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Need some info. Twin 750's vacuum secondarys, in line on a 468/ 671 /15 over/ 10 -12 lbs. boost @ 6500. Boat runs great, starts good, idles great, no hesitation upon acceleration, just explodes and runs great, plug color nice and dark tan. Now the problem. When I idle through a long no wake zone, seems like the blower 'dry's out' and when I punch it hard I get a big lean pop. Also big lean pop when I make a pass then slow down, go to turn around and punch it. My fix was to go to 2" spacer plates and put 50 cc accelerator pumps on the primarys. I would like to keep the vacuum secondary carbs, where I run it I need to go 35 miles without xtra fuel. Rt now it is fairly fuel efficient when cruising. ................ What do you guys think of the 50 cc pump idea??????
 

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i have a bbc 476ci twin turbo motor with one 850 holly @ 13lbs of boost & i had to go to 50cc acc. pumps because i had a bad bog.if yours doesn't then i dont think you should change the acc. pump. it sounds like the power valve isn't kicking in soon enough & it is leaning out in one spot?
 

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Cantard
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Mine will pop after a long idle. Didnt know what it was at first but got it figured out to be fuel pooling in the blower. Fuel hits the cylinder when blower speeds up. More like a spark pop. This sound right?
 

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Discussion Starter #4
Mine will pop after a long idle. Didnt know what it was at first but got it figured out to be fuel pooling in the blower. Fuel hits the cylinder when blower speeds up. More like a spark pop. This sound right?
It pops up through the blower, like a lean back fire. Sometimes even stalls the motor. You could be right, might be fuel pooling in the blower, It doesn't do it when I warm it up at the dock, paddele it out start it up and nail it. Takes off great. Also when I cruise, slow down for just a short distance and hit it again it works. It does seem to puke fuel out of the air scoop when it does it after the long idle thing. As far as the lean pop on the turn around after a hard pass, I don't have a fuel rail and I think I just ran the system low on fuel. So you are probably right, I have 2 problems............. Question is how to stop the idle pooling?
 

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Cantard
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Question is how to stop the idle pooling?
I am still working on that answer. There is a spot I go were the no wake zone is a couple miles, so it idles for about 15-20min each way. Every time I get back in the open give it a poke and sure enough every time its followed by about 3 or 4 pops. If I roll into it real light it doesn't do it. On my wide band it is only a little rich at idle but not enough to even think about. I think I would also like to try a hotter plug. Maybe the -9,s are to cold for that much idling??
 

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Discussion Starter #8
One sneeze could have hurt them, then they'll leak consistantly.

Just a thought.
I also thougt about that, but the motor runs way to well at idle and off idle everywhere else to have a blown power valve, Actually after Hallets post, I'm thinking gas pooling rich instead of lean and different # power valves may be in order It has 65's any suggestions??? higher or lower???
 

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Cantard
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I also thougt about that, but the motor runs way to well at idle and off idle everywhere else to have a blown power valve, Actually after Hallets post, I'm thinking gas pooling rich instead of lean and different # power valves may be in order It has 65's any suggestions??? higher or lower???
What plugs are you using?
Mine runs perfect, air fuels are right on the money, turn the key and it runs...never any head ackes. Just feel like a tool when it pops. Just wondering if getting on the throttle is washing the plugs causing this. At extended low blower speeds maybe the rotors are able to get wet?
 

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Discussion Starter #10
What plugs are you using?
Mine runs perfect, air fuels are right on the money, turn the key and it runs...never any head ackes. Just feel like a tool when it pops. Just wondering if getting on the throttle is washing the plugs causing this. At extended low blower speeds maybe the rotors are able to get wet?
I gotta tell ya, you were right on about the way to start it, I went and ran two more galons of antifreeze through it. I ran out when I did it 2 wks ago, and instead ot pumping the gas 3 or 4 times, I just patted' it a couple of times, rolled it over, let it breathe a little and then rolled it again. Even in 28 degrees, It started and Idled without popping. I was thinking backwards, when it pops through the blower, it is rich. Thanks for the tip, I really don't think I even need the 50 cc pumps. I think the secret for the no wakes pooling is going to be in the power valves and maybe leaning the primarys and richening the secondarys a little............ has 78's and 80's I'm pretty sure. forgot will have to look in the spring. We are definately on to something!!!!!!!:)hand
 

