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  1. #1
    Senior Member red baron's Avatar
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    parts interchangability

    I have a flat head 4hp, what parts will interchange with a 5hp? or what is available for performance parts for this motor?
    Last edited by red baron; 01-28-2018 at 07:19 AM.

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    OND's Avatar
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    I'm not real familiar with the 4hp Briggs , so I don't know if 5hp parts will interchange or not. I know people who have used the 4hp head on there 5hp Briggs because it is a better compression head .
    But you can get a better exhaust system like a header , do some porting on the intake and exhaust ports and even throw a little more timing in it. Free flowing air filter will help to.
    Last edited by OND; 01-28-2018 at 09:28 AM.
    Lil Indian, Ruttman, DB30, Warrior, lil Bill, EZ Rider, Savage SSC , Powell, BONANZA

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    Senior Member red baron's Avatar
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    Thank you for the tips.
    Last edited by red baron; 01-28-2018 at 06:21 PM.

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    roccosbike's Avatar
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    You can put a 5hp crank in it and it will give it a little more stroke and give you a way to put a billet rod in it (must use 5hp rod with 5hp crank). Oh and everything else that fits a 5hp briggs will fit your 4hp accept the piston unless you bore it then everything will interchange.
    Basically the crank con rod and piston are different, hope this helps you.
    Bonanza brotherhood, Chicago

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  6. #5
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    Do you have the model number for that 4 HP ??

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    If its the old one,looks like a flathead 5hp, not much interchanges. Block,crank,rod,piston,head,flywheel all different.5hp crank is too wide to fit into Block without machine work. Piston is smaller diameter.
    If you hopping up,better money spend on 5hp.if you really like the way the 4hp looks,swap tins....

  8. #7
    Senior Member The.MiniTard's Avatar
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    I have a 4hp and a 5hp. Internals do not interchange, different wrist pin sizes, and journal dia.

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    Member tecumseh power's Avatar
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    There is a 3HP based 4HP Briggs engine that they made in the 80's. I've only seen a few of them it was like a big bore 3 HP engine that nothing interchanged with the 5HP engines.

    The other 4HP as others have mentioned looks like 5HP, but is a good bit different. We used to use the heads on 5HP engines as others have said.

  10. #9
    roccosbike's Avatar
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    Quote Originally Posted by The.MiniTard View Post
    I have a 4hp and a 5hp. Internals do not interchange, different wrist pin sizes, and journal dia.
    It depends on what year engines your working with and yes there are parts that interchange.
    Bonanza brotherhood, Chicago

  11. #10
    Senior Member The.MiniTard's Avatar
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    Quote Originally Posted by roccosbike View Post
    It depends on what year engines your working with and yes there are parts that interchange.
    Guess ive got some work to do then. i have a 5hp with a messed up valve guide and a raggedy eyebrow cut job.....and a beautiful 4hp block that has a grinded up crank....ill see if the cranks interchange. Both are 70's era flathead Briggs

 

 

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