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Mercruiser 3.7 Build, 1970 Cj5? Big Block Hurricane!

Discussion in 'Early CJ5 and CJ6 Tech' started by 70cj5134f, Sep 27, 2018.

  1. Oct 15, 2018
    Keys5a

    Keys5a Sponsor Sponsor

    Florida Keys
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    200 hp is going to require a re-profiled cam and the 4bbl intake. This is not a high performance engine. Remember, Mercruiser recommends a 4300 rpm limit on continuous use (what boaters call Wide Open Throttle) under load. I expect a very short life if this is exceeded. The beauty of this engine is most of the torque is all in by around 2200 rpm, reletively flat the rest of the way up.
    -Donny
     
    Last edited: Oct 15, 2018
    70cj5134f likes this.
  2. Oct 16, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    The 470 merc gasket has special sealer on it , to my understanding.
    No ridge, just a light rust coating above ring travel.
    .038 compressed thickness on gasket.
    See what it would cost to ship to 37891?
    Thanks
     
  3. Oct 16, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Can't believe all I read on the Hamb, but several were claiming to spin
    these things to 5500-6000rpm for short burst, their theory, not near the load
    on engine in a car vs the constant load of a prop?
    I hope u r right bout that torque curve, I love this little tractor motor 134f torque.
    The 3.7 should pull well from idle to 4k?
    Not really concerned with the hp.
    But twice the torque I have now will be great.
    And Ford planned to offer this engine as a platform for some kind of race engine,
    But the deal fell through. I found that researching the 3.7 on web, not on Hamb.
    Hamb claiming 300hp+, with a custom cam and alum 460 head,and 4bbl.
     
  4. Oct 16, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    As far as decking the block, I c no negitive effects, the tighter the quench, the
    more power and less chance of detonation Is what I find doing research.
    I hope so.
     
  5. Oct 17, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Found this on Ford 460 site.

    There is more power than just raising the compression by using quench. Here is a quote from Scott Johnson and Paul Kane on the subject of the importance of quench and engine performance. In all the engine builds, this is factored in.

    “Quench is the distance between the flat portion of the cylinder head deck and the top of the piston. The early BBF's set the piston about .010" below deck at TDC. Combined with a head gasket of about .040" thick this made for a quench distance of about .050". The later 460's set the piston even further below deck at TDC to further reduce static C/R with a resulting quench distance of some.065" which is really marginal.

    The reason quench is important? As the piston approaches TDC the air fuel mixture in that area is violently forced into the chamber proper and serves to: rehomogenize the mixture in the chamber and cool the chamber resulting in greater detonation tolerance for a given static compression ratio. The name is derived from the fact that the small crevice area there serves to quench the flame front.

    A quench distance greater than .060" loses much of the effectiveness of the design. I set most of my combos at Deck height for higher RPM use and about set the piston about .005" out of the hole for lower RPM use. Tight quench makes more torque for a given static C/R plain and simple. 7 to 10 pound feet for every .010" you close the quench distance is nothing to sneeze at.
     
  6. Oct 17, 2018
    TIm E

    TIm E Member Sponsor 2019 Sponsor

    NW Arkansas
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    Very interesting...and very interested to see a big block 4 cyl in a Jeep! :watch:

    All this popcorn and quench talk is making me thirsty...
     
  7. Oct 17, 2018
    Mcruff

    Mcruff Earlycj5 Machinist Sponsor

    Albertville, AL
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    That is fine but decking the block .025” will increase your compression and with iron heads will cause pre detonation due to the increase in compression. Hi performance guys rarely if ever use anything but aluminum heads. The whole reason for sinking the pistons farther down the bore was to lower the compression to run on pump gas. You won’t be able to remove enough material in the chamber to bring the compression back down without milling it. So with this setup mid or premium fuel will be in your future. Polishing the chamber smooth will help some with pre detonation but it won’t cure the problem completely.
     
  8. Oct 17, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Running premium fuel ok by me, I'm used to it in all my classic cars anyway. Most 9-9.5 to 1
    Approx how much will .025 increase compression?
    4.36 bore.

