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496 mercruiser

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    Member shadlee's Avatar
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    Default 496 mercruiser

    Anyone converted one of these to a carb and distributor? Got a dart intake and looking for the rest of the parts. Ignition, cooling and such. Any advice appreciated!

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    Default 496

    I think the trouble you will run into is the intake ports are way different and many other things will come up also, there will be other guys come along that will let you know, thats what came to mind first for me though. Probably could be done but it would take some modifying

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    Member shadlee's Avatar
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    My dart intake is actually made for the 8.1. Trying to figure out the cooling set up mostly and what size carb to run.

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    Oh ok cool

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    New here Beer:30's Avatar
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    You're actually wanting to go BACKWARDS? Are you also going to take the EFI off of the PU, SUV, or sedan you drive daily?
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    Senior Member Hass828's Avatar
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    Quote Originally Posted by Beer:30 View Post
    You're actually wanting to go BACKWARDS? Are you also going to take the EFI off of the PU, SUV, or sedan you drive daily?
    Here we go again. I dont think hes wanting to put the 496 in the wifes SUV.
    I own both and have much more BS from the 502 mpi in my daytona than I will ever have from my C&S carb on the jet.
    To each their own man but when I get tired of playing with the jet I'm going to build a twin turbocharged, intercooled engine with a blowthrough carb for the 25' daytona and sh-t can that pos efi . Then the only problem will be trying to come up with a drive that will live.
    Last edited by Hass828; 05-08-2012 at 06:15 PM.
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    New here Beer:30's Avatar
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    Name ONE BENEFIT to going backwards from EFI to CARB on a Vortec 8100. Just ONE.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    Senior Member EVILFORCE's Avatar
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    Quote Originally Posted by Beer:30 View Post
    Name ONE BENEFIT to going backwards from EFI to CARB on a Vortec 8100. Just ONE.
    A average old wrench can still work on it. You need to be young and smart to work on F.I.

    Right Bob?
    No Fool Like A Old Fool is there?

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    New here Beer:30's Avatar
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    Quote Originally Posted by EVILFORCE View Post
    A average old wrench can still work on it. You need to be young and smart to work on F.I.

    Right Bob?
    I have yet to see anyone on the lake WORKING on theirs.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    New here Beer:30's Avatar
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    496mag/HO Pros vs. Cons of converting backward from EFI to carb.

    PROs:
    1. "Anyone" can wrench on a carb.

    CONs:
    1. No more ECM to tell what sensor has gone bad.
    2. No more ECM to save the motor if there is low oil, low oil pressure, low fuel pressure, high water temp, low water pressure.
    3. No more knock sensor to keep the motor from detonation.
    4. Now have to pump throttle for cold starts.
    5. Now have rich warm starts.
    6. No more compensation for altitude / density altitude.
    7. Lack of precise fuel distribution.
    8. Possibility of fuel puddling in the intake.
    9. Have to run the blower EVERY time you start.
    10. Lack of RPM compensation when in-gear / out-of-gear.
    11. Power valve(s) to blow out / leak.
    12. Possibility of vapor-lock.
    13. Fuel available when key is off (run-on / dieseling / hydro-lock)

    I'm sure I left some out.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    Member shadlee's Avatar
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    Ok. Heres the deal. I got this long block from a local boat shop not being really familliar with the 8.1. So now i have this motor and not sure what is possible to do with it. I cant afford to buy a stand alone efi or come up with all the stocker crap and stuff. I have a carb intake for this motor and thats it. Throttle bodies? I dont know. Keep the suggestions coming! Any help is appreciated. Should I sell this and get a 454 or 502? My ears are open. Thanks guys.

  14. #12
    Senior Member Hass828's Avatar
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    Quote Originally Posted by Beer:30 View Post
    496mag/HO Pros vs. Cons of converting backward from EFI to carb.

    PROs:
    1. "Anyone" can wrench on a carb.

    CONs:
    1. No more ECM to tell what sensor has gone bad. No sensors to go bad
    2. No more ECM to save the motor if there is low oil, low oil pressure, low fuel pressure, high water temp, low water pressure. Never had any of those problems
    3. No more knock sensor to keep the motor from detonation. Never had my stuff that far out of tune, guess i must be good , huh?
    4. Now have to pump throttle for cold starts.Lazy
    5. Now have rich warm starts. Not with the C&S
    6. No more compensation for altitude / density altitude. I dont fly my boat that high
    7. Lack of precise fuel distribution. Wrong
    8. Possibility of fuel puddling in the intake. Never had a problem with that, must be lucky.
    9. Have to run the blower EVERY time you start. should be doing that anyway
    10. Lack of RPM compensation when in-gear / out-of-gear.
    11. Power valve(s) to blow out / leak. No worse than all the sensor to go bad
    12. Possibility of vapor-lock. That can happen with some efi systems too
    13. Fuel available when key is off (run-on / dieseling / hydro-lock) Must just be me but you seem to have alot of trouble with something so simple.
    I'm sure I left some out.
    Yet as great as you think efi is, they still give fits that even some of the guru's cant figure out. On my 502 MPI for instance. If you rev it up in neutral it will stay @ 1100 rpms and if you kill it and refire it idles back down just fine. Have put a new IAC or what ever you call the pos and checked everything they PROS could come up with but still does it.
    Another issue, If you run hard for a mile or so then come down off plane and let it idle the temp guage starts dropping and when it gets below 140* the engine thinks its cold and start blubbering from being to rich, if you idle it up a little the temp will stay up and all is fine. Put new sea water pump, thermostat, pulled all the hoses and everything is clean. Doesnt ever run to hot. Seems as though with the 29pitch dual props on the Blackhawk drive that it pulls the motor down low enough at idle that the circulator pump isnt flowing as much water as the seawater pump and the seawater pump is just flowing cold water past the temp sensor and out the exhaust.
    I've learned to deal with these issues and dont have any trouble using the boat, but with that being said I wouldnt have to be dealing with that BS with a carbed engine. The boat I had before this one was a carbed BBC in a 23ft Regal, it was an older boat . Had it for yrs and never touched the carb or hell the whole engine except to change the oil. And it NEVER had any of the issues you claim. And it didnt give the BS this new EFI deal does either.
    Dont go telling me just how easy it would be to fix the little problems either. I've talked to some of the best in the business on here and tried it all. Still does it. Doesnt cause any problems as long as you dont free rev it , which I seldom ever do, and when coming off plane just keep it above idle for a few seconds , but still no carb.

