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The elusive 224/3.7 MerCruiser banger

Discussion in 'The Hokey Ass Message Board' started by tjm73, Apr 9, 2008.

  1. There is not much room for a distributor and a water connection to co-exist up there, so in that one way, the original Mercruiser water outlet had an advantage.

    I'm presently rejetting for lower fuel consumption and a quadrajet is really good in being able to get economy and power too, but I never could see the need for their gigantic secondaries. The only downside is that it is harder to set up. I decided to use an autolite 2100 instead as it is easier to set up and is excellent although it lacks the performance range of a quadrajet. the 4100 is also well regarded and I'm told it is easy to set up.
     
    Last edited: May 15, 2012
  2. The Motocraft or Autolite 2100 is appropriate for a Mercruiser 470 in a car.
    It is simple, trouble free, easy to set up, cheap and appropriate in size, so
    I prefer it to the carburetors which come on a Mercruiser 470.

    I am posting hard to find jetting information from old Ford factory service manuals. 1964-1968
    It is pre smog era, sea level jetting. go two numbers leaner for altitudes over 5000 feet

    note: the jets are ford jets, the number is its diameter in thousandths of an inch

    note: Holley jets don't fit and are sized differently

    note: the power valves in these carbs often rupture on engine backfire

    note: my engine needed jets several steps smaller than standard for proper running.
    I determined that with an oxygen meter, vacuum gauge & exhaust gas temp meter

    note: mid-range mixture is determined by jet size, float level and boost ventruri size combined

    note: wet float level settings are commonly listed in carb repair kits, but the jets aren't..

    note: about the carb number [example C5ZF-G]
    1 the first letter represents the decade (C)= the 1960's
    2 the first number is the year of the decade (5) = fifth year of the decade =1965
    3 the second letter is the vehicle designator (Z) = Mustang



    __________________wet_______boost
    carburetor__jet____float______venturi____ transmission_ engine_other things affecting mixture
    _________________setting
    ________________________________1964__________________________________________
    C4ZF-F____43F____0.750"____1.010(CD)____manual____260____ positive crankcase vent 1964
    C4ZF-E____42F____0.750"____1.010(CA)____automatic_260 ____pcv

    ____________________________1965__________________________________________________
    C5ZF-A ____51F___0.875"____1.145(CG)___ manual____289____vent tube______________1965
    C5ZF-G____51F___0.875"____1.145(CG)____manual____289____pcv____________________1965
    C5ZF-B____48F____0.875____1.145(CE)____automatic__289____pcv____________________1965
    C5ZF-H____49F____0.875____1.145(CE) ___automatic__289____vent tube_______________1965

    ___________________________1966_______________________________________________________
    C6OF-A____51F__0.875____1.145(CG)___manual______289__________________________1966
    C6DF-B____50F__0.875____1.145(CE)___automatic____289__________________________1966
    C6DF-E____50F__0.750____1.145(P)____manual_______289___thermactor exhaust_____1966
    C6DF-F____49F__0.750____1.145(P)____automatic____289___"thermactor" exhaust____1966
    -------------------------------------------------------------------------------------------------------------------
    C6OF-B____57F__0.880____1.231(D)___manual______390_________________________1966
    C6OF-C____60F__0.880____1.330(D)___automatic___ 390_________________________1966
    C6OF-K____56F__0.810____1.231(P)___manual______390_____"thermactor"_exhaust__1966
    C6OF-L____60F__0.750____1.330(P)___automatic___390______thermactor___________1966

    _______________________________1967____________________________________________________
    C7DF-E_____ 44F__0.750___1.028____manual_______289_________________________1967
    C7DF-F_____ 42F__0.905___1.028____automatic_____289_________________________1967
    C7DF-G_____45F__0.905___1.028____manual________289___thermactor exhaust____1967
    C7DF-H_____45F__0.905___1.028____automatic______289___thermactor exhaust___1967
    C7DF-N_____53F__0.781___1.028____automatic______289___thermactor exhaust___1967
    C7DF-V_____50F__0.750___1.145____automatic______289___thermactor exhaust___1967
    -------------------------------------------------------------------------------------------------------------------
    C7OF-J______56F__0.875___1.231____manual_________390_______________________1967
    C7OF-L_____ 57F__0.905___1.231____manual_________390__thermactor exhaust___1967
    C7OF-M_____57F__0.905___1.231____manual_________390__thermactor exhaust___1967
    C7OF-U_____57F__0.875___1.233____automatic_______390__thermactor exhaust___1967
    C7OF-AD____54F__0.781___1.233____automatic_______390_______________________1967
    C7OF-AE____54F__0.781___1233_____MANUAL________390_______________________1967
    C7OF-AF____ 53F__0.781___1.233____automatic_______390__thermactor exhaust___1967
    C7OF-AK____54F__0.781___1.233____automatic_______390________________________1967
    C7OF-AL____54F__0.781___1.233____automatic_______390________________________1967
    note: The 2100 was modified for the 390 engine by having a larger throttle bore.
    it is 1.564 for C70F-J , C70F-L , C70F-M & 1.687 for the rest.
    The 2100 for the smaller engines (289/260) had a smaller 1.437 bore.
    The letters following the booster ventruri are its identity code.

