1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Mercruiser 3.7 Build, 1970 Cj5? Big Block Hurricane!

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

  1. Oct 3, 2018
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
    Joined:
    Sep 22, 2002
    Messages:
    5,000
    Anybody who has ever owned a 225 dauntless would probably tell you the vibration is a non issue.
     
    Keys5a likes this.
  2. Oct 3, 2018
    73 cj5

    73 cj5 Not ready for the junkyard yet 2020 Sponsor

    Mississippi
    Joined:
    Jan 10, 2014
    Messages:
    1,228
    Sage advice has been given in this thread. Build your drivetrain then put it in the Jeep when all your ducks are in a row unlike someone I know (y):)
     
  3. Oct 3, 2018
    Keys5a

    Keys5a Sponsor

    Florida Keys
    Joined:
    Jan 23, 2014
    Messages:
    2,634
    I know the durability of these engines is tried and true from a good friend with a pair in his 26 ft SeaRay. Late '80s vintage and it gets run hard. Trips are often 3 1/2 to 4 hours each way out in the ocean, running 20 -24 knots, almost every other weekend.
    Alternators flinging magnets is the most consistent problem. The engines got rebuilt about 7 years back, and the cams got machined for a pressed stainless sleeves. As long as the Mercruiser head gaskets are used, the open deck and iron/alloy expansion rates are not an issue. Put a Sierra gasket in there, and in 20 hours it will be leaking.
    -Donny
     
  4. Oct 3, 2018
    Keys5a

    Keys5a Sponsor

    Florida Keys
    Joined:
    Jan 23, 2014
    Messages:
    2,634
    Chevy Vega had an iron head on an alloy block, but they weren't the longest lived engine! I was inferring the corrosion factor of raw water cooling, with the two dissimilar metals at the head gasket. These Mercruiser engines don't usually have problems from the open deck.
    -Donny
     
  5. Oct 4, 2018
    gunner

    gunner Member

    Washington state...
    Joined:
    Dec 4, 2012
    Messages:
    598
    Great dialogue from the forum- makes the HAMB appear incoherent and easily distracted in comparison. I read that 64 page thread maybe 2-3 years ago. I recall it a tortuous read.

    I found the mercruiser head gaskets in the 2.5 and 3.0 engines to be all metal- stainless I'm sure. They seemed pretty thin but that could be to increase compression ratios a bit as much to reduce deterioration from raw water. The marine head gaskets are pretty pricey.

    I wonder if a copper head gasket would benefit that engine. Or just go with an aluminum head- love to see the power to weight ratio on it then!

    I hope you take it on- I like the inline 4s, though the tried and true 4.3 gets brought up for a reason.
     
    Last edited: Oct 4, 2018
  6. Oct 4, 2018
    Rich M.

    Rich M. Shoe pusher

    Maryland
    Joined:
    Mar 23, 2008
    Messages:
    746
    Copper and aluminum don't jive.
     
  7. Oct 4, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    I'm on page 32 of 64?
    To my understanding some of the head problems (I'll use the stock cast iron
    Head the first time build), are to do with the bolts being 9/16 instead of 1/2?
    Someone turned the center length down for more stretch clamping force, for when
    The head and cyl heat up at different rates?
    And use a mercruiser brand gasket only?
    And it should not heat up loafing around in a jeep, compared to the load that a prop puts on it?
    Problem 1 solved!
    Carefull assembly of the speedy sleeve and water pump seals?
    Problem 2 solved!
    Belt driven alt , fab some brackets, use pulley on stock balancer?
    Problem 3 solved!
    Use the stock 2bbl carb, a cast iron 460 ex manifold, points triggered msd ign,
    All the rest is easy but time consuming fab work?
    Except hooking to trans???
    Hope to have some pics up by Sunday!
    Back to my reading!
     
  8. Oct 4, 2018
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member

    Tantallon, Nova...
    Joined:
    Nov 22, 2003
    Messages:
    6,296
    No, they expand at different rates when they warm up. With the wrong material for the head gasket and/or not toquing the head bolts *exactly* right you could develop leaks or even permanently warp something. :(
     
    70cj5134f likes this.
  9. Oct 4, 2018
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
    Joined:
    Sep 22, 2002
    Messages:
    5,000
    Aluminum expands at around 2 1/2 times the rate of cast iron for the same temperature.
     
