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V4 engine, want to bore it out, tilt head or bob?

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  • V4 engine, want to bore it out, tilt head or bob?

    I have a V4 outboard motor I will be boring .020" over this winter on the Lagun. I see videos of some people mounting the motor to a shaft which then gets put in a positioner. Just seems like to many places for it to possibly 'slip' during the operation, and more room for flex and vibration. I'd like to clamp the block strait down on the mill bed and then just bob or tilt the head to the 45 degrees (90 degree block). But is there a 'better' way than the other? Bob the head and going from one cylinder hole the other is done with the y axis. Or tilt the head so going from one cylinder to the other would use the x axis.
    Andy

  • #2
    having both quill and knee in the same axis gives you more room for tooling.

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    • #3
      running a shaft (on big V-blocks, f'rinstance) through the crank main bearings ensures that you're correctly in the cylinder axis once propped on machinist's jacks, if it's along the X-axis you can do each bank and know the bores are going to be parallel when you shift along the X-axis, then rotate the block on the shaft, prop again and repeat?

      Dave H. (the other one)
      Rules are for the obedience of fools, and the guidance of wise men.

      Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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      • #4
        Option c) build fixture to hold engine crankcases at correct angle rigidly.
        Might be machined, or something as simple as a sine table set to the angle and the cases clamped to it.
        My fixtures have either been machined subplates or the aforementioned large sine table I have for this purpose set to the correct angle.

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        • #5
          There's option d) also, find someone with one of these locally. Its a hydraulic boring bar that fixtures onto the cylinder surface itself (it was designed to bore radial engines in situ still bolted onto the aircraft.

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          • #6
            You've got a CNC plasma cutter.......

            Pretty easy to make a 45* angle plate that you can jam between the block and table. then you can just spin the block around to do the other bank. Make it generic enough that it can be used as a general fixture plate so you won't see it as a waste of time making it for a one off job.....

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            • #7
              Can you clamp the head surface solidly to the table and bore from the bottom?

              Or, as mentioned above: take it to a shop that has the proper equipment.

              Mike

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              • #8
                If you can clamp to head surface, make a plate with a hole and mounting holes, the bolt to mill table with hole hanging over the side. Then bring cases up to bottom of plate, and bolt on, then start boring..
                If you need pics look up S & S big bore case boring plate.,

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                • #9
                  Originally posted by Dan Dubeau View Post
                  You've got a CNC plasma cutter.......

                  Pretty easy to make a 45* angle plate that you can jam between the block and table. then you can just spin the block around to do the other bank. Make it generic enough that it can be used as a general fixture plate so you won't see it as a waste of time making it for a one off job.....

                  Something similar could be used if it is a 90* V block. Use a right angle plate to bolt to the opposing bank. That would put the off bank 90* to the table and the working bores perpendicular to the table top. Indicate the right angle plate parallel to the Y axis so the bores only have to move in the Y axis to do the second bore.

                  lg
                  no neat sig line
                  near Salem OR

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                  • #10
                    Originally posted by MrFluffy View Post
                    There's option d) also, find someone with one of these locally. Its a hydraulic boring bar that fixtures onto the cylinder surface itself (it was designed to bore radial engines in situ still bolted onto the aircraft.
                    Van Norman boring machine. I've seen those and even used one in small engine shop years ago. I'd like to have one but money is tight.

                    Originally posted by MikeL46 View Post
                    Can you clamp the head surface solidly to the table and bore from the bottom?

                    Or, as mentioned above: take it to a shop that has the proper equipment.

                    Mike
                    Unfortunately no, it is a 2 stroke without removable jugs.




                    Originally posted by Dan Dubeau View Post
                    You've got a CNC plasma cutter.......

                    Pretty easy to make a 45* angle plate that you can jam between the block and table. then you can just spin the block around to do the other bank. Make it generic enough that it can be used as a general fixture plate so you won't see it as a waste of time making it for a one off job.....

                    Originally posted by larry_g View Post
                    Something similar could be used if it is a 90* V block. Use a right angle plate to bolt to the opposing bank. That would put the off bank 90* to the table and the working bores perpendicular to the table top. Indicate the right angle plate parallel to the Y axis so the bores only have to move in the Y axis to do the second bore.

                    lg
                    no neat sig line
                    That is an idea! I would think over all I would get more use with a 90 degree plate than a 45. I have some 1/2" plate on hand, you guys think that is plenty or should I look for thicker? Seems most angle plates I see are around the 3/4-1" thick area.
                    Andy

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                    • #11
                      Originally posted by vpt View Post
                      Van Norman boring machine. I've seen those and even used one in small engine shop years ago. I'd like to have one but money is tight.



                      Unfortunately no, it is a 2 stroke without removable jugs.








                      That is an idea! I would think over all I would get more use with a 90 degree plate than a 45. I have some 1/2" plate on hand, you guys think that is plenty or should I look for thicker? Seems most angle plates I see are around the 3/4-1" thick area.
                      Bigger is always better, but you could probably make one work with 1/2" and some strategic gusseting. Jack screws, and other supports to take the weight of the case, will leave the angle plate relegated more to alignment duty and not having to bear the full weight.

                      I bet being marine it's a weird "lets see how much **** we can have on the same casting" type of deal instead of an automotive style assembly of components. Sounds fun

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                      • #12
                        Hanging it off a 90 degree angle plate will never be as rigid as hanging it over the side of the mill table.. but you need a thick plate..

                        Comment


                        • #13
                          forget useing x axis

                          Originally posted by vpt View Post
                          I have a V4 outboard motor I will be boring .020" over this winter on the Lagun. I see videos of some people mounting the motor to a shaft which then gets put in a positioner. Just seems like to many places for it to possibly 'slip' during the operation, and more room for flex and vibration. I'd like to clamp the block strait down on the mill bed and then just bob or tilt the head to the 45 degrees (90 degree block). But is there a 'better' way than the other? Bob the head and going from one cylinder hole the other is done with the y axis. Or tilt the head so going from one cylinder to the other would use the x axis.
                          If you tilt head 45 toward you or away from you,you will get a big surprise. Nothing will be in machineing reach.I guess you want to do this for enjoyment. In 2004 ,I had an 8 cly 350 chev engine bored and honed ,for about $175. Maybe prices are up a lot because not many are rebuilding engines now.Edwin Dirnbeck

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                          • #14
                            A vertical milling machine is most rigid in the Z axis.
                            Bearing that in mind, I would fixture my work to orient
                            the bore to be completed with the Z axis.
                            Basic physics.

                            -Doozer
                            DZER

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                            • #15
                              Originally posted by Edwin Dirnbeck View Post
                              If you tilt head 45 toward you or away from you,you will get a big surprise. Nothing will be in machineing reach.I guess you want to do this for enjoyment. In 2004 ,I had an 8 cly 350 chev engine bored and honed ,for about $175. Maybe prices are up a lot because not many are rebuilding engines now.Edwin Dirnbeck
                              I had a 3 cylinder outboard bored some years ago and honestly it wasn't to bad of price either. But then what do I have the mill for then?

                              I did just do a setup where I had the head tilted and bobbed. Yes stuff starts to get tight and in awkward positions.



                              I also resurfaced an intake manifold for my brother this spring where I had to bob the head to a 45. Again awkward but doable. It does sound like a much better idea to get the motor up on its side so the cylinders are vertical. I am going to try for that way somehow.

                              Originally posted by 754 View Post
                              Hanging it off a 90 degree angle plate will never be as rigid as hanging it over the side of the mill table.. but you need a thick plate..
                              Not sure if I have enough room to hang the engine off the side of the table, but I will check.
                              Andy

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