air fuel screws
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=3566
Printed Date: November-15-2024 at 5:13pm
Topic: air fuel screws
Posted By: woodboy
Subject: air fuel screws
Date Posted: May-14-2006 at 3:59pm
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Any one know a good baseline for adjusting the screws on both sides of a holley 4160 carb? This is on a 79 commander 351W. It seems to run best 1/4 turn on spotter side 1/2 on driver side. Seem way lean to me but anyting else is rich enough to make your eyes water. The boat did backfire this spring. Could this be a compensation for a shot powervalve. I need a carb doctor. Thanks Rob ------------- Lake Livin' Rocks |
Replies:
Posted By: jameski
Date Posted: May-14-2006 at 10:31pm
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Yes Rob, that does sound too lean for your idle enrichment screws. The typical baseline is 1.5 turns off the seat. Your diagnosis of a shot power valve sounds right on. If you haven't done a full rebuild in a while, then you might want to go ahead and get a full kit. ------------- current boat http://www.correctcraftfan.com/diaries/details.asp?ID=1977 - 94 Sport Nautique previous boat http://www.correctcraftfan.com/diaries/details.asp?ID=601 - 78 Martinique |
Posted By: GottaSki
Date Posted: May-15-2006 at 8:36am
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That setting is not lean, its rich.
Else I agree with james something else is amiss. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: john33617
Date Posted: May-15-2006 at 12:36pm
| backfire = blown power valve |
Posted By: Tim D
Date Posted: May-15-2006 at 1:36pm
Holley + backfire = you need a new power valve.
power valve is # 40 ------------- Tim D |
Posted By: 88skisupreme
Date Posted: May-15-2006 at 5:50pm
Is that starting with it screwed all the way in? 1.5 turns counter clockwise? |
jameski wrote:Posted By: skyhawkflyer
Date Posted: May-15-2006 at 6:26pm
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Correct, lightly seated, then counter c/w 1.5 turns... that should work out pretty close.
Items 40 & 41 are the power valve. There's been lots of discussion and heated debates about what number (relating to vacuum drop)to put in with regard to when the power valve opens and supplies additional fuel. The guys on the board have been saying that some of the marine carb kits have been coming with a 2.5 power valve, and seems to work ok. Others, Correctcraft, and myself highly recommend the 6.5 for a better holeshot from a dead stop used on a 4160/351 setup, I noticed a much better holeshot going to the 6.5. You should put in an entire kit, but that's up to you, a PV may be all you need. Chances are you won't get that fuel bowl and metering block off without destroying the gaskets though. |
Posted By: skyhawkflyer
Date Posted: May-15-2006 at 6:46pm
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Also:
If you have springs on the bowl bolts then replace with a bolt kit from Discount Inboard Marine. Shorter bolts using washers for better bowl torque down. Items 19 & 20 (x 8). Pay close attention to your float levels, and don't change them if your boat ran good. They both may be the same, or your rear float may be set lower than the front float. Put in the new needles and seats and set them the same as they currently are. Soak your carb in laquer thinner and the gaskets nearly disolve and it doesn't hurt the finish, don't scrape gaskets with a screwdriver, instead use something such as a plastic knife and sharpen and shape it on a grinder. Pay attention to detail and you'll be fine! |
Posted By: Derby
Date Posted: May-16-2006 at 1:56pm
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skyhawkflyer,
I'm in the process of closing my carb up. It appears as I had a 3.5 PV originally and the kit came with the 2.5 PV. Can you buy just the valve somewhere? More pressing is the length of the valve. The spring seat on the end of the shaft seems to be threaded on quite a few more turns on the existing PV. I can’t see a way to make the new one the same size with out ripping the diaphragm. Any ideas, or is this what makes 3.5 a 3.5? Thanks for you help. The first rebuild is going super smooth....so far. ------------- So It Goes! |
Posted By: GottaSki
Date Posted: May-16-2006 at 2:53pm
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Jegs, p/n 510-125-65
8 bucks. Most opt for the 6.5. I've used up to an 8.5 with excellent results. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: skyhawkflyer
Date Posted: May-16-2006 at 10:30pm
| When installing hold the pv between your thumb and pointer finger with the small end pointed up. Put the gasket on the valve and center it. Hold the pv still and spin on your metering block until the gasket is seated. This way your gasket wont get off center and cocked-causing a leak. Torque to 80 inch lbs and your done. Ahh, maybe it was 50 inch lbs? I can't remeber, does anybody out there know off hand? |
Posted By: skyhawkflyer
Date Posted: May-16-2006 at 10:52pm
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I found this:
Power valve: If you have to change the power valve then use an adjustable wrench or socket. Place in a vise with wood on each side of the vise jaws so you don't damage it. Tighten to the following specs. For power valve with multiple drilled fuel opening, torque to 40-50 inch pounds. For power valve with 2 rectangular fuel openings, torque to 100 inch pounds. |
Posted By: fredo68
Date Posted: May-17-2006 at 2:45pm
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sounds like a power valve...
but woodboy doesnt have a torque wrench. ha ha fredo68 ------------- fredo68 |