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Question: Short crank in a 400

Discussion in 'The Hokey Ass Message Board' started by raven, Jul 8, 2008.

  1. raven
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    raven
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    What would be the ending cubic inch displacement of a sbc 400 block with a 283 crank?
    327 crank?
    r
  2. tjm73
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    tjm73 Member

    cubic inch = (bore/2)^2 * pi * stroke * # cylinders

    soooo......

    283 crank; (4.125/2)^2 * 3.14 * 3 * 8 = 320.6
    327 crank; (4.125/2)^2 * 3.14 * 3.25 * 8 = 347.3
    Last edited: Jul 8, 2008
  3. billbrown
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    billbrown BANNED

    really stupid cubic inches. just use a 3.48 stroke and build the greatest small block combonation of all time.the 377.
  4. raven
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    raven
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    Thanks for the good and stupid answers.
    The idea is a sizeable cubic inch displacement and a short stroke for revving.
    r
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  5. Put a 283 crank in a 327. That makes a 302.
  6. tjm73
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    tjm73 Member

    Traditionally recognized rev limits have piston speed around 4000 feet per second.

    If you take (4000fps * 6) / stroke = pratical rpm limit. The 6 is a constant.

    You can re-arrainge to calculate specific fps based on rpm. fps = (rpm * stroke) / 6

    Personally, I would add stroke for a street car and make the rpm range top out at 6000ish rpm. That's a stroke up to around 4.00-4.25" which gives 427-454 cubic inch.

    I feel rev'ing is for race cars and torque is for street cars.
    Last edited: Jul 8, 2008
  7. 53sled
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    53sled Member

    Robin,

    Hot rod built a 400 with a 327 crank a while back with ford 300 rods, it made ridiculous torque. It had a slight bore and came out to about 352 cubes. Here is a link
  8. tjm73
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    tjm73 Member

    HR did a "The 351W Ford Should Have Built" too. Same kind of results. I missed this article. Interesting.
  9. patrick2965
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    patrick2965 Member

    Add 10lb boost with twin T3 turbos with good flowing cylinder heads and you have a beast. Over 1000 hp at the crank with correct components
  10. raven
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    raven
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    I appreciate the serious responses. The other ones I can do without.
    This is an exercise in thinking outside the box, for those of you who choose to make stupid remarks.
    This is not for a street car, so free-er thinking is allowed.
    And yes, I know a 283 crank in a 327 makes a 302.
    I'll build one of those later...
    r
    Last edited: Jul 8, 2008
  11. raven
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    raven
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    Does anything need to be done to the rods?
    Are the Ford 300 rods big ends the correct diameter?
    r
  12. tjm73
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    tjm73 Member

    Probably not as they correct size as they are the same as a 302.
  13. I believe the Ford 300 rods need to be narrowed a bit to use in the Chevy. They are used because they are a cheap alternative for a longer rod.
  14. 408 AA/D
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    408 AA/D Member

    tjm73 formula simplified:

    0.7854 x bore x bore x stroke x number of cylinders.

    Example 350 cu. in. small block Chevy

    0.7854 x 4.00 (Bore) x 4.00 (Bore)= 12.2664 x 3.480 (stroke) = 43.731072 x 8 (number of cylinders) = 349.848576 cu. in.
    Or your basic 350 chevy or any other engine with the same bore and stroke combination.
  15. Dick Dake
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    Dick Dake Member

    You might have clearance issues or even finding pistons with the right pin height. I am not an engineer but I remember a Hot Rod article that talked abut that combo. I can't remember the issue, 1994-95 ish.
  16. Homespun91
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    Homespun91 Member

    You will have a bearing problem to solve, so far as I remember.

    The main journal diameter of a 283 crank is 2.30" (std., nominal). Also, so far as I know, ALL 283 cranks are the "small journal" diameter.

    The main journal diameter of the 400 crank is 2.65", as above.

    You can use either bearing spacers, or special "thick" bearings, to install the "large journal" (actually, medium, really) 2.45" main 350 & late 327 cranks in the 400 block.

    You could also get the same kind of bearings/spacers to put the 2.30" journal cranks into the 2.45" journal blocks....but I have not seen those for some time & I don't know availability nowadays. There likely is not much call to do that anymore, frankly...

    So far as I am aware, there was never any kind of bearing or spacer made to put a 2.30" journal crank into the 2.65" journal 400 block.

    I have seen, one time, an attempt to do this, using the 2.45"-2.65" spacers, AND the "thick" 2.30"-2.45" bearings.....much for the reasons you described. The engine failed on the dyno, and had severe heat damage to both the crank mains and the block. There was not enough heat transfer to adequately cool the bearings...this with slightly wide (by today's standards) clearances, and an external Peterson 5-stage pump.

