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LS based V4 engine shenanigans

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    LS based V4 engine shenanigans

    So, I'm a teacher now. I have students that will get bored if I don't get silly with things in class every now and then, and we're a machine shop class. Most of my students *wanted* to get into automotive repair class, but it was full, and I was the second choice.

    One of my students threw down the gauntlet and said I couldn't build a V4 from an LS engine. I told them it was totally doable, as the AFM/DOD system does it in the car already. That wasn't good enough. To make matters worse, the auto shop teacher was walking by the open shop door and overheard, and he chirped up and said he bets I could do it. So I've got his backing for some parts and a run-in stand to work on.

    The cutting and welding of the block won't be a problem. I've got a stack of busted blocks that was offered by the auto shop class, but most are broken in ways that make them difficult to use for this. I have two more blocks that I need to drive an hour and pick up, one is a 6.0L LS2 block that has had #8 liner bored completely out to be replaced due to a broken rod that tore it up, and one is a 5.7L LS6 block that also had a broken rod, but I don't know where in the block or how bad the damage is. Both are freebies, so I'll go get them anyway.

    The block has been done before but I don't think anyone has made it run, and I don't think the heads were ever finished, just stuck together for a talking piece. I could be wrong, but I haven't seen one running yet. Good news, though, as GM sponsors the auto shop class and we have plenty of aluminum crate LS engines upstairs in the mezzanine, I'm sure a student will fuck one up this year and so I essentially have unlimited attempts if I keep going long enough. Plenty of trick parts, including a broken LS9 engine block, but it's busted out the back of the block right above the rear main as well as the entire rear cylinder pair.

    To do the welding, the rear two cylinders have to have the liner completely bored out anyway, so that 6.0L block is looking good if there really is no other hidden damage. There are still multiple problems to work out regarding the crankshaft. This is going to be the toughest job of building the demo engine, but I honestly think we'll be OK if it just fits together, I don't think we'll have enough time in the year to get it to actually run and so I'll get a pass on a "functional" crank. That won't stop me from actually making it run eventually, but maybe not this school year. (unless Covid has me locked in an empty classroom where I have to teach machine shop virtually...)

    There's an obvious question to ask here: what's the crank got to look like? Clearly, I can go with a 360* design, having both crankpins in line with each other, a 180* design, with the two crankpins 180* opposed, or a 90* design, with the front crankpin leading the rear by 90* of crank rotation.

    Assume the following Cylinder Positioning:

    Cylinder 4 --- Cylinder 3
    Cylinder 2 --- Cylinder 1
    Timing Cover

    The 360* crankshaft would produce a 1-2-3-4 firing order and a 0*-270*-360*-630* firing interval, so 1-0-0-2-3-0-0-4. (Aprilia RSV4, I think)
    Alternatively, another cam can go 1-4-3-2 firing order with the same firing interval, for 1-0-0-4-3-0-0-2. (Honda RC30, pretty sure)

    The 180* crankshaft would produce a 1-4-3-2 firing order and a 0*-90*-180*-270* firing interval, 1-4-3-2-0-0-0-0. (Honda VFR800)
    A different cam can go 1-3-2-4, firing interval 0*-180*-270*-450*, 1-0-3-2-0-4-0-0 (Saab Sonnet)

    The 90* crankshaft produces a firing order of 1-3-4-2, and a 0*-90*-360*-630* firing interval, so 1-3-0-0-4-0-0-2. (Pretty sure this would be "half an LS Crank" with standard LS cam timing)

    Another 90* crankshaft produces a firing order of 1-3-2-4, and a 0*-90*-270*-360* firing interval, so 1-3-0-0-2-4-0-0 (this is the "half an LS Crank" with altered cam timing),

    Obviously, I'd lean towards the half-an-LS crank, where I just have to bore and braze in a crank snout and fix the oiling hole for the #1 rod, then figure out how to get a thrust bearing in that middle crank journal.

    But, since I have to get a thrust bearing in there anyway, I might as well look at all my options.
    Last edited by Xnke; 11-08-21, 11:32 AM.

    #2
    Didn't Lincoln do something similar with a porche motor?
    .... because every driver experiences the destructive potential of the effortless surge of power available through the smallest of body movements.

    Dr Hoon
    .

    DrNick is king!!!! No, Mark Webber is now! Long live the king!... hold on a minute mate, Ricci is in charge now

    Comment


      #3
      Hmm given the success of Porsche's V4 in the 919 I'm watching with interest . . .
      " Racing cars don't have doors. Toilets have doors" : Keke Rosberg

      Comment


        #4
        I'd go with 90 degree so you don't have to fuck around as much with cutting and shutting cranks and cams.
        Last edited by Sealioning; 11-08-21, 08:27 PM.

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          #5
          If it only has to run and will never have a clutch or converter pushing on the crank, there wouldn't be much need to have a thrust bearing at all. Even if the plan is to put it on a test stand or pinch the use of a dyno and you really need/want a thrust bearing, make the thrust external and do it like the crank supports used on blown engines.
          Last edited by greenhj; 11-08-21, 07:11 PM.

          Comment


            #6
            Have an uncle that races midgets in speedway.

            Fontana do a Ford

            Scat racing do a sbc v4 version that he ran in his car.
            Is a work of art with kingsler mech injection as it runs methanol etc
            I helped pit crew with him when he was racing in home town when in high school.

