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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 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Flywheel has holes in it for pressure plate, they must have used one out of Ford stock,6 of them threaded 5/16,coarse thread.
    Exhaust off, it must have weighed 50lbs.
    Oil on dipstick looks good, no water in that.
    New problem, 29in puts the pulley under the rad(slightly), if I can't get the pulley on back of balancer,
    I may have to shorten grill rad shell for a couple more inches clearence?
    I'd plate has numbers on it,wish I knew what they meant, what year? 4887142 ? 20181007_134109.jpg 20181007_123640.jpg 20181007_140305.jpg 20181007_140342.jpg 20181007_140315.jpg 20181007_134224.jpg
     
  2. Oct 7, 2018
    gunner

    gunner Member

    Washington state...
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    Clean looking engine. Stuff around here is all used in el pacifico and the salt water environment really takes its toll on metal.

    Get onto some of the marine sites or just google that serial number- probably give you the year of manufacture.

    Keep a loose eye out for a stock 460 cast exhaust manifold- bear in mind to look for the correct side. I'll bet you can get them all day long for cheap on ebay.

    If it came with a starter, keep it as I don't think chevy ones will fit. Notice the hole for the starter is on the drivers side, unlike the stock chevy position of pass side. That bell pattern is not an exact chevy 90* but maybe a bell would still fit with some adaptation.

    The marine exhaust manifold may have some value- they don't make them anymore I don't think
     
  3. Oct 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Goung to use a pas side exhaust and dump it forward like the 134!
    Hamb said int scout starter, its open back, without any bendix support.
    This is supposed to go in a std bell?
    They also mention a jeep bell from an iron duke???
    Figuring the right bell may be pita?
    Gave the flywheel a da standing with 50gt.
    20181007_201624.jpg
     
  4. Oct 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
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    Goung to use a pas side exhaust and dump it forward like the 134!
    Hamb said int scout starter, its open back, without any bendix support.
    This is supposed to go in a std bell?
    They also mention a jeep bell from an iron duke???
    Figuring the right bell may be pita?
    Gave the flywheel a da standing with 50gt.
    View attachment 44893
     
  5. Oct 7, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Number search results, 76-79 ?
    Hard to believe it's this old?
     
  6. Oct 8, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    The Iron Duke (ID) bell has a Chevy block pattern and was used with the light-duty 4-speeds the SR-4 and T-4 and the 5-speed T-5. I would not recommend any of these transmissions for a swap, just because they are considered marginal behind the Iron Duke and they won't easily adapt to your transfer case. I believe the ID bell can be drilled to a Ford pattern (according to Nick), and used with any of the Ford pattern transmissions including the T-18, T-19 and NP435 truck 4-speeds, or the top loader passenger car transmissions. Of these, only the T-18 can be readily adapted to your transfer case using junkyard parts. It should be possible to make the T-90 look like a Ford transmission using an adapter and bolt up to the redrilled ID bell, or even use the GM T-90 conversion and fit that to the ID bell.

    However, 1) the word is out about this bell, and I believe they are no longer widely available. Ask Daryl. 2) if you want to keep the T-90, you may as well use a SBC bell and the GM adapter for the T-90. These adapters come up on the used market pretty often. Not sure there's any advantage to the ID bell over a Chevy bell for this purpose.
     
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  7. Oct 8, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Ok help this dumbass hillbilly out?
    To keep my t90.
    Please give me a link to the correct bell and 90 adapter.
    I need to go into the 90 and rebuild anyway.
    So any sbc bell, and then an adapter for the 90?
    Should have this thing torn down by next weekend?
    Thanks all.
     
  8. Oct 8, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Sorry, I can't give you a recipe for this. Maybe someone else can. Donny says it's a Chevy bell pattern. Many thousands of Chevy V8s and V6s have been adapted to the T-90. There are adapters for that, available from both Novak and Advanced Adapters, and other makers in the past. Here's the Novak page - Adapting the Chevrolet & GM Standard Shift Bellhousings to the Jeep T90 Transmission These adapters can be found used, if you look around.

    Pretty sure this is such an unusual engine you're going to have to figure out the details on your own. If you can make the Chevy bell fit and work with the starter location, then you should be able to use an adapter to mate to the T-90.

    What I would do - I would buy a Chevy bell and see how it fits on the back of the engine. Then find or buy the GM-to-T90 adapter and fit that and my T-90 to the engine.
     
    Last edited: Oct 8, 2018
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  9. Oct 8, 2018
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    An added issue for 70CJ5134f to convert is he should have the later T90 "C" version with the 16 tooth main drive gear. All of the T90 to Chev adapters I know of use the wagon/truck 226 T90-J long main drive gear that only comes with 18 teeth. This would require he change the cluster gear to match the main drive input. These Chev adapters are aluminum about 2 1/2" thick and the front bearing retainer/throwout nose bolts on the front.
    The biggest setback I see with the 470 engine is machining the back of the crank for a pilot bearing. I will need to increase this bore to accept a converter nose for an automatic.
    -Donny
     
  10. Oct 9, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Have a friend trying to locate a bell for me to borrow?
    I question the (on hamb thread) 5/8 some say to mill
    Off back of block, to move bell closer to crank?
    Also, what to bore crank for, which pilot?

    Got the head off, pics tomorrow.
    It's std bore, hardley any ridge in top.
    759-6610-10 = 76 to 79 std forged piston. 4.35 bore(measured with caliper?).
    They set .025 in the hole.
    To help eliminate detonation, tighten quench , piston even with hole to .005 out.
    I'll have .025 milled off block.(hamb recomdation ) .
     