    booster ventruri
    code__ size
    CA___1.010
    CD___1.010
    CE___1.145
    CG___1.145
    D____1.231/1.330
    P_____1.145/1.231/1.330 ( size depends on year made)

    __________________________1968________________________________
    CARB_____MAIN JET_PWR JET_PWR VALVE_FLOAT_BOOST V.
    C8AF-AK___ 49_____0.031_____7 TO 8___.750___1.080 ____MANUAL T. ___289/305__thermactor__287cfm

    C8ZF-G____48_____0.035_____5 TO6___.750____1.080____AUTOMATIC__289/305__287CFM _________________________________________________________________________________
     
    Last edited: Jun 22, 2012
  3. res0wc18
    Joined: Feb 2, 2012
    Posts: 14

    res0wc18
    Member

    nice work guys cool stuff going on here.

    I actually have moved on to another engine

    the 3.0l 181 gm engine found in boats

    trying to find some info on bellhousing pattern. i know they were marine specific and as much as people say i dont think they have anything in common with a 90 degree SBC pattern
     
  4. US_Marshall
    Joined: Oct 26, 2011
    Posts: 85

    US_Marshall
    Member

    I spent half a day working on an intake plug for casting, it's coming along nicely.

    [​IMG]

    [​IMG]

    I am using Buell 55-59mm throttle bodies.
     
  5. Mummert
    Joined: Jun 3, 2012
    Posts: 119

    Mummert
    Member

    A buddy and I built one of these a few years ago. This thread is pretty long and I haven't read it all.
    Some of the things we did.

    - Lightened counterweight on lathe beveled towards mains
    - stroked . 200"
    -6.7 Bbc rods and readily available .030 stroked pistons flattop.
    -reground stock cam. They have 1.5" basecircle so you can just about anything
    -crank to cam centerline like. 013" shorter than a 460. So we got a rollmaster line hone set and drilled
    the 3 bolt pattern on a rotary table. Crank an cam snout dia. same as 460
    -viper main studs had long thread engagement
    -We used arp head stud for a 460 they work great I think we torqued to 125 with oil and let er go.
    -As far as the deck goes we used an end mill 3/8 I think and milled down a1/4 and lather up some alum pins with. 005" press and pounded them to tie the open parts of the to adjacent parts of the the block before we bored it.

    There were other things... I can't remember if we used 351c main bearings or just loved up the stockers.
     
  6. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member

    I think you'll find those a bit big. 47.5mm like I am using (Chrysler Intrepid 3.5 94-95) flows about 345 CFM. The formula is 146 cfm/inch x .88 for the butterfly x area of the circle.
    Your 56mm throttles flow about 490 cfm.
    Bigger is not always better- you'll have to make a very very progressive linkage or all the engine's airflow needs are going to be taken care of in the first 15-20* of motion.
    It will be inherently very jumpy.
    You want to maintain at least 260 ft/sec mean (average) airflow through the intake tract at torque peak, and up to around 335 at hp peak/redline. You might be surprised by how small that is. I know my calcs are based off by bore of 4.40 and stroke of 4.17" (which equate to larger than most's) and the above-average volumetric efficiency of the Boss head...both of which skew my numbers larger. I know I had 52mm throttle bodies figured in my mind and for street use I decided they were too big.

    I am not just pulling numbers out of the air... I can do a much longer post about understanding mean airflow calculations, but I am at my desk at work on a Sunday, and nows not the time..lol
     
  7. It looks like fun casting a manifold. Take lots of photos to share with us.

    Buell as in motorcycle? A friend ran his ultralight engine with a carburetor which worked normally to half throttle, but above that, nothing changed when the throttle was opened wider...the carb was oversize for the engine. A different friend raced in a class where entrants were required to run a specific carb which had been specified too large by error...he won by getting the engine to hold together at higher rpm than the competition so he was able to use the big carb effectively. The Merc is not a high rpm engine, but with work that can be changed.
     
