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Question about 4150 mech secondary carb |
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nuttyskier2002 
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Joined: September-28-2005 Location: United States Status: Offline Points: 669 |
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 Topic: Question about 4150 mech secondary carbPosted: March-22-2007 at 2:56am |
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This question is mainly to 79 Nautique but I invite all who have experience to please chime in. I got a really good deal on a new Holley 4150 Mechanical secondary carb through e-bay. This carburetor is also a double pumper (has accelerator pumps on both primary and secondary sides). I am collecting parts for an upcoming mod to my 95 Malibu Echelon. It has a 5.7 Mercruiser Magnum (350 Chevy) rated at 265 HP. My mods will consist of Vortec heads (unported), Weiand 8121 Intake and a Comp Cams Extreme Marine camshaft (212/218 and .487/.495 w/112 lobe separation). My question is this: Will this carb provide decent fuel economy? I know mech secondary (especially double pumpers) aren't known for economy, but in theory they only use more fuel on acceleration, right? If this carb is tuned properly, can it deliver the same economy as a 4160 vacuum secondary? I'm looking for real world answers and experiences if anyone has them. 79, let me know if you have any other suggestions. Thanks! Brian
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95 Malibu Echelon w/Mercruiser 350 Magnum Skier
Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
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79nautique
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Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
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Posted: March-22-2007 at 9:07am |
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Double pump and fuel ecconomy. now that is funny, With the mech secondary's that might not be a bad idea, little easier to control when they are open or closed and could save some gas.
I like mech secondary's have heard pros and cons for marine applications, due to the loading of the motor, kinda like the dist and no need for vacum advance. your spec's look pretty good should be a decent up-grade. |
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Munday
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Posted: March-22-2007 at 9:55am |
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You can change or remove the plastic cam on the secondary accel. pump linkage to lessen or remove that fuel spray.I believe if you tune this carb to your needs it will be fine.I'm wondering how the dual power valve would effect
can you enlighten us on that Chris? Munday |
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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Posted: March-22-2007 at 4:48pm |
No such animal in typical 4150's |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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87BFN owner
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Joined: August-25-2006 Location: Ypsilanti, MI Status: Offline Points: 2194 |
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Posted: March-22-2007 at 6:14pm |
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nutty, didn't you read the box, right on the side it say not fuel economy friendly. Well that was what the box for my 750 double pumper sitting atop my built 400 in my truck says.
Not saying it's impossible, but not likely to be fuel friendly. When you drop the hammer it will respond though. 79 as long as it is a marine carb, I would think the mechanical secondaries would be ok. What are your concearns with the mech. secondaries. Always interested in new bits of info. |
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nuttyskier2002
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Posted: March-22-2007 at 9:40pm |
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This one's a 600 CFM. I knew before I bought it that it was a mech secondary. What I have learned since is that all 4150s that are mech secondaries are also double pumpers. I bought this one for a couple of reasons.
1) It was for a great price! 2) It has a secondary metering block which means it's easily tunable. 3)The float level is adjustable externally. It is a marine carb by the way. So, yes I bought something without knowing completely what it is. I'm just trying to decide which is my best option. Should I sell this one and get a 4160 and upgrade it with a sec metering block. Or should I try to use what I've got. Can I disable the sec accel pump and maybe bend the linkage between primary and secondary side to delay the secondary opening? Will this save me fuel or am I pissing in the wind? One more question: Is it better to use a carb with side hung vs. center hung floats? Are the center hung floats more sensitive to running angle? |
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95 Malibu Echelon w/Mercruiser 350 Magnum Skier
Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
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79nautique
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Posted: March-23-2007 at 9:37am |
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the side hung floats are better and less sensitive to engine angle, messing with the secondary accel pump is a waiste of time and will not help ecconomy. Adjusting the linkage for the sec to open later would help economy out some.
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JoeinNY
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Posted: March-23-2007 at 10:52am |
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If you have it, run with it. At least with mechanical secondaries its very consistent with where they open, you should know what rpm that is and realize when you are getting close to that line the ben franklins are about to start falling out of your wallet... I would adjust them to open as late as you can get away with without choking the poor girl off if fuel economy is your primary goal.
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Munday wrote: