New to the jet boat world...455 olds question
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New to the jet boat world...455 olds question

  1. #1
    Senior Member neattouch648's Avatar
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    Exclamation New to the jet boat world...455 olds question

    Hey everyone! i just got my first jet boat! a 1973 Tahiti with a 455 olds and a berkeley pump!

    I'm new to the whole carburated engines thing and i can't seem to get it running right. One thing i noticed is there is no vaccuum line running from the carb to the distributor (its an HEI) Is this a bad thing?
    I figured it needed it so i put one one, now i have to re-time the engine but i can't even get it to idle anymore. Its backfiring into the carb. Even when i unplug the vacuum line (not having changed anything else) its not running right anymore....any help is appreciated!!
    Thanks,
    Gerrit!

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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by neattouch648 View Post
    I'm new to the whole carburated engines thing and i can't seem to get it !

    Welcome to PB forums I quoted this (above) because it occured to me that to alot of young people these contraptions (Carbs) are new and different, made me feel like a dinosuar


    re your Olds the backfire thru the carb could be a multitude of maladys from closed up/dirty points to a flat cam , start with basics , get a good compression tester and run a compression test you should see no more than 15lbs variation and around 125 psi cranking compression on all 8 cyls ,also keep the spark plugs in "order" and look at them for consistancy (color and deposits) more info and pictures would be helpful to make your diagnosis Tom

    re "vac advance" they have no place on a jet boat IMO , set you ttl timing around 32 to 36 all in at 2500 (depending on altitude and compression ration , fuel type etc )

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    Senior Member hihosilver's Avatar
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    x2 plug the vac line, if it has a alum. manifold get it running and spray wd-40 around base of carb and where manifold bolts to heads listening for rpm to increase this is checking for vac. leaks, the hei is alot better than points but check for dirt and corrosion under the wires and coil, look inside cap for cracks, the list goes on if that is not it

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    Senior Member 74glencoe's Avatar
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    Default Timing

    Timing was my problem when it came to my 455, but listen to the guys at jet boat performance, Tom and Josh have never steered me wrong. Get rid of that vacum advance. I timed mine at 16 degrees at 1500 rpm to get me out on the water and then fine tuned while on the water. The compression thing is cheap to check, I picked up a compression tester from sears for about 30 bucks that had everything needed.

    If I could go back I would have turned the motor over by hand and watched all the rockers with the valve covers off and looked for anything unusual (bad lobe in cam or stuck lifter). Good luck, Be careful, soon someone will catch you tying a belt around your arm and injecting high octane gas into your veins.
    Boating is nothing like cocaine, boating is much more addictive and results in bigger parties!

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    NW Spectraholic Malcolm's Avatar
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    Check you fuel system over good too, they will pop out the carb if they are running low on gas. The old tanks could be coming apart or full of muck inside and plugging the filter(s). One Olds problem (esspecially with a Q-jet) is not enough fuel pump. They usually starve at anything past 4500 rpm. An hp pump can be found at robbmc performance or you could go electric.
    Last edited by Malcolm; 11-04-2009 at 07:11 AM.
    Malcolm

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    Senior Member Texgo's Avatar
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    Just got my Olds motor running a couple of weekends ago. Mine was doing the same thing. It would start and run (bad), and not idle. I checked the timing and determined that I had the distributor on the right tooth. Finally I slipped a feeler gauge under the front of the carb between the base of the carb and the intake. There was a gap. I pulled the carb and put on a different gasket, and fixed the gap (vacuum leak) problem. Problem solved. I have a Q Jet on mine and it is not warped. It was the gasket. If you have a Q Jet, I wouldn't crank down on the mounting bolts too hard.

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    AKA OhOneWS6 Last Mohican's Avatar
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    I just locked out the vacuum advance on my HEI tonight. If you remove the vacuum advance unit you will see a boss with no hole. I drilled and tapped it for a 6-32 screw and then locked it in place with jam nuts. Here is a couple of pics so you can see how I did it.




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    Senior Member neattouch648's Avatar
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    okay, well i'll do that...why is it that they don't use the vacuum advance on boats? When i got the boat it didn't have the advance on it. Also, i noticed that on the carb (holley 650 4 barrel manual secondaries) during idle the primaries are giving a real nice spray of fuel and the secondaries are just dripping fuel down there. Its running rich and when i kill the engine, the secondaries keep dripping fuel until the pressure is gone. Like i said i don't know a lot about carbs but this doesn't seem right.

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    Senior Member 1975sleekcraft's Avatar
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    Quote Originally Posted by neattouch648 View Post
    okay, well i'll do that...why is it that they don't use the vacuum advance on boats? When i got the boat it didn't have the advance on it. Also, i noticed that on the carb (holley 650 4 barrel manual secondaries) during idle the primaries are giving a real nice spray of fuel and the secondaries are just dripping fuel down there. Its running rich and when i kill the engine, the secondaries keep dripping fuel until the pressure is gone. Like i said i don't know a lot about carbs but this doesn't seem right.
    your rear floats are not working, or are out of adjustment or there is something holding them open

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    Senior Member neattouch648's Avatar
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    I guess i'll take that part of the carb apart then...I would like to rebuild the entire carb, and i'm not worried about taking it apart and putting it back together but what i am worried about is tuning it after i have it back together....
    Thanks for all your help!!

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    Senior Member 74glencoe's Avatar
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    Default holley vs edelbrock

    I will probably catch hell for this, but Holleys seem to me to be over complicated with too many parts and hard to keep tuned. My buddies Holley is a PITA compared to my edelbrock. Many many posts in disagreement and mockery are to follow, but it is just my opinion.

    You might look into getting a rebuild kit for your carb. It will give you most of the parts you need to freshen it up and it will also help expose any problems and worn parts. an exploded view of your carb will help you understand it better and know what part does what, no matter how many internet pages you look at nothing like working on something will help you understand it better, . I would go ahead and pick up a float kit too. Better to freshen it up now while you arent trying to be on the water than have to do it halfway through a weekend. the water somehow always looks smoother while you arent on it.
    Boating is nothing like cocaine, boating is much more addictive and results in bigger parties!

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    Senior Member neattouch648's Avatar
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    i think i'll definately go pick up a rebuild kit...they're pretty cheap and then tear it apart and see what kind of damage i can do

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    Senior Member neattouch648's Avatar
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    Well....bought a holley rebuild kit and did it myself! haha it wasn't as complicated as i originally thought it was going to be and and i replaced everything that came in the kit
    It actually runs a lot better now but now i need to do the timing...which i'll do tomorrow and then take it to the lake and try it out on sunday!!!!
    wish me luck!

  16. #14
    AKA OhOneWS6 Last Mohican's Avatar
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    Have Fun. Be sure to report back with results.

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