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So from what I've read here,if I understnd correctly, It's common to plug the sec powervale on my 850 4150 ? is it that simple,just plug the threaded hole,don't worry about the 2 small holes on either side?
Is this a mod a guy should just do,having not yet run this motor ?
460 ,280 comp cam ,9.6:1,basset o/t's& stealth intake.
thanx :D
 

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If the motor runs good ,leave it alone. But if you do decide to plug it(there is a special solid power valve plug, thats all you need to plug) dont forget you will need to increase the secondary jets by about 8 sizes to make up for the fuel you are plugging off.It will run richer at idle because of this, so you may not like it set up that way. The carb was built with the valve for a reason. Just try it first.
 

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thanks ronboat,so why do guys plug it? Whats the benifit? the"special plug" is what I was wondering about
 

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Why plug it? I don't know. I tried it once on my car, but it idled way too rich. I think Jegs sells those plugs if you wanted to try it.I think maybe guys plug it and increase the jet size if thier valve isnt opening soon enough,causing a bog as the thottle is opened-kind of a band-aid fix. Better to get the proper size valve if you get this problem.( probably a higher number valve that opens sooner if there is a bog)
 

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Ronboats right if the carb had one from holley it should be the way to go on your 460 . for racing you can plug it if you don't want to lean the secondaries .
 

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nope no Brian
 

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So from what I've read here,if I understnd correctly, It's common to plug the sec powervale on my 850 4150 ? is it that simple,just plug the threaded hole,don't worry about the 2 small holes on either side?
Is this a mod a guy should just do,having not yet run this motor ?
460 ,280 comp cam ,9.6:1,basset o/t's& stealth intake.
thanx :D

I would be surprised if you found a power valve on the secondary side of an 850. They are usually on the primairy side to enrichen the mixture at full throttle, only reason to remove is usually in a full race application, however some improvement could result from replacing a faulty or incorrect PV. They are rated to open according to a drop in vacumn.
 

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Most Holley 850 DP carbs will have one on the secondaries

Can cause leaning if Lateral or Acc G's are reasonable, its alot higher than the main jets and will become uncovered quicker due to fuel slosh than the main jets. This isnt usually a problem on the primary side as the Acc G's force the fuel towards the PV and main jets, forced away on the sec side
(assumes normal carb mount direction)

People with sideways mounted on T-rams may want to think about this (if concerned with straight line running only)

Amazing to see people put secondary jet extensions in and leave the PV to its own demise.
Pretty much a no brainer on a hard leaving drag car to remove and rejet to compensate

On a boat probably only nessacerry if pulling over 1 G Acc or over 1.5 G lateral, definitly shows up at 2 Lateral G's and above

Fill your carb with fuel to the correct level then tilt it sideways and for - aft and see what angle you can get it to before fuel pours out of the boosters (this is static only without any intake vac pulling on the booster)

Most holleys pour fuel at around 20-22 degrees lateral tilt, when you can get a carb to 45 degrees without this happening you are on your way
 

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Most Holley 850 DP carbs will have one on the secondaries

Can cause leaning if Lateral or Acc G's are reasonable, its alot higher than the main jets and will become uncovered quicker due to fuel slosh than the main jets. This isnt usually a problem on the primary side as the Acc G's force the fuel towards the PV and main jets, forced away on the sec side
(assumes normal carb mount direction)

People with sideways mounted on T-rams may want to think about this (if concerned with straight line running only)

Amazing to see people put secondary jet extensions in and leave the PV to its own demise.
Pretty much a no brainer on a hard leaving drag car to remove and rejet to compensate

On a boat probably only nessacerry if pulling over 1 G Acc or over 1.5 G lateral, definitly shows up at 2 Lateral G's and above

Fill your carb with fuel to the correct level then tilt it sideways and for - aft and see what angle you can get it to before fuel pours out of the boosters (this is static only without any intake vac pulling on the booster)

Most holleys pour fuel at around 20-22 degrees lateral tilt, when you can get a carb to 45 degrees without this happening you are on your way
HUH??? What do you mean by getting it to tilt without fuel pouring out the boosters?Why would fuel pour out the boosters??And what do you suggest as the "cure"? And what does this have to do with the power valve or jets?
 

