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mkmiller

Holley Carb Floods at idle

I'm writing this post, so that it might help someone else out in the future. Because after hours of talking with

I recently purchased a 1999 Sportster LX, with the Indmar 5.7L Chevy Vortec 350 Engine and has a Holley 4150 600cfm, duel feed, double pumper with vacuum secondaries.

The previous owner had cracked the block and I had to rebuild the engine. After the rebuild I had all kinds of carburetor issues. The engine was running extreamly rich and would barely run at all power settings. I rebuilt the carbuetor and the engine ran much better but my secondaries would not open and could not achieve more than 2000rpm. I remedied this by replacing the small cork gasket on the secondary vacuum housing, that I had over looked during the rebuild. After, this the engine ran great for a couple hours and then I began to have flooding problems at idle. It was most noticable after I had applied power, got on plain, and would slow down back to an idle. The engine would flood out, black smoke would bellow out the exhaust, and you could see the excessibe fuel being spilled into the primary venturies.

To make a long story short, after rebuiding the carbuetor again, adjusting and re-adjusting the float levels over and over again, replacing the CARB with a new one, (a $500 expense) a friend of mine who is an old car racing carb guy told me to check my fuel pressure. I did what he suggested and had 17psi of fuel pressure coming into the carb. In case you don't know, this is fuel injection pressure on some engines and more that 2x the fuel pressure for a Holley carb. The self regulating Electric CARTER fuel pump was not regulating a 5-7 psi the way it was supposed to. I replaced the fuel pump, installed a permanent gauge on the fuel rail (for future monitoring) and engine has been running great. According to Holley and many blogs I have read, on a Holley carb anything ober 7.5 psi fuel pressure and you could start having irregular and intermittent carb problems as the excessive fuel pressure flows past the float needle seat and over fills the fuel bowls which will over flow into the carb.

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I'm writing this post, so that it might help someone else out in the future. Because after hours of talking with

I recently purchased a 1999 Sportster LX, with the Indmar 5.7L Chevy Vortec 350 Engine and has a Holley 4150 600cfm, duel feed, double pumper with vacuum secondaries.

The previous owner had cracked the block and I had to rebuild the engine. After the rebuild I had all kinds of carburetor issues. The engine was running extreamly rich and would barely run at all power settings. I rebuilt the carbuetor and the engine ran much better but my secondaries would not open and could not achieve more than 2000rpm. I remedied this by replacing the small cork gasket on the secondary vacuum housing, that I had over looked during the rebuild. After, this the engine ran great for a couple hours and then I began to have flooding problems at idle. It was most noticable after I had applied power, got on plain, and would slow down back to an idle. The engine would flood out, black smoke would bellow out the exhaust, and you could see the excessibe fuel being spilled into the primary venturies.

To make a long story short, after rebuiding the carbuetor again, adjusting and re-adjusting the float levels over and over again, replacing the CARB with a new one, (a $500 expense) a friend of mine who is an old car racing carb guy told me to check my fuel pressure. I did what he suggested and had 17psi of fuel pressure coming into the carb. In case you don't know, this is fuel injection pressure on some engines and more that 2x the fuel pressure for a Holley carb. The self regulating Electric CARTER fuel pump was not regulating a 5-7 psi the way it was supposed to. I replaced the fuel pump, installed a permanent gauge on the fuel rail (for future monitoring) and engine has been running great. According to Holley and many blogs I have read, on a Holley carb anything ober 7.5 psi fuel pressure and you could start having irregular and intermittent carb problems as the excessive fuel pressure flows past the float needle seat and over fills the fuel bowls which will over flow into the carb.

Where did you come accross a 4150 double pumper that has vacuum secondaries. When I was looking for one I could not find one that carried the marine specification. They were all mechanical. Was yours converted?

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I'm writing this post, so that it might help someone else out in the future. Because after hours of talking with

I recently purchased a 1999 Sportster LX, with the Indmar 5.7L Chevy Vortec 350 Engine and has a Holley 4150 600cfm, duel feed, double pumper with vacuum secondaries.

The previous owner had cracked the block and I had to rebuild the engine. After the rebuild I had all kinds of carburetor issues. The engine was running extreamly rich and would barely run at all power settings. I rebuilt the carbuetor and the engine ran much better but my secondaries would not open and could not achieve more than 2000rpm. I remedied this by replacing the small cork gasket on the secondary vacuum housing, that I had over looked during the rebuild. After, this the engine ran great for a couple hours and then I began to have flooding problems at idle. It was most noticable after I had applied power, got on plain, and would slow down back to an idle. The engine would flood out, black smoke would bellow out the exhaust, and you could see the excessibe fuel being spilled into the primary venturies.