  11. Oct 9, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    Because other Mercruiser engines are sourced from General Motors, Mercruiser designed the 3.7 L engine with a GM bolt pattern on the motor mounts and bellhousing. Therefore, the 3.7 is interchangeable in boats with other Mercruiser engines

    Mercruiser 3.7 Specifications

    Found this in spec sheets on the 3.7.
     
  12. Oct 9, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    The G9N is 3/4" thick and does not require a new input shaft or cluster gear. It utilizes the factory input gear and works with the 2.79:1 first-gear T90A or the 3.34:1 first-gear T90C. This version will not work with the T90J, long input shaft transmissions. It is machined from 6061-T6 billet aluminum. Included are the adapter, GM bellhousing locator / throwout sleeve, seal and hardware.

    [​IMG]
    Kit G9N, adapting GM bellhousings to the Jeep T90A & T90C transmissions. Special short version
    Part #:
    G9N
    Price:
    $294.00
    weight:
     
  13. Oct 9, 2018
    gunner

    gunner Member

    Washington state...
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    I was going to mention this; it's the one I'll use with the Chevy 153 if I retain the T90..
     
  14. Oct 9, 2018
    gunner

    gunner Member

    Washington state...
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    5/8" of the back of the block (or maybe off a bellhousing)? Means the input shaft is not quite long enough to reach a pilot bushing, maybe. If that's the case, maybe you could just use the T90 and lose the 3/4" adapter mentioned above. The T90 input is ~5/8 to 3/4" longer than the chevy input (I think it's something like 7 1/4" vs 6 1/2"). You'd have to size the throwout bearing retainer and drill and beef up some mounting holes in the chevy bell (dodgy, I know, but I've seen it done most recently with a T98). The HAMB guys would not have been considering a T90. More likely a chevy transmission was being adapted. Just crazy enough to work? :confused: OK back to the padded cell.
     
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  15. Oct 9, 2018
    70cj5134f

    70cj5134f Member

    East Tn
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    So loose the adapt?
    Maybe drill the bell for the T90 pattern?
    Don't I need the adapt to center in bell?
    From what I've read finding a shop to mill the back of block amt easy, too large for most machines?
    That would be great if it works, and save me 3 C notes?

    Head and block pics.
    759-6610-10 std bore factory forged 76-79 piston.
    1539111553532295282725.jpg 15391115834101516649448.jpg 1539111630498174966654.jpg
     
  16. Oct 9, 2018
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    The bearing retainer is what centers the transmission in the bell housing. Machining the back of block is a disaster waiting to happen no matter what the guys on HAMB say. It will take a big machine to do it but please don’t. It will severely weaken the back of the aluminum block. 5/8” is alot on a cast aluminum part and I guarantee something will warp with that much material being removed.
     
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  17. Oct 9, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    $300 is cheap if it will make this combo work. Unlikely you're going to put any custom-machined combo together for less than that if you aren't a machinist with a full shop at your disposal. And yeah, machining 5/8" of the back of the block seems nutty - I can't see where that's coming from. The G9N will work with a conventional GM bell and a T-90 ... what's the hangup? Put the parts together on the shop floor and stop guessing.
     
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  18. Oct 9, 2018
    gunner

    gunner Member

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    We're starting to spin in circles (from all the guessing)- just like the HAMB guys eventually did with this engine!

    Here's my thinking on this last bit of talk of machining:
    1. ~5/8" needs to be machined off the bell or block to accept a Chevy trans such as Muncie or Saginaw (this is the HAMB- they deal with jalopy trannies, not T90s). The Merc is apparently set up differently from a stock Chev with 90* bellhousing
    2. Conversely, maybe the 5/8" can be added via the normal length of the T90. It's all the same.
    3. T90 stickout is ~7 1/2", GM trans stickout is 6 1/2". The GM trans is too short by ~5/8". Try the T90
    4. If the above works out, the G9N adapter would not be necessary, nor would it necessarily work in this application. Just because a GM bell will bolt up (are we sure it does?) doesn't mean flywheel, clutch, pilot bushing, crank location, etc will allow the adapter to line everything up. Nowhere in Novak's description does it say anything about a 470 Merc application.
    5. Mike's caution is similar to some of the guys of the HAMB talking about big milling machines etc. When the HAMB thread started in that direction, I sensed they were doomed:banghead:

    There's certainly no guarantee of the above working, but messing with an easily found and therefore disposable GM cast iron bellhousing is virtually free (I've got 2 extra bellhousings he can have to experiment with- there's plenty out there- saw 30 of them at the swap meet last weekend). Admittedly, it wouldn't hurt to have a machine shop at his disposal.
     
  19. Oct 9, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    If the SBC bell / G9N / T-90 will not work, that means the crankshaft end is deeper than a GM engine would be. If there is no pilot bearing pocket, wouldn't it make more sense to machine a pilot bearing assembly that extends from the crank end to meet the pilot tip? Perhaps something supported by the crank bolts? Could be significantly cheaper/easier than machining the crank end in situ. Supposedly there's no crank pocket now, so the engine's going to spend some time in the machine shop anyway. I know that some of the Jeep TH400 applications use a puck that goes into the crank end and sticks out to support the front of the torque convertor. Would not something like this be possible for the pilot tip?
     
    Last edited: Oct 9, 2018
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  20. Oct 9, 2018
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    Making this type of pilot would be relatively easy.
     
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