[Question] Pandora's Box?--> Blower carbs!
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Pandora's Box?--> Blower carbs!

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    Default Pandora's Box?--> Blower carbs!

    I just picked up a 79 Howard mini day cruiser... 540 BBC, 871 BDS blower. As far as I can tell (the boat is in storage right now) I have 2 Holley 850 double Pumpers on it. There not boost reference, and the original owner told me that before he changed the cam to a little more lakeable cam... He found that cylinders 7 and 8 had small amounts of damage due to leaning. It was jerked out of the boat and sent back to the engine shop and they replaced the pistons, ceramic coated them, and put a different cam in. He bore scoped for a couple seasons to ensure there are not any lean spots on the pistons since. HOWEVER!!! I am always looking at improvements. I have only bean able to drive this thing once (let alone see it a few more) since the purchase but I am assuming that without "blower" carbs (non boost reference pv's) it most likely has the power valves blocked off and the jets are x stages richer. So here is my thinking on all this. When you set non blower Holleys to run on blowers, I hear you usually go about 6-8 stages richer on jets (pv's blocked off). This would create nice AF ratio under WOT, however, idle and cruise will be extremely rich. This would cause the engine to not be as "lakeable". So if a happy medium was found that made the engine idle and cruise good but lean at WOT... then ceramic coating/cam change solves a possible lean at WOT then I am good right??? That's a rhetorical question... Only a wideband or reading plugs can offer that answer but I want to know if my logic is even close. Now lets just say I've got all this thinking pretty good so far. So if I was in the market for buying some boost reference carbs to better match the AF ratio at idle/cruise/and WOT then what carbs would be the best choice? It looks like Holley makes a blower carb, I don't like BG stuff to much, I am temped to call up BDS and get some from them but I've heard really great things about Quick fuels also. Now so far the only carb I have found that is both a "marine" and a "blower" carb is from Quick fuel. I'm not sure BDS coats there carbs to resist water corrosion or has the overflow port for the fuel. I bet BDS could make whatever I want but there already more expensive than the Quick Fuel so now I'm thinking Quick Fuel. Any thoughts on carbs? Do I even need to worry about getting "blower" carbs?

    I know

    I know

    I just need to wait till summer and get this thing out and look at what I specifically have (carb model, jets, pv's, etc), but I'm chomping at the bit here to gain as much knowledge as I can before boating season starts.

    Another thing
    I've talked with the original owner and he said I might want to look into the systems that have fuel injectors at the base of the intake manifold along with the fuel from the top. Is there such a thing as carbs on top and FI ports to "make sure" AF's are correct? My thinking is that if you have FI ports at the base then you would have to have like a EFI bird/buzzard catcher system on top? Also It looks like that all the lower intake manifolds that have these FI ports also have the burst disk port which is cool, but they also seem to have restricted or non standard coolant passages. For instance if it were used in a street car, there is not a thermostat boss. This style of lower intake seems to not be what I am looking for...
    ALL I WANNA DO IS MAKE SURE I DON'T LEAN OUT CYLINDERS AND STILL HAVE A WELL MANNERED 800 HP MONSTER! lol
    All day long I see pics of twin Holleys on 871's and all is well. No leaning, no super rich mixtures at everything but WOT, but maybe I'm just looking at a picture rather than knowing any real data about that engine. I refuse to belive that all these years before "blower" carbs that there is no such thing as a good safe all around tune for a blown engine.
    I live in Montana, so an engine dyno? No way. Not within couple hundred miles at least. So if I want to verify top notch AF's of each cyl, what's the "approved trade method" for tuning my carbs for a blower? Hard passes and pulling plugs? Shoving my homemade 02 up the water exhaust? (never had to use it on a boat before)
    This is the first supercharged ride I've owned so I am newer to all of this. I have tuned many carbs to get awesome mileage and great color on the plugs. When possible I use my O2. Almost all of them are NA engines though. What I'm worried about is leaning specific cylinders out. It seems in boosted engines you can have drastically different mixture in each cylinder. Right? Or is this foul thinking? Do BDS blower intakes for a 540 have inherent flow issues? Do Cams on blower motors have a bigger play in leaning out specific cylinders?

    I have so many questions

    I hope not to overwhelm... sorry.

    You guys are the experts! And I thank you in advance for all the info!

