SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: BIG JOHNSON on February 08, 2012, 06:50:52 AM
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Marine tech buddy of mine says I oughta clean or rebuild my quadrajet if its never been done. Guaranteed shit be floating or caked in there. I never messed w/ an automotive carb before.. another buddy of mine has a good Holley 750 for the taking, I just don't know how to tune the damn things.
So the question, am I better off rebuild the q-jet, or slap on the Holley and figure it out?
On side note, I think the boat runs rich to begin with, I always smell fuel. There's a tiny pump with its own linkage that sprays fuel down the hatch when you crack the throttle, I'm gonna back the setting off on the linkage and see what happs. If I mash throttle four times in a row quickly, I can almost turn the engine off.
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Only thing that scares me is screwing around with a perfectly good boat engine that starts and runs bitchin for what it is and its size.
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well if it aint broke dont fix it! in all the quadrajets i have dealt with , you leave them along. when they go bad. put a holley on. ;D
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Only thing that scares me is screwing around with a perfectly good boat engine that starts and runs bitchin for what it is and its size.
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IT'S CALLED PREVENTATIVE MAINTENANCE!
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really????? tell that to the guy who said yah! i can do this it looks easy!!!! ;D
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really????? tell that to the guy who said yah! i can do this it looks easy!!!! ;D
I said that once, now their is a holly in its place.
Fat fingered from the phone-Corey
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Only thing that scares me is screwing around with a perfectly good boat engine that starts and runs bitchin for what it is and its size.
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dont touch it. unless its to add a blower. >:D
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dont touch it. unless its to add a blower. >:D
And then shatter my pump, Hahahaha
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Gonna pull carb and rebuild this week. Decided against my buddie's Holly, ain't nothin wrong with mine and no sense in trying to get more power, 400hp but a heavy turd that won't dry out anyway.
Pops says his '89 Hallett gots same carb as mine and he may/may not have a brass float and coffee can full of jets, anyway.. anything specific I need besides a rebuild kit w new gaskets, accelerator pump, needle n seat, metering gizzy blah blah..? Hope Napa or someone sells it so I can get it quickly, no dice at O'reilly. Does Rochester sell kits or Fo aftermarket? Never piddled with a carb I've only owned diesels and fuel injected and the last boat just ran so never dicked with it.. Seems like it runs rich cuz I smell a little unburnt fuel here and there, maybe supposed to be like that? Pops says go down a jet size and try out.
Spark plugs that came out looked good but were gapped around .0025, I set mine to 45 cause that's what pops said and he's got gray hair so I sometimes listen.. could the shy gap cause a "rich" running condition?
Sorry lots of jumbled questions just wanna get as much done as I can while waiting for my Eff'd up upholstery to be finished.
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Pulled carb and rebuilt today. Got the kit, Napa.
Good thing I took it apart, original float was disintegrating.
Turns out the main jets are not serviceable, kinda sucks but oh well. Put in a new brass float, accelerator pump, gaskets and whatever else could interchange with the kit.
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Pulled carb and rebuilt today. Got the kit, Napa.
Good thing I took it apart, original float was disintegrating.
Turns out the main jets are not serviceable, kinda sucks but oh well. Put in a new brass float, accelerator pump, gaskets and whatever else could interchange with the kit.
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Rotten Chesters use different size metering rods, not jets.... :thumbup: :thumbup: :thumbup:
Do you need to fatten it up?
Talk to me Goose... :sly:
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Rotten Chesters use different size metering rods, not jets.... :thumbup: :thumbup: :thumbup:
Do you need to fatten it up?
Talk to me Goose... :sly:
No, was looking to lean it a shade. Thought I may have found my problem with the sunken float.. I backed off the accelerator pump one hole on its linkage to not dump so much fuel each time I flick throttle.
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No, was looking to lean it a shade. Thought I may have found my problem with the sunken float.. I backed off the accelerator pump one hole on its linkage to not dump so much fuel each time I flick throttle.
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Leave the accelerator arm where is was and go up one metering rod size...Does it run fat at WOT? that is really rare for a q-jet...Sounds like the plug gap was too tight and possibly to little timing...What ignition? What plugs?
