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Bogging issues

  1. #1
    BBC Hydro 71ShovelNose's Avatar
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    Default Bogging issues

    454ci BBC, 10.5:1, .660/.680 258/[email protected] on a 108 c/l solid roller, 990 heads, Team G intake (single plane), 750 holley (proform main body, 72's in the front w/4.5 powervalve, 84's in the rear w/o jet extensions), 17 pitch prop, 18 gears, early 70's Howard shovelnose.

    When in neutral the motor has excellent throttle response with 0 bog. Put it in gear and wack it and it stumbles around and won't recover until you back off and then roll back into it. Otherwise the carb is working flawlessly-makes a bunch of power and idles perfect. I want to get this bog sorted about before trying to spray it.

    Thanks,
    Sammy
    Howard Shovelnose Hydro "Wide Spread Panic", 454ci BBC on tha dope, Radiece Performance 3-blade cleaver, and 25% gears...

    Big thanks goes out to Tom Bentley of Menkins V-drives, and Tommy "Flatbottom" Hughes the man resonsible for getting me hooked on hotboats!!!

    My build> http://www.performanceboats.com/v-dr...e-project.html

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    Senior Member jockorace's Avatar
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    Sammy, there have been a few similar threads on this subject recently. Take a look through the past few pages of the Dyno section. Lot's of good info. Without getting into all of the different things to dial in on a Holley (jets, squirters, pump shot cams, power valves, etc) , the FIRST THING to check is your float level with the boat in the water. Set the floats at least midway on the clear sight bowl plugs (if you have them). If not, they should dribble fuel when you open the standard bowl plug. That's step one, run it again and let us know if that helped. Jocko

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    gn7
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    Like Jocko posted, double check the float level first and foremost. You need to post you shooter size, and if possible you accelerater pump cam color. Remeber, the carb was most likely originally set up for a dual plane manifold, with a much better signal strength, and a much small plenum to cover with the accelerater shot.

    Also, the PV seems way to low for a single 4 bbl IMO. You have to get the manifold vac below 4.5 to get it to open, yet your running a 12 jet spead primary to secondary. Thats a ton! With a single plane Team G, your looking at some pretty drastic distributions difference front to rear in the engine. Ideally the engine would like you to run square jetting to start, and jet according to plug readings. I understand if your want to run a PV for milage, but you can only take the idea so far.

    WHERE IS YOU TIMING, AND IS IT LOCKED OR DOES IT HAVE A CURVE!!!!!!!!



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    BBC Hydro 71ShovelNose's Avatar
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    Quote Originally Posted by gn7 View Post
    Like Jocko posted, double check the float level first and foremost. You need to post you shooter size, and if possible you accelerater pump cam color. Remeber, the carb was most likely originally set up for a dual plane manifold, with a much better signal strength, and a much small plenum to cover with the accelerater shot.

    Also, the PV seems way to low for a single 4 bbl IMO. You have to get the manifold vac below 4.5 to get it to open, yet your running a 12 jet spead primary to secondary. Thats a ton! With a single plane Team G, your looking at some pretty drastic distributions difference front to rear in the engine. Ideally the engine would like you to run square jetting to start, and jet according to plug readings. I understand if your want to run a PV for milage, but you can only take the idea so far.

    WHERE IS YOU TIMING, AND IS IT LOCKED OR DOES IT HAVE A CURVE!!!!!!!!
    The float level is set to 3/4 up the sight glass on both front and rear bowls. I only ran the PV because it was already in there and I needed somewhere to start. I will find out the squirter sizes, and the accelerater pump cam color. I now have a PV block off so I will put that in and put 84's in the front and jet extensions in the rear.

    Thanks for the help guys!!!

    Sammy
    Howard Shovelnose Hydro "Wide Spread Panic", 454ci BBC on tha dope, Radiece Performance 3-blade cleaver, and 25% gears...

    Big thanks goes out to Tom Bentley of Menkins V-drives, and Tommy "Flatbottom" Hughes the man resonsible for getting me hooked on hotboats!!!

    My build> http://www.performanceboats.com/v-dr...e-project.html

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    Boat Nut sleekcrafter's Avatar
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    I see it was posted (no jet extensions) from what I've read, 0-60 ft in one second or less, will require a j/e, in a single carb application. The bigger jets in the back, reflect the lack of pv in the secondary.
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    gn7
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    Quote Originally Posted by 71ShovelNose View Post
    The float level is set to 3/4 up the sight glass on both front and rear bowls. I only ran the PV because it was already in there and I needed somewhere to start. I will find out the squirter sizes, and the accelerater pump cam color. I now have a PV block off so I will put that in and put 84's in the front and jet extensions in the rear.

