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Thread: Too small a carb?

  1. #1


    This is about my new Magical 427 Tall Deck motor. I put on an Edelbrock Performer w/ manual chocke. When I drive the truck (hot or cold) I have to have the choke closed about 1/4 of the way for it to run right.
    If not it bogs down. I tested this throughtout a 2 hour drive that ranged in rpm from 500 to 3000.

    Barry told me that a 600 cfm carb was too small- is this what he meant?

    Also, does anyone know what this motor times out at? I have it at 6* btdc, but the starter drags when the motor is hot.

    And on some side info- it ran at 175* all day and didn't leak a drop. The exhaust pipes that Ben threw in and that I stuck on made the truck run quieter than my '99 GMC. I could finally hear my tires hum.


  2. #2


    B, how do you have your starter wired? Also where are your battery cables attached? This can make a big difference in how a Chevy starts when hot.

  3. #3


    My starter has the main feed straight from the battery. The solenoid feed comes from a pushbutton that feeds from the battery.
    I never had any trouble with the starter before when it was on a 350. Are you saying that the timing is right and that I need to examine my starter?


  4. #4


    You may need a shim under the starter. That should cure the drag problem.

    Is this the Performer from the trash pile? That may answer some questions on that. If not, you may need to fatten up your jetting a bit, at idle, a 427 is going to take a bit more fuel than the 350 did. You won't notice a big problem with the 600 until upper RPM's, which is not a TD427 strong area anyway. For grunt and low RPM power, the 600 will be fine.

    Timing, you should be somewhere from 6-10*, that will be a trial and error thing, but should be pretty close.

  5. #5


    Thanks Jesse! It runs anywhere in that timing range, but I was afraid to get it too far from TDC. Is it that I go farther from TDC to make it stop the backfiring (it pops when I'm coasting)? I had it at about 10* and it was getting hot, so I backed it down. The motor was set at 6* when I got it.

    The carb was the one I was running on my 350, but when I got the truck on the road and goosed it and it bogged I assumed that mabye the carb had a needle clogged and so I swapped it out with the one that I got from the trash pile. Same thing. I noted that when I took the carb off and turned it over the gas that ran out onto my hand was about boiling hot. I think I need to add a spacer.

    I only wanted to take it up to about 3K rpm's. It worked alright, but when I tried to stomp it it bogged. You think that's the jets?


  6. #6


    The Performer on my 350 does the same thing. I am planning on Re-jetting it, I bought it used from a guy that was running a mud dragger with a 383. I'm guessing mine is flooding, due to the mild nature of my 350, compared to an all out hi rpm 383. It also could be the accelerator pump is not giving you enough of a squirt to get it up in the Rs. I'm not sure if its adjustable, but it seems like it has 2 holes in it.

    What dizzy are you running? Did you swap the HEI in from the 350? You may need some different springs and weights to go with the BB, not sure on that one. If you didn't, do it now!!!

  7. #7

    Default Turbo 350 question???

    Yup, I swapped the HEI in there. It's springs and weights are set up to get all the advance in by 2500 as I plan to stay around that RPM as a max.

    I do have the 3 holes in my accelerator pump....and it's on the middle one. I hear about the jets alot, but no one really seems to know for sure if a bone-stock 427 that never planst to see 3500 rpm will work with the stock jets.

    HEY! If you need new jets for your Edelbrock, e-mail me as I have a complete stock 1406 that you can have the jets out of.

    I think I may call the Edelbrock help line and tell them my tale of woe.

  8. #8
    Join Date
    Dec 2003
    Giddings, Texas


    Like with your overheating last summer. The choke when used will add more fuel to the mix. It does this by restricting the air entering the carb. If you need the choke to make it run right, then the above post are correct, you are running lean. The Edelbrock you bought new came with a book. Inside the book is a chart that shows you what jet and needle combination to use for different size engines. It also tells you what to change to get the desired combination. Take the needles and jets out of both carbs and see if you have the needed parts to richen it up. If you don't, look in the book, call your buddies at Jegs up and order what you need.

    How did you run the exhaust to the back?

    I was planning on making mine come out the side until I was driving it after a heavy rain the other day with the top off. Everytime I hit a puddle, steam from water hitting the exhaust would come between the cab and bed and into the cockpit. I don't think I want to live with exhaust doing that all of the time.
    Remember if you didn't build it you can't call it yours.

    6.2 powered M715, 5 M1009's, M416, 2 M101's, 2 M105's, 3 M35's, M1007 6.5 turbo Suburban project called Cowdog.

  9. #9


    What are the stock jets supposed to be? I can tear it down and check them out, see if my theory is any good. I'm trying to get the truck ready to go to the Badlands for Memorial day.

  10. #10


    It's very important for the solenoid start wire to have as much voltage as possible in a hot start situation, the way you're hooked up should be fine but might be worth checking the voltage anyway. Also make sure your negative cable is attached directly to the motor, this can make a big difference.

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