4.5 stroke
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4.5 stroke

  1. #1
    Senior Member wagspe208's Avatar
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    Default 4.5 stroke

    A while back, there was discussion about a 4.5 stroke. Many of you did not like em???
    Forgot why??
    Wags

    I'm a fan.
    Just bored I guess.

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    Urban Cougar Trapper Gopher711's Avatar
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    Tall or Short deck ?

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    Senior Member Bubbletop409's Avatar
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    I think the consensus was that over a 4.375" stroke, oil windage becomes a real problem with a wet sump oil system.
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    Senior Member Hass828's Avatar
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    I remember this discussion with GN7, the consensus was that the overlapping of the main/rod journals was all but gone , that decreases the strength of the crankshaft. Then also windage issues. Bad geometry in the rod'stroke ratio if not careful.
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    I'd like to hear more about this. 4.5 stroke is a easy way to get more cubes, but it seems like a lot of people have some reservations about it. I'm thinking about another engine to replace my 548 but don't want to compromise my reliability or power output.

  8. #6
    steelcomp was here
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    Not reasonable in a standard deck block. Fine in a tall deck as long as you take into consideration the issues that go with more stroke which are mainly windage and rod angle/piston speed. If the windage isn't addressed, it can cost you any power you might gain with added displacement, or even more. Rod angle means more side loading on the piston, more friction, more wear. It also means an increase in peak piston speed which puts an added demand on the induction. It also means a little different approach to what the engine might want, cam wise. It all pretty much depends on what you want to build. Low rpm cruiser engine....I wouldn't lose any sleep over much more than making sure it's got a good pan on it and decent set of heads. Race engine with 4.5" stroke needs to be looked at more carefully.
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    IN my case I use a blower,(10;71), with innercooler, and have a tall deck block and will try to get whatever rods, cam, and heads I need to work with the combination, maybe a 14;71 also. The boat is a 21' Howard V drive fun boat, but I still want power along with reliability. Have also thought about a 4.375" stroke. I,m also using a solid roller cam. Thoughts ??

  10. #8
    Senior Member wagspe208's Avatar
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    It's a tall deck. I remember the windage discussion now... Thanks
    BUT, riddle me this riddler...
    You see 600"stuff becoming "norm". That is a 4.75 stroke.
    Wags

  11. #9
    steelcomp was here
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    Quote Originally Posted by wagspe208 View Post
    It's a tall deck. I remember the windage discussion now... Thanks
    BUT, riddle me this riddler...
    You see 600"stuff becoming "norm". That is a 4.75 stroke.
    Wags
    Well I wouldn't call it "norm"...
    Lot of people into the big engine thing...600, 700, 800" and bigger. Not my cup of tea. The one 600+" engine I've built is a 4.65 x 4.5 BB Ford with a 10.3" deck and a 6.8" rod. It doesn't have the windage issues the BB Chev has because of the block design.
    I see lots of 632 BB Chev combinations that are less than impressive other than they have 632 cubic inches. The ones that do impress have addresses the issues and are willing to accept the trade off's. Taller decks, longer rods, BIG heads, dry sump, etc. Most are dedicated race engines with lots of money spent. Regular freshen, regular race schedule maintenance. Not saying it can't be done, just saying there are compromises to be made, but that's the case with any engine. I don't see a 4.5" stroke as that big of a deal, just needs to be done right.
    Last edited by scott foxwell; 02-15-2016 at 07:47 AM.
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    Senior Member wagspe208's Avatar
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    F me.... How do I import a word doc?
    This site is goofy wihth this computer.
    Wags

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    Senior Member Hass828's Avatar
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  14. #12
    Senior Member wagspe208's Avatar
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    So, we started building these things back in the early 90’s.The only block available was a bowtie. It took a lot of work to get stuff to fit. (I’m dating myself, but giving background)
    So, the only crankshaft failure we saw was in a BA piece. I think it was Gravedigger. It was not a crankshaft issue. The crank came out in 3 pieces. The hub was welded to the snout. (from detonating), (double key, yes) DETONATION. Tuneup issue. Mag issue…well, mag ignorance issue.
    So, the point is… I am not sure if I agree with crankshaft strength (if using a primo piece). NOT scat, eagle, etc. Especially under 1500hp ish.
    Cubic inch gain… if we were not using stroke, (for additional CID), I would agree. IE… taking a new block and boring it to the max just to gain a few inches. I think that is idiotic for a bracket piece.
    BUT, we are adding stroke. More stroke=more torque (assuming airflow is adequate).
    BUT, I will agree with more windage, especially in wet sump stuff.
    I was just bringing it up, as a PE guy wants a 4.5 piece. I think it is “to much” for his application. I believe in building an engine for its specific application. (ie, trying to build a fuel motor to run 8.0 is an exaggeration… but that is the point)
    Wags

    I see guys with way to much engine struggle to slow them down.
    Last edited by wagspe208; 02-15-2016 at 03:44 PM.

  15. #13
    Already miss the 310/562 2manymustangs's Avatar
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    Quote Originally Posted by wagspe208 View Post
    So, we started building these things back in the early 90’s.The only block available was a bowtie. It took a lot of work to get stuff to fit. (I’m dating myself, but giving background)
    So, the only crankshaft failure we saw was in a BA piece. I think it was Gravedigger. It was not a crankshaft issue. The crank came out in 3 pieces. The hub was welded to the snout. (from detonating), (double key, yes) DETONATION. Tuneup issue. Mag issue…well, mag ignorance issue.
    So, the point is… I am not sure if I agree with crankshaft strength (if using a primo piece). NOT scat, eagle, etc. Especially under 1500hp ish.
    Cubic inch gain… if we were not using stroke, (for additional CID), I would agree. IE… taking a new block and boring it to the max just to gain a few inches. I think that is idiotic for a bracket piece.
    BUT, we are adding stroke. More stroke=more torque (assuming airflow is adequate).
    BUT, I will agree with more windage, especially in wet sump stuff.
    I was just bringing it up, as a PE guy wants a 4.5 piece. I think it is “to much” for his application. I believe in building an engine for its specific application. (ie, trying to build a fuel motor to run 8.0 is an exaggeration… but that is the point)
    Wags

    I see guys with way to much engine struggle to slow them down.
    It wasn't the ONLY tall deck block that was available...

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  16. #14
    Senior Member wagspe208's Avatar
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    ^^HAHAHHAHA
    The only one worth a fuck.
    Wags

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