltage to ignite the mixture you will experience problems like you describe. Many times carburetor problems are ignition related, don't be so fast to touch that 3461.Comment
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Re: 63 carb replcacment
thank you, I have forwarded your suggestions to my mechanic( a professional who does this for a living), I'm going to have him do this. thank you, JOEComment
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Re: 63 carb replcacment
Duke and Tim;
Thanks for coming on board to help Joe. I read his first response late last night and I expected to give him similar advice this morning, if no one else came on. Glad you endorsed my "keep the 3461S comments". There are a lot of guys out there who'd love to cheat him out of that carb as they know the value. The folks here on the TDB aren't that way.
Stu FoxComment
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Re: 63 carb replcacment
"a professional who does this for a living"
There are all lot of "professionals" that do things like plug the vacuum advance, get rid of the PCV system, rebuild Corvette engines with such low compression that they'll run on unleaded regular (and thus give up a lot of torque, power, and fuel economy), and install high overlap cams on automatics so they won't idle properly or have any low end torque to name some of their major offenses.
So be careful. Being a "professional" can mean a guy you pay a lot of money to screw up your car. The TDB is full of such stories.
DukeComment
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Re: 63 carb replcacment
I just got my 63 back from the garage. we put the 3721 carb on the car for now and it runs great, accelerates smoothly ,warm and cold starts are good, idles nice and smoothly. my mechanic took off the original carb and says that he needs to re-sleeve the accelerator pump channel and he thinks it will work fine again. I'm inclined to believe him as he was right about the carb being the issue for now. I will post you all this Fall when I get the original carb back on the car ,and thank you all for your input, JOeComment
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Re: 63 carb replcacment
can any of you guys tell me the best person(preferably in New England) to refurbish my 3461 carb. I've been messing with it for some time and can't get the car to accelerate properly. I put the 3721 carb back on and its perfect. I have a feeling the the accelerator pump channel is worn. thanks JOe tassoniComment
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Re: 63 carb replcacment
Joe;
To be honest with you, I have never known an AFB that had a worn accelerator pump bore (as you say channel), unless "bubba" tried to enlarge it to fit an Edelbrock pump. If you have done a "squirt" test (operated the throttle lever on the carb and checked to see if fuel is squirting into the throttle bores), and you find little or no gas coming out of the nozzles, you might have a frozen check ball (in a brass check ball holder near the base of the accelerator pump chamber (bore), or a stuck/frozen check needle under the pump squirter. Or, if your lucky, you may just find the most common problem that being a worn pump leather. Either condition can be caused quite easily today with the residue left after the ethanol laced gas evaporates from the fuel bowls (overnight or up to a week of sitting, depending on your areas ambient conditions). Generally, if your carb looks dirty on the outside it may also be dirty on the inside which can lead to all kinds of problems with plugged jets, air bleeds or pump circuit.
What happened to the "professional" that was going to sleeve your accelerator pump bore??
My concern for you is what you may be up against trying to find a good carburetor shop where you live. I have seen some examples of work done by "professionals" and they can include people who, by accident or on purpose, mix and match parts from different models and different customers carburetors. Though they may look the same on the outside, they may have oddball parts on the inside. That was one of the problems I ran into on my 3461S. Then once you have identified this problem, you will play heck trying to find just that one correct internal part like say a venturi cluster.
Good luck. I hope you can get some help in your area or from some friend here on the board who will endorce a good shop or individual. I nominate Tim B.
Stu FoxComment
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Re: 63 carb replcacment
Joe,
I would call Bob Kunz and tell him what you have and get a price for a quality rebuild. He is the most knowledgeable guy I know of when it comes to Carter AFB's and that may be you best bet when it comes to the hard to find 3461.
Whatever you do don't give it to someone for a trade in. Can you describe what type of acceleration problem are you having?
His phone # is probably here in the archives or check the driveline.Comment
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Re: 63 carb replcacment
car runs fine at idle and at rpms over 1500. when step on the gas in first or second gear car lugs down, bucks then almost stalls. I put a 64 carter afb on it and the problem is gone. I have the 3461 in box ready to go out when I find right guy and have the time. I'm just glad aftr this long Winter that the car now runs good with the 64 carb. I will look up bob kunz. thanks, JOEComment
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