  8. US_Marshall
    Joined: Oct 26, 2011
    Posts: 85

    US_Marshall
    Member

    Iadr: without doing the math my self, your numbers seam close.

    I was searching for 50mm throttle bodies but could not locate any at resonable price. The buell motor cycle ones that I got are 59mm, a tad over kill but not too bad for fuel injection. The engine is going into a model a so I can't be rough with the throttle any ways.
     
  9. The Buell S1 Lightning's injection fed two 600cc cylinders. Each cylinder produced 45 to 50 hp. With 4 throttle bodies you have the capacity to meter 400 hp. There will not be much pumping loss!

    There are enough changes involved in this to make it interesting. I think the key in getting it to work will depend on being able to adjust the injection system.
     
  10. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    On an inline four cylinder engine there is no overlap of intake events. The throttle body needs to be big enough to supply the peak flow requirements of one cylinder. Tha means; disregarding the effects of intake volume, the size of throttle body needed for one throttle body feeding all four cylinders is the same size needed for when four individual throttle bodies are used. That's why you see Weber set-ups on small blocks that have a total flow capability of 2400 CFM. If you could find one, a single 2400 CFM carb on a four barrel manifold would obviously be too big. What that engine effectively has is a 300 CFM carburetor. Or if we were talking about dual plane manifolds(remember those are actually two separate four cylinder manifolds with half the carb feeding each half), the equivalent of a 600 CFM carb.
     
  11. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member

    That seems off. They used 59mm throttle bodies and had 90-100 hp?

    And even if it is correct, the math is wrong: 4 x 45-50 hp is 180 to 200
     
  12. So is there benefit in using a dual plane manifold on a 4 cylinder engine?
    I am already using a 2 barrel carb and it would be an interesting experiment.
    Yamaha used a manifold which switched back and forth between dual plane operation and single plane operation as it ran. [ I think they called it "V Boost"].
     
  13. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member

    Anyway I will come back to throttlebody size, but I thought I'd post a few attachments of the parts gathering I've done so far.

    You remember I had wanted .500" shanked studs- well I got the exact dimensions I needed by buying C&C Motorsport's studs and having them machined down.
    I also am showing a pic of the 3 angles of the intake bolt holes on a Boss head. The side of the head is 9 degrees to vertical (99 to deck). Then NONE of the intake bolt holes are 90* to that. I was just doing casual measurements for later, but my hand written notes seem contradictory- it seems one pair is 45* to Deck, another is 22.5degress to deck, and one is something in between- about 33 degrees. Looks to me like in at least two of the 3 cases, they referenced the deck rather than the actual mounting surface when chosing machining angles.
    I looked elsewhere where I'd drawn some not-to-scale doodles and see when I referenced the intake mounting surface I called out 38(142)*, 9*, and 60(120)....?? Obviously I am confused. Not too many are using Boss heads, so this is mostly my problem..lol

    The black corrogated tubing is stuff I use to lay out tubing runs- it holds its shape very well. The "closed up" sections would be where I position the throttle bodies. The rest is to get a "tuned length". Also shown is the D-shaped tubing- I will weld on a "tongue" to the intake flange that sits on the floor of the port to decrease area.

    The other pics show changing from dual "roller" cam springs to single "flat tappet" springs using the very trick cam action compressor loaned to me by a friend.
     

    Attached Files:

    Last edited: Jun 16, 2012
  14. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    Sorry about the confusion. A dual plane manifold for a V-8 is two four cylinder intakes. That eliminates overlap between cylinders, and the tendency for some cylinders to rob from adjacent ones. Some divided inline four cylinder intakes have been done for packaging or improved runner shape. But the simple answer is no, there is no benefit gained by dividing an inline four cylinder intake manifold.

    Yamaha V-Boost bikes have a carb for each cylinder. At higher RPMs a buttery fly opens allowing adjacent carbs to help each other. That alloows a 'proper" sized carb for normal use, and more casburetor flow at higher loads/RPMs. It would be the same as connecting the two halves of a dual plane V-8 manifold together at at the carburetor, at high loads/RPMs. Or another way to think of it; a 2 or 4 barrel carburetor with electronically controlled secondaries.
     
