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Thread: Block talk

  1. #1
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    Block talk

    I have to replace the block in the Minx due to a score in the jug from a failed spark plug ,I have an another 4.0 bore DIA stock block and rotating assembly .This would be the most economical way for me to fix it.



    Buttttttttt. I don't think that will due. I.m thinking more on the lines of a big bore dart block.

    That parts pretty straight forward, it's just a matter if you want to punch it out .030.
    I'm a little skeptical on the oversize 4.156" bore,as if something should happen like a score. There would only be one more time i could resize the block, or if the score was deeper than .030" it would be scrap.

    Does piston displacment add torque or horsepower? Both?


    So now were at stroke. and there are alot to choose from. I'm thinking full all out 3.875"
    This set up would require modified pistons to keep the compession ratio down.
    Merc runs there 380 hp scorpion in the 9's most all Mercruiser stuff is.I'm assumming there runnig 72cc heads. at the moment I have 64cc heads. With a 15cc piston the 4.155 x 3.875 would be in the 10.3. Deck height i'm sure would play a roll. The Dart I'm lookig at is .205.
    Where does a higher compression ratio change the torque curve?



    The other option is to go a little milder with the same block at the stock bore of 4.125 and a 3.75 stroke macking a nice small block 400 and would also lower the compression ratio.



    Any Input is greatly apprieciated
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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  2. #2
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    Joe, rule of thumb says the largest bore will give the greatest HP, longest stroke will offer greatest torque.

    One of the main reasons for multi-cylinder engines in Formula racing (10-12 cylinders) is they will produce the maximum piston surface area for a given displacement, and therefore more HP.
    George Carter
    Central Florida
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    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

  3. #3
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    BTW, Dart blocks are beautiful things to behold.
    A very good investment.
    George Carter
    Central Florida
    gcarter763@aol.com
    http://kineticocentralfl.com/


    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

  4. #4
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    I have always been partial to the 383 over the 400, I like the larger journals.

    Compression adds quite a bit of power, many years back I was running a 302 Jimmy out to 320 trip two barrels and a Schaller 1/4 speed cam. I popped a head gasket and while it was apart I had the head shaved .080, the Jimmy was in a very lightened 38 Chevy coup which was running very consistent 14.3 14.5. With the shave job and a little better tire I could on a good day pop into the upper 13's, but more of a kick was beating a buddy who had stuffed 265 in a 52 Chevy. He was the first to beat the krap out of his firewall to stuff a SBC in his car, A month later with some massaging to the 265 he blew me away getting into the lower 13's.

    Phil
    No matter what your beliefs are "GOD BLESS AMERICA"

    Fully retired marine tech near 60 years in the biz.

  5. #5
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    Joseph ~
    Have you ever considered getting your old block's scored cylinder wall bored-out & a cylinder repair sleeve chilled & pressed-in ?

    This is great, and very successful way to save the old engine block.

    I have had a number of very rare, & almost irreplacable, very early Brass Era "Antique" auto engines successfully repaired in this manner.

    Diesel engine rebuilders use this cylinder sleeve repair method all the time.

    The cost to do such a cylinder re-sleeve repair is very nominal at most engine machine shops.
    And the sleeved cylinders will then be just like new.
    Last edited by silverghost; 12-02-2012 at 12:04 PM.
    "BENCHSEAT 18" ~~YellowJacket~~ project owner~
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    There is no such thing as going too fast ~ ~~
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  6. #6
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    now your talking...

    I turned a 3.625 x 4.155 to 8400

    392"

    I just happen to have a 400 block and 3.875 crank and rods and cam and solid lifters too

    and the trick heads, the whole package was in my stock appearing Nova that at one time was the fastest stock appearing small block Chevy anywhere..

    it's a 2 piece seal block and crank though, so all you need is an early flywheel and flat top pistons and rebalance the asembly since the crank has mallory metal in it now
    Charter Member - WAFNC, SBBR, KWOSG
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    I think you have to be very careful with rod choice on a 3.875 crank with regards to clearance. H-beam might even need a reduced base circle cam. That being said I used a Scat 3.750 I beam combo in a stock block and have tons of room.

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    massaging it would be a chore for sure.. probably be more trouble than it's worth
    Charter Member - WAFNC, SBBR, KWOSG
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    The engine in my Minx was tired when I purchased it. I opted to go with a mercruiser crate motor. It is a 377 cu 325 hp and gives me 68 consistantly with a spinelly prop. I will have to check my records but I think it was just under 4k. I wanted reliability, and it has all the modern parts-center mount valve covers, roller cam, good flowing heads, the latest electronic ignition with knock sensors along with a new carb. Not to mention a 1 year warranty.

    Keep in mind if you are looking to add alot more power, you still have to worry about the alpha drive. Then there is the steering safety issues. I am adding full hydraulic now.

