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Hot Rods What Will My Displacement Be?

Discussion in 'The Hokey Ass Message Board' started by Fortunateson, Jun 23, 2020.

  1. Fortunateson
    Joined: Apr 30, 2012
    Posts: 3,110

    Fortunateson
    Member

    As the title states that's my question. Starting off with a 255 ci Mercury and will be adding .060 overbore. I'm thinking 265ci?

    Thanks!
     
  2. saltracer219
    Joined: Sep 23, 2006
    Posts: 748

    saltracer219
    Member

    Bore x bore x .7854 x stroke x the number of cylinders = displacement in cubic inches
     
  3. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 6,517

    Bandit Billy
    ALLIANCE MEMBER

    I was going to say the unconscious transfer of an intense emotion from its original object to another one,
    Saltracer was likely more accurate though.
     
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  4. Penetrator
    Joined: Aug 25, 2011
    Posts: 383

    Penetrator
    Member
    from SK CAN

    Yes.

    .
     
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  5. It is really simple math as Saltracer219 explained.:confused: I don't know how to do it but apparently he does.:rolleyes:
     
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  6. AngleDrive
    Joined: Mar 9, 2006
    Posts: 767

    AngleDrive
    ALLIANCE MEMBER
    from Florida

    Bigger than it was
     
  7. 1971BB427
    Joined: Mar 6, 2010
    Posts: 5,674

    1971BB427
    Member
    from Oregon

    Probably closer to 263c.i.
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 46,070

    squirrel
    Member

    265 almost exactly, according to my calculator. But I could be wrong.
     
  9. pitman
    Joined: May 14, 2006
    Posts: 4,918

    pitman

    Pies aren't square...
    And "thinner than a tin gasket."
    (to bump up the ratio)
     
  10. Fortunateson
    Joined: Apr 30, 2012
    Posts: 3,110

    Fortunateson
    Member

    Well, using the formula given I got 264.6971237797227ci so I'll stay with my original mental estimate of 265ci. I guess all those years of teaching Math paid off!
     
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  11. squirrel
    Joined: Sep 23, 2004
    Posts: 46,070

    squirrel
    Member

    I used pi/4 instead of .7854, so I got a slightly higher number...265.05something.
     
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  12. saltracer219
    Joined: Sep 23, 2006
    Posts: 748

    saltracer219
    Member

    I am not saying that this is etched in stone, but it is the formula that the S.C.T.A. and the F.I.A. have used to determine displacement for many years. I always figured if it is accurate enough for them, I will roll with it!
     
  13. Fortunateson
    Joined: Apr 30, 2012
    Posts: 3,110

    Fortunateson
    Member

    I'm picking up my C8BA, that was originally assembled with Mercury components, tomorrow after an initial cleanup bore. Final will be .060 over. I picked up my re-ground cam yesterday with a M70 grind similar to an Isky Max1. They reground it for $225 CDN which would be around $160US.

    Waiting to order my bearings, pistons, etc. as the border is closed right now so I wouldn't be able to pick them up until it reopens. Local parts house said they could get me Scat pistons for between $1800-1900! I called a place I've used before where I got pistons for my 292 Y block for $98 US and they'll get me pistons for the flathead for $199US which is a wee bit better than the Scat stuff...
     
  14. jimmy six
    Joined: Mar 21, 2006
    Posts: 6,323

    jimmy six
    Member

    Kinda like all the 301 Chevrolet’s we built out of 283’s.... But when GM did it somehow it was a 302.
     
  15. squirrel
    Joined: Sep 23, 2004
    Posts: 46,070

    squirrel
    Member

    Oh, the formula is fine. It's not exact, but it's definitely close enough.
     
  16. Speed Gems
    Joined: Jul 17, 2012
    Posts: 2,571

    Speed Gems
    Member

    Figure .005 equals about 1 cubic inch so .030 is 5 cubic inches, .060 is 10 cubic inches etc.

    That's because if you do the math it comes out to 301.59 so instead of coping all those uneducated (Non engineering type) Hot Roders:rolleyes: they bumped it up to 302.
     
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  17. Deuces
    Joined: Nov 3, 2009
    Posts: 18,539

    Deuces
    Member
    from Michigan

    Yep! 302 it is.....
     
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  18. squirrel
    Joined: Sep 23, 2004
    Posts: 46,070

    squirrel
    Member

    I like the story I made up that they were a .120" over bored 283, instead of 4.000" bore, and that actually gives you 301 CI.

    But I wasn't around back then, and don't know what the actual piston and bore size was.
     
  19. 51504bat
    Joined: May 22, 2010
    Posts: 1,816

    51504bat
    ALLIANCE MEMBER

    Back in the late '60's when I was in HS if you had a 301 Chevy you were hot stuff.
     