  15. carburetor sizing...I just got more data
    The carburetor I am using, rated at 287 cfm was for a 289 or 305 ford.
    merc 470 at 225 cubic inches would displace:
    312 *cfm at 5000 rpm
    260 cfm at 4000 rpm
    195 cfm at 3000 rpm.

    It runs very strongly at 4000 rpm so this carb seems sized properly to 4000 rpm

    * ( 225 in^3 x 5000 rpm / 1725 in^3 per ft^3 ) /2 = 312 cfm
    it is divided by 2 as being a 4 stroke engine, it rotates twice to have one power stroke.

    the carb is at its maximum airflow when the engine is at 4600rpm
    so it is sized properly for my use.
     
    Last edited: Jun 22, 2012
  16. dawford
    Joined: Apr 25, 2010
    Posts: 499

    dawford
    Member

    I can't imagine why the fools at Mercury Marine would put a 750 cfm QuadraJet on their 3.7 liter 190 hp engine that is set up to work optimally at 4800 rpm. They must not use real engineers. :D:D

    GM must of made an even a bigger mistake by using a similar QuadraJet on the early 3.8 liter Buick Grand national Turbo. :D:D

    I like to leave as much alone as possible with the exception of the cast iron head as I firmly believe that the original engineers probably knew a lot more than I do about getting the most reliable power out of this engine.

    Dick :) :) :)
     
    Last edited: Jun 22, 2012
  17. Isn't there a wide range of flow rates for different quadrajets? Its complexity is compensated for by its ability to deal with a wide range in flow rates. Would the huge secondaries even be open on an engine flowing 313 cfm? It must have some attribute to be chosen over the Rochester "2 jet".
    I believe you wrote that the engine responds well to more breathing, but which quadrajet would be appropriate?

    For an application running 14 psi boost, a large capacity carburetor or fuel injection would be a clear requirement.


    An Autolite 2100 is much simpler (making it less expensive) and has an easier setup but this involves a more restricted operation range. For a humble carburetor it works very well.

    As to their engineering, their error in deck height/compression ratio is abundantly documented. Their water pump drive was "too clever" to keep antifreeze out of the oil and the rationale of a water cooled voltage regulator remains a mystery to me. After discussing deck height with Mercruiser, I have the impression that some members of this discussion group have a better understanding of its effects on detonation.

    No one has all of the answers. At best we learn form our mistakes and from the mistakes of others. That is why this thread is so valuable.
     
  18. dawford
    Joined: Apr 25, 2010
    Posts: 499

    dawford
    Member

    Dennis,

    I definitely don't have all of the answers as to how to best convert these engines for use in a car so that is why I try to change as little as possible.

    I certainly agree with you about Mercury Marine Engineers trying to use outboard engine design techniques in the engineering of this engine.

    As to the 8.8 to 1 compression ratio and the problem with predetonation I understand that that problem was caused by an unexpected change in gasoline formulation.

    That caused them to have to retard the timing as a solution.

    With California gasoline I believe that using this engine in a light weight car it will be possible to run regular 87 octane gasoline at full timing, however if that is not possible I will still have the option of using mid range or premium.

    My experience with engine knock has been that when under full power and under extreme load engines have a tendency to knock. The conditions the 470 engines came up against in a boat.

    I do not expect to have the engine ever experience much of a load unless it is going up hill in too high a gear.

    With a standard transmission it is always possible to over load the engine.

    The QuadraJet carbs that I use are off the 190 engines and have been jetted for the 190.

    I am fortunate to have a boat mechanic who is an expert in making the QuadraJet perform reliably.

    Dick :) :) :)
     
    Last edited: Jun 23, 2012
  19. My engine has never knocked, even overgeared with 6.00 16 tires and a 3.07 axle ratio. My car weighs 1800 lbs. and the engine has tight squish. It seems immune to knocking.

    The aluminum head is a good idea, less weight and as it resists preignition.
    I do not think you will encounter knocking.

    Dennis
     
    Last edited: Jun 26, 2012
  20. Above is a simplified list of Autolite/Motocraft 2100 carburetors appropriate for a mercruiser 470.

    I bought 6 of these carburetors paying no attention to the carb id tag.
    Some worked well others didn't, I assume due to a sizing issue. So if you buy one, read the tag first.

    2100's made for the 260/289/305 are the ones I would choose.

    There is a negative side to these carbs. Power valves blow out when the engine backfires. Holley can be equipped with a valve to prevent this, autolite can't. On the other hand, you will not need the backfire valve if the engine is tuned well and the 2100 is much cheaper to buy. The best two cost $5 each but $20 is a common price.
     