    Meanest ballencer I've ever pulled?
    Whack center bolt with shop hammer, turn bout 15 degrees ,then whack again.
    Coming apart as we speak.

    1539793460088384900042.jpg
     
  9. Oct 17, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Kinda ugly amt it?
    Several on I-boat forum recommend removing the magnets,(may come loose
    and damage timing cover), what do youall think?
    I question it because of messing up the factory ballence but I'll
    be adding weight on the other end,pressure plate?

    15397944245411668587148.jpg
     
  10. Oct 17, 2018
    Mcruff

    Mcruff Earlycj5 Machinist Sponsor

    Albertville, AL
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    Removing the magnets is akin to removing the oil pump on a 2 stroke engine. Sounds good but on paper is not reasonable. The magnets are bonded on the hub, the hub spins and holds the magnets in place with centrifugal force. Don’t really see them coming loose.
     
  11. Oct 17, 2018
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Is that a Yamaha RT180 in the background?
     
  12. Oct 17, 2018
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

    Tantallon, Nova...
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    I'd leave them alone. You can loose the stator coil though.
     
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  13. Oct 17, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Yes it's a yam 80, my 8 year old son. I got a rmx 250, kinda like 2stroke.
    Yes stater is staying off.
    I'll leave mag in.
    Again, meanest time cover ove ever removed, had to drive putty knife in gasket to free.
    Lh threads on pump impeller.
    Theirs some slack on chain, maybe why it has tensioner, still looks low hours engine.
    Small amount of sludge in water passage.
    15397988160521205255391.jpg 15397988160521205255391.jpg 15397988618392050860513.jpg 15397988160521205255391.jpg 15397988618392050860513.jpg
     
  14. Oct 17, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Chain tensioner, hardley any wear.
    66 pin chain. May be BBC. Both sprockets look good.
    Cam snout .871 , grove .870. I'll speedy sleeve for. A permanent repair.
    Problem 1, broken cam retainer thrust plate ,(friend says looks like a Ford part?)
    Cam bearings nice and snug.Lobes look good.
    15398082698541729448822.jpg 1539808307872636403260.jpg 15398083622862113632183.jpg
     
  15. Oct 17, 2018
    Keys5a

    Keys5a Sponsor Sponsor

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    On these engines used in a salt water environment, the magnets bonded in the balancer frequently liberate themselves. I may still have some photos of the engine box on a friends Wellcraft where several segments of magnet were imbedded in the fiberglass. There is also a plastic coolant overflow bottle on the front of the engine that was shredded by flying magnets.
    If your magnets are tighly bonded, you may leave them alone. If one is loose, a chisel will loosten the rest.
    -Donny
     
  16. Oct 18, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Their all nice and tight (magnets), think I'll leave them in.
    Got # 1 piston out (pic tomorrow), crank looks good,
    Rod Bearing has merc logo and clevite 77 stamp.
    Piston skirt, minimal scuffing , but top ring rust stuck?
    I'll soak them in brake fluid when all out (it melts the black carbon).
    Except for the stretched chain, all looks like low hour engine.
    It does have the early cam snout and alum oil pump. 76-79
    Found a cam thrust plate,15$,it ordered.
     
  17. Oct 18, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Repair for cam cam snout
    Federal Mogul 99087 Redi-Sleeve, for Mercruiser 4-cyliner 3.7-Liter (224 cu. in.) Aluminum Block Engine Cam Shaft. Models 170, 470, 485.

    Federal Mogul 99087 Redi-Sleeve Cam Shaft 3.7-Liter

    Their priced all over the place local Napa also has.
     
  18. Oct 18, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    1539895786392142908395.jpg 1539895810730137969316.jpg crank will only need a polish.
    Hardly any ridge in cylinder after I took my dingleberry hone through it couple times.
    Some light rust spots in bottom of cylinder below ring travel.
     
  19. Oct 18, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Got tired of grease work, had to do a little clean-up?

    15398979734641562277363.jpg
     

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