Engine Popping?????
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Engine Popping?????

  1. #1
    jetboataholic HawaiianJet's Avatar
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    Exclamation Engine Popping?????

    I have an issue, but I don't know what's causing it. I think I either have a slight timing issue and maybe a carb issue. When I took the boat out yesterday, the highest I got the GPS to was 46 mph at a little over half throttle. When I try to give it more gas, it starts going pop, pop.......pop, pop, and the boat actually feels like it slows down a little bit every time it pops. The 46 was the first run I made, and everything after that I could only get it up to about 33 mph, then the popping would get worse. If I held my foot steady, it wouldn't pop, but if I tried to give it more gas, it would start popping. It's been doing this since the first day we put it in the water. I don't have a working tach (I think the tach is broken, we've wired it every way possible) so I have no idea what rpm I was running at. I'm "guessing" it's because we're setting the timing at idle (or with the engine off) instead of at RPM because we have no tach. But, I really have no clue. I checked the fuel/water seperator for water and there was only a tiny bit of water that came out, and the gas is all brand new 89 octane.

    I'm going to check the float level in a few minutes, and I'll let you know what I find.

    It is a BBC w/ a Mallory Unilite distributor (mechanical advance) and a Holley double pumper w/ mechanical secondaries (I think it's a 750).

    Thanks guys.
    HJ

    ***FOR SALE*** 1978 19' Full Stringer Hawaiian Molokai Jet Boat w/ Berkeley 12JC-AB and Chevy 440 Tall Deck ***FOR SALE***

    Quote Originally Posted by mako shark mark View Post
    Oh yeah, Forgot to mention that the hull is a special mixture of speedcote, herculiner and rain-x, all blended together- good for another 8 mph top end.

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  3. #2
    Cantard 71hallett's Avatar
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    Popping intake or exhaust?
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    jetboataholic HawaiianJet's Avatar
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    Quote Originally Posted by 71hallett View Post
    Popping intake or exhaust?
    I think exhaust.
    HJ

    ***FOR SALE*** 1978 19' Full Stringer Hawaiian Molokai Jet Boat w/ Berkeley 12JC-AB and Chevy 440 Tall Deck ***FOR SALE***

    Quote Originally Posted by mako shark mark View Post
    Oh yeah, Forgot to mention that the hull is a special mixture of speedcote, herculiner and rain-x, all blended together- good for another 8 mph top end.

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    Cantard 71hallett's Avatar
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    Quote Originally Posted by HawaiianJet View Post
    I think exhaust.
    Start turning the distributor counter clock wise.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  7. #5
    Cantard 71hallett's Avatar
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    Timing gun is always the answer. Then you can rule out that option.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Cantard 71hallett's Avatar
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    Was just thinkin. lol if you are not sure of the pop and cant say it is exhaust or intake it is prob more like fuel. internal pop?
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Senior Member wajetboy's Avatar
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    you shouldnt need a tach to set your timing just bring the rpms up until it stops advancing.
    1978 Southwind Tunnel Dragster/1980 SWTD center steer

  10. #8
    jetboataholic HawaiianJet's Avatar
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    Quote Originally Posted by 71hallett View Post
    Was just thinkin. lol if you are not sure of the pop and cant say it is exhaust or intake it is prob more like fuel. internal pop?
    You mean bad fuel? Or not enough fuel or something like that? The fuel is new. I'm going to go check spark plugs, to make sure that all the cylinders are burning properly, and that none of them are running lean or something like that.

    Thanks.

    Quote Originally Posted by wajetboy View Post
    you shouldnt need a tach to set your timing just bring the rpms up until it stops advancing.
    How do I know when it stops advancing? I don't know much about this stuff.

    Thanks.
    Last edited by HawaiianJet; 10-17-2008 at 11:09 PM.
    HJ

    ***FOR SALE*** 1978 19' Full Stringer Hawaiian Molokai Jet Boat w/ Berkeley 12JC-AB and Chevy 440 Tall Deck ***FOR SALE***

    Quote Originally Posted by mako shark mark View Post
    Oh yeah, Forgot to mention that the hull is a special mixture of speedcote, herculiner and rain-x, all blended together- good for another 8 mph top end.