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    Senior Member Hass828's Avatar
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    Quote Originally Posted by Melinko09 View Post
    I just picked up a 79 Howard mini day cruiser... 540 BBC, 871 BDS blower. As far as I can tell (the boat is in storage right now) I have 2 Holley 850 double Pumpers on it. There not boost reference, and the original owner told me that before he changed the cam to a little more lakeable cam... He found that cylinders 7 and 8 had small amounts of damage due to leaning. It was jerked out of the boat and sent back to the engine shop and they replaced the pistons, ceramic coated them, and put a different cam in. He bore scoped for a couple seasons to ensure there are not any lean spots on the pistons since. HOWEVER!!! I am always looking at improvements. I have only bean able to drive this thing once (let alone see it a few more) since the purchase but I am assuming that without "blower" carbs (non boost reference pv's) it most likely has the power valves blocked off and the jets are x stages richer. So here is my thinking on all this. When you set non blower Holleys to run on blowers, I hear you usually go about 6-8 stages richer on jets (pv's blocked off). This would create nice AF ratio under WOT, however, idle and cruise will be extremely rich. This would cause the engine to not be as "lakeable". So if a happy medium was found that made the engine idle and cruise good but lean at WOT... then ceramic coating/cam change solves a possible lean at WOT then I am good right??? That's a rhetorical question... Only a wideband or reading plugs can offer that answer but I want to know if my logic is even close. Now lets just say I've got all this thinking pretty good so far. So if I was in the market for buying some boost reference carbs to better match the AF ratio at idle/cruise/and WOT then what carbs would be the best choice? It looks like Holley makes a blower carb, I don't like BG stuff to much, I am temped to call up BDS and get some from them but I've heard really great things about Quick fuels also. Now so far the only carb I have found that is both a "marine" and a "blower" carb is from Quick fuel. I'm not sure BDS coats there carbs to resist water corrosion or has the overflow port for the fuel. I bet BDS could make whatever I want but there already more expensive than the Quick Fuel so now I'm thinking Quick Fuel. Any thoughts on carbs? Do I even need to worry about getting "blower" carbs?

    I know

    I know

    I just need to wait till summer and get this thing out and look at what I specifically have (carb model, jets, pv's, etc), but I'm chomping at the bit here to gain as much knowledge as I can before boating season starts.

    Another thing
    I've talked with the original owner and he said I might want to look into the systems that have fuel injectors at the base of the intake manifold along with the fuel from the top. Is there such a thing as carbs on top and FI ports to "make sure" AF's are correct? My thinking is that if you have FI ports at the base then you would have to have like a EFI bird/buzzard catcher system on top? Also It looks like that all the lower intake manifolds that have these FI ports also have the burst disk port which is cool, but they also seem to have restricted or non standard coolant passages. For instance if it were used in a street car, there is not a thermostat boss. This style of lower intake seems to not be what I am looking for...
    ALL I WANNA DO IS MAKE SURE I DON'T LEAN OUT CYLINDERS AND STILL HAVE A WELL MANNERED 800 HP MONSTER! lol
    All day long I see pics of twin Holleys on 871's and all is well. No leaning, no super rich mixtures at everything but WOT, but maybe I'm just looking at a picture rather than knowing any real data about that engine. I refuse to belive that all these years before "blower" carbs that there is no such thing as a good safe all around tune for a blown engine.
    I live in Montana, so an engine dyno? No way. Not within couple hundred miles at least. So if I want to verify top notch AF's of each cyl, what's the "approved trade method" for tuning my carbs for a blower? Hard passes and pulling plugs? Shoving my homemade 02 up the water exhaust? (never had to use it on a boat before)
    This is the first supercharged ride I've owned so I am newer to all of this. I have tuned many carbs to get awesome mileage and great color on the plugs. When possible I use my O2. Almost all of them are NA engines though. What I'm worried about is leaning specific cylinders out. It seems in boosted engines you can have drastically different mixture in each cylinder. Right? Or is this foul thinking? Do BDS blower intakes for a 540 have inherent flow issues? Do Cams on blower motors have a bigger play in leaning out specific cylinders?

    I have so many questions

    I hope not to overwhelm... sorry.

