Power Valve on a Holley 4160 |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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Posted: July-31-2010 at 8:21pm |
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Not certain i follow... |
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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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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Nice boat... |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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After reading Allen's posts and TR' posts a little more, and I followed a little more on Holley's website on the 4160, learned alot about power valves and it finally clicked.lol Holley says standard vacum levels on a stock 4160 carb can run anywhere from 8-12 and the 6.5 is just about right.
Yesterday fixed the valve and gasket with a 6.5 and boat ran real good. Had no probs or backfires. Fixed! |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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SS 201
Senior Member Joined: October-20-2003 Location: United States Status: Offline Points: 232 |
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The norm for the 600-650 Holley is 6.5 and for most of the carbs. True when you stab the throttle the vacuum drops however it doesn't stay there unless you are pulling a load. Also if you know your prop vacuum drop at what RPM that helps as each prop is different as each boat.
the starting numbers are a guide as everything else. While wide open throttle you probably will still have 2-3 inches of vacuum,, again depend on many variables, engine, CFM, timing etc you get the picture. To back up these theories put on a vacuum gauge and run the boat thru its paces. |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4945 |
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I'm just learning about carburetors myself, so take this with a grain of salt:
It sounds like, from what the guys have said above, that the higher number power valves, will open/add additional gas sooner on an acceleration curve. The lower number like a 2.5, will open later, further out on the acceleration curve. The guy from Holley was probably telling you that the 6.5 will run "richer" because in a sense it will, it's giving you more fuel sooner. Can you get a number off of your old power valve? If it was running fine and to your liking with that one for a long time, and simply got damaged, you're probably fine replacing it with whatever was in there. I think some of the other guys were saying you'd get a little more throttle response with a higher number. But, I'd say if a 2.5 was working good for you before, you're probably good with a new 2.5. Also, if replacing with the same PV doesn't fix it, then you can move on to something else to check, like ignition etc. If you change to a different power valve, you're kind of introducing new variables. |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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sure?
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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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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Never mind, got it... |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Well I am off to the lake tomorrow, but still have a question guys? After speaking with you on here, and emailing back and forth with Rick from Holley, he made me think twice about what I wuz gonna do. Install the 6.5 power valve, but he made a comment that make sure you have enough vacum at idle for that power valve. I, off course asked why and he said it will run to rich and run poorly. So I have no clue what power valve to put in there? I do not know my vacum is at idle, so does anyone have a suggestion to be on the safe side... "Pretty Please with sugar on top"... But off course I dont want it to run to lean neither...
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1985 CC 2001-SOLD
Lee Michael Johnson |
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trophyyride
Newbie Joined: July-30-2010 Status: Offline Points: 3 |
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Hi skicat. How can you handle it? I really love to see how can you do it. :D
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Andy,
I think I can handle that... Thank you kindly... |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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Waterdog
Grand Poobah Joined: April-27-2006 Location: United States Status: Offline Points: 2020 |
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For the first timer
Changing the Power valve. 1) Put some paper towels or a rag on the intake under the fwd bowl you'll spill 4 oz. ish of gas, pull the fuel line. 2) Remove the front carb bowl (4 long 5/16 bolts /screws) if you remove the top 2 screws first no fuel should come out (a simple check of the float set to high. 3) Remove the bowl (a tap w/ the HANDLE of a screwdrive maybe needed)with the bowl in your hand pump the accel pump lever (EASY) it should squirt a small amount of fuel that was in the pump, from the bowl. 4) Remove the metering block behind the bowl,(a tap w/ the HANDLE of a screwdrive maybe needed) note the jet size.(the P/V is screwed in on the back side) Putting it back together 1) There are 2 different types of P/V gaskets use the one w/ the new P/V snug it down but not tite. 2) MAKE SURE the carb body, metering block, and the bowl gasket faces are clean be don't gouge them up to get them clean. 3) Use HOLLEY blue gaskets there re-useable if you don't already have them. 4) The fuel transfer tube (fwd bowl to aft bowl) has o-rings on the ends. If the o-rings stayed in the bowls gently pull it out put a drop of lube on it and install it on the tube.( when i try to put the tube in the aft bowl w/ the o-ring in the bowl it's 50/50 if i cut the o-ring or not) 5) Install the fwd bowl by installing the fuel transfer tube, lift the accel.pump lever arm to clear the bowl and install the 4 bolts/screws JUST SNUG. 6) Re-install the fuel line 7) Start & pressure check It took longer to write it down than to do it. Truely it's not a hard thing to do. Hope i don't get blasted for leaving out a detail! |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Holley's web site says anything before 1992 |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Well, you guys made some strong points there. I heard from somebody else that if you smell exhaust fumes out the exhaust, the power valve has leaked or ruptured. But I dont know, I am probally going to change it anyways and just see what happens. I get a lake day next friday, can not wait till then. More though, probally gonna see if she does it again, and go from there.