    The builder eventually had to have a billet crank made with the stroke & journal diameters he wanted. Nowadays it might be cheaper to do this, depending on the crank model & source...at the time it was around $2000. You could probably get Scat to specially machine even one of their 9000 series cast cranks & get it done under $1000, although depending on what you are doing you may want a better starting point.

    EDIT: All this assumes that you are going to use a Chevy crank....SCAT lists a 7000 series forged 4340 lightweight SBC crank that you can spec to whatever rod, main, & stroke you want that is reasonably priced, so far as aftermarket cranks go. :)

    There may be another PROPER way to do this that I am not aware of....
    Last edited: Jul 8, 2008
  17. Engine Pro 5X
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    Engine Pro 5X Member

    400 blocks are shit and the day that the last one on earth breaks I'm going to throw a party. I hate these blocks cause of the thin ass cylinders. Take the 327 crank and put it in a 327 block. Keep it simple as it worked 40 years ago>>>>.
  18. E.C.
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    E.C. Member


    Ford 300 rods are a waste of money, and the money you would spend to machine those odd ball rods. I would buy some Scat 4340 I beam rods for floating pins $ 300 maybe a little more but well worth it.

    If you already have a 400 block sell it and buy a good used Bowtie block with 350 mains. Then bore it out to a 4.125 + With the 350 mains just use spacer brgs no big deal.

    Big bore short stroke is the only way togo.

    -E
  19. Dyce
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    Dyce Member

    My opinion of coarse. The best crank for a 400 is a 400 crank with 5.7 rods. CID=HP is the formula I use. Start building a short stroke high reving engine don't skip on the valvetrain or it will bite you in the ass. The short stroke engines are normally used in class racing with CID limits. And then a short stroke big bore engine isn't always the ideal combination. Some are running 3.875 bore and a 400 crank. Depends on the track. I always tell the street people to stick with factory combinations and save their money for heads and camshaft. Just my 2 cents.
  20. sdluck
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    sdluck Member

    I love 400sbc built a few,have worked on sprintcars when we still ran cast iron block,377,394 406,.The current cup motor is 358 with a 4.185 bore long rods and a short stroke.
    RO7 Motor http://www.roadsters.com/sbc/#R07
  21. Larry T
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    Larry T Member

    It looks to me that the engine that is going to make the most horsepower is the one that moves the most air (and fuel). The engine that has the easiest time moving the most air is usually the biggest one. But, if there is a cubic inch limit, the best way to move more air is more rpms. If you're gonna turn mega rpms, about the only way to keep things together and not have all of the parts working against each other is to keep the piston speed down. That adds up to big bore/short stroke. I guess there's a lot more to it than that, but it's a start.
    .00000002 worth,
    Larry T
    BTW I looked at an old Richie Stevens 500 inch ProStock engine a while back and it had 3.50" stroke and close to 5" bore. Crazy stuff.
  22. Shifty Shifterton
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    Shifty Shifterton Member

    Lotta guys have done a lotta things with small block chevys, pretty hard to think outside the box. Damn big box. If you're not seeing something done, it's because there's probably a better/cheaper way.

    The combo you describe could certainly be made to work. But the finished $$ to HP ratio will suck. It would work really well for a specific racing class with CI limits and gear or weight limits that favored high revving engines. It would not work well for a class that allows 377s, 383s, and 400s.

    How hard are you gonna turn this puppy? I'd throw a stock-stroke forged rotating assembly in that 400 block and spin it 7k without hesitation. Stock car racers do it all the time. No offense, but it'd stomp the de-stroker into dust all other things equal.

  23. You my friend....GET IT !!

    Rat
  24. RacerRick
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    RacerRick Member

    I would throw good cylinder heads onto a bowtiw block, and a 4" stroke. Lots of cubes, little weight, and then gear it to match. It would be a winner.

    Torque wins races, not HP. HP is just a product of torque and RPM. Make more torque everywhere and HP naturally will be higher.
  25. raven
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    raven
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    The basic idea behind this is a large bore (cubes) and a short stroke (revs) combo.
    Something that has the size but would revs quickly.
    Look at the Richie Stevens motor as an example.
    r
  26. Bruce Lancaster
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    Bruce Lancaster
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    One of Grumpy Jenkin's books gives his formula for bearing adaptors in SBC crank transplants...he simply align bores the original bearing shells to take the smaller ones, notched them, and I think added in some extra crush to keep it all in place.
  27. Drive Em
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    Drive Em Member

    I built a 352 for my IMCA modified using a 400 block, 327 crank, late model 9.40" powdered metal rods, and an off the shelf JE piston. It was the most responsive,torquey engine I have ever raced with. The PM rods were about $200.00 new from the Chevy dealer, and required no machining to fit the crank.
  28. Jack Luther
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    Jack Luther Member

    Robin-- Have you been reading that article I sent you? Looks like it.
  29. billbrown
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    billbrown BANNED



    AMEN brother. AMEN. Can I get a witness!
  30. raven
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    raven
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    That's right Jack.
    Looking better all the time.
    r

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