SBC 5.7 vortec ??????????? please help
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SBC 5.7 vortec ??????????? please help

  1. #1
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    Default SBC 5.7 vortec ??????????? please help

    i got a used 5.7 vortec from a 96 tahoe and i got a nice intake from summit and a edelbrock 600cfm carb. iam running the mallory unilite marine dist. anyway i got it started up it run great. but going down the lake it would bog out when i nailed it in the secondaries.so after a couple burn runs up and down the lake adjustment after adjustment still no change.primaries everything fine seconds not so good.
    so here is what i have done. changed the carb,checked timing,new plugs, compression test which all cyl's look good,checked dist which is brand new,so iam stumped.so to give you a better insight here is what i've got..

    5.7 vortec totally stock bottom end and stock vortec heads.
    weiand dual plane intake
    edelbrock 600 cfm
    mallory marine dist
    carter elect. fuel pump
    stock roller cam ?????
    this motor is in a 88' miller 21' open bow with a omc cobra outdrive.

    any help with this would be greatly appreciated

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    you've gotta tdc the motor, if you're goin by the frt stock marks, they're not right, that's for initial crankshaft variation put a dial indicator thru the #1 plug hole and get the motor to tdc with it, then mark the balancer and retime it. those efi cams on carbs only like about 34* total timing.

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    Strap on the JATO konajet74's Avatar
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    My suggestion is to ck Edelbrock's website for the tuning
    on a Marine Carb. What carb do you have? Both the 1405
    & 1406 Edelbrock's are way leaner on the secondary side
    than the marine version's. Get the spec's from the website
    & re-jet your carb........

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    Quote Originally Posted by konajet74 View Post
    My suggestion is to ck Edelbrock's website for the tuning
    on a Marine Carb. What carb do you have? Both the 1405
    & 1406 Edelbrock's are way leaner on the secondary side
    than the marine version's. Get the spec's from the website
    & re-jet your carb........
    his timing is too slow, everytime someone uses the frt marks on the vortec 350's, that's gonna happen its to retarded now to hit on the secondaries

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    when i was running it up and down the lake i did advance the time a little each time slowly to the point of pinging then back it off a couple deg. could it be the stock cam. i was looking into getting a marine can befor summer
    Last edited by mvtile1; 01-26-2010 at 01:25 PM. Reason: added more

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    Quote Originally Posted by mvtile1 View Post
    when i was running it up and down the lake i did advance the time a little each time slowly to the point of pinging then back it off a couple deg. could it be the stock cam. i was looking into getting a marine can befor summer
    that's not timing it you either know it right, or not if the carb is a fresh 600cfm edelbrock and getting plenty of fuel pressure at wot, it should work just fine on a stock vortec 350, without any jet changes.

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    i agree on the timing thing, but it wouldn't get WOT. as soon as it started the sec.it bogged and sputtered.

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    what are some other possablitys. i did try a 800 cfm carb just to try it but it was the same thing.iam going to try the timing like you suggested. thank you very much for all yout input.

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    Senior Member ap67et10's Avatar
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    Quote Originally Posted by IMPATIENT 1 View Post
    you've gotta tdc the motor, if you're goin by the frt stock marks, they're not right, that's for initial crankshaft variation put a dial indicator thru the #1 plug hole and get the motor to tdc with it, then mark the balancer and retime it. those efi cams on carbs only like about 34* total timing.
    What the.....

    Tom, really??? why in the world would you say such a ridiculous thing?


    AP

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    Quote Originally Posted by ap67et10 View Post
    What the.....

    Tom, really??? why in the world would you say such a ridiculous thing?


    AP
    because the cam timing is slighty advanced in those motors i know them very well hyd roller with alot of advance already in the camtiming won't appreciate much timing from a dizzy unless the cam and timing chain has been changed. seems like the last time i tdc'd 1 of those on the stand the balancer was off almost 15* from tdc, that's why i was sayin to double check it.kinda like the ole bbf's how they'd jack with cam timing for emmission, same deal
    Last edited by IMPATIENT 1; 01-26-2010 at 02:04 PM.

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    just do a checklist while its runnin sick:

    look at the fuel pressure gauge while its sick, make sure it has at least 6-7psi

    put your timing lite on the balancer while its sick, make sure its not in the ignition system

    then i'd start lookin at the carb tune, but personally i've never seen a 600 edelbrock run lean on a vortec 350, generally to fat if anything.

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    what intake gaskets did you guys use? composite or the plastic replacement style?

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    Default By the way

    What altitude are we talking about? Where is this Vortec motor being asked to run? Generally, high altitude would affect both primary and secondary runability, but Impatient1 bringing up being too fat jogged my memory about N/A motors and altitude.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


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    Senior Member EVILFORCE's Avatar
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    Anyone check for fuel presure or did I miss that?
    No Fool Like A Old Fool is there?

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