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Discussion Starter #1
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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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 :D


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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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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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.
 

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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.
 

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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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Discussion Starter #8
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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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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Discussion Starter #10
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!!:)hand
 

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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.:):)punch 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.:)hand
 

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Discussion Starter #12
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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Discussion Starter #13
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!
 

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For all you boat guys not familiar with oldsmobile/hei/vacum advance problems...olds distributors pull a lot of degrees with their vacuum advance units and the pickup wires tend to break...so if you connect the vacuum advance and the motor takes a shit...disconnect the vacuum advance, it won't do anything in a boat anyway..the only time there is enough vacuum to pull it is when ya chop throttle...and do fix the pickup wires, one is broken and it will leave you floating somewhere
 

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Discussion Starter #16
So...i have good news and i have bad news haha!

The good news is the engine runs! had power for a while and sounded great!!!! once you killed it it would start right back up so no problems there! about 15 minutes into cruising around the lake today it started making an odd noise...It sounded as if one of the push rods was bouncing up and then down and so on...took the valve covers off and all the rods are just how they're supposed to be...

It sounded as if it came from inside the flywheel cover but i pulled the engine out and found nothing....does anyone else have any idea what could be making the noise?

At idle it only occurs maybe three of four times in a minute but at 4000rpms its a constant

Thanks
 

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ANY "odd engine noise" would be a huge concern IU would run a manual oil pressure test , cranking compression test and cylinder leakdown for a "base line" Call if we can help Tom
 

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its been a while since my old 455. mine had some plugs to block the crossover on the intake manifold when i went from cast to aluminum and sometimes they would rattle.
 

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Discussion Starter #20
I pulled the engine out and can't see anything wrong on the outside....nothing wrong inside the flywheel cover so i'll pull off the oil pan tomorrow and see if anything is bad down there. I'm thinking a piston rod bearing could cause that noise but we'll see.

while i'm doing that i'm going to replace the intake manifold to head gaskets cuz its leaking a bit of oil there....and since i'm pulling that off i might as well take the heads off and see what the cylinders look like....haha guess i'm in for a rebuild :) haha
 
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