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I gotta tell ya, you were right on about the way to start it, I went and ran two more galons of antifreeze through it. I ran out when I did it 2 wks ago, and instead ot pumping the gas 3 or 4 times, I just patted' it a couple of times, rolled it over, let it breathe a little and then rolled it again. Even in 28 degrees, It started and Idled without popping. I was thinking backwards, when it pops through the blower, it is rich. Thanks for the tip, I really don't think I even need the 50 cc pumps. I think the secret for the no wakes pooling is going to be in the power valves and maybe leaning the primarys and richening the secondarys a little............ has 78's and 80's I'm pretty sure. forgot will have to look in the spring. We are definately on to something!!!!!!!:)hand
I am also going to lean up the idle. I just hope it doesnt get into that start/quit nonsense when its cold. I also think we are having the same issue. Boy is it nice knowing I am not alone on this. We will have to compare notes in the spring, There has to be an answer......we will find it.:)devil
 

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I gotta tell ya, you were right on about the way to start it, I went and ran two more galons of antifreeze through it. I ran out when I did it 2 wks ago, and instead ot pumping the gas 3 or 4 times, I just patted' it a couple of times, rolled it over, let it breathe a little and then rolled it again. Even in 28 degrees, It started and Idled without popping. I was thinking backwards, when it pops through the blower, it is rich. Thanks for the tip, I really don't think I even need the 50 cc pumps. I think the secret for the no wakes pooling is going to be in the power valves and maybe leaning the primarys and richening the secondarys a little............ has 78's and 80's I'm pretty sure. forgot will have to look in the spring. We are definately on to something!!!!!!!:)hand
I am also going to lean up the idle. I just hope it doesnt get into that start/quit nonsense when its cold. I also think we are having the same issue. Boy is it nice knowing I am not alone on this. We will have to compare notes in the spring, There has to be an answer......we will find it.:)devil
In regards to Caves learning experience. Powervalves and a blower don't work as well as no powervalve. What I'd say is when you punch it remember the powervalve right now is set up to work on a normally aspirated motor, really in a car and when the transmission downshifts the load on the motor increases and the power valve opens. What I'd say is in a blower application you are already overcompensating for vacumn, thus you have boost and not as high negative intake pressure. How do you know that the power valve isn't open all the time? Also if the carbs are side mounted and the linkage between the carbs doesn't open in a 1:1 ratio (primaries linked to secondaries) then one whole side of the engine as your rolling in and out of the throttle in running leaner and or richer. I can and explain how you can modify them to get the correct ration you use the same piece of link wire and there is a screw hole on the primary rod cam that you drill out .030 and ta da 1:1.
I've personally talked with Don of Don Hampton blowers on this subject trying to get Cave's motor dialed in.

And 50cc do it. even if 50's on the fronts and 30's on the back (of each individual carb).

I have had it happen doing initial starting after a motor rebuild. One backfire and the powervalve's toast. Looks like the float is set waaaay to high.

Just sharing knowledge, hopefully it'll help
 

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Violater, I blocked off my power valves for these vary reasons. To many people PMed me telling me to ditch the PV or do them up right and drill a hole to the PV circuit and get a hose to the manifold. Its less complicated to block them off. Is there an advantage to using Power Valves with a blower set up?

So both youz guys use Power Valves with your blower setups? What Size and are they set up to the manifold?
 

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Cantard
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Violater, I blocked off my power valves for these vary reasons. To many people PMed me telling me to ditch the PV or do them up right and drill a hole to the PV circuit and get a hose to the manifold. Its less complicated to block them off. Is there an advantage to using Power Valves with a blower set up?

So both youz guys use Power Valves with your blower setups? What Size and are they set up to the manifold?
No pv,s here.
 

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Violater, I blocked off my power valves for these vary reasons. To many people PMed me telling me to ditch the PV or do them up right and drill a hole to the PV circuit and get a hose to the manifold. Its less complicated to block them off. Is there an advantage to using Power Valves with a blower set up?

So both youz guys use Power Valves with your blower setups? What Size and are they set up to the manifold?
I am no expert, but I believe boost referencing carbs is supposed to give you a truer signal to the power valve, which could give you a little better fuel economy. Not always necessary, and could be compensated by jetting up if you block off the power valves.

I run 2-HP 830's per engine, with (non-referenced) power valves. Not sure what size.
 