To make a long story short, after rebuiding the carbuetor again, adjusting and re-adjusting the float levels over and over again, replacing the CARB with a new one, (a $500 expense) a friend of mine who is an old car racing carb guy told me to check my fuel pressure. I did what he suggested and had 17psi of fuel pressure coming into the carb. In case you don't know, this is fuel injection pressure on some engines and more that 2x the fuel pressure for a Holley carb. The self regulating Electric CARTER fuel pump was not regulating a 5-7 psi the way it was supposed to. I replaced the fuel pump, installed a permanent gauge on the fuel rail (for future monitoring) and engine has been running great. According to Holley and many blogs I have read, on a Holley carb anything ober 7.5 psi fuel pressure and you could start having irregular and intermittent carb problems as the excessive fuel pressure flows past the float needle seat and over fills the fuel bowls which will over flow into the carb.

Where did you come accross a 4150 double pumper that has vacuum secondaries. When I was looking for one I could not find one that carried the marine specification. They were all mechanical. Was yours converted?

They don't make one. It's either a four barrel with vacuum secondaries or it's a mechanical double pumper=dual accelerator pumps. I'm sure the OP has a Vacuum secondary four barrel carb on His Malibu.

Yeah , that was way too much fuel pressure and it was over powering the float needle so it wouldn't seat or close. A $30 fuel pressure regulator would've let you use that bad boy fuel pump.

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I'm writing this post, so that it might help someone else out in the future. Because after hours of talking with

I recently purchased a 1999 Sportster LX, with the Indmar 5.7L Chevy Vortec 350 Engine and has a Holley 4150 600cfm, duel feed, double pumper with vacuum secondaries.

The previous owner had cracked the block and I had to rebuild the engine. After the rebuild I had all kinds of carburetor issues. The engine was running extreamly rich and would barely run at all power settings. I rebuilt the carbuetor and the engine ran much better but my secondaries would not open and could not achieve more than 2000rpm. I remedied this by replacing the small cork gasket on the secondary vacuum housing, that I had over looked during the rebuild. After, this the engine ran great for a couple hours and then I began to have flooding problems at idle. It was most noticable after I had applied power, got on plain, and would slow down back to an idle. The engine would flood out, black smoke would bellow out the exhaust, and you could see the excessibe fuel being spilled into the primary venturies.

To make a long story short, after rebuiding the carbuetor again, adjusting and re-adjusting the float levels over and over again, replacing the CARB with a new one, (a $500 expense) a friend of mine who is an old car racing carb guy told me to check my fuel pressure. I did what he suggested and had 17psi of fuel pressure coming into the carb. In case you don't know, this is fuel injection pressure on some engines and more that 2x the fuel pressure for a Holley carb. The self regulating Electric CARTER fuel pump was not regulating a 5-7 psi the way it was supposed to. I replaced the fuel pump, installed a permanent gauge on the fuel rail (for future monitoring) and engine has been running great. According to Holley and many blogs I have read, on a Holley carb anything ober 7.5 psi fuel pressure and you could start having irregular and intermittent carb problems as the excessive fuel pressure flows past the float needle seat and over fills the fuel bowls which will over flow into the carb.

Where did you come accross a 4150 double pumper that has vacuum secondaries. When I was looking for one I could not find one that carried the marine specification. They were all mechanical. Was yours converted?

They don't make one. It's either a four barrel with vacuum secondaries or it's a mechanical double pumper=dual accelerator pumps. I'm sure the OP has a Vacuum secondary four barrel carb on His Malibu.

Yeah , that was way too much fuel pressure and it was over powering the float needle so it wouldn't seat or close. A $30 fuel pressure regulator would've let you use that bad boy fuel pump.

Here is the website I bought it from. It may not be a double pumper, but thats is what Indmar told me it was. I not a Holley carburetor expert and all this has been a learning curve. Your right, Holley does not show a 4150 on their website with vacuum secondaries and none of the part #'s on my carb match any of those on Holley's website. I called Indmar and they said Holley makes this carb for certain engine manufactures. I don't know if I believe that or not or if its even a 4150, but here the link to ebay and the company I bought the replacement. I'm not a carb guy and didn't think about too much fuel pressure being a problem. Most of my experience has been with FI motors where fuel Pressure is critical. The thought never crossed my mind. I checked that I had fuel flowing. The old carb was corroded extremely bad from salt water use, so at the time it seemed logical. As far as the $30 regulator fix. Bought two from the autoparts store and they would only put out 2 psi. These $30 regulator were only rated for an input psi of 10. My pump was spitting out 17psi and causing the regulators to malfunction. I bought a $44 dollar fuel pump rated at 5-7 psi from the autoparts store and everything worked fine.

http://cgi.ebay.com/ebaymotors/Holley-4150...essoriesQ5fGear

Edited by mkmiller

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Is your new pump that is working fine rated for marine use? Marine pumps have the vent hole for the diaphragm plumbed up to the carb so you don't leak any gas into the bilge should the pump fail. This is a very real issue. I have seen boats burn or heard of them exploding.