  21. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member

    I don't see why the link bar is being thought of as unchangeable. It's a flat bit of steel, easily welded etc. When the below link bar dropps down it will be below deck. Its odd shape doesn't mean anything- it just needs to keep the lifters aligned. Ther are not great or unusual forces on it.
    Of course you'd still need a steel core. I suspect what Neff and From did on the 9600 rpm dragster is run a steel machining that didn't have oil pump /distributor gear due to running dry sump/crank trigger
     

    Attached Files:

    Last edited: Jul 2, 2012
  22. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member


    Deck plate
    also clearly visible in the following two pics (934+935) and the attachment of Clint Neff's (maybe still with help from Canadian David From??) newest build, which is to supercede the engine that went 7.78 all motor.
    So, I guess those who wanted an "option" to get around the open deck liner design, there you have it. Machine the stock bore tops' outside diameters round (or for a full race build you will already have installed new liners), machine a ~23 x 8 piece of .75 or .875 or 1.0 alloy to fit the 4 bores at 4.900" spacing and the headbolts, cut away the outer perimeter of the Mercruiser OE block, press together. Route cooling as you see fit.
    Not 100% sure how sealing to the block & liners is best done, but anyway, two experienced engine builder both came to this solution separately.

    Note the photoed build using the race heads with 4 extra small external head bolts/studs per side, and that these are tied to the deck plate, which makes me curious how the deck plate is held to the block? or does it just mean then deck plate is sandwiched to the block by the primary 10 head studs and the outer ones just leverage off that?

     

    Attached Files:

    Last edited: Jul 2, 2012
  23. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member

    No, each cylinder on a Buell has it's own throttle body:

    http://www.ebay.co.uk/itm/Buell-112...rcycles_Parts_Accessories&hash=item43ac7cec9a
     
  24. US_Marshall
    Joined: Oct 26, 2011
    Posts: 85

    US_Marshall
    Member

    The link bar can be changed, its clearance that is an issue. The "U" shaped link bar isn't a bad idea, if they are dropped in with the link facing the cylinders.

    The steel core is not a must, just increase longevity.
     
  25. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member

    Running a cast core and rollers seemed to work for late 80's early 90's small blocks of both Chev and Ford, but in the aftermarket it is a bit hits and miss. I used to be a counter person at a speed shop, and before that a supervisor of warehouseman for the same company, and I've handled a lot of "warranty" cast iron core rollers, and gave a sympathetic ear to the owners of 'em.

    That said, I also don't think you can treat *any* cast core to be roller suitable,- I think the core itself is different material.

    What distributor is that you are using? Fiero?

    (I want to get back to a airflow .DOC I wrote up, and also back to the cooling system, though on that I think I am going to sit on my hands until the headgaskets arrive, in case they need to show me a detail of the cooling)
     
  26. US_Marshall
    Joined: Oct 26, 2011
    Posts: 85

    US_Marshall
    Member

    The diagram you made up for your cooling sysytem looks good.

    The distributor is off the mercruiser 3.0, pretty much the same one on the fiero.
     
  27. Fuel consumption reduced: My mercruiser engined car was getting 15 mpg but I rejetted it and took it on a 250 mile drive. It got 23 mpg pulling a teardrop camping trailer.
     
  28. Bad Zuk
    Joined: Mar 10, 2011
    Posts: 11

    Bad Zuk
    Member
    from US

    Could you please share your jet sizes? I just got mine running and driving but it is running really rich. Almost undriveable. I drilled another hole in the accelerator pump linkage and that helped, but it needs to be leaned out, my guess is a lot.

    Sent from my SPH-D710 using Tapatalk
     
  29. Bad Zuk
    Joined: Mar 10, 2011
    Posts: 11

    Bad Zuk
    Member
    from US

    Never mind, I see you are using a different carb.

    Anyone have any experience with these 2bl Rochesters? Dennis what is the reason for switching to the auto lite carbs?

    Sent from my SPH-D710 using Tapatalk
     
  30. iadr
    Joined: Apr 14, 2007
    Posts: 147

    iadr
    Member

    Tell us about your project? By your nickname it could be a Sidekick? That's what I am building my Mercriuser based motor to go in.

    As far as carb issues- read what stractor has to say here:
    http://www.breezeworks.net/cgi-bin/...ads.asp?ForumID=1&TopicID=2110&PagePosition=2
     

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