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1985 CC 2001-SOLD
Lee Michael Johnson |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3333 |
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Any holley made since the early eighties do not need the PV check valve kit . Some models have it already, others have the throttle plate orifice resized smaller so that the pressure from a pop doesn't rupture the diaphram.
The problem of the PV rupturing every time the engine pops died with disco, unfortunately the myth lives on. |
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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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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Lee I don't know why but due to this statement from Holley,the check valve protects the powervalve
Features •Spring •Brass Seat •Check Ball •Protects Power Valve •Easy To Install •Proper Drill Bit Size w/Stop •Detailed Instructions |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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After reading more tonight, what causes this? A lean postion, bad fuel pump, or just a bad power valve? I seem to can not find a real answer...
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1985 CC 2001-SOLD
Lee Michael Johnson |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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I read on Holley, that is the first place to start, seen some of these guru's on here say the same thing. My mechanic said this as well, so I am going to start there and work from there. If it becomes too difficult after I replace the the PV, and she still farting, I guess I get to go pay my 125 hr and get her fixed right... |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Hey TR,
That makes since. In that 351 you are running, do you have big time specs in that motor? Myself, I have always had good throttle repsonce so wondering what is in mine. My fuel economy has always been awful. The 351 or 350's are quite thirsty on gas. I can easily burn a 1/2 tank of gas if I put a couple hrs on it in a afternoon. But I guess I wont know until I pull it. I like better throttle reponce on the low end. Long as if I put a 6.5 in there and dont damage anything else. |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4945 |
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I've seen backfiring associated with ruptured power valves on a few different threads on this site.
I still can't get a handle on whether the ruptured power valve is a cause of backfiring, a result of backfiring or potentially both? |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21113 |
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While this statement is completely true, Im not sure you (Lee) understand why. A stock engine, with its (relatively speaking) restrictive intake, heads and cam, will have no problem pulling a lot of vaccuum- and thus, no problem opening a 2.5 PV in a timely manner. Furthermore, stock carbs are generally on the rich side, so you stand little chance of leaning out the A/F ratio and causing damage. Thats not to say that if you were to install a 6.5 PV in a stock engine, that you wouldn't notice a slight increase in throttle response (and possibly a corresponding decrease in fuel economy). In a modified motor that breathes better (due to improved heads/intake/cam), you wont pull as much vacuum- and thus, might benefit from a higher PV that will open more easily. Personally, Im running a 7.5 in my 351w. |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Thanks Alan.. Well explained... Why did Chris imply that I needed a 6.5 power valve? But will check to make sure and put a 2.5 in there if that what is calls for.. Thanks
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1985 CC 2001-SOLD
Lee Michael Johnson |
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81nautique
Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5768 |
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So how do you set the carb at a certain level of vacuum? You don't. Also the power valve has nothing to do with the accerator pump. I'll try very briefly to explain. The acel pump is only one short squirt of gas immediatley at throttle up, picture hitting the throttle real hard, what happens? The butterfly opens and your air fuel mix goes incredibly lean and the boat stumbles. To counter that carbs incorporate an accelerator pump which gives a short burst of fuel to offset the additonal air and create a mix that can be burned. Your power valve hasn't even come into the picture yet. Your accel pump is used to adjust mixture at the low rpm of operation and the power valve is used to adjust mixture at the higher end of rpm. Power valve is probably not the correct term for what it actually does. It's function is to enrich the fuel mixture from approx 14:1 at normal running down to approx 12.5:1 at WOT