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Technical 292 to 700R4

Discussion in 'Traditional Hot Rods' started by george.barnes.754, Jan 14, 2018.

  1. My plan for a 5 speed for Lizzie just got shot to shit. Not enough clearance for a clutch pedal and an exhaust between the frame rails. Buddy has a 700R4 (non computer controlled) that I can HAVE so long as I go get it out of his yard. What flexplate/torque converter etc do I need to put it behind the hopped up 292 Chevy 6 in my 27 ford?

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  2. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    You need a 700R4 specific converter. A stock 292 flexplate should be fine, but the bolt pattern for the converter may be a different diameter. You can re-drill the flexplate. It it is not a hard thing to do. The converter is supporter by the front pump on the transmission side, and the crankshaft on the engine side. The pilot on the converter sets into a recess in the back of the crankshaft. That is what keeps it centered. All the bolts do is keep it tight against the flexplate, so even if you drill them a little off, it's no big deal, as long as the bolts fit.

    Use a flange bolts (and nuts, if required):
    [​IMG]
    Use bolts no longer than necessary.
     
    Last edited: Jan 14, 2018
  3. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    Make sure you know what a TV cable is, how it works, what the correct geometry for it is, and how to set it.

    None of that is hard, but messing that up means a wrecked transmission.
     
    belair likes this.
  4. Apparently in 75 (the year my motor was made) you could get a th350 or th400 behind it. Which flexplate do I need?

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  5. Joe H
    Joined: Feb 10, 2008
    Posts: 1,304

    Joe H
    Member

    I suspect it's the same flex plate with a duel bolt pattern drilled in it. The rings are different sizes depending on which starter you have.
     
  6. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    The stock flexplate has 168 teeth.

    From 1967-1989, I am seeing 11-1/2" and 11-1/4" converter diameters.

    There are common converters-a-plenty, for the 700R4 with a 11-1/2" pattern.

    11-1/2" is a common TH400 bolt circle.

    Flexplate: https://www.summitracing.com/search/part-type/flexplates/make/chevrolet/engine-size/4-8l-292/engine-family/gm-inline-6-cylinder/converter-bolt-pattern/11-500-in?N=4294949232+4294949315+4294951398+4294948673+4294949217+4294949308&SortBy=Default&SortOrder=Ascending

    Unless you have seriously hopped up the 292, a stock converter should be fine.

    Early 700R4 had a different input spline count. It is not an issue unless you are making huge power, but the converter needs to match. There should be a code on the side of the pan rail. From that, you can get the year.
     
  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    [​IMG]
    If there it a big letter K on the bell, or MD8 on the bell, that is a heavy duty case.
     
  8. I was looking at the autozone listings for a 75 c30. It showed 2 different plates

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  9. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    This is the proper TV cable geometry:
    [​IMG]
    If you are using a GM stock carburetor, or an aftermarket one, the cable attachment point is NOT correct for a 700R4. It is correct for a TH350. For most aftermarket carburetors you can acquire a geometry corrector. If you have a unique setup, you will need to roll-your-own,, to the above specs.
     
  10. 2 rochesters so guess I'm building my own

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  11. gimpyshotrods
    Joined: May 20, 2009
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    gimpyshotrods
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    Just grab the flexplate for a TH400 application. If it is not the right pattern, the holes are far enough away that they won't interfere with you re-drilling for the correct pattern. It is seriously easy.
     
    george.barnes.754 likes this.
  12. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    Maybe not. Are they Rochester 2-Jet's.

    If they are you might be able to adapt an off-the-shelf geometry corrector.

    If not, it isn't that hard.
     
  13. indyjps
    Joined: Feb 21, 2007
    Posts: 5,257

    indyjps
    Member

    The HAMB is amazing, less than an hour, complete build plan. Sounds like Gimpy has been down this road before.

    I just wanna know how it runs, 292 torque with the low first gear, should be a fun ride.
     
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  14. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    Yup. This ain't my first rodeo.
     
    josedigitaciones and indyjps like this.
  15. Stock crabs off a 75 chevy pickup (got them with the motor), going on an Offy intake

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  16. My kid put a 700R4 behind the 292 in his [my old] chevy pickup.....got rid of the 3 speed overdrive. The lock up converter was controlled with a toggle switch under the dash. He had to buy a little black box to make it work. I'll post a photo of the TV cable setup as soon as my finicky computer decides to cooperate with me...
    BYW, a 292 flex plate has it's own number of dowel pins in the back of the crank [I think its' 3?] and the balance weights are welded to the flex plate...has it's own balance.
     
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    ^^^Yup, exactly like that.^^^

    If you are running 2-carburetors, that's the setup for the rearward one. After that, a link just goes between the two.

    You can do a single-wire (no switch) torque converter lockup, if you want. With that, it locks in 4th, all by itself, unlocks everywhere else.
     
  18. driverquality
    Joined: Sep 17, 2017
    Posts: 22

    driverquality
    Member

    The converter bolt pattern should be the same as a TH350. Also, if your 700r4 valve body has tcc valve train (not all do as some were strictly computer controlled) TransGo 700-LU will make it lock up without any wires attached. Works pretty slick other than it may lug the engine in 4th depending on power and gearing.
     
  19. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    That works too.

    The 292 has a fair amount of torque, and it is going in a 27T. Even if he has tall gears, it still should scoot along just fine.
     
  20. squirrel
    Joined: Sep 23, 2004
    Posts: 52,772

    squirrel
    Member

    you want a flex plate for the TH350.

    The TH400 flex plate has 6 holes in the large pattern that won't fit the 700 converter. It is designed for a 6 lug TH400 converter.

    The 350 plate has 3 in the large pattern, and 3 in the smaller pattern.
     
  21. If the motor makes the power we hope it will make I should see 300hp and 400ft-lbs of torque easy. (The head actually flows enough to support 375hp) and when I get the quick change built my final drive should be around 3.50 in 3rd little less with the OD in the 700R4 4th gear. 1700lb car (at least that's what I'm going for) and a 28" rear tire should put me cruising at 80 right around peak torque output so it should be a damned fun ride. And able to light those skinny bias plies on demand down low.

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  22. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,829

    gimpyshotrods
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    Hold on, with both hands!
     
  23. Does the 292 have the same bolt pattern as the 235 ?
     
  24. I set up my 235 with a 200R4 OD tranny, Holley 390 4bbl, on a Clifford manifold. Got the tranny adaptor/flex plate from Patrick's I think or maybe Chevs of the 40s? Don't remember. Then got a TV cable adaptor from BowTie Overdirves.

    IMG_0590.JPG In progress frame front.JPG
     
  25. squirrel
    Joined: Sep 23, 2004
    Posts: 52,772

    squirrel
    Member

    the bellhousing is the same as the V8 engines. The crankshaft...not quite the same as the 235, but it looks similar with the three dowels. The 292 uses 1/2" bolts. And the early 292 engines have the normal single dowel 7/16" bolt circle.
     

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