Power valve |
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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Posted: February-02-2011 at 1:23pm |
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85' 2001 ford 351W I pretty sure I blew out my power valve due to having the timming way off after replacing the distrbutor and a big backfire . I turn the air mixture screws all the way in and nothing ...
Heres the question looking at previous post theres a lot of debate on which valve to use I think I am going to settle for the middle ground for 4.5 I could not get a clear answer here. Also should I put in the ball valve to prevent the power valve from blowing out again ? I will need the fuel bowl and metering block gaskets any others ? What is the bore spread for the bottom gaskets ? thanks again DC |
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Waterdog
Grand Poobah Joined: April-27-2006 Location: United States Status: Offline Points: 2020 |
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Holley blue gaskets are best.
The power valve has nothing to do with a blocked idle circuit. When you hammer the throttle and the boat stumbles you have power valve troubles. (blown or wrong # P/V) |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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No,he's right he's got a bad power valve.
Here's right from Holleys site- If you have a carburetor older than 1992 (or you have experienced an extreme backfire) and expect a blown power valve, use this simple test. TEST: At idle turn your idle mixture screws (found on the side of the metering block) all the way in. If your engine dies the power valve is not blown. Here's a link to a previous discussion about power valves |
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horkn
Platinum Member Joined: September-10-2007 Location: Cedarburg, Wi Status: Offline Points: 1511 |
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That's what I would say as well. IIRC, I used a 6.5 PV, and that's what most of these came with. I had a PV on my CC that had the slightest pin hole leak in it that made it act like the needle was not seating properly. Mine would however not fail the idle screw test..... |
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78 martinique- refloored, reinforced, stringers re glassed, re engineered interior
GT40P heads Edelbrock Performer intake acme 4 blade http://img.photobucket.com/albums/v64/horkn/fish/nautique.jpg |
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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Any ideas on the check ball valve to keep it from happening again I guess I will go with the 6.5 I think the rebuild kit had a 2.5
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Well I put one in mine after I popped a valve a couple of years ago,haven't had a backfire to try it yet You might as well put one in since you have it all apart.
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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is it difficult ? it look like it comes w/ a drill bit what is there to drill ?
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Here is Holley's instructions.Holleys kit is nice since they do provide a drill stop where some of the cheaper kits don't so you have to be careful not to drill too deep.
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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it says you have disassemble and then buy the "proper renew kit" does that mean rebuild ? I just had it rebuilt and don't have the expertise not to mention 50$ rebuild kit . will that base plate come off w/o complete disassemble ? don't wanna mess it it up
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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You might as well wait than,I didn't remove the plates or throttle shafts etc,but you do have to remove that base and then replace the gasket but it worked out fine for me.
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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I think you could replace the PV without taking the carb off the boat, take the front bowl off and then the metering block where the PV goes in.
Make sure to adjust the PV to spec and be careful with the transfer tube O-ring. I'd get the blue reusable gaskets. You'll have some fuel dropping in the intake so make sure there's good ventilation and have some towel for cleaning. As for the PV size you might consider keeping it the same unless you're feeling underpowered when doing whathever you use the boat for. |
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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it goes in on the side with fuel line comes into the carb right ? your saying to save putting on new base gaskets? I have the original pv but I cannot fine anything written on it
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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It should have 2 small numbers stamped on it at 90º.
Did you remove the carb? did you tore the base gasket? if not, you dont need to replace it. I didnt get the fuel line question. |
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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what I meant was there are 2 bowls the side that has the PV is the side where the fuel line screws in and I will need to take that bowl off right ? I have not taken it off yet . thanks for all the help ... the pv has the numbers stamped on it right
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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The PV is located in the metering block, to reach this you need to take off the primary fuel bowl, yes, that's the one getting the fuel line. You'll need to remove the metering block as well in order to change the PV.
The numbers are stamped on the larger face of the PV at 90º each. 2 and 5 means a 2.5 PV, 6 and 5 a 6.5 and so on. By the way, why do you think the PV is blown? what's the engine simptoms? |
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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I had a big back fire then screwed the air mixture screws in all the way and nothing happen engine runs ok but maxes out about 4200 rpm a little under power with a large load compression all about 115 -120 it is winterized now thought i would do it while it is cold
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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What timing did you set it to? Are you getting fuel out the main boosters while at idle? black smoke out the exhaust?