    Steve

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    check my math

    Here goes


    4.155 bore x 3.750 x 6.0 rods 64 cc cnc combustion chamber with a static CR 10.7 : 1

    The cam is XM270HR / LSA 112*, lift with 1.5:1 rocker I .495/ E .503
    Intake event: open 25* BTDC, close 65* ABDC,
    Exhaust event: close 24* ATDC open 72*BBDC

    http://www.compcams.com/Company/CC/c...?csid=169&sb=2


    intake closes 65* leaving 8.53 :1 Dynamic CR.
    Attached Images Attached Images
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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    interesting...

    is that with flat top pistons and zero deck?
    Charter Member - WAFNC, SBBR, KWOSG
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  12. #12
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    Quote Originally Posted by BUIZILLA View Post
    interesting...

    is that with flat top pistons and zero deck?


    -16cc or -21cc Dish 9.7 or 10.3 compression ratio I think a .030 deck height.

    10.3 comes out to 8.22 with the cam. My understanding is 8.5 is optimal dynamic compression ratio. What do you think?


    http://kb-silvolite.com/calc.php?action=comp
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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  13. #13
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    COMPRESSION RATIO CALCULATOR
    Static and Dynamic Compression Ratio



    (Considers Cam Timing and Rod Ratio)

    ENTER YOUR DATA CALCULATED DATA
    Cylinder Head Volume (cc) Cylinder Head Vol (cubic in.) 4.392
    Piston Head Volume (cc) Piston Head Vol (cubic in.) 0.000
    Gasket Thickness (in.) Swept Volume (cubic in.) 50.847
    Gasket Bore (in.) T.D.C. Volume (cubic in.) 5.069
    Cylinder Bore Diameter (in.) Gasket Volume (cubic in.) 0.596
    Deck Clearance (in.)Note: Neg. nubmer above deck, Pos. number below deck Deck Volume (cubic in.) 0.081
    Stroke (in.) STATIC COMPRESSION RATIO 11.031
    OPTIONAL DATA
    Rod Length (in.) Adjusted Stroke (in.) 2.913
    Intake Closing Point (degrees)ABDC @ 0.050 lift plus 15 degrees DYNAMIC EFFECTIVE COMPRESSION RATIO 8.792


    Return to United Engine & Machine Calculator Listing
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  14. #14
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    Zoinks

    ppppp




    I've been reading alot on this principle of dynamic compression related to octane rating, and how compression and duration with lift effects cylinder pressure.It's almost worth buying a pre-engineered motor, butttttttttt.NOOOOO!! IT Isn't





    I'm at the point where I got the hammer back and my fingers on the saftey.
    I just need to figure where I,m going to ship the block, home or work.

    Some things I've found: To run 89 to 93 octane the dynamic compression ratio needs to be between 7.5 to 8.5. This value is governed by the intake closure angle. By adding duration( the intake valve stays open longer ABDC) decreasing dynamic compression ratio. Because Merc stuff has such a low Static compression and the use dish pistons and iron heads, high duration is counter productive to engine performance.For instance if you look at a 377 scorpion the static compression is 9.5:1 with low duration and high lift achived by a 1.6:1 rocker ratio.The key was the added lift with rocker ratio ,but kept the duration realativly the same to keep the dynamic compression low enough to run on 89 octane. As the overall static compression is low, cylinder presure would also be lower. The higher lift helps create more pressure but the cam has modified architecture to prevent reversion.

    By the way reversion is a loose term, as there is water reversion and exhaust reversion, meaning a land motor can also suffer from reversion. Reversion is mainly caused by low cylinder pressure with a late closing exhaust valve, closing further past ATDC. exhaust reversion is the culprit and water ingestion is the by- product. So remember the vacume break theory in the riser . This is because that factory gm stuff is old technology used for more than 50 years, that rides on the edge of detonation right at the get go, cam modications are limited, because cylinder pressure is low causing reversion.


    2013 brings alot of development break throughs for combating detonation. Higher Static and Dynamic compression ratio's can be achieved with the same octane ratings as the yester year motors.

    For instance by the use of aluiminum heads the transfer of heat to the coolant is greater. This alone alows .5:1 more dynamic compression ratio or 1:1 in static compression ratio. This equals more cylinder pressure

    Piston development has also contributed to the reduction. by eliminating a full dish piston and incorperating zero deck with a pocket under the cumbustion chamber and leaving a flat top where the head is flat .reduces detonation dramtically. Meaning more more dynamic compression ratio /static compression ratio. This equals more cylinder pressure.

    Now that we have all this static compression we can throw more duration into it to put the dynamic compression into the range of the fuel octane we want to run with. As we add lift , the higher the volume moving through the intake and exhaust evacuating the the chamber and cylinder faster. Greatly reducing any chance of detonation.



    SOOO!!!! after all of this with 64cc head my Static CR will be 10.3 (flat top piston with a 16CC pocket) the Comp cam XM270HR with a 65* ABDC leaves 8.22:1 which is high for an iron head but should just be right for an aluminum head running 90 octane. I think this will be a great running 406ci..
    if i keep my
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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  15. #15
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    I like your thinking...

    the chart I did above was with 72cc alum heads, zero deck, and flat top pistons using 1.6 rockers too.... it just didn't post like I wanted it to when I pasted the work sheet... this *might* work better against detonation, instead of a 64cc head and the slug .030 in the hole,, to keep the flame travel more even and the bang in the chamber, not in the hole

    just my .02 of course
    Charter Member - WAFNC, SBBR, KWOSG
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