The accelerator pumps on these are actually a bit inadequate, so in this case more is better, it will not cause it to run fat unless the check ball is FUBAR.
Where does it run fat? I love these carburetors, very tunable and they can run good, just need a little finesse.....
We will get through this bud, I got your back.... :sly: :screwy: ;D
GT
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I almost always smell raw fuel when I come to a stop or if idling and a breeze from the stern. Boat runs fine.
Maybe just how carbs are? I dunno chit, but it always smells gassy with no drips and it FOCKING EATS FUEL.
Maybe I'm overthinking without enough understanding.
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I almost always smell raw fuel when I come to a stop or if idling and a breeze from the stern. Boat runs fine.
Maybe just how carbs are? I dunno chit, but it always smells gassy with no drips and it FOCKING EATS FUEL.
Maybe I'm overthinking without enough understanding.
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I will tell you that idle fat has absolutely NOTHING to do with jetting....Purely idle mixture adjustment.... ;)
Get everything back together and I'll get you the 411. :sly:
GT
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Not HEI.. gonna set plugs to 35 thou.
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Not HEI.. gonna set plugs to 35 thou.
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Does it have points? Or electronic? Gonna go out on a limb and assume electronic. It actually has a GM HEI coil from a late model style ignition system which could very well be .045", but .035" will run regardless.
GT
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Does it have points? Or electronic? Gonna go out on a limb and assume electronic. It actually has a GM HEI coil from a late model style ignition system which could very well be .045", but .035" will run regardless.
GT
crate motor is a 93 marine power 454 sport-pac rated @ 390 HP... That's really all I gots. Internet seems of no help and engina owners manual just says its a Delco EST ign..
Edit: the manual does state .035 for plug gap, though I was advised by Google and a boat tech buddy to go .045..
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crate motor is a 93 marine power 454 sport-pac rated @ 390 HP... That's really all I gots. Internet seems of no help and engina owners manual just says its a Delco EST ign..
Edit: the manual does state .035 for plug gap, though I was advised by Google and a boat tech buddy to go .045..
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You should be at a .035" plug gap and 36*BTDC timing at 2500+ RPM. :sly:
The two idle mixture screws should be adjusted to achieve a proper fuel mixture at idle, idle speed should be approx 850-900 RPM in the water and engine warmed up with the choke completely off then open (counter clockwise) both idle screws about a turn and a half (will run fatter than all hell) then slowly turn closed (clockwise) until the engine idle begins to fall off, then back out 2/3 of on turn. Do this a few times for each screw backing it out 1/2 turn each and go back and forth (left and right).
Altitude and fuel quality both have an effect, so keep that in mind when going to different lakes.
Good hunting. :thumbup:
GT
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FWIW, previous guy had screws 2.5 turns out.
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FWIW, previous guy had screws 2.5 turns out.
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A good starting point is 2.5 turns out, I guess I should have clarified that the turn and a half was after an initial starting point of the 2.5 turns, if it is too lean when you go to do your turns in it will die out and you get frustrated... :banghead:
Good luck!
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A good starting point is 2.5 turns out, I guess I should have clarified that the turn and a half was after an initial starting point of the 2.5 turns, if it is too lean when you go to do your turns in it will die out and you get frustrated... :banghead:
Good luck!
Many thanks. It's still early enough in the year to figure things out. I wanna fire it up today for shits and grins but quickly found out I can't just take a u joint out to keep from spinning that new MPD pump
:banghead:
At least if I had a driver's seat I could go fool with it at Puddlestone.. guess I have to wait till Parker. Is like to try it with the accelerator pump backed off and just leave a small hammer and pin-pusher in the toolbox so I can change it back easily on the water if it pops and sneezes when I mash it.
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And does this thing really need a choke on it? It's got the heat riser dealy but even when its cold out the choke flap is almost wide open on it...
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And does this thing really need a choke on it? It's got the heat riser dealy but even when its cold out the choke flap is almost wide open on it...