  10. Oct 4, 2018
    Keys5a

    Keys5a Sponsor

    Florida Keys
    Joined:
    Jan 23, 2014
    Messages:
    2,634
    To the best of my knowlege, there is not a speedy sleeve that will work for the camshaft nose. A tried and true fix is to machine down the nose extension of the cam, and machine a stainless sleeve (out of the proper alloy so it doesn't wear rapidly), press it in place, and finish machining to the original diameter.
    These engines have a bad reputation of leaky head gaskets because most rebuilds use an inferior aftermarket head gasket (even FelPro). If the OEM Mercruiser head gasket is used and surfaces correctly prep'ed, the head gasket doesn't present problems.
    I have looked at the aftermarket alloy 460 heads, but haven't opened my wallet yet!
    -Donny
     
  11. Oct 5, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    SKF 99087 Speedi-Sleeves

    Amazon.com: SKF 99087 Speedi-Sleeves: Automotive
     
  12. Oct 5, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    Or, maby and, turn down a bit and use a slightly smaller one?(1 poster did this).
    To my understanding u get 2 selves, one for each seal.
    Then if u get it all sealed up, the sleeve won't wear like the original cast did?
    I'm on page 44 of 64, lots of off topic reading to go through to get the meat of the story!
     
  13. Oct 5, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
  14. Oct 5, 2018
    gunner

    gunner Member

    Washington state...
    Joined:
    Dec 4, 2012
    Messages:
    598
    That was a good how-to. Takes away quite a bit of the mystery and the link to the alternator conversion should be looked at also. Along with Donny saying he bolted up a chevy bellhousing to the block has the project looking much more promising. Compared to this information, the HAMB thread doesn't help a whole lot.

    By the way, from what I've read, inline 4s- older ones without any counter balance or rotating shaft- tend to have a rougher idle. Especially once they get above 2.5 liters. AT 3.7L the 470 is going to have a rough idle. It's not something they worry about too much in marine use. Even the old 153 Chevy- a 2.5L- can benefit from softer motor mounts. Figuring out the motor mount system for the 470 could end up being a hurdle. Did you say that your engine had bosses on it?
     
    70cj5134f likes this.
  15. Oct 5, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    I'll know more Sunday, hope to get some close up pics of block up!
     
  16. Oct 5, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    I'm getting excited, happens each time I do an engine build, don't matter if it's
    The kids Yamaha 80 dirt bike, or my 455 powered rebel, I get all out of sorts,
    Thinking how to make things better.
    Ok, this 3.7 boat motor will probably be my most challenging build to date?
    A little about me.
    60 year old ,East TN ,hillbilly, GEARHEAD!
    When I was 12, I tore my dad's tiller apart, (And after his scolding, I put it back together,)
    And it actually ran?
    Benn wrenching ever since, had 2 years of auto shop in high school(learned more at home and
    in neighbors shop) then 2 years at NADC gas,diesel, and body shop, college in
    Nashville TN.
    Never wrenched for a livinng( except 1 summer working on small engines for father's hardware
    Store), but theirs always a project or two in my shop.
    I have several classic jap bikes, and 4 classic made in USA autos.
    I Couldn't have afforded any of these if I wasn't able to do the build work myself.
    I do all my own work, except upholstery, and some glass work.
    Now on to the 3.7

    My goal - a reliable , modestly powerfully, 200 ft. Lb torque engine for my willys cj5.
    All power in by 3500-4000 rpm. Don't need to start breaking the Dana 27?
    Budget I'd like to have it rolling for 1K, but I'll double that for a cap! 2K max, if at all possible.
    First build, maybe only build, stock everything except repair problem areas,
    Cam seal leak.
    Belt driven alt.
    And hooking it to my driveline?
     
  17. Oct 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    Bell housing bolt pattern?
    And some measurements .
    And I do have the side mount bosses!
    Tried to get it hung on engine stand, didn't have the right bolts,tomorrow maybe?
    It's about 29-30 in long. Bell mount to balancer
    Sprayed pb on every exposed bolt.

    20181006_205533.jpg 20181006_210702.jpg 20181006_210714.jpg 20181006_211616.jpg 20181006_211559.jpg
     
    Last edited: Oct 7, 2018
  18. Oct 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    Measurements?

    20181006_210814.jpg 20181006_210944.jpg 20181006_211027.jpg 20181006_210905.jpg
     
  19. Oct 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    Passed this in Ashville Nc on way home from myrtle beach.
    Belong to any y'all ?

    20181006_160620.jpg 20181006_160626.jpg 20181006_160700.jpg
     
  20. Oct 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    730
    Looks like the stock flywheel is drilled already for pressure plate?
    The hamb said some were? 20181006_210714.jpg
     

Share This Page

New Posts