    You guys are the experts! And I thank you in advance for all the info!
    Coating the pistons and the cam change really isnt the correct fix for a lean condition, and coating the pistons does help them live but if its lean it will still eventually hurt itself. You are going in the correct direction with the boost referenced power valves, they will allow you to add enough jet to fatten up the WFO a/f ratio and still keep a nice clean cruise. BUT! you will need to spend some time in the boat with a vacuum guage deciding on a powervalve value and then a permanent 02 sensor would be paramount to dialing in a nice fuel curve.
    Reading plugs is OK~ on a drag only deal, but on a lake boat like this, when get specs on a plug, or burn the corners off the strap, how do you know were in the fuel curve that it happened? It could be fine at WFO but be to lean at a 3/4 throttle cruise. An 02 sensor will tell the story.
    Depending on the load & application-jet-v-drive-ect. Some engines can get away with blocked powervalves. Esp. drag racers.
    If your boat is under such a load at cruise speed that the powervalves are open anyway, then it will be a waste to add them. jmo.
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  4. #3
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    Send the carbs to AED and have them set them up for your application. I had a set of thier 850's on a 489 with an 871 and the fuel curve was spot on right out of the box. Never touched them. Engine made 853 @ 6700 with less than 10#, pump gas, hyd. roller. The only thing that really makes a blower carb a "blower carb" would be boost referencing. You might also look into a better intake manifold if you have fuel distribution problems that are that bad. Fuel distribution is not the carb's fault.
    If these aren't in an enclosed engine compartment then they don't need to be "marine" carbs, either.
    Last edited by scott foxwell; 02-20-2014 at 06:51 AM.
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  6. #4
    gn7
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    Quote Originally Posted by Hass828 View Post
    An 02 sensor will tell the story...
    Howard cruiser=wet exhaust. MMmmmmm


    Quote Originally Posted by steelcomp View Post
    Send the carbs to AED and have them set them up for your application. I had a set of thier 850's on a 489 with an 871 and the fuel curve was spot on right out of the box. Never touched them. Engine made 853 @ 6700 with less than 10#, pump gas, hyd. roller. The only thing that really makes a blower carb a "blower carb" would be boost referencing. You might also look into a better intake manifold if you have fuel distribution problems that are that bad. Fuel distribution is not the carb's fault.
    If these aren't in an enclosed engine compartment then they don't need to be "marine" carbs, either.
    Ditto, no need to buy new carbs, Send them off to be done. AED is an excellent shop.
    Like Steel said, the carbs and even the blower have little to do with distribution, its the manifold. No, you don't want to try to fix it with injectors in the manifold plus carbs together.
    But you are getting ahead of yourself. You have no way of knowing if the cylinders that were lean, were only slightly leaner. The whole engine could have lean, there were just the 2 that were a little too lean, and maybe only when it was WOT.
    Like Steel said, if you can see the carbs thru the hatch, or there is no engine cover, you don't need marine carbs. As for a marine coating, don't bother.



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    Last edited by gn7; 02-21-2014 at 07:32 AM.

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    Ok, all that sounds great. I'm going to get some spacer plates that have o2 ports in them. I'm looking at the AEM boost/wideband gauge. It seems to have a 2 hour data logger of a/f and boost. I figure I can run this in the even side for am hour, then shut it off and swap the sensor to the odd side and un another hour. Then it will show me a graph of a/f points at any given rpm and boost level. I will post the graphs on here to get you guys as much info as possible. I'll probably start a new thread for specific tuning on my carbs. Thanks everyone!
    If anyone else can think of any more info, feel free to chime in.

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    Quote Originally Posted by Melinko09 View Post
    Ok, all that sounds great. I'm going to get some spacer plates that have o2 ports in them. I'm looking at the AEM boost/wideband gauge. It seems to have a 2 hour data logger of a/f and boost. I figure I can run this in the even side for am hour, then shut it off and swap the sensor to the odd side and un another hour. Then it will show me a graph of a/f points at any given rpm and boost level. I will post the graphs on here to get you guys as much info as possible. I'll probably start a new thread for specific tuning on my carbs. Thanks everyone!
    If anyone else can think of any more info, feel free to chime in.
    Who makes these "spacer plates" that have the O2 ports in them?



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    Quote Originally Posted by gn7 View Post
    Howard cruiser=wet exhaust. MMmmmmm




    Ditto, no need to buy new carbs, Send them off to be done. AED is an excellent shop.
    Like Steel said, the carbs and even the blower have little to do with distribution, its the manifold. No, you don't want to try to fix it with injectors in the manifold plus carbs together.
    But you are getting ahead of yourself. You have no way of knowing if the cylinders that were lean, were only slightly leaner. The whole engine could have lean, there were just the 2 that were a little too lean, and maybe only when it was WOT.
    Like Steel said, if you can see the carbs thru the hatch, or there is no engine cover, you don't need marine carbs. As for a marine coating, don't bother.
    My thought exactly. I was wondering how they knew (or decided) the cyls were lean, or didn't get damaged for some other reason?
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    No bank O2 can tell you what cylinders are rich or lean, so OP's 2 lean holes would necessarily show up. Push the tune to the edge of so called ideal, and down goes a lean hole.
    Right Unchained?

    Without seeing the exhaust system, I have no idea how you install a O2 in a wet exhaust without damaging it.



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    Quote Originally Posted by gn7 View Post
    No bank O2 can tell you what cylinders are rich or lean, so OP's 2 lean holes would necessarily show up. Push the tune to the edge of so called ideal, and down goes a lean hole.
    Right Unchained?

