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I have a performer edelbrock intake manifold on my 72 sbc 400. It is all stock. Aside from the intake. I am planning on in stalling better flowing headers and electronic ignition and that is all. What make and size carb would best fit this application? I tried a q jet from a bb 425 but its way off. Local shops want 250 to rebuild/ jet / test it so i figured i might as well go with a new one.
My buddy put a holley street avenger 670 on the 400 in his Monte. He had a stock bottom end and heads, a performer rpm manifold and a stock hei. He ended up jetting it up a little bit but it ran strong for a bone stock engine. However, I bet the guys on here could recommend a cheaper way out. good luck.
Is your manifold for spread bore (Q-jet) or square?
The 750cfm Q-jet, properly prepared is perfect for this engine. Summit has an Edelbrock 9972 - Re-manufactured Q-Jet Carburetor for $359. It will, in all likelihood, need some jet tweaking, but you could try it out of the box and might be surprised. Once dialed in, the Q-jet has awesome performance and nothing sounds like those big secondaries coming to life.
If your manifold is a square bore, a Holley 4150 or an Edelbrock 750cfm would be good. The Holley will run close to $500 with manual choke. I like the Edelbrock 1411, available for $325 from a lot of sources. It's is an electric choke simple bolt on however, my experience has proven that they are a bit rich out of the box and you may need to go down a size on the rods and jets. Easy to do, but make sure you use new gaskets if you change jets.
My manifold is the q jet spread bore. How do i identify which q jet carb i have? it seems like the cheapest option at this point.
A properly set up and tuned Q-Jet will work great with your mild 400. Q-Jets are identified by the part number, on a pad behind the secondary throttle shaft.
A Q-Jet set up right will suport up to 500hp, the carbs on big cubed caddy'd and some big block chevy, Buicks and others are 800's which if you look down the front barrels you can tell the differnace, but you Don't need the 800 on a 400 sb, unless your got big horses.
What do you mean by "I tried a q jet from a bb 425 but its way off."
What did it do, and what did you do to it, that you say it's way off?
Did you just install a Q-Jet and then turned the air mixture screws, and the idle screw, and then quit? <---Q-Jet problem # 1
You are most likely to high on the idle ports. First make sure your timming is set right! Then set the idle screw front butterflies with the right feelers gage, start the motor and then set the air mixture screws to the highest vacuum, using a vacuum gage. If it runs to rich you most likely need to expoxy the plugs on the bottom of the fuel bowls. Which you should do any ways.
carb manuals ---> http://www.tocmp.com/manuals/Carbs/R...QJet/index.htm
Pat
Thanks for the info guys. I have played around with the carburetor, and ended up rebuilding it. The needle was not seating and fuel was coming out the plunger hole. After i rebuilt it, i installed it on the motor and tried to tune it. I can get it to run and idle, however it is very bogged down while idling. It has no problem revving, it just will not idle right. It has size 75 jets in it currently. Is this too big? do the jets affect the idle? Someone has been in this carb before and epoxyed all the apropirate places. The timing has also been checked and is good.
did you replace the float never rebuild a q-jet without replacing the float they absorb fuel and get heavy......ted
I did not replace the float, however i will as soon as i cn get my hands on one. Also it has jet size 72 in it not 75, my bad.
Q-Jet floats ---> http://www.carburetion.com/floats.asp
Other parts ---> http://www.carburetion.com/
Pat