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I would leave it on it until you get a chance to run it...The butterfly should be open by 3/16" when cold (checked by using a 3/16" drill bit inserted between the choke horn and the butterfly ;) )
I think you will find it will pop back through the carburetor with the accelerator pump backed off...Maybe not.... :-\
GT
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GT, got your ears on?
Ok an update. Got the carb on and was gonna fire it to ensure it will start. On mine I have to use a jumper wire to the fuel pump to bypass the oil pressure switch to prime the carb. I jumped it and the pump sang and never built pressure to shut off. I look down the hatch and its dumping fuel down the throat! My float is set correctly and I think the pressure from the pump is forcing through the needle and bypassing everything. There is no pressure regulator, does this mean I need to add one?
This should definitely explain why I smell raw fuel at idle, not accelerator pump pushing too much..
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not to beat a dead horse but this is why i dont like quadrajets. you have a float issue or something else stuck open take your screw driver handle and tap the float bowl as the fuel is dumping in it should stop! good luck!
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Got a copy loud and clear Big J...Come back ;D
What fuel pump are you using? :-\
I am thinking several things;
Please forgive the potential blunderings, I have spent the last few hours doing some much needed shop clean up with a very sore knee and have utilized some liquid frosty pain reliever, guess I go to the doctor tomorrow... :thumbdown:
If you are using a "performance" fuel pump, you will most definitely need to use a regulator.
If you have to use a jumper wire to get the pump to run to get the pump to start, you have the switch wired wrong (should be a three prong switch with a signal coming from either a momentary toggle on the dash or a lead coming from "I" on the starter solenoid. More on this later....
The pump should run continuously and not shut off on any sort of pressure (unless this is a special type of pump with a cut out switch (don't think I have ever seen one...)..
Rochester carbs need no more than 6 PSI to work right...There is a chance that the needle/seat have a problem, but if you put as much pressure to the carburetor that I am thinking you did, there is no way it will hold it back (most electric fuel pumps can generate over 20 PSI without a problem...
Was this the pump you were using before...Too damn lazy (and a little tipsy) to go back and read the whole thread... :-[
GT
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Tis the pump that came with the boat from Ultra, see below. Can't find any markings or anything in owners manual 'yet' still looking. Wiring is stock I am guessing. Where oil pres sender is, there's a T with sender on one side, pressure switch on the other.
Brand new float, needle and seat and chit from Napa.
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All I know about the pump is not to step on it.
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All I know about the pump is not to step on it.
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Hahaha!
You should be good with that setup.. :thumbup:
Need to pull the carburetor top and take a look see..
I recommend ALWAYS pulling the carburetor off the boat, taping closed the intake and work on the carburetor on a bench (or like me, on the kitchen table :o )..
Did you adjust the float height with the supplied paper gauge? Is there a possibility it did not go together correctly? Was the fuel coming out of the venturis or the accelerator pump ports?
GT
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Hahaha!
You should be good with that setup.. :thumbup:
Need to pull the carburetor top and take a look see..
I recommend ALWAYS pulling the carburetor off the boat, taping closed the intake and work on the carburetor on a bench (or like me, on the kitchen table :o )..
Did you adjust the float height with the supplied paper gauge? Is there a possibility it did not go together correctly? Was the fuel coming out of the venturis or the accelerator pump ports?
GT
Fuel was coming from venturis. Brass float was set at .25" per instruction sheet. Pops, whom has owned 6 carbureted big blocks, and my marine tech buddy was at the bench with me. It was the correct kit for the carb.. I think I need to put a gauge on it and see what's pushin, or go around that and put a regulator in that line from pump to carb. Is that normal to not have a regulator?
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Fuel was coming from venturis. Brass float was set at .25" per instruction sheet. Pops, whom has owned 6 carbureted big blocks, and my marine tech buddy was at the bench with me. It was the correct kit for the carb.. I think I need to put a gauge on it and see what's pushin, or go around that and put a regulator in that line from pump to carb. Is that normal to not have a regulator?
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Totally agree with checking the pressure at the supply line...And yes, that type of pump has a regulator in it.. 8)
GT
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Totally agree with checking the pressure at the supply line...And yes, that type of pump has a regulator in it.. 8)
GT
Float must be too high.