  11. #9
    Senior Member H20MOFO's Avatar
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    If your r's go up and the mark doesn't move your advance is all the way in.
    Another Hot Boat refugee

  12. #10
    Boat Nut sleekcrafter's Avatar
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    How did you break in the cam? I assume it's a new motor, right?? Cam break in is crucial, to avoid a cam lobe, or cam lobes to go flat.
    Upper Midwest Power Boat Association
    DRAG BOAT RACING UMPBA #926


  13. #11
    cfm
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    Quote Originally Posted by HawaiianJet View Post
    How do I know when it stops advancing? I don't know much about this stuff.

    Thanks.
    With a timing light being used, as you rev the motor slowly faster, the timing mark will stop moving at some point. This point is where your max timing is and where this rpm is.

    A slight interuption based on what I see your knowledge level is and want to figure out stuff:

    Go to your local Borders or Barnes and Noble. In the 'Transportation' isle you will find many books on engines/engine building. From 'How to Hotrod your BBC' to 'How to build your BBC' to 'Holley Carb modifying' to 'Ignition Systems' to 'Carbs and intake Manifolds' on and on and on.

    Yes, true way to get more knowledgeable is hands on as your doing, but the more info you know the faster the hands on knowledge will happen.

    You'll be hard pressed to find any mid level and upper level tuners not having any books.

    If you aren't near either store they both have online stores.

  14. #12
    jetboataholic HawaiianJet's Avatar
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    Quote Originally Posted by cfm View Post
    With a timing light being used, as you rev the motor slowly faster, the timing mark will stop moving at some point. This point is where your max timing is and where this rpm is.

    A slight interuption based on what I see your knowledge level is and want to figure out stuff:

    Go to your local Borders or Barnes and Noble. In the 'Transportation' isle you will find many books on engines/engine building. From 'How to Hotrod your BBC' to 'How to build your BBC' to 'Holley Carb modifying' to 'Ignition Systems' to 'Carbs and intake Manifolds' on and on and on.

    Yes, true way to get more knowledgeable is hands on as your doing, but the more info you know the faster the hands on knowledge will happen.

    You'll be hard pressed to find any mid level and upper level tuners not having any books.

    If you aren't near either store they both have online stores.
    Ok let's see if I understood this correctly. When using a timing light, are the numbers (on the damper) supposed to jump around a lot at idle, then as the rpms go up, the numbers will settle down, until only one number shows up, and that is the total timing? Am I close?

    Yeah, I've thought about going out and picking up some books, a few times. It's just that books can be expensive. I'm definitely going to go get a Holley carb book though, now that I've gone ahead and started taking apart the carb. Just the bowls guys, nothing serious. Cause I just don't want to screw anything up, especially on the carburetor.

    I've also received some good information and ideas on my other thread, in the jet section. If you haven't seen it, here's a link.

    Hawaiians on the Water

    Thanks guys. I'll get this thing figured out and running right, eventually.

    HJ

    ***FOR SALE*** 1978 19' Full Stringer Hawaiian Molokai Jet Boat w/ Berkeley 12JC-AB and Chevy 440 Tall Deck ***FOR SALE***

    Quote Originally Posted by mako shark mark View Post
    Oh yeah, Forgot to mention that the hull is a special mixture of speedcote, herculiner and rain-x, all blended together- good for another 8 mph top end.

  15. #13
    Or Seth, either one Budweiser's Avatar
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    Timing should always remain stable, no matter what rpm. And yes, it will finally max out somewhere between 2000 and 5500 rpm, depending on the weights and springs in the mechanical advance mechanism. Most will say it should be tuned (by changing weights and springs) to get max advance right around 2500rpm.

  16. #14
    Senior Member H20MOFO's Avatar
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    Default Timing

    Hey HJ At idle mine will jump around a little. when I said quit moving, I meant in relationship to the pointer. So in other words as your r's pick up your timing will chance because of the advance mechanism. Do you have access to a dial back timing light? That is the only way to find your total other than timing tape and everytime I've ever tried to use that shiat it just flys off. If you want I could give ya my ph#.
    Another Hot Boat refugee

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