I am not happy with the performance of the new Edelbrock 750cfm carb on my '66 GS 401. I read a post on another auto board that the Edelbrock 750 was a poor carb, unlike the smaller versions. I was wondering if I should buy a rebuilt Carter AFB(stock carb), Holley Street Avenger 670cfm, or try and get a Q-Jet manifold and rebuild Q-Jet?? I am not looking to bump up HP, but don't feel that the current setup makes much power and has poor fuel economy. I have a highway ratio and auto and can't seem to get better than 12mpg? Thanks
I stuck one on a 401 and had awesome low end, but up in the revs (for a nailhead, like 3500!) it balked, went lean, misfired and was bad. I spoke with Carmen and he thought the bores were slightly different sizes and the lip would cause turbulence and "reversion", causing a lean condition. He keeps recomending the original carb. I used a 600 edelbrock on my Riv 401 and had excellent service from that. It runs better with the original (not even rebuilt) carb, though. you could have the manifold ported to have a smooth transition. Good Luck Carmen Faso 716 693-4090
Somewhere in the fine print on the instruction sheet, it states that the carb is shipped with generic jetting that should run on most engines, and that the vehicle owner is responsible for final tuning the springs, rods, and jets to his/her particular vehicle/engine combination. If you decide to buy the Holley, buy a fire extinguisher to go with it.
Edelbrock 750 I also have a 66 Skylark GS. For what it's worth, I used an Edelbrock 600 CFM electric choke model as a replacement for my Carter AFB when it was being completely redone. The Edelbrock ran fine. The only problem was jury rigging a linkage for the kickdown switch. I fooled around with the jets and rods but ended up back with the settings as shipped from Edelbrock. Ultimately I went with dual quads and, after some period of adjustment and experimentation, I'm very happy with that choice.
Thanks guys. I know that the jetting and rods, etc are generic, and was prepared to buy the kit from Edelbrock to rejet. I read a post on another auto site that pretty much said that it would not do much good to rejet/tune as the 750 Edelbrock was a poor carb which would be difficult to tune to any application and got poor mileage. He indicated the 600CFM and smaller Edelbrock carbs worked fine. The author of the post owned a garage and purported to have knowledge, although he doesn't sell carbs. I too was wondering if there is a mismatch on the intake carb ports between the big Edelbrock 750 carb and the stock manifold. I may try and find a rebuilt stock Carter AFB.
I am running an older carter competition 750 afb. I rebuilt it, and it runs fine. parts interchange with the edlebrock carbs. I do know the edlebrocks come set up (jetting) for a 350 chev.they include a pretty good manual on setting up. There are a multitude of settings you can swap around.
Steve, I put an Edelbrock 750 model # 1407 with manual choke on my 65 401 GS and except for the rewiring of a micro switch and bracket from Edelbrock for the trans kickdown and carb linkage it runs beautifully and I havent messed with the jetting yet, although it is running rich at our altitude of 3200 feet. I noticed a lot more pull on hard accelertion and you can really hear the motor scream for more air when you hit the throttle. John Everett had driven my car with the stock 600 rebuilt Carter before I got the Edelbrock and he advised me to gett the Edekbrock 750 #1407 and a different air cleaner and "let that engine breath" Fuel milage is not a concern of mine but I would guess around town I get 11 to 12 MPG and on the hiway around 14 MPG. I run 91 Octane gas. I had to ask these fine folks on this forum for help to hook up everything after I purchased the new Edelbrock and with their help it is a beautiful addition to my engine compartment. Good luck with any thing you decide to do Steve. Bill Bailey
I should try running my 1407 on a better running engine... What I tried to do was make a poor performing engine feel better by replacing the carb. Then the distributor, then the wires, then the carb again. None of these changes made it right, but the '66 Q-Jet seemed to feel better. So, I like the idea of rebuilding a stock carb for your engine. Like I mentioned before, my Riv ran just great with the old original carb back on it, without even rebuilding the thing. (I took it off because of the choke tube passage leaking in the exhaust manifold) Holley has a bracket (to use with the Edelbrock) that can be made to operate the stock transmission switch. I have to find the part # and take some pics on how I rigged it.
Must have been a Chevy site. But yes, the AFB is a little more difficult to tune than a QJet. I get 11-something city, 14-15 highway, poor mileage is a benefit of driving a big block car. So is poor wear on the rear tires. Yes, there is a intake carb port mismatch on the secondaries with a 750, at least there is on my 64 squarebore intake. Primaries match up ok. All four mismatch with a 800 cfm AFB. The good news is that the intake can easliy be milled for bigger carb bores. The kits that Edelbrock sells suck, IMHO. Assuming you have the instruction book and have read and understand the tuning procedure and the graphs, if you think real hard about it, the parts in the kit don't follow the tuning procedure. The Edelbrock parts just let you make large changes all over that graph. You need parts that will take you straight out to the right on that graph in small steps, then up or down for cruise mileage from that point. The parts just aren't there unless you buy a lot of separate stuff. And then there is the math - Edelbrock's math is sloppy and those points are usually off by a couple of %, some as bad as 5% or 6%. The Carter strip kit isn't much better. The jets are useful, but the rod selection doesn't give you a richer WOT power mixture with a leaner cruise mixture. I redid those Edelbrock instruction book tuning graphs in Excel, I'd post them if I had time to figure out how. Also did a similar graph for the Carter strip kit.
I know my GS isn't an economy car, but cruising on the highway only returns 12MPG, so in town is worse. My car(engine rebuilt) won't burn rubber from a stop. I know the car is running rich. Part of the problem might be the stock air cleaner. John K. after what you said about the Edelbrock tuning kit and instructions I don't think I will try and tackle.
Heck, my 4250 lb Land Yacht (64 Rivi) will burn rubber from a stop with a 3.07 rear. Have you curved your distributor? My 70 GS picked up a honest .5 sec at the strip with distributor tuning. I'll have to find those Excel sheets. You may just need a set or two of rods for $6, not an entire $50 kit. You definitely need an open element air cleaner.
I appreciate any help you could offer John K. Come spring I'll be doing something to the carb. I can't answer about the distributor, supposedly the engine was rebuilt and car restored before I bought it. but of course no receipts!
Nobody has mentioned the factory q jet setup that was available in 66. By far the best overall single carb application. If performance is important and stock apperance doesn't matter, then use a 71-74 q jet from a 455 Buick. If your engine is stock, most likely you can bolt it on and go. Sometimes there is a linkage interferrence problem, however it is easly fixed. Mike
The nail head will take a lot more carb than most people think it will , I did like the other fella said and had my stock iron intake bored out as big as possible[the price is the same] and then put a 950 cfm holley 3bbl on it and the car screamed. a nail head really likes a cold air set up also. believe the man when he says to calibrate your dist. [its worth it] good luck Doc
Thanks for all the replies. Does anybody know who can calibrate and tune a distributor in the Central Illinois area? Also I need information as far as metering rods, and jets for a Edelbrock 750CFM carb for a 66 GS 401 automatic? If somebody has done this and would be willing to share it would be great thanks