The air mixture screw test wont work either if the idle circuit is boogared or the idle is set too high on the ralenti screw making the carb work on the transition circuit. What engine? what prop? how did it perform before the new distributor at wot with the same load? |
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malibud
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idle is about700 I haven't checked at idle no black exhaust the engine is a 351w acme 542 prop it did a little better w/ the old dist. it took me a while to get the timing right w/ the new dist I set at -8 instead of 8btdc so I got that right . I also thought changing the PV to 6.5 would give me more mid and top end gain also
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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Just found you distributor topic so I see you got a mallory electronic unit.
With the 542 you're indeed underperforming, those make the 351's over rev easily at wot. You are missing 500rpms at least. I dont think your PV is out, it's a chance though, but my bet is something else is going on there causing the performance loss. I think you're looking for a carb rebuild/tunning in the near future, but before you get into it, you could pay attention to a few other things. Recheck timing is at 8-10º at 700rpms. What is spark plug condition and gap? You should check if there's any accelerator left on the carb while the throttle is at wot, you would have to unattach the accelerator cable off the carb throttle braket and move it. Check the secondaries are fully opening while at wot. You'd need the engine running on the water for this. Dont know if it can be done on the trailer, dont think so as the secondaries work on vacuum. Check fuel pump pressure. If you dont find anything odd in there, you should be taking off the carb, besides cleaning it, check for the float level being too low, clogged main jets. and idle circuit on the metering block as well as the air bleeds on the main body and base. Replace primary and secondary diaphgrams as well. Hope it helps. |
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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thanks for the info I felt like I am missing some rpms some where .. I will have to wait for some warm weather .. so I should run wide open and take the spark arrestor off to check secondaries ? I can check linkage in the garage right ? the carb was just rebuilt by my shop teacher (i work in a high school) . the plugs are golden brown but they bosh twins (by the PO) I thought about going back to the original I have a set of PCM I think they ac delco. do you know off hand what the gap should be I can look it up in a the manual if not ... i will give it a shot still got a couple months before hitting the water here
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horkn
Platinum Member Joined: September-10-2007 Location: Cedarburg, Wi Status: Offline Points: 1511 |
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You can't check the secondaries when the boat is not under load. So that you will have to check while it is in the water, and on the open water. Yes, the flame arrestor will have to be off, and you'll need a second person to operate the boat.
The linkage can be checked in the garage without the boat running preferably. As far as the plugs, leave them as is. The bosch work fine in ford 302 / 351 motors, despite what some on here might say. I personally would not run delco plugs in a ford, but I suppose they would work if you already had them. Those PV's can easily rupture and leak, even if you can't see the pin hole. They are cheap, so you might as well replace it to take that variable out. Its a rubber diaphragm and even a couple years old they can take some abuse. Any ethanol in the gas won't help to make them last any longer either. |
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78 martinique- refloored, reinforced, stringers re glassed, re engineered interior
GT40P heads Edelbrock Performer intake acme 4 blade http://img.photobucket.com/albums/v64/horkn/fish/nautique.jpg |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Tom, Wow! You working for Krones must be having a effect! Next thing you'll be not pro Ford and going with Mercedes!! |
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Luchog
Grand Poobah Joined: April-17-2007 Location: Argentina Status: Offline Points: 2135 |
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PCM's for the Ford should be autolites. I ran NGK on mine. Dont remember the gap, I think it's 0.35, check the manual, you could give it a tad more since you're running an electronic distributor now. |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4945 |
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Worth checking to make sure your choke is operating properly as well. If it's staying closed, that could reduce your top speed.
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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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thanks I won't really know for a couple of months got the power valve replaced w/ 6.5 I will let yall know
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3327 |
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Different Pv won't change your top end power issue.
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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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malibud
Gold Member Joined: July-08-2009 Location: north carolina Status: Offline Points: 603 |
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I think it was blown because turning in the air mixture screws did not kill the engine. so I replced it. i did fine that the perfect pass was keeping me from reach full throttle by about a 1/2 inch or so so i hope this helps.
I talked to the ranger today he said 3 months before the lake goes up because of fixing of the damn ...looks i will be driving come spring |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3327 |
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Yes, that should help!
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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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horkn
Platinum Member Joined: September-10-2007 Location: Cedarburg, Wi Status: Offline Points: 1511 |
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Actually I prefer Audi, then BMW. Mercedes are far too ornery;) I used to run bosch plugs in my 5.0 mustangs, along with other ford motors with good results. Those were pre Krones employee days. As far as Bosch, yeah Krones uses a lot of Bosch and other German suppliers. If you look under the hood of my Audi, all electronics are Bosch. silly Germans. ;) |
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78 martinique- refloored, reinforced, stringers re glassed, re engineered interior
GT40P heads Edelbrock Performer intake acme 4 blade http://img.photobucket.com/albums/v64/horkn/fish/nautique.jpg |
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