edelbrock carb tuning
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edelbrock carb tuning

  1. #1
    Senior Member matt1840's Avatar
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    Default edelbrock carb tuning

    ive never really had to tune an eddy before. got my boat on the water yesterday and it runs great mid range to top end. olds 468 10:1 comp xe274h cam 1.6 rockers big port ka heads and 8 degrees adv at idle. dont know my time at 3k+ rpm twin 750s. outa the hole if i stomp it, it has a huge stumble then catches up on its own or if i feather the throttle. can you guys throw me some tips and or scenarios you have dealt with with edelbrock carbs.

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    Cas
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    It could be a couple of things- step up springs, float level, too rich or it could even be the length of the stroke for the accelerator pump.
    In order to check for the right step up springs, you need to use a vaccum gauge to find out what kind of vacuum it's pulling. Once you find that out, you can size the springs accordingly.
    Float level- pull the air horn assembly and adjust the floats
    too rich - time for playing around with the jets and metering rods
    accelerator pump adjust - the linkage for the acc pump adjustment is probably in the center hole of the pump arm. You can easily change that adjustment by moving the location of the linkage arm to a different hole.

    Here's the link to the Edelbrock carb manual-
    http://www.edelbrock.com/automotive_...ers_manual.pdf

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    Cas
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    oops, you should get the timing right before digging into the carbs. It would be best to set the timing to, I believe, 34º total advance all in by 3000 rpms. Where the initial timing is doesn't matter all that much.

    I'm not sure on the total advance on an Olds, can't remember back 30 yrs when I had one in my first boat

    Also, fuel pressure on the Edelbrocks shouldn't be more than 5.5lbs.

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    Senior Member matt1840's Avatar
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    steve its harder than hell posting from my phone gimme a buzz if u can. 916 802 5256

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    What the Hell is That? 72Hondo's Avatar
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    Matt,

    These things have to be babied to the extreme. They clog and get gummed up easily, the needle and seat assembly sucks (upgrade to the off road version) The factory float setting is off. You really have to take your time to tweak them.
    Quote Originally Posted by Kyle View Post
    Log off and go float, hang in the party coves, Show and shine on the trailer, fill up the boat, wax it, v-drive, jet, outdrive, and if you got a canoe and your reading this, you sir, need to phucking upgrade.

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    Senior Member matt1840's Avatar
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    ok so i got my mits on some needles, jets and springs for these carbs..

    Bog when i hit the throttle means not enough or to much fuel??

    i put the accel pump on the lowest setting and it seemed to help on immediate acceleration, but still a small stumble..

    I know im way rich on the low end so im going to lean that out for sure using the rods.. Im gonna try to lean out my carbs with just rods, hopefully not having to rip into the body and change jets.. See how lucky i get.. At about 3k if i give it all she has ive got a small stumble, so im sure i can fix that with the springs pretty much slow the rate the needles open, or speed it up.

    Beings ive got a tunnel ram im not really able to set the idle mixture screws using a vaccum gauge correct? What im hearing from a few guys i know with tunnel rams the vacuum readings wont be correct?

    Id really like to get my idle screws adjusted properly before playing with the rods/springs.. Right now ive got them at 2 full turns out and it idles pretty good, but if i press throttle barley it kinda chokes out a little before im fully on the primarys. Possibly to lean?? maybe 2 1/2 3 out?

    Trying to learn these carbs as ive never adjusted..

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    Half a bubble off jrork's Avatar
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    Matt,
    The link that Steve(Cas) posted up is a wealth of information and follow that thing start to finish and you'll get it.
    If you can, pick up a calibration kit and you'll have everything you could ever need.

    Good luck

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    Senior Member matt1840's Avatar
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    I printed that manual and ive completly read it twice.. today i reset the float height and drop the drop was off about 1/8" the height was prefect. reinstalled the tops, and went ahead and dropped in new metering rods. with leaned the mixture out 1 stage for cruise and power. If that does any good ill from there mess with the springs to lean it out a tad more.

    only problem is i have no way to pickup manifold vaccum to set idle mixture... Unless i can individually tune each carb with a vac gauge off one of the ports in the front? But ive got a tunnel ram so i dunno how thats gonna work.

    Otherwise im just guessing at watching tach and adjusting the mixture screws blindly...

    opinions on that?

    This is the chart for my carb.. stock settings are the dark #1 in the center.. I dropped my calibration to #19 depending how my plugs look after a WOT run i may bump it back up to 6 or 7 depending how rich i am in the top... I believe i can control how rich the cruise is messing with springs..

    Last edited by matt1840; 08-30-2009 at 11:55 AM.

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    Edelbrock are not the fastest to jump into secondaries, they work BASIC on the counterweight not full vacumn like Holley.So to play with the springs and rods are a very sensitive part of tuning. If you can find a active user to give you active tips is the way to go to save some BS.
    I remember after more BS I called and spoke with a carb tech and learned lots of things, They like everyone there are good techs and there are good techs.

  12. #10
    Senior Member matt1840's Avatar
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    A few guys i know through the years that have dealt with alota dual carb setups said to disconnect the secondaires and just run only on the primaries... what you guys say to that?


    Im coming to the conclusion i want different carbs.. either 2 450's or 2 eddie 500's..

    Expert opinions??? i leaned out one stage on cruise and power, and dropped to a weaker spring.. These plugs have 4-5 WOT passes on them.. I adjusted the floats, which were off outa the box which suprises me, and am at 3 turns out on the mixture screws... That gave me best idle, the vaccum gauge was reading 5 which is really low but no matter how much i adjusted the vaccum wouldnt climb... The holly regulator i have really bounces around at WOT. I looked back once and saw it at 8psi!!! which was giving me stumble at top end a bit.. Adjusted to 6 and WOT best it could be jumping and gained a bit of performance.. 4.5-5psi at idle..

    I have a slight dieseling issue at WOT shutdown still to rich or timing? im at 34 total at 3600.

    spanked the shit outa some jetskis today it was a bit amusing..


    Last edited by matt1840; 09-01-2009 at 08:38 PM.

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    Put a can of octane boost in the fuel, not for power, it will put a quicker color on the plug. There are so many additives takes lots of passes for color.

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    What the Hell is That? 72Hondo's Avatar
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    Matt,

    I would say dump the Eddies. I have been trying season after season with my 750's I'm done with them.

    I'm going to go the route of two 450's

    http://www.summitracing.com/parts/HL...6/?image=large
    Quote Originally Posted by Kyle View Post
    Log off and go float, hang in the party coves, Show and shine on the trailer, fill up the boat, wax it, v-drive, jet, outdrive, and if you got a canoe and your reading this, you sir, need to phucking upgrade.

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    Senior Member matt1840's Avatar
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    Quote Originally Posted by Btnhtillidie View Post
    Matt,

    I would say dump the Eddies. I have been trying season after season with my 750's I'm done with them.

    I'm going to go the route of two 450's

    http://www.summitracing.com/parts/HL...6/?image=large
    Are those a sideways or front to back mounting carb?

  16. #14
    What the Hell is That? 72Hondo's Avatar
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    It looks as of its a front to back thing. I'm trying to find more info on them. me personally i just don't like the look of a single carb.

    Does anyone have any info on these?
    Quote Originally Posted by Kyle View Post
    Log off and go float, hang in the party coves, Show and shine on the trailer, fill up the boat, wax it, v-drive, jet, outdrive, and if you got a canoe and your reading this, you sir, need to phucking upgrade.

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