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HUH??? What do you mean by getting it to tilt without fuel pouring out the boosters?Why would fuel pour out the boosters??And what do you suggest as the "cure"? And what does this have to do with the power valve or jets?
It related directly to the rest of my post and the uncanny ability of the rear PV (the topic) to become uncovered during operation (hence the desire to remove it and recalibrate in some instances)

Just trying to get people to think about what actually happens to the fuel in their carbs when its not sitting on the trailer, on the dyno or the workshop bench (ie in a boat or vehicle)

Take the carb off or use a spare, holding it in your hand over a catch tray tilt the carb 45 degrees backwards with fuel in it and see what happens (rough approximation of operating under 1G of acceleration) The fuel will pour out of the primary boosters and on the secondaries run away from the metering block to the back of the bowl and uncover the rear PV before it uncovers the rear jets.

(and your imaginary engine emits a lean cough, stumble with an open rear PV sucking air instead of 6-10 jet sizes of fuel into your already emulsified mixture in the secondary main wells)

Now refill the fuel bowls and tilt it sideways 45 degrees and observe again (rough approx of 1 lateral G)

It has everything to do with the main jets and more so the PV, especially the rear one.

Have a look at this rough diag with the same amount of fuel trapped in a Holley bowl when subjected to different lateral G's

Although different to the Accel issue with a rear PV, what effect do you think the differing fuel heights "stacked" against the two main wells have on the boosters ability to draw fuel (ignoring the fact that even under no intake vac, raw, unatomised fuel will pour from the boosters on one side of the carb under any moderate lateral G's)

Just trying to give a "real world" reason as to why you may or may not want to delete the rear PV and instances where its desirable

Altough this diag doesnt show what happens under Acceleration look at the height of the PV (plugged in this instance) Vs the main jets and think "why bother with jet extensions, if my 850 Holley has a rear power valve, that will be the first to uncover during acceleration"
 

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Secondary PV removal is a common practice umong the Rock Dodger (white water boats) because of the way they sometimes run.

******* 12 is "on the money" with the reasoning behind it...

The PV cannot do it's job if it's dry....

Check this out! There are many more video's and pictures that show extreme hull angles while getting these badboys on plane, while doing that, tha rear bowl runs damn near dry and leans them to the point of disaster...Happens often.

http://www.youtube.com/watch?v=cuIO2mMIHTc
 

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Good example GT Jets

There are alot of ways of creating the same fuel issue with different types of boats and vehicles

The main issue I have is large lateral G's (over 3) and Accel G's at the start of a race. Even though the boat sits fairly flat in corners the large lateral G's make the carb (class restriction) act like its lying on its side LOL !!!!

Another video example of my boat putting a carb under these conditions

No rear PV by the way even though the carb came with one

http://www.youtube.com/watch?v=3ffCw0rR8pI&feature=related
 

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I've always used jet extensions, but never thought about the pv going dry on launch(drag car) It's a good point,A real reason to eliminate the pv. But why is my hp dominator equipped with a pv in the secondarys, if this is a common problem? is there an extension made for the pv?seems like you could screw one into the same threads the pv uses, if the pv doesnt extend all the way through.Something to look at next time I take my bowls off, I guess. As far as differing fuelpressure(weight) from one jet to the other on lateral g load, have you ever tried making a jet extension in a"Y" so both jets draw from the same extension in the center of the bowl? That should keep them equal, I would think.Just a thought.
 