    Thanks for the help guys!!! Sammy
    84s square is pretty big for 750. I would think someting in the mid to high 70's would be a better start. Something like 78's maybe. I think who ever set this thing up was trying to cover for a lean primary with a rich secondary jet. Not the best set up unless some thing in the manifold distribution led them that way. That would a huge distribution problem that the Team G isn't know for.
    Again, where is your timing. the timing plays a huge part in how well a carb gets on the main circuit. Whats the timing and is the dizzy locked out, or is there a curve and how fast.


    Quote Originally Posted by sleekcrafter View Post
    I see it was posted (no jet extensions) from what I've read, 0-60 ft in one second or less, will require a j/e, in a single carb application. The bigger jets in the back, reflect the lack of pv in the secondary.
    No doubt the secondary is covering for no PV, but 12 jet sizes is huge.



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    Last edited by gn7; 08-15-2011 at 12:52 PM.

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    Quote Originally Posted by gn7 View Post
    84s square is pretty big for 750. I would think someting in the mid to high 70's would be a better start. Something like 78's maybe. I think who ever set this thing up was trying to cover for a lean primary with a rich secondary jet. Not the best set up unless some thing in the manifold distribution led them that way. That would a huge distribution problem that the Team G isn't know for.
    Again, where is your timing. the timing plays a huge part in how well a carb gets on the main circuit. Whats the timing and is the dizzy locked out, or is there a curve and how fast.




    No doubt the secondary is covering for no PV, but 12 jet sizes is huge.
    Sorry gn7 I totally overlooked where you asked about the timing. It is set at 36deg and it is in fact locked out.
    Howard Shovelnose Hydro "Wide Spread Panic", 454ci BBC on tha dope, Radiece Performance 3-blade cleaver, and 25% gears...

    Big thanks goes out to Tom Bentley of Menkins V-drives, and Tommy "Flatbottom" Hughes the man resonsible for getting me hooked on hotboats!!!

    My build> http://www.performanceboats.com/v-dr...e-project.html

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    Quote Originally Posted by gn7 View Post
    continue concentrating on the carb.
    I will do some wrenching and testing!!!

    Thanks
    Howard Shovelnose Hydro "Wide Spread Panic", 454ci BBC on tha dope, Radiece Performance 3-blade cleaver, and 25% gears...

    Big thanks goes out to Tom Bentley of Menkins V-drives, and Tommy "Flatbottom" Hughes the man resonsible for getting me hooked on hotboats!!!

    My build> http://www.performanceboats.com/v-dr...e-project.html

  12. #10
    cfm
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    Quote Originally Posted by 71ShovelNose View Post
    454ci BBC, 10.5:1, .660/.680 258/[email protected] on a 108 c/l solid roller, 990 heads, Team G intake (single plane), 750 holley (proform main body, 72's in the front w/4.5 powervalve, 84's in the rear w/o jet extensions), 17 pitch prop, 18 gears, early 70's Howard shovelnose.

    When in neutral the motor has excellent throttle response with 0 bog. Put it in gear and wack it and it stumbles around and won't recover until you back off and then roll back into it. Otherwise the carb is working flawlessly-makes a bunch of power and idles perfect. I want to get this bog sorted about before trying to spray it.

    Thanks,
    Sammy
    No load in neutral - thus why most motors have 'awesome throttle response' in neutral. This tells you nothing.

    72's seem awfully small to me - for almost any 454. But, your the one tuning it so you'll have to find out. Personally, I'd start upping the primary jet size while leaving all else alone- edit in: for now :edit done. If you get within 6#'s to the secondary's and the motor wants more fuel, then start upping the secondary's the same amt you up the primaries.

    How do you know when you've added enough jet ? It will start to run slower than the last 'best' tune. "Let the motor tell you what it wants."
    Last edited by cfm; 08-15-2011 at 02:18 PM.

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    gn7
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    Quote Originally Posted by cfm View Post
    No load in neutral - thus why most motors have 'awesome throttle response' in neutral. This tells you nothing.

    72's seem awfully small to me - for almost any 454. But, your the one tuning it so you'll have to find out. Personally, I'd start upping the primary jet size while leaving all else alone. If you get within 6#'s to the secondary's and the motor wants more fuel, then start upping the secondary's the same amt you up the primaries.