    Sorry to jack your thread OP , but I would stay carbed, JMO.
    Last edited by Hass828; 05-08-2012 at 08:14 PM.
    "if we keep doing it the same way we always do..we will always get the same results"
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    New here Beer:30's Avatar
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    OK, so the original poster now says he only has a long-block. While carb STILL is going backwards, at least he is not contemplating pulling off a MPFI intake and all of it's efficient hardware. He just looking to COMPLETE a motor. And in that respect, I would suggest you just look at a complete Gen IV, V, or VI motor instead of mess with a Gen VII. Not being familiar with it, you will be hunting for the pieces and parts to make it what you want - and that won't be easy.

    Hass, you are going to the wrong people on that hanging-at-1100-deal. If you had a laptop connected, you could watch either the TPS being hung-up just long enough for you to shut it off, or you would be able to see the marker hanging around either a map reading or IAC follower reading that it shouldn't. Someone is missing something, and it's not THAT hard. I tune EFIs all the time and you can watch ANYTHING YOU WANT - you just have to know which screen to watch. Rinda makes laptop software to view all of the tables. There are others too that make software to adjust and follow the MEFI ECMs.

    The 140-degree thing is probably as simple as MOVING the CTS to somewhere more stable? REAR water runner of the intake where flow is not as prominent AND cold water is not present? That being said - a carb is blind to temp and CAN'T ADJUST for cold/hot motor/water temps. So, you WILL have an un-correctable in-efficiency at some point in the temp spectrum. Be it rough cold-start or rich hot starts/idling. Jetting is FIXED on carbs, whereas it's constantly variable on EFI. Yes, the motor will PULL what it wants throught the venturies, but what's on the other side is STILL LIMITED and fixed. The EFI will adjust for altitude, heat, loaded boat / empty boat. EFI adjusts HUNDREDS of times per minute / if not per SECOND (some systems), a carb just sits there with a dunce cap on.

    I rode on a friend's Magic deck a month ago. 604" BBC, carbureted. It runs nice. Calm cam, 750hp, nothing outrageous. But without a choke, he fires it cold and it idles at about 500, just chugging. Not smooth at all. HAS to let it warm up a bit before going for fwd/rev on the outdrive. THEN, even when warmed up, that 30" prop drops it 300-400 rpm. So it dips and then recovers - with a bit of a brown "puff" from the tips. A bitchen carb just can't do the multitude of adjustments necessary to make in/out of gear transitions NEAR as smooth as even a HALF-ASS EFI tune can. Plus, he complains of a bit of fuel puddling on real cold mornings - where MPFI has the fuel being shot right at the intake valve. DO THAT with a carb.

    What SUPER car or SUPER boat COMES WITH A CARB THESE DAYS??? You can't tell me Alexi is really worried about EMISSIONS on his 800ci, 2000hp super motor! I don't see any carbs NEAR that thing. If carbs were ALL THAT, they would have a place there as well.

    You're a smart guy, Hass. You can't tell me otherwise. So, I know YOU know that all of the drivability and efficiency you get in your daily driver is JUST AS GOOD for a boat. Do we still play RECORDS and TAPES? Still ride on BIAS tires?? Do we not POWDER COAT more stuff than paint?? I have every bit of belief that you have your blow-through dialed in just as you want it. To be perfectly honest, you probably COULDN'T improve on your particular setup with EFI - aside from a few touches to under-the-curve (cold / high altitude) areas of the fuel curve. BUT, we're not talking specifically about blow-through turbo setups here. We're talking modest HP, ANYONE behind the wheel, turn-key drivability.

    So, touching on emissions - we all know that is why all mfgs have gone to EFI for their package engines. So that poises the question to you - - why CAN'T they make just as much HP/TQ and maintain their emissions with carbs??? If carbs are the end-all-be-all of fuel-mixers.......why are they so obsolete in the air - on land - and sea???

    Again on the CTS issue - I wholeheartedly believe ALL boats should have closed-cooling! Heat-exchangers are so prominent now, I don't see why someone would want to run WITHOUT one. Mine sits at 150-160 (160 therm) no matter what. WOT, idling, cruise. So, the motor doesn't get shocked with cold water. Every time you fire your 502 up, it gets a shot of cold water through it from the lake. No bueno.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

  16. #14
    gn7
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    I imagine you got a SMOK'N deal on this thing because anything the marine sealer got over scrap was a blessing.

    to my knowledge, you can use a stock standard deck dizzy with the Dart manifold.

    As much of a loser this motor is, the single best thing that you could do to the long block you have is drop a carb on it. If cammed correctly, it has the potential to bury a Merc 496 HO without mercy.
    It will, and never can be what a MKIV thru Gen 6 is. But your on the right track to making it better than you could ever hope for with the stock Merc/GM EFI without breaking the bank.

    I have to laugh at the guys that buy into Raylar's BS, and dump tons of cash into these things when Dart has now come to their rescue for a lot le$$ and alot more potential.

    Some good qualified head work and the right camshaft, thing can crush a Merc/GM EFI 8.1 and for alot less ca$h.



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