throttle. This is done for a couple of reasons, one to make power but most importantly to protect the engine from running too lean at high rpms and burning a piston. The added gas actually cools the combustion chamber. That along with the correct heat range spark plug can save a high performance engine from self destruction. The power valve rating is just as waterdog stated. it is the vacuum at which the valve will open. The lower 2.5 number will open later and the 6.5 will open slightly sooner or at a lower rpm. As your engine gets put under a load and rpm increases the vacuum drops and your secondaries and power valve are actuated. I would say that a stock 240 hp 351 will be fine with a 2.5 PV. IF you stray from stock and more importantly increase your compression ratio and or max rpm range then you should perform plug chops and determine which power valve is correct for your application. Hope that helps a little but find a minute and pick up a holley tuning book, it will be money well spent. |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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I would have to agree.. Still trying to figure out here if I should go ahead and replace the power valve and prime gasket, or see if it backfires again.... |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Alan, Love those pics of the boat at the renunion.. After reading up on the power valve,does it not depend on vacum to the carb. When the carb is set at a certain level of vacum, then the power valve kicks in and allows enough fuel to pump in gives power to the accerlator pump. If you have a low power valve, it has to go below that point of vacum load and then the power valve kicks in. If I decide to put in a 2.5, my vacaum load my be different than others. What do you think? |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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Waterdog
Grand Poobah Joined: April-27-2006 Location: United States Status: Offline Points: 2020 |
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2.5, 4, 6.5 that # is the inches of vacuum it opens at. When at "cruse" idle, half throttle, 3/4 what ever steady speed, the engine is pulling pretty much full vaccum (over 10 in). So nail the throttle wide open (hit it) the vacuum drops to 0(zero)as the vacuum drops passed the number on the power valve the power valve opens and adds fuel. Ski boats engines need that quick throttle response so a higher number power valve advantagous. |
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81nautique
Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5768 |
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Come on Lee, what the heck settings are you talking about. That doesn't make any sense. Go online and do some reading to get up to speed on the Carb's components and their functions and then we might be able to help you. Didn't I send you a link a while ago with Holley basics, it's a good basic info read and worth your time. |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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I think my settings are set for a 6.5 power valve.
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1985 CC 2001-SOLD
Lee Michael Johnson |
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Chris4x4gill2
Senior Member Joined: August-25-2008 Location: Smith Lake, AL Status: Offline Points: 358 |
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I used a 2.5PV in my rebuild becasue that was what came in it.(89 SN) I talked at length with guys here and elsewhere about swapping ot the 6.5 but in the end decided to stay with the 2.5. Still have the 6.5 in the garage.
According to the Holley book I have, you can test to see if your PV is busted by tightening the fuel mixture screws on the side of the metering block all the way in with the engine running. If it dies, PV is good. If it continues running, PV is busted. go slowly and count the number of turns it takes to tighten them so you can put them back to the correct location afterwards. |
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skicat2001
Platinum Member Joined: November-24-2008 Location: Ft. Worth TX Status: Offline Points: 1950 |
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Thanks Gary.. Do not worry about the hijack, you are a friend of mine and so is Pete... I will use the thread you provided to help me down the road. Thanks! I apperciate everything.. |
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1985 CC 2001-SOLD
Lee Michael Johnson |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Steve gave me a pump for the horns I got from work but it would not power them,so after realizing all the parts needed to get them to work and the fact they would need a rechrome I bought these.They look really nice and are LOUD! Oh and don't forget my new wheel. Thanks for asking Pete and sorry for the hijack Lee.
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