    Without seeing the exhaust system, I have no idea how you install a O2 in a wet exhaust without damaging it.
    I want to know where these "plates" go...
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    Scott, talk him into a ROOTZ EFI kit...works great...
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    This boat has Dana performance Marine exhaust manifolds on it. Dana marine makes 1 inch billet spacer plates that go between the manifold and the riser with o2 bungs. I called Dana marine and talked with them about making sure that it is dry for the o2 sensors. I also talked with him about problems with these manifolds cracking and causing damages to the engine. We spoke for quite awhile. I'm going to inspect the manifolds with a bore scope and pull the risers off. If I need to change the manifolds out I will. But $$$$$. Maybe I should change to a different style exhaust. What would you guys switch to?

    I'm on my phone and I can't copy the link right now, but if you google Dana marine exhaust and go to there site you can find these o2 plates easy.

    I love the idea of EFI but, it's not gonna happen. If I can't ensure this current engine setup is good to go then I shouldn't be putting my hands on this stuff. I'm new to boats of this caliber, and I'd rather act stupid to learn as much as I can rather than add my 2cents in also. So thanks a ton for the help. (and keep it coming!)

    This boat has been run as is for a couple years now with absolutely no problems or anything. Not that I don't trust the previous owner, I just like making sure my investment is going to last. One other thing to note. I live at a higher elevation than he did. I did not do any jetting changes yet for the elevation, the reason being is now it should be even richer than it was for him. But yet again I want to make sure I'm not to rich so it all boils down to just getting an o2 and giving it a whirl.
    what do you guys think about Dana exhaust manifolds and these o2 spacer plates? Like I said, Dana insured me that the o2 sensors are dry at these plates.

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    Quote Originally Posted by Melinko09 View Post
    I want to make sure I'm not to rich
    Boating makes sure that is never going to happen............

    The stainless Dana risers that I looked at had the cracks in the corners right at the joint where they bolt onto the exhaust manifolds. Easy to see but it would be difficult to fix.

    We did check them with a magnet and it would stick to the older units but it would not stick to the newer ones so they must have changed to a different grade stainless material.

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    Are we talking about this manifold? This is actually a re-bop of a decades old design that Dana revived with a couple tweeks. Its pretty decent manifold. Is it the manifold itself that has been known to crack, or the risers as Unchained mentioned. The risers are one thing, the manifold is entirely different issue.


    Putting the O2 under the riser is probably the best place for it. If it gets wet there, you'd probably have water in the cylinders as well. Not sure how he could say you won't get it wet without knowing everything about the engine build, unless it was on the assumption that you haven't experienced any water in the cylinders, and the spacer won't make things any worse.

    But if you have a distribution problem, the O2 sensor isn't going to save you bacon. If your send X fuel in the engine, the sensor can't tell you which holes it went in, only that the AVERAGE AF is correct.

    Curious, are these carbs mount inline, or sideways?



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    Last edited by gn7; 02-22-2014 at 10:35 AM.

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    Quote Originally Posted by Melinko09 View Post
    This boat has Dana performance Marine exhaust manifolds on it. Dana marine makes 1 inch billet spacer plates that go between the manifold and the riser with o2 bungs. I called Dana marine and talked with them about making sure that it is dry for the o2 sensors. I also talked with him about problems with these manifolds cracking and causing damages to the engine. We spoke for quite awhile. I'm going to inspect the manifolds with a bore scope and pull the risers off. If I need to change the manifolds out I will. But $$$$$. Maybe I should change to a different style exhaust. What would you guys switch to?

    I'm on my phone and I can't copy the link right now, but if you google Dana marine exhaust and go to there site you can find these o2 plates easy.

    I love the idea of EFI but, it's not gonna happen. If I can't ensure this current engine setup is good to go then I shouldn't be putting my hands on this stuff. I'm new to boats of this caliber, and I'd rather act stupid to learn as much as I can rather than add my 2cents in also. So thanks a ton for the help. (and keep it coming!)

    This boat has been run as is for a couple years now with absolutely no problems or anything. Not that I don't trust the previous owner, I just like making sure my investment is going to last. One other thing to note. I live at a higher elevation than he did. I did not do any jetting changes yet for the elevation, the reason being is now it should be even richer than it was for him. But yet again I want to make sure I'm not to rich so it all boils down to just getting an o2 and giving it a whirl.
    what do you guys think about Dana exhaust manifolds and these o2 spacer plates? Like I said, Dana insured me that the o2 sensors are dry at these plates.
    Learning how to properly read spark plugs will help tremendously and tell you everything you need to know.
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