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  20. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,813

    gene-koning
    Member

    Back when I was in high school, if you talked the right game, everything could be hot stuff. If you could back it up You were indeed hot stuff.
    I had a buddy that bought a late 60s Nova with a small block with a 3 speed on the floor. To hear him tell the story, it was some hot stuff. All I had to drive around was daddy's 4 door Oldsmobile. With 4 guys in the car, daddy's Olds would put a whooping on my buddy's Nova anytime we lined up. I guess the 394 4 bbl was more hot stuff then the "special" mix of small block Chevy in the Nova. Then a couple years out of HS, my Nova buddy traded in the Nova on a brand new 76 Camaro with a "supped up" motor (he probably put some Accel plugs in it, that would have been at the limit of his automotive knowledge). At that time I was driving my future wife's Sport Satelite with a 383 and it whopped his new small block Chevy every time, without much effort. I don't think the cam, 780 Holley, and the 391 sure grip rear end made much difference.... It wasn't until we did a double date and used the Satelite before he understood something other then a small block Chevy could be fast too. Gene
     
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  21. DemonTweaks
    Joined: Mar 16, 2016
    Posts: 20

    DemonTweaks
    Member
    from T-Town, WA

    The simplest for V8's is:

    Bore x Bore x Stroke x 6.283 = Cubic Inches.
    Example:
    4.125 x4.125 x 4.000 x 6.283 = 427.636. (And using standard math to round it to closest full number gives 428. So all Chevy guys are driving around 'Ford' 428's! )
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 46,070

    squirrel
    Member

    My Chevy 427 is .040" over so it's a 435, but if it were standard bore and stroke, it would be 4.250" x 4.250" x 3.76" x 6.283 = 426.71 cu in which rounds up to 427

    not sure what you're on about? :)
     
  23. DemonTweaks
    Joined: Mar 16, 2016
    Posts: 20

    DemonTweaks
    Member
    from T-Town, WA

    All the LS fan boys (and most people stroking small blocks) say their 428's are 427's since the Z-06 Corvette made the same calculation error.
     
  24. squirrel
    Joined: Sep 23, 2004
    Posts: 46,070

    squirrel
    Member

    oh...this is a traditional forum, so we only talk about real 427s. not that late model crap.
     
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  25. indyjps
    Joined: Feb 21, 2007
    Posts: 3,822

    indyjps
    Member

    .030 over 255 Merc
     
  26. jimmy six
    Joined: Mar 21, 2006
    Posts: 6,323

    jimmy six
    Member

    Not to long ago I built a “stroker” SBC. Started with a cherry 1967 283 block. Bought a forged light 1/4” arm from SCAT while they had them. . . It was a great running 307.
     
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  27. jnaki
    Joined: Jan 1, 2015
    Posts: 4,485

    jnaki

    upload_2020-7-8_4-27-9.png
    Hello,

    We have known a friend from our high school days. His 1956 Chevy Bel Air hardtop was one fine hot rod and racer. It was a daily driver with his stock 265 that was replaced with a newer 283. Then all of a sudden, it sounded a lot better and was faster. The 56 Chevy now supported a 1/8th over bore and he now had a 301 c.i. for his challenges and cruising. He ran with that new set up for a while and then one day a rumor started by everyone that knew him. He had installed a custom Reath Automotive ½ inch stroked crankshaft and new accessories, now was rumored to have a 352 cubic inches.

    It was very fast and he would not deny or confirm the rumors. The 56 Chevy had no takers at any time during this time period. (Except me and my Impala.) Against a bored and stroked 352 cubic inch Chevy? What was I thinking? (Stories in the HAMB threads)
    56 Chevy at Lions Dragstrip

    Jnaki

    So, an 1/8th over bore is 301. Add in a ½ inch Stroker kit crankshaft and it is now 352 cubic inches. That was the way it was in So Cal. Lots of 1/8th over 283 motors for a fast, but reliable motor for everyday use and races at those times on the street. But, hardly anyone ran a 352 cubic inch motor for everyday use and then raced on Friday/Saturday nights with regularity. There was a thing about being huge and fast, but not as reliable as just a 301.

    Jump up many years after we were married and living in the OC. Our young couple neighbors drove up in a dark green z-28 Chevy. The first thing we said was…wow! The rumble, the look and when he took me for a drive, so much power going down Coast Highway in all 4 gears. Positraction plus 4:11 gears and it was a strong contender for many stock car wins without any other modifications. This was a factory hot rod and a neck snapper through the gears. What did he have for a motor? A factory listed “302” cubic inches.
     
  28. Boneyard51
    Joined: Dec 10, 2017
    Posts: 4,008

    Boneyard51
    Member

    I always figured cubic inches the old fashioned way I was taught in school back in the fifties. Back when 2+2 =4! Lol Pie are square! ( Pi x R squared). You take the radius ( 1/2 diameter) and square it (the number times itself) then you multiply times pi . What you use for Pi depends on how far you carry the decimal point, but I usually use 3.1416. Then you multiply by the stroke and then times the number of cylinders. That’s the way I was taught in math, back in the previous century. I use this, mainly because I can remember it! Lol






    Bones
     
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  29. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,007

    jaw22w
    Member
    from Indiana

     
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