I'm going to stat working on getting the bugs out of my 472 and need carb advise. i have a stock 1974 cadillac motor in my Merc and it is choking out and the carb seams to just not be working correctly. the carb is the stock Quadrajet and has a weird choke set up. i want to eliminate the current choke set up and maybe go with a electric choke set up or anything better. I just want to get advise on the best carb set up is best for a big cad. i dont have an aftermarked intake yet but would like to upgrade eventually and want the carb set up too work with the new intake at a later date. i just want advise on what direction to go.
The carb decision may effect the intake decision. The Q-Jet is a spread-bore design. If you go with another carb that works on your current intake, it will limit the purchase of another (aftermarket) intake to a spread-bore design. What I consider to be the best advice would be to try determining the issue with your existing carb, and fix it. If at some time in the future you wish to purchase an aftermarket intake, you can ask again; and a great argument will ensue over whether you should buy a Carter, a Holley, a clone, or a Demon. Should you decide you wish to go ahead and replace what you currently have with your current Q-Jet intake then: Carter spreadbore: 800 CFM electric choke - part number 9800s 850 CFM manual choke - part number 4846sa 1000 CFM manual choke - part number 4847sa Holley spreadbore: I am told Holley made both 650 and 800 CFM spreadbores. Since I don't do Holleys, I don't know the numbers. Rochester spreadbore: Virtually all 1976 and newer Rochester Q-Jets are 800 CFM. Some of these have electric chokes. If you want an 850 (and don't mind the expense) part numbers: 7041267, 7041268, 7041270, 7041273. All of these numbers utilize a divorced choke. Jon.
Thanks for the guidance, the intake I'm looking at accepts the quadrajet carb. That is why I am considering a newer style quadrajet just need to look at what cfm it requires. I guess I could adapt a manual choke to my current carb but just need some advise from someone more experienced with the cad. I just don't like the choke set up and need to change it.
X3.......... On the 472 in my COE I just went a new Eldelbrock 1406 with electric choke - LOVE the electric choke. My reasoning was it would be new, over a rebuilt Q-Jet. But you have to use an adapter and that adds to the height and expense. Also the fuel line fittings are different. Had to do over I would get a rebuilt Q-Jet with electric choke from Cad Company. Ton of info on their site. Chris there was very helpful in the redux and giving advice when it came to lack of oil issues I had. (When no HAMB members really had the answer). They most def have earned a customer, have my eye on their stainless steel timing chain cover.
I have done a little with the cad company and the are great. I am just trying to get it running good without breaking the bank. I am just hoping to find a latter model quadrajet with electric choke that will work.
I do not recall any issues ever with choke or moderate weather starts on my 472. The original set up is benefit for what you are asking. Good luck with the project.
You could go manual choke cable that would be my 2nd choice. Kept my Q-Jet just in case - heck the 472 ran fine with it even after sitting 18 years. Great carbs.
Rebuild the stock carb. If the choke is set up correctly it will work just fine. They worked fine when the car was new, why shouldn't if work fine now if it is working correctly?
i think I will just rebuild the carb for now and decide on what carb to use next when I get a new intake.
I just want to add to what Jon has said here. I have never raced a 472 but I have owned 2 or 3. Stock on a 472 you reeally can not beat the original carb. If I was going to try and beef the engine up (as if it needs that) I would go looking for different carb and intake options, if I were to leave it stock I would work either with the original carb or an original type carb.
Q-jet carb has a chronic internal leak issue; The plugs at the bottom of the jet wells habitually leak. When you remove the throttle body (carb base) from the body, there is , or should be,, a foam pad, which is there to absorb said leakage. Manifold vacuum is supposed to remove what the pad absorbed. One fix was to clean off the area around the jet well plugs, and coat the area with a good epoxy. Another was more involved,...you removed the plugs, and tapped the holes to accept small screw in plugs. This problem was the cause of many poor running Cadillac, and I'm sure, other engines. We owned a 68, and I replaced the Q jet with an "application" spread bore Holley. 4TTRUK
I will have to take off the carb clean it and epoxy the holes. I also do not have the foam pad on the carb so may be needed to get the carb up high enough to make the choke work properly. so correct me if I am wrong first put on the gasket then the foam pad last the carb.
The foam pad is under the baseplate. You can buy replacement "thick" gaskets. They are basically just an isolator that keeps the carb from getting too hot do to the cast iron intake.
Oh so true for 1965~mid-1968. Corrected by Rochester in mid-1968. The later Q-jets don't have this issue. Jon.
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