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Thread: "HOW TO" port an engine

  1. #1
    The Doctor cabbie's Avatar
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    Before I start this thread I take NO responsibility for any damaged or none running engines should you chose to follow this porting "HOW TO" guide.

    I'm not saying this is the only way to do this work it's just how I do it.

    As the project progresses I'll explain what I'm doing and why.

    First the engine will need to be stripped completely, bearings seals etc etc.

    I'm using a +1mm stuffed crankshaft and a 29cc billet head kit, I'll explain why later in the thread.


    The first job is to pin or "dowel" the cylinder to the crankcases.

    You'll need two small dowels around 2.5mm (old shock shafts are good) these are savage diff pins


    I use a copper base gasket as a jig to drill the dowel holes


    Only drill the holes to a 5mm depth and tap the pins in place


    Next the cylinder gets the same treatment


    Here's the cylinder and cases doweled together, this is done so the cylinder has zero movement for the port matching of the two parts. (I'm holding the cylinder away from the case here to show the pins)


    Next we need to increase the amount of fuel/air entering the crankcases, fuel/air is drawn in to the engine when the piston opens the inlet port on it's up stroke, to increase the volume we need to open the inlet sooner.
    Two ways of doing this: 1 lower the inlet port or 2 cut the piston skirt.
    Cutting the piston skirt is best for this thread.

    Take 3mm away as shown (the inlet is the side with the pin in the piston groove)


    I leave the edges on but you can cut straight across, that's all that needs doing to the piston.


    Tomorrow I'll start port matching the cylinder and cases.


    NEXT UPDATE............................................ .............................................


    The crankcases need to be smoothed out, modern CNC machines are good but can't finish an item to a hand finish

    Crankcases


    I start with an alloy cutter


    I've removed the machining marks and given the transfers a flowing shape


    Here's why dowling the crankcase and cylinder together is so important, ain't much point making them a perfect match if the cylinder can still move around in the cases!

    With the cylinder bolted in place you can see the ridges and areas that need cutting back


    Still using the alloy cutter start removing the unwanted material


    This is with the cylinder walls cut in and finished matching


    These are Diamond burs used for fine cutting and finishing


    This is one side done, if you are "new" school then it's done, if you are "old" school then polish.


    Repeat the process for the other side.
    Last edited by HOSS; 10-01-2010 at 23:09.

  2. #2
    Adminicastrator Hiks's Avatar
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    Subscribed

  3. #3
    Administrator
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    Ohhhh This ones gunna be good

  4. #4
    Advertiser Sonic@OBR-UK's Avatar
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    liking this

  5. #5
    Baja-Forum Maniac jjrc01's Avatar
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    top work m8

  6. #6
    Moderator HOSS's Avatar
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    cant wait to watch this unfold

  7. #7
    Now then, It's TOPPER! Topper's Avatar
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    This is ganna make me a millionaire

    I was down Machine Mart tonight on a VAT free night, was looking at the pillar drills and mills and things

    Great stuff Cabbie.

  8. #8
    Senior Member
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    i like a slow engine than a broken one.... lol


    kieran

  9. #9

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    this is gunna be summat i'll keep an eye on, i tried porting my old cylinder head but due to a lack of a dremel, knowledge, and the head actually being a working one in the first place it didn't work.

  10. #10
    Adminicastrator Hiks's Avatar
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    Can we have a "HOW NOT TO" dyno an engine thread? Merlin can give us a guide....or two

  11. #11
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    ohhh hardy haaa...the black eye next time i see you award goes to you terry.

  12. #12
    UberRC product Tester MiniJOD's Avatar
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    this is going to be a good one, good work so far cabbie

  13. #13
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    looking forward to the next update - nice one cabbie

  14. #14
    Senior Member seanmcgrath48's Avatar
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    I'll be watching this...Dremel and piller drill at the ready.....

  15. #15
    Buy my stuff! ukbajadave's Avatar
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  16. #16
    The Doctor cabbie's Avatar
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    Update to post 1.

  17. #17
    Senior Member seanmcgrath48's Avatar
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    When this thread is finished all comments should be remover, and just cabbie part left and pined.....

    Good work Cabbie

  18. #18
    BFUK-aholic™ Echlin W's Avatar
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    definetly should do that sean. Fantastic Thread. Well done!

  19. #19
    Moderator HOSS's Avatar
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    once its finished,we will clean the thread up
    an lock it
    an leave it just as a show piece on what to do

  20. #20
    BFUK-aholic™ Echlin W's Avatar
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    The problem is if you dont use those machines for mch else as i dont think i would and so would alot of peolpe. You have the expenses of the machines when whole new 29cc engine from MMR is £149 and a 29cc 36mm head is £57.99.

    It would be good if some people outside shops would start selling them though.

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