Have a 65 LeSabre 400 conv with the Carter 4bbl. How many CFM does that small block factory carb flow? My original carb needed to go. I got an exact 65 (correct carb) and had it rebuilt. I re established the choke tube from the manifold. Choke spring works, snaps closed nicely, good spring. Made sure the vaccum passage was open so the choke will open. Still won't open properly. Had some problems initially w/ float just a touch too high, fixed that issue. No gas leak now. I'm sick of fooling with choke issues. I was going to go with a manual choke kit and say the heck with it but I like the auto choke best. If I decided over the winter to go with a new Edelbrock (Carter knock off anyway) which Edelbrock carb works correctly with the 300 4V engine? I don't want to over carb the thing. They have an electric choke so I can keep the car close to original and have a nice choke set up trouble free. They aren't so expensive either as far as I can see and should be a direct bolt on unless kick down would be a problem? Thoughts?
the stock carb on my 340 is 400 cfm i would say the same as yours. carter made 400 500 575 and 625. a 500 should be fine.
I have 500 cfm with elec choke on my 300. Happy with it. You can easily change out jets and metering rods till you find the sweet spot. You will probably find that you need to lean it out a bit vs the out of the box set up.
Finally located your post. I have put a Edelbrock 1406 600CFM on my 300 inch engine, which hasn't run right in awhile (not carb's fault). Do you have a switchpitch in your car or is it a dynaflow? If it's a switchpitch, you can see the simple mods I made to my Edelbrock to use the standard linkage and keep all the kickdown and solenoid intact. I ground off the linkage attachment off an old AFB and then did the same on the Edelbrock. Carefully, and quickly (heat transfer) weld the AFB linkage on the Edelbrock. Piece of cake and everything fits. You cannot use a drop base aircleaner with this mod, as the linkage will hit the aircleaner base. I bought a spacer at Autozone to go between the carb and aircleaner to correct this problem. If you go to the Edelbrock you will need a new aircleaner as the AFB is smaller (intake) than the Edelbrock. Good luck.
Update: My rebuilt Carter AFB carb is NOT the problem. Figured it out the hard way. Carb works right, bi-metallic spring works fine and I replaced the hot air tube from the exhaust manifold. Instead of internal vacuum inside the choke assembly pulling the butterfly open, hot exhaust is finding it's way in somewhere and actually forcing the butterfly closed. Took choke housing off, went to put my finger over the vacuum passage to feel the vacuum and to my surprise I felt it blowing out instead!!!! I thought I was nuts! Either I have a blocked exhaust passage under the carb, possibly a small hole in the intake somewhere internally or a bad intake gasket. I'm gonna have to pull the intake and check it. Funny thing is the darn thing runs smooth, idles like rock and never gives me any trouble even now at 113,000. Bad thing is a 300 4V intake mainfold will be somewhat difficult to find if I need to replace it.
Man I feel your pain. I have a string going with all the vacuum problems I've been having with my 300/4 set up. I have epoxyed the heat crossovers closed. This weekend I will have it on the car and see how it all has come out, I'm hoping for a smooth running car finally. Make sure you have the plated between the intake and the carb base securely sealed as that has been a leak point in the past on these setups. Have you checked it out with a vacuum gage yet?
A 300 would really enjoy a 600 cfm carb....sounds like some mechanic turned the choke spring around backward at rebuild... another mistake is not getting the little tab at the end of the spring properly engaged to the choke linkage.... I dont think that I would start pulling the intake just yet,,, I would do a lot of isolating, checking stuff to see if it is to buick specs... ect.. before pulling the intake....you are supposed to have open passages down thru the carb to the area under the carb inside the intake manifold and there should be high vacume there... not pressure.... but the problem would not be with the intake , it would be with the carb.... the air is supposed to come up thru the exhaust manifold tube and be pulled into the choke assembly by the vacume coming up thru the carb from the intake manifold....
That's the problem.........it's not vacuum pulling, it's exhaust pushing out the passage that is supposed to be supplying vacuum. The carb guy that did it is a real pro.....the spring is NOT in backwards. All is right on the linkage/choke housing side of things. The tube connecting the passenger side exhaust manifold is cold! The carb is not getting exhaust heat from the tube. Exhaust is somehow blowing out from the little vacuum port into the choke housing. There is only a couple of places it can come from. I never run anything but a stock base gasket on the bottom of either Carter AFB I've run. When I pulled the choke housing off the old carb it was caked full of black! I ran that one on the car with no choke for years because I only drive the car in warm weather so cold starts aren't so bad. The carb I put on is an exact correct 65 Buick AFB from California that I picked up years ago. It is in beautiful shape. So you see, 2 different carbs same result - inoperable choke. Other than that the car runs nice, idles smooth, no blow by, valve trainb ticks etc. You could stand a wine glass on the intake while it's idling and it wouldn't spill. I have the choke housing off the carb right now, and wired the butterfly straight up for now. Cold weather is coming to PA shortly so I have the winter to mess with it.
Do you have the stainless steel plate that goes under the carb between the the carb and intake manifold installed? If not you could be getting exhaust crossover gases coming up through the manifold and into the carb. This will kill off your vacuum and will fill the carb and intake runners with black deposits. If you have the carb SS plate installed properly then you need to look for a crack or hole in the intake letting exhaust into the intake (carb) side of the system. If you don't need the carb base heat feature you might want to epoxy the holes in the manifold closed to eliminate the possibility of exhaust gases getting into the intake side.
That's the only explanation that makes sense. I've seen it before. The vacuum port at the choke leads to a point directly in front of the front throttle bores in the base of the carb....which is directly over the ex heat channel in the intake. If the steel plate isn't sealed, it'll draw in exhaust gas. The aluminum 1964 manifold used water only. 65-up iron intakes had exhaust passages for intake heating.
My car never had a thin metal plate heat shield. I had a heat shield on my 350 Skylark back years ago while running a Holley spreadbore on it. The original carb on my 300 had just the cardboard gasket, just like the one that came in the rebuild kit. The gasket has the slot in front of the primaries that matches the groove in the intake. Gonna play with it a little bit before I go ripping the intake off of the thing. Wet snow falling this evening in Pa. Big fat flakes melting on contact cause the ground is still too warm for it to stick. I'll have plenty time to mess with it now that the cold weather is coming.
No SS plate = no cure to your problem. Buy the plate, they are on on e-bay and available through aftermarket suppliers. Good $20 investment.
It's worth a shot. I just wish that there was more aftermarket support for the 300. A nice aftermarket intake would probably be a hot item. Lots of guys want to add a 4 bbl to their cast iron 300. Mine is factory 4bbl but really there is nothing out there really for this engine.
Yeah, I believe I saw headers out there somewhere but I checked T/A Performance and didn't see an intake, maybe I missed it. For what you would pay for a used one if a reasonable aftermarket one was available you couldn't lose. Especially if you had the 2 bbl version of the 300. My car is a LeSabre convertible. It's a nice clean classy full size conv but I wouldn't really want to put speed equipment on it. It's not that kind of car. With the 300 4V stock engine and a nice TH400 and posi it gets up and goes well enough for a big car. With relatively small displacement that engine will get up and go, super reliable even at 113,000 miles. My kids (2 of them now in their mid 20's) grew up in it. We cruised all over and the car is truely is a part of the family. I just finished my 1966 Wildcat 2 dr cpe, that one is more of a muscular brute with the 401.