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I've always used jet extensions, but never thought about the pv going dry on launch(drag car) It's a good point,A real reason to eliminate the pv. But why is my hp dominator equipped with a pv in the secondarys, if this is a common problem? is there an extension made for the pv?seems like you could screw one into the same threads the pv uses, if the pv doesnt extend all the way through.Something to look at next time I take my bowls off, I guess. As far as differing fuelpressure(weight) from one jet to the other on lateral g load, have you ever tried making a jet extension in a"Y" so both jets draw from the same extension in the center of the bowl? That should keep them equal, I would think.Just a thought.
IMHO Power valves in the secondaries are almost always sized the same as the primaries and really only change things when the engine is running a mid power, that being said, they are closed only at low throttle ranges and really would only be used for keeping the engine "clean" while doing some mid throttle runs and warming things up.
For racing, I would think they are unnecissary, I would be of the mindset that jetting up 6-7 jet sizes and using a PV elimination plug really could not hut anything, could be mistaken, but I don't think so...If you are "snapping the throttle" past the point of the PV getting any time do do it's job, I would think the difference would be negligable...

Now I'm not saying that secondary PV's don't have a use. One thing they do is make tuning more "idiot proof" by making jet changes less critical. it makes the AFR more uniform during different throttle ranges, but if it's WFO, or on and off (like most jet boats) where is the harm. I really don't think a mileage difference could be realized and that is what the PV was origionally designed for....Just another .02c...:)grn

GT:)hand
 

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The one thing I didn't like about plugging my pv's (I think I did them both as I recall. It was a couple years ago) was that in the staging lanes It was eye burning rich,(I raised the jets from 88's to 94's) Seemed to run the same on the track, so I put the pv's back in.
 

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The one thing I didn't like about plugging my pv's (I think I did them both as I recall. It was a couple years ago) was that in the staging lanes It was eye burning rich,(I raised the jets from 88's to 94's) Seemed to run the same on the track, so I put the pv's back in.
Sounds like you had an idle circuit problem, they do get a bit more difficult to get to idle clean if you have low vacuum and have to have the butterflys even a little open, I always do things the old school way and drill some holes in the primary butterflies to get the idle circuits to function properly..:)bulb

Did you use PV plugs?

GT :)hand
 

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Sounds like you had an idle circuit problem, they do get a bit more difficult to get to idle clean if you have low vacuum and have to have the butterflys even a little open, I always do things the old school way and drill some holes in the primary butterflies to get the idle circuits to function properly..:)bulb

Did you use PV plugs?

GT :)hand
Yeah I used the real pv solid plugs. I wasn't sure enough about what I was doing to drill the butterflys-didn't want to wreck a 600.00+ carb. On the starting line I have it at 6000 rpm on the rev limiter, so it didn't really matter during a run weather or not the pv's were in. My carb has four corner idle circuits, and the needles seem to be working right.Havn't used it for a while.I hurt a bearing (and the crank) in it last summer when a rocker arm came loose-hell it came all the way off and the lifter came out of its hole and lost the oil pressure. The engine builder was too busy to take in my work, so I spent all my money( and keep spending all my money) on a boat. Got the boat in running condition now, so I hope to get my car back together this winter. 'coarse, thats what I said LAST winter.
 

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Yeah I used the real pv solid plugs. I wasn't sure enough about what I was doing to drill the butterflys-didn't want to wreck a 600.00+ carb. On the starting line I have it at 6000 rpm on the rev limiter, so it didn't really matter during a run weather or not the pv's were in. My carb has four corner idle circuits, and the needles seem to be working right.Havn't used it for a while.I hurt a bearing (and the crank) in it last summer when a rocker arm came loose-hell it came all the way off and the lifter came out of its hole and lost the oil pressure. The engine builder was too busy to take in my work, so I spent all my money( and keep spending all my money) on a boat. Got the boat in running condition now, so I hope to get my car back together this winter. 'coarse, thats what I said LAST winter.
You and I are living the same life, if I have the money, I don't have the time and vice versa....l):ame

GT :)hand
 
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