BBC advance timing
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BBC advance timing

  1. #1
    Cole SS cole ss's Avatar
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    Default BBC advance timing

    What is best to use on a jet boat, a single, or dual stage advance curve for your ignition. Not sure what total advance to use. 454, 9.5 comp. performer rpm heads, bowtie/ rpm intake., comp cam XM270 cam. I am thinking a 34-36 degree total on premium gas. Trying to come up with the right starting point for my mild build. Any advice would be helpfull. Thanks

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    Senior Member riverrat4lfe's Avatar
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    My mechanic told me 35 degrees at 3000 rpm

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    Junior Member MikesB12's Avatar
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    What kind of distributor are you running? The Edelbrock heads have a more efficient combustion chamber than a typical GMchead (exception being the 990 casting GM Head).

    I would start with 36 total, check the initial and go from there. What kind of gas are you going to run?

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    Senior Member cyclone's Avatar
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    Have all the timing in by 2500 rpm or run a locked out distributor at full advance.

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    Cole SS cole ss's Avatar
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    I am running a mallory magnetic mechanical advance. I will be using 91 octanr gas. Thanks

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    Junior Member MikesB12's Avatar
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    As Cyclone said, ensure the timing is all in by 2500 or so. The biggest issue I had was making sure the mechanical advance is working as it should. My original Mallory was very sticky and sometimes wouldn't advance at all. A new HEI solved that for me. I ended up with 36 total and 14 inital, all in at 2800 RPM. Good luck.
    1989 Carrera 205 Elite Open Bow, Hardin 454, Berk 12JG. "Snake Farm".

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    Cole SS cole ss's Avatar
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    Did you do a single stage curve? What you did is kind of what I was thinking of doing. What kind of compression are you running?

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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by cole ss View Post
    What is best to use on a jet boat, a single, or dual stage advance curve for your ignition. Not sure what total advance to use. 454, 9.5 comp. performer rpm heads, bowtie/ rpm intake., comp cam XM270 cam. I am thinking a 34-36 degree total on premium gas. Trying to come up with the right starting point for my mild build. Any advice would be helpfull. Thanks
    Like said above all in at 2500 , depending on altitude 34* is likley a good start What distributor ?

  11. #9
    Cole SS cole ss's Avatar
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    My distributor is Mallory magnetic breakerless #5048201H. I think it was orginally set up for 24* advance. I plan to set it back to 24* with 10* or 12* intial timing. I do have the timing kit with springs and gauges. I"m thinking a quick single stage advance is the way to go. Thanks

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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by cole ss View Post
    My distributor is Mallory magnetic breakerless #5048201H. I think it was orginally set up for 24* advance. I plan to set it back to 24* with 10* or 12* intial timing. I do have the timing kit with springs and gauges. I"m thinking a quick single stage advance is the way to go. Thanks
    With no "data" on Mallory rates like those provided with MSD , you'll have to use a timing lite to determine if and when it goes to full advance throw in some light springs and try it ,when you indicate quick single stage advance not sure what your meaning?

  13. #11
    gn7
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    Quote Originally Posted by jetboatperformance View Post
    quick single stage advance not sure what your meaning?
    Because of the way a Mallory dizzy is built, you can use 2 different spring rates that bring in the advance in one or 2 stages. 2 springs the same color will create a single stage linear advance curve. 2 springs of different colors will create a spike, then a slower curve. It falls somewhere between useless, and totally useless, specially in a boat. May be SOME benefit to a tow vehical or high compression street engine. Not sure. Never messed with them. I think the idea is something like a vac advance in a fully mechanical advance mechanism. I guess

    Cole, either toss the lightest springs you have in it(PINK, grey or one of each), or lock the thing out.

    LINK: Mallory advance mechanism



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    Last edited by gn7; 07-02-2012 at 09:54 PM.

  14. #12
    Cole SS cole ss's Avatar
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    The change curve kit is what I have. At what rpm do most people set there idle at? The cam (xm270) is not a lumpy cam. I"m thinking 800rpm. Should I start my advance at that rpm or a little after. If I advance it to fast will it cause it to ping. I like the idea of having the total advance in the 2000 to 2500 range. I do have alum. heads, will that take more total advance? thanks again.

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    Senior Member jetboatperformance's Avatar
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    Just set the total running at 34* and rock it , if you know "how much and when" re the centrifugal advance the initial is sort of immaterial unless you expirience crank/start issues, starter "kick back" etc (not likley at that compression)

  16. #14
    Living in a cage of fear thatguy's Avatar
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    What Tom said. ^^^^^

    Mine is opposite of what you suggested a few posts ago.
    I used the lightest springs, and the biggest stop bushing for only about 14* total advance.
    Initial is 22*, all in to 36* at 2400 or so.
    MSD R2R Pro Billet.
    9.5:1, 91 octane, Brodix BB1, comp 302 hyd. Roller.

    If I put lake gas in I bump down to 34 with a scribe mark on the distributor.
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