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ok, i was setting up a procharger on my boat (502) , the carb i had for the system ran ok but was a bit lean in a few spots. i am having nickerson build me a carb, and will not have it for a week or so. i removed the carb box for the procharger system and replaced it with my old carb. i left the areomotive fuel pump i had installed for my procharger and just reduced the pressure to about 7-8 pounds. It starts, runs, and revs fine. As soon as I put it in gear( under load) it spits sputters, backfires and pretty much will not even run. if i do get it to stay running i can only idle, or a bit above or it backfires. what the hell is going on? did i knock a wire loose? i messed with different fuel pressures, but nothing helps. it would be a great running boat if i just never put in into gear. please give me some advise. if anyone out there has a msd ignition for sale for this 502 please let me know
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If your carb is set up for a pressurized blower box, it's not going to be jetted for normal atmospheric pressure.
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Well to start off...If you have backfired, and your powervalves are still in the carburetor..then they are blown! Hands down...it sounds like you need to pull those carburetors and tear them down for inspection. Replace the powervalves, and check your engine vacuum to make sure they are the correct valves for your motor.
Then jett accordingly!
Ty Lofstrom
Texas Performance Carburetors
sales@tpcracing.com
Originally posted by 502procharger:
ok, i was setting up a procharger on my boat (502) , the carb i had for the system ran ok but was a bit lean in a few spots. i am having nickerson build me a carb, and will not have it for a week or so. i removed the carb box for the procharger system and replaced it with my old carb. i left the areomotive fuel pump i had installed for my procharger and just reduced the pressure to about 7-8 pounds. It starts, runs, and revs fine. As soon as I put it in gear( under load) it spits sputters, backfires and pretty much will not even run. if i do get it to stay running i can only idle, or a bit above or it backfires. what the hell is going on? did i knock a wire loose? i messed with different fuel pressures, but nothing helps. it would be a great running boat if i just never put in into gear. please give me some advise. if anyone out there has a msd ignition for sale for this 502 please let me know
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the carb i have on there now is the one that was on the boat when i bought it and it ran great. what is involved with changing the power valves? so anytime i have a backfire it blows out the power valves? would bab powervalves be causing my problem of it running great until i put it in gear, or does this sound electrical
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Bad powervalves can cause fuel to dump into the carburetor, over-richening the motor. It will run like shit also. When the motor backfires, it pushs air up through the carburetor (and all air orifices) pushing this valves little rubber diaghragm out backwards (usually tearing it).It's real hard to visually check this valve, unless you have a checker. But new valves are about $7, and by the time you get to it (you know the main bearings, rods, pistons, theory) you might as well re-fresh (rebuild) this carburetor. Only because you remove all the gaskets but the baseplate to carb body. Just FYI.... Now if you have a device installed in the baseplate to prevent this, then you might be ok. But the only way to know is to take off the baseplate and look for a little nipple type thing with a check ball in it.
When the motor goes into drive...you place a load on it. This in turn creates a different vacuum reading then at idle. The power valves operate of engine vacuum (IE hg.) If the valve is the wrong size, or blown, it will just dump fuel into the motor...and bog (rich) it down. Or vice versa, it won't open when your accelerating (transition circuit) and your motor won't run right, until it builds enough vacuum to open that valve...then it's too late....you kicked and sputtered to get up on speed....so the valve is closed again, and your running off your boosters..."Smell what I am cooking?"
The powervalve needs to be 2.0hg less then the vacuum reading with a idle load. If not, then this powervalve won't perform likes it's suppose to. Then you have to re-jet again once this is all accomplished.
Time consumming I know....But that's why we like Hotrods and such! Right?
Originally posted by 502procharger:
the carb i have on there now is the one that was on the boat when i bought it and it ran great. what is involved with changing the power valves? so anytime i have a backfire it blows out the power valves? would bab powervalves be causing my problem of it running great until i put it in gear, or does this sound electrical
[This message has been edited by Hotcrusader76 (edited June 10, 2002).]
[This message has been edited by Hotcrusader76 (edited June 10, 2002).]
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hotcrusader, maybe you can throw some info my way. I'm having what was backfire, now seems like a stumble when boat goes over wakes. nickerson rebuilt carbs, have locked out dist, and still happened last weekend. 468 bbc w/ 420 mega bl. boat seems ok as long as flat water, but any wakes, bumps seem to cause problem. Could i have something other than fuel problem? I'm lost on this one. Like i said i had nickerson rebuild carbs and i locked out dist. at same time. Ran great 1st time out, then problems again. any info appreciated
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Originally posted by blowncarrera777:
hotcrusader, maybe you can throw some info my way. I'm having what was backfire, now seems like a stumble when boat goes over wakes. nickerson rebuilt carbs, have locked out dist, and still happened last weekend. 468 bbc w/ 420 mega bl. boat seems ok as long as flat water, but any wakes, bumps seem to cause problem. Could i have something other than fuel problem? I'm lost on this one. Like i said i had nickerson rebuild carbs and i locked out dist. at same time. Ran great 1st time out, then problems again. any info appreciated
If it is big wakes, fuel is splashing out of your float bowl vents and into the engine. Otherwise sounds like a loose wire to me.
[This message has been edited by Infomaniac (edited June 17, 2002).]
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Originally posted by blowncarrera777:
hotcrusader, maybe you can throw some info my way. I'm having what was backfire, now seems like a stumble when boat goes over wakes. nickerson rebuilt carbs, have locked out dist, and still happened last weekend. 468 bbc w/ 420 mega bl. boat seems ok as long as flat water, but any wakes, bumps seem to cause problem. Could i have something other than fuel problem? I'm lost on this one. Like i said i had nickerson rebuild carbs and i locked out dist. at same time. Ran great 1st time out, then problems again. any info appreciated
I will have to agree that it sounds like an electrical issue. Sounds like maybe you have a bad ground somewhere. Perform "continuity" checks on all your circuits, and look for some possiable opens while your shaking your wires with your hands.
If the check comes up negative, then go ahead and look into returning the carburetor for a re-inspection. Not to put down the carburetor builder, but if I was aware of your issue and I built the carburetors, I would want to see them again to cover my ass. It's just being courtious. It's not like you drive it everyday to work, and you couldn't be without a carburetor for 8-9 days.
Just my 0.02
Check the electrical, then ignition, and then fuel system...Sounds to predictable to be a carburetor...LOL
[This message has been edited by Hotcrusader76 (edited June 18, 2002).]
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Call your carb guy and see if he put in the spring to help the floats from being so senitive to side to side movement. Off roadfloat set up. I also think you have an electrical problem with IGN. for the rest of your running problem. You did not give any info on IGN system. I could give you some things to look at if I knew what your running.
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Originally posted by sgdiv7:
Call your carb guy and see if he put in the spring to help the floats from being so senitive to side to side movement. Off roadfloat set up. I also think you have an electrical problem with IGN. for the rest of your running problem. You did not give any info on IGN system. I could give you some things to look at if I knew what your running.
I would have to disagree on the "Off-road" Needle/seat/float set-up. Now if he was running off-shore style, then consider it.
You can suffice with the stock float spring assembly, but make sure you have that little spring installed!
But again I have to agree that you need to contact the carburetor guy and ask for his insight to the problem. Give him the option to over-look his build-up for you.
Good luck bro, and hang in there....it can be a headache sometimes!
Ty