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Summit Racing sells the marine version Holley 600...

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I'm writing this post, so that it might help someone else out in the future. Because after hours of talking with

I recently purchased a 1999 Sportster LX, with the Indmar 5.7L Chevy Vortec 350 Engine and has a Holley 4150 600cfm, duel feed, double pumper with vacuum secondaries.

The previous owner had cracked the block and I had to rebuild the engine. After the rebuild I had all kinds of carburetor issues. The engine was running extreamly rich and would barely run at all power settings. I rebuilt the carbuetor and the engine ran much better but my secondaries would not open and could not achieve more than 2000rpm. I remedied this by replacing the small cork gasket on the secondary vacuum housing, that I had over looked during the rebuild. After, this the engine ran great for a couple hours and then I began to have flooding problems at idle. It was most noticable after I had applied power, got on plain, and would slow down back to an idle. The engine would flood out, black smoke would bellow out the exhaust, and you could see the excessibe fuel being spilled into the primary venturies.

To make a long story short, after rebuiding the carbuetor again, adjusting and re-adjusting the float levels over and over again, replacing the CARB with a new one, (a $500 expense) a friend of mine who is an old car racing carb guy told me to check my fuel pressure. I did what he suggested and had 17psi of fuel pressure coming into the carb. In case you don't know, this is fuel injection pressure on some engines and more that 2x the fuel pressure for a Holley carb. The self regulating Electric CARTER fuel pump was not regulating a 5-7 psi the way it was supposed to. I replaced the fuel pump, installed a permanent gauge on the fuel rail (for future monitoring) and engine has been running great. According to Holley and many blogs I have read, on a Holley carb anything ober 7.5 psi fuel pressure and you could start having irregular and intermittent carb problems as the excessive fuel pressure flows past the float needle seat and over fills the fuel bowls which will over flow into the carb.

Where did you come accross a 4150 double pumper that has vacuum secondaries. When I was looking for one I could not find one that carried the marine specification. They were all mechanical. Was yours converted?

They don't make one. It's either a four barrel with vacuum secondaries or it's a mechanical double pumper=dual accelerator pumps. I'm sure the OP has a Vacuum secondary four barrel carb on His Malibu.

Yeah , that was way too much fuel pressure and it was over powering the float needle so it wouldn't seat or close. A $30 fuel pressure regulator would've let you use that bad boy fuel pump.

Here is the website I bought it from. It may not be a double pumper, but thats is what Indmar told me it was. I not a Holley carburetor expert and all this has been a learning curve. Your right, Holley does not show a 4150 on their website with vacuum secondaries and none of the part #'s on my carb match any of those on Holley's website. I called Indmar and they said Holley makes this carb for certain engine manufactures. I don't know if I believe that or not or if its even a 4150, but here the link to ebay and the company I bought the replacement. I'm not a carb guy and didn't think about too much fuel pressure being a problem. Most of my experience has been with FI motors where fuel Pressure is critical. The thought never crossed my mind. I checked that I had fuel flowing. The old carb was corroded extremely bad from salt water use, so at the time it seemed logical. As far as the $30 regulator fix. Bought two from the autoparts store and they would only put out 2 psi. These $30 regulator were only rated for an input psi of 10. My pump was spitting out 17psi and causing the regulators to malfunction. I bought a $44 dollar fuel pump rated at 5-7 psi from the autoparts store and everything worked fine.

http://cgi.ebay.com/ebaymotors/Holley-4150...essoriesQ5fGear

That carb is a vacuum secondary but not a double pumper. It is easier on gas than a double pumper. Since it's a 4150 and not a 4160 it is also more tunable.

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This is great info. I am chasing a similar problem now.

Will you post a picture how you plumbed your fuel rail and pressure guage?

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Have 2001 sunkicker 5.7l carburated looking for electric fuel pump does it need to the Carter pump or is there alternative also looking to upgrade Carb any input would be great

Edited by malibu1538

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