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Fuck this carburetor. Gonna go buy a Holley. I've checked and double checked lowered float... Fuel pushes right past needle unless I push the needle down with my thumb.
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It's hard to go wrong with holly
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sorry man ! but there a real b---h to get right!
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mine doin the same crap...
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**** this carburetor. Gonna go buy a Holley. I've checked and double checked lowered float... Fuel pushes right past needle unless I push the needle down with my thumb.
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x2 im real close 2 this same outcome :banghead:
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$35 Holley pressure regulator and a few brass fittings fixed it. My pump was putting out 8psi and I regulated down to 6 psi.
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$35 Holley pressure regulator and a few brass fittings fixed it. My pump was putting out 8psi and I regulated down to 6 psi.
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8) :thumbup:
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Just a kind word of advice to anyone who has no clue and dinkin around with this stuff.. if you pull the top section of the carb off to see how your float is reacting to fuel influx, be sure and hold the piviot point between float and needle when you buzz the fuel pump. If you don't hold it down, the fuel will launch that needle and float off the carb. Gasoline burns like a bitch in your eyes and sizzles in your ear.
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So I'm told this carb doesn't require more than 4.5 psi to keep motor well-fed. Is this adjustment going to change with engina running or need to be adjusted at idle?
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So I'm told this carb doesn't require more than 4.5 psi to keep motor well-fed. Is this adjustment going to change with engina running or need to be adjusted at idle?
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just my opinion but keep it at around 6 PSI (I thought I read you have a closed motor compartment), if the carburetors needle and float can hold it back with the engine off it will be fine...Lower than about 6 PSI and you run the risk of vapor locking the supply line at idle for long periods because of heat build up in the engine bay...
Rochester's have a very close ratio float assy., this is why they don't need the pressure. If you have a spring adjusted type regulator, the regulating valve will go wide open if needed to keep that 6PSI at the needle valve, so further adjustment should not be needed IMHO...I think you fixed it...Now go put that accelerator pump linkage back where it was, fill the fuel tank and the ice chest and go have some fun :beer: :beer: ....Sheese :screwy:
GT
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just my opinion but keep it at around 6 PSI (I thought I read you have a closed motor compartment), if the carburetors needle and float can hold it back with the engine off it will be fine...Lower than about 6 PSI and you run the risk of vapor locking the supply line at idle for long periods because of heat build up in the engine bay...
Rochester's have a very close ratio float assy., this is why they don't need the pressure. If you have a spring adjusted type regulator, the regulating valve will go wide open if needed to keep that 6PSI at the needle valve, so further adjustment should not be needed IMHO...I think you fixed it...Now go put that accelerator pump linkage back where it was, fill the fuel tank and the ice chest and go have some fun :beer: :beer: ....Sheese :screwy:
GT
Last thing I did was put accelerator pump back to max setting. Gauge sits at 6psi with motor off and needle holds it back. 7.5 psi is where needle gives way.
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Today's shakedown went awesome. Got only a small list to take care of.
I feel like I got 5mph more outa this thing with the major fuel fix and live timing adjustment. (it was redneck but it really free'd up the motor.)
No one in the guard shack at Elsie so free launch to boot!
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Just for your info, Quadrajets are known for leaking fuel from the bowl thru the throttle plate. There are a set of casting plugs in the bottom of the fuel bowl that over time can leak. The fix is to use 5 minute epoxy and seal them.
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Just for your info, Quadrajets are known for leaking fuel from the bowl thru the throttle plate. There are a set of casting plugs in the bottom of the fuel bowl that over time can leak. The fix is to use 5 minute epoxy and seal them.
In this case it was pushing the needle open no matter how low float was set. I'll be on the lookout for anything else that may start to leak such as you mentioned.
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Boat runs like a pink scalded dog. Only thing I encountered this past weekend in Parker is when idling, if I smash the throttle and hold it down I get a lil bit of pop-pop noise from exhaust and slight hesitation. If I roll into the pedal, then mash it, its fine.