    How do you know when you've added enough jet ? It will start to run slower than the last 'best' tune. "Let the motor tell you what it wants."
    I agree CFM, 72 in the primaries are small, which is why I think the secondaries are overly large, in an atempt to richen the total mixture up at WOT. But that just creates a distribution issue. He could richen the pri, and it may very well help the bog issue, but be fat at WOT, even with a PV of 4.5 which is way to low for a N/A engine with a single 4 bbl of that size. He may only be below that for a short time before engine demand will raise the vac back up above that. 750 on that engine is pretty small. I wouldn't get to over large on the jetting. when that thing gets into the upper R's its going to create a pretty good pressure differential, and the jets are going to flow a shit load compared to the same carb on a 350 street engine. The smaller the carb gets, the greater the pressure differential, and the more fuel that will flow thru a given jet size.

    Very first thing I would do is dump the 4.5 PV. Its most likely only on line part time. If you wish to blank the PV, fine. But if he square jets it at 84 like the secondaries currently are, I guarantee it will be pig fat. Which s why I suggested mid to high 70's square with no PV to start.

    I wouldn't be one bit surprised with a 750 on that engine, it could easily be 72-74 pri with a 6.5 PV and 78-80 in the secondary, and still be a touch fat. Specially as it gets close to max R's. PV with that vac rating is adding nothing to the mix, at least not for very long. So with a non functioning PV, 72 are small. With a funtional PV, not som much. Specially on a 454 with the RPM potential of this thing. The thing will be trying to suck the boosters right out of the carb.



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    Last edited by gn7; 08-15-2011 at 02:07 PM.

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    cfm
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    Quote Originally Posted by gn7 View Post
    The thing will be trying to suck the boosters right out of the carb.
    LOL.


    Well, a vacuum guage will be his best friend. If this thing get's remotely close to 4.5"HG on the top end it's time to throw that 750 on the bench. Costing way too much power in the airflow department. If it's getting to 2.5:Hg or thereabouts, I agree, the thing could be in perfect tune and then as the RPMS get up there, a rich condition can happen because of the increasing pressure differential. Thus why smaller carbs on blow thru's.....always fighting to get more fuel.

    FYI: I'd be all over a 850 or tad larger. In my experience, 750's are for small blocks. Only big block I'd consider one for is a 330hp 454. Over 1.5"HG at WOT is too restrictive...in my book.

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    gn7
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    Quote Originally Posted by cfm View Post
    LOL.


    Well, a vacuum guage will be his best friend. If this thing get's remotely close to 4.5"HG on the top end it's time to throw that 750 on the bench. Costing way too much power in the airflow department. If it's getting to 2.5:Hg or thereabouts, I agree, the thing could be in perfect tune and then as the RPMS get up there, a rich condition can happen because of the increasing pressure differential. Thus why smaller carbs on blow thru's.....always fighting to get more fuel.

    FYI: I'd be all over a 850 or tad larger. In my experience, 750's are for small blocks. Only big block I'd consider one for is a 330hp 454. Over 1.5"HG at WOT is too restrictive...in my book.
    Exactly! It may not hit 4.5 at WOT, and the PV may stay open. But I still believe he would be better served with 6.5 and be sure. Your right, a vac guage would very usefull in telling him he is leaving HP on the table. But at 10 1/2 to 1 and that cam + a Team G, I would say it goes with asking.
    Biggest problem I see this thing having is trying to maintain a decent mix across the RPM range. What could be prefect ot 4000 part throttle could go dead rich at WOT and 6500. The carb was never intended to flow the air he is trying to pull thru it, which tends to throw it off its fuel curve as the R's climb. It could be fixed with air bleed correction. Look at 390 Nascar carbs. They work, but they are set up for it. Fighting an undersized carb can be every bit as frustrating as fighting an oversized dominator on a street small block. Just on opposite ends of the RPM scale.

    None the less,none of this is why it bogs. In fact it should have pretty decend response on the water until it hits some R's. Its probably the shooter size, or it needs jet extensions on the secondaries. depending on WHEN it hesitates.



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    Last edited by gn7; 08-15-2011 at 02:53 PM.

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    cfm
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    I like to get the basics tuned in first. IE: jetting, idle circuits, PV, and timing. SOunds like everything in that 'basics' list is okay for now, other than jetting. 72 is very low even with a PV. I'd crap myself if 72 is right on.

    Once that's all set, then playing with all the accelerator pump pieces is next.

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