timing issues ?
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timing issues ?

  1. #1
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    Default timing issues ?

    im running a small block 383, world heads, 750 cfm carb and msd hei ignition. im getting popping at idle, and back firing at mid throttle. runs fine at full throttle but major hesitation at half throttle. is this a timing issue or should i look in another direction ?

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    gn7
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    You came on here asking about a potential timing problem, without giving the current timing? Or don't you know it?



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    i do not know my current timing. i will be timing it tomorrow so i will have a number to go off of.

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    well my timing light took a shit, but i did find this...

    it was back firing and missing alot last saturday at mid throttle and at idle. at wot its fine, but struggles to plane out. this might explain the horrible gas mileage and spark black plugs.

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    Dont want to seem "alarmist" but that type of complaint of "popping" particularly at idle and part throttle coupled with that black soot in the airhorn of the carb would make me want to pull the valve covers and crank the motor by hand to observe the all valve action checking for potential valve spring and cam issues Tom

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    Verify the firing order...............Just sayin'...I don't care if you think it's "running good" at WOT.

    Either something is broken internally on the heads, or you have two shock noodles in the wrong hole.
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    Quote Originally Posted by jetboatperformance View Post
    Dont want to seem "alarmist" but that type of complaint of "popping" coupled with that soot in the airhorn of the carb would make me want to pull the valve covers and crank the motor by hand to observe the valve action checking for potential valave spring and cam issues Tom
    like tom said or the timing chain

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    this is sounding like a bigger problem than i thought i had. so the cam could be wrong for the heads i have? i was told they are "world heads". the guy i got it from said he switched cams to a less agressive cam. i have the cam papers, but nothing on the heads. im going to replace the plugs and wires, make sure the plugs are right, and see what i get. whats this about the timing chain? stretched out, skipped a tooth?

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    Quote Originally Posted by jeffz0rz View Post
    this is sounding like a bigger problem than i thought i had. so the cam could be wrong for the heads i have? i was told they are "world heads". the guy i got it from said he switched cams to a less agressive cam. i have the cam papers, but nothing on the heads. im going to replace the plugs and wires, make sure the plugs are right, and see what i get. whats this about the timing chain? stretched out, skipped a tooth?
    A "flat " cam or broken valve spring etc could cause a "stacato" rythemic "tat tat tat" depending poping on I or E

    * so would a switched plug wire BTW but different sound and action

  12. #10
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    Don't paint the devil yet. Pull the valve covers.

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    there is nothing rhythmic about the popping. if i advance the timing it almost stops, just a random pop now and then. but thats no fix. the idle smooths out but there is no power. would incorrect timing, and wrong jetting cause this by any chance? the boat did come from colorado and is now here in san diego. not sure if that could have an effect on the backfiring.

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    Do your'e self and wallet a favor and do alittle simple analysis before throwing money at it! Compression check-timing check-firing order and so on. Off the top without a visual I would lean towards a carb issue, verified by you saying it runs better at wot. At wot the carb tune PARTIALLY becomes less of an issue for the symptoms you describe, also the fact that it runs better when you throw a butt-load of timing at it! One last ?--Have you had it in the water prior with no problems at this altitude?

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    Like what has been alluded too, popping thru the carb means intake side of the engine problems.

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    i have only had the boat in the water here in san diego. never anywhere else. i do not know how it ran in colorado. correct me if im wrong, but if there is soot in the carb from it back firing, that means a cylinder is firing before one (or more) intake valves are closed completely, correct? im performing a compression test, verifying the firing order, and hopefully setting the timing this afternoon so this should eliminate a few possibly culprits in the process like many of you have suggested. after that i will turn my attention toward the carburetor.

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