Here again, before I put the regulator on it was constantly leaking fuel from venturis, so it always had more than ample fuel supply. Will any adjustment of air screws be the fix? I know GT mentioned the accelerator pumps on these are inadequate... I doubt its timing related, could be altitude as it didn't do this at Elsinore on the shakedown cruise. FWIW, the engine will turn 5-5200 rpm with no detonation/pinging and doesn't miss a beat except from idling to stabbed wide open.
Next time out I will back timing off and rule that out and fiddle with the air mixture screws though I have no clue what those screws effect.
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Boat runs like a pink scalded dog. Only thing I encountered this past weekend in Parker is when idling, if I smash the throttle and hold it down I get a lil bit of pop-pop noise from exhaust and slight hesitation. If I roll into the pedal, then mash it, its fine.
Here again, before I put the regulator on it was constantly leaking fuel from venturis, so it always had more than ample fuel supply. Will any adjustment of air screws be the fix? I know GT mentioned the accelerator pumps on these are inadequate... I doubt its timing related, could be altitude as it didn't do this at Elsinore on the shakedown cruise. FWIW, the engine will turn 5-5200 rpm with no detonation/pinging and doesn't miss a beat except from idling to stabbed wide open.
Next time out I will back timing off and rule that out and fiddle with the air mixture screws though I have no clue what those screws effect.
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Need more accelerator pump....One redneck fix would be to slow down the secondaries just a wee bit....In all honesty it sounds as though it is running pretty stout.. :thumbup: :thumbup:
To attempt slowing the secondaries it is a bit of a touchy adjustment, so in water testing would be paramount. There is a really small spring in the upper secondary butterfly that has a very small allen screw holding the shaft that has a small roll pin retaining the spring end. If you turn this pin with a small screw driver you are adjusting the secondary spring tension and allows the "fuel to catch up with the air" so to speak.
I have also had some success cutting some transition slots into the upper secondary butterfly, but this gets really touchy, especially given yours seems to run pretty well as it sits.
Fiddle slightly with the tensioning spring but be sure to mark it before you begin so you can get back to where it is now if things don't work out. If memory serves (rarely does) I always used 7/8 of a turn from touch on that shaft....
Good luck, sounds like it's pretty close to me... 8)
GT
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Boat runs like a pink scalded dog. Only thing I encountered this past weekend in Parker is when idling, if I smash the throttle and hold it down I get a lil bit of pop-pop noise from exhaust and slight hesitation. If I roll into the pedal, then mash it, its fine.
Here again, before I put the regulator on it was constantly leaking fuel from venturis, so it always had more than ample fuel supply. Will any adjustment of air screws be the fix? I know GT mentioned the accelerator pumps on these are inadequate... I doubt its timing related, could be altitude as it didn't do this at Elsinore on the shakedown cruise. FWIW, the engine will turn 5-5200 rpm with no detonation/pinging and doesn't miss a beat except from idling to stabbed wide open.
Next time out I will back timing off and rule that out and fiddle with the air mixture screws though I have no clue what those screws effect.
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Your pop-pop likely means you're a little lean in the power circuit. To eliminate it, you'll need to richen up the primaries a bit by changing your metering rods and/or power spring. Unless you're lucky and someone has already modified the power spring circuit with an external adjustment (unlikely). Does it have a small allen set screw (plug) on the top of the carb?
The idle mixture screws will only affect idle mixture. Set them for maximum (smoothest) rpm at the desired idle speed.
Sounds like you're real close. Make small changes from here on out. Good luck.
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I'm not lucky, I was the first person to touch the carb on this boat.
I am positive that the motor runs better now than it ever has.
Thanks for the advice guys, gonna try and swing going to Elsinore and get myself happier with how it runs.
Gonna dick with the air screws bc it does idle a bit shakey at 750 rpm compared to before.
With some more fine tuning I will be more than happy with the q-jet, I sure was impressed this past weekend even with the pop-pop. If I flick throttle before mashing, I can fool it with a squirt of fuel. I'll get'r figured then polish, wax and oil changes from here out!
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