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Discussion Starter #17 (Edited)
In regards to Caves learning experience. Powervalves and a blower don't work as well as no powervalve. What I'd say is when you punch it remember the powervalve right now is set up to work on a normally aspirated motor, really in a car and when the transmission downshifts the load on the motor increases and the power valve opens. What I'd say is in a blower application you are already overcompensating for vacumn, thus you have boost and not as high negative intake pressure. How do you know that the power valve isn't open all the time? Also if the carbs are side mounted and the linkage between the carbs doesn't open in a 1:1 ratio (primaries linked to secondaries) then one whole side of the engine as your rolling in and out of the throttle in running leaner and or richer. I can and explain how you can modify them to get the correct ration you use the same piece of link wire and there is a screw hole on the primary rod cam that you drill out .030 and ta da 1:1.
I've personally talked with Don of Don Hampton blowers on this subject trying to get Cave's motor dialed in.

And 50cc do it. even if 50's on the fronts and 30's on the back (of each individual carb).

I have had it happen doing initial starting after a motor rebuild. One backfire and the powervalve's toast. Looks like the float is set waaaay to high.

Just sharing knowledge, hopefully it'll help
Thanks for the info. What I actually have is 750 cfm carbs/ tops milled off/ vacum secondarys single pump/ mounted inline. I put 650 bowls and transfer tubes on them so they would mount in line, It runs great, no hesitation hole shots good, no dead spots, great mid range drivability and with 32 gears gets GREAT fuel milage. Just the problem with a big pop after idling for a 2 mi streach and if I make a hard pass, get out of it and then go to turn around and I'm not careful BIG pop. Sometimes kills the motor then it won't start right away. Embarrasing, plus I could wash the back and sink. THAT WOULD REALLY SUCK........... Maybe take the power valves out w/ block off's and install 2' spacers w/ 50 cc pumps will compensate???? I already bought all the stuff.....
 

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Thanks for the info. What I actually have is 750 cfm carbs/ tops milled off/ vacum secondarys single pump/ mounted inline. I put 650 bowls and transfer tubes on them so they would mount in line, It runs great, no hesitation hole shots good, no dead spots, great mid range drivability and with 32 gears gets GREAT fuel milage. Just the problem with a big pop after idling for a 2 mi streach and if I make a hard pass, get out of it and then go to turn around and I'm not careful BIG pop. Sometimes kills the motor then it won't start right away. Embarrasing, plus I could wash the back and sink. THAT WOULD REALLY SUCK........... Maybe take the power valves out w/ block off's and install 2' spacers w/ 50 cc pumps will compensate???? I already bought all the stuff.....
What fuel pump are you running on your set up? I saw something like this once where the mech. pump would push the floats open for a second at high rpm and out of the throttle. If I remember correctly it was an edelbrock pump. Mine does it on the long idle but not after a hard pass.
 

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Discussion Starter #19
What fuel pump are you running on your set up? I saw something like this once where the mech. pump would push the floats open for a second at high rpm and out of the throttle. If I remember correctly it was an edelbrock pump. Mine does it on the long idle but not after a hard pass.
I have the Big holly mechanical I have it set on 7 lbs idle and it will go to about 9 at wot. Actually I had the wrong regulator on it last year. It wasn't a by pass and I had a fuel rail with a bleed back to a canister filter. So I just put a pet **** on my return hose and adjusted it to 7 at Idle Thats why it went to 9 at wot. I have a new by-pass regulater I'm going to install before I run it again, and the fuel pressure should stay consistent at 7 lbs at WOT.......
 

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Cantard
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I have the Big holly mechanical I have it set on 7 lbs idle and it will go to about 9 at wot. Actually I had the wrong regulator on it last year. It wasn't a by pass and I had a fuel rail with a bleed back to a canister filter. So I just put a pet **** on my return hose and adjusted it to 7 at Idle Thats why it went to 9 at wot. I have a new by-pass regulater I'm going to install before I run it again, and the fuel pressure should stay consistent at 7 lbs at WOT.......
A pet WHAT? lmao:)hand

I am going to put a bypass or small return on mine aswell. My reg has an extra guage port I might run a realy small line from. My race pump holds pressure and on the trailer to and from the river it will/can bounce the floats. Every once in a blue moon (twice last year) it makes the driver curse his azz off.
 
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