            Comment


              #7
              Originally posted by Roadsailing View Post
              I'd go with 90 degree so you don't have to fuck around as much with cutting and shutting cranks and cams.
              If the goal is to get it running for this year's class, then Roady makes a good point. It wouldn't prevent you form doing a custom crank and cams for next year's class either...
              Originally posted by Marlin
              Chickens will slip under water in the cover of darkness like a seal team and FUCK YOU UP.

              Comment


                #8
                The crank is gonna have to be custom-I did the math on the counterweights today and it just isn't there. I'd have to cut and weld the crank to get all the counterweights in the needed locations-Basically need the front and rear rod journals+associated counterweights. I could bore the main journal that will become the thrust bearing out hollow, turn the main journal for the front crank through and snout down to be a snug slip fit in the bored out main, peck it with a centerpunch to get it a tight fit with clearance and furnace braze it back in, but then I still have to weld up the crank enough to grind in the thrust bearing area. This would allow me to change the crank timing to a 360* or 180* crankshaft, though, which makes the cam and ignition timing a little more regular.

                The cam I could just cut off behind the 3rd cam bearing and it'd be usable. Firing order would be 13004002 13004002 13004002 but at least a cam is easy to get going.

                Making a custom cam core and getting it ground and hardened isn't a big deal-it's a simple job to turn a cam core as short as this one from 8620, I'll CNC the lobes in the approximate positions and there are several grinders who have already offered to grind the cam if I provide a core. As for the main cam bearings, we can grind those in our shop already, no problem. I have a Gen IV cam sprocket set, but it won't matter as I'll just run the ignition from the crank sensor and we'll not fuck with injection, just a pair of Weber 38/38 DGAS synchronous carbs to start with and then we'll make some throttle bodies to hold injectors that bolt onto the same DGEV/DGAS pattern if the damn thing actually works.

                I fired up our badly-neglected Haas Mini-Mill today and it's been 494 days since last startup, and some of my students are threatening to drop my class if they have to pick up a broom and clean up the shop.
                Last edited by Xnke; 12-08-21, 11:03 AM.

                Comment


                  #9
                  Originally posted by Xnke View Post
                  some of my students are threatening to drop my class if they have to pick up a broom and clean up the shop.
                  Make sure the door hits them in the ass on the way out.

                  Did you get my PM?

                  Comment


                    #10
                    I did, thank you. And yes, I told them as much. If they show up tomorrow not dressed for class, don't follow safety instructions, or just sleep in the corner, they're out. Already cleared it with my principal.

                    I drew the engine up in Esprit tonight and started the CAM pathing to use the tools available to pre-machine both a crankshaft and camshaft. I'll have to do some interesting setups on the largest milling machine in our shop to be able to bore the cylinders but they're bridgeport-style mills, I got lotsa options. It will be an excellent demonstration of why the floppy, noodle-soft bridgeport-style machine is so sought after for small shops.

                    If I assume infinite table load capacity (I will) then I can stand the V4 block up on its transmission mounting face about mid table, turn the turret 45*, rotate the head 90* counter clockwise (so the oil doesn't run out the oilers), extend the ram as far as it will go, nod the head 45*, and use the X-axis power feed to bore the cylinders ala horizontal boring mill. To get things square, I will bolt a cylinder square to the table top and indicate it in before I set the block up, get the spindle dialed in relative to the square, then clamp said square against the main bearing bores. Now, the block is aligned along the main bearings, I can use an indicator to sweep the deck surface of the block in (after having previously corrected the deck) and then locate, bore the original cylinder sleeves out completely, (as I'll have to remove the ones that get cut through during block welding) and make room for some mahoosive ductile iron sleeves.

                    The LS2 block has siamesed bores, and the OD of the aluminum cylinder casting is 4.8" instead of 4.6", so after boring the cast-in-place iron liners out I can easily cut the cylinder casting to 4.200, press in a sleeve, and bore said sleeve to whatever size pistons are handy that day. (I have lots of pistons/rods that are survivors of grenaded blocks, so I'll just pick weight-matched sets of four, I guess)

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                      #11
                      Is the class teaching how to complete monumental wastes of time? Surely there is some better tasks to do.
                      3D scanning
                      3D modelling
                      Structural certification
                      3 and 5 axis milling

                      Comment


                        #12
                        Originally posted by TROLLA View Post
                        Is the class teaching how to complete monumental wastes of time? Surely there is some better tasks to do.
                        No, it's a machine shop class. He says that right in the OP.

                        Comment


                          #13
                          yeah, I know I hate learnin' stuff by doing something stupid but interesting and I've never remembered anything I actually paid attention to because I enjoyed it.

                          Comment


                            #14
                            Originally posted by Captain Kermit View Post

                            No, it's a machine shop class. He says that right in the OP.
                            Yea I get it but it's only to do something to do something, it's not going to be good/awesome, or ever really be done again. Imagine turning up and being like hey boys you know this fucked LS, well let's be fucking sick cunts and make custom liners to fix this up and while we are at it, let's build a stroker crank for it. Also I thought it be good practice to make a gear drive for the cam and billet timing cover.
                            3D scanning
                            3D modelling
                            Structural certification
                            3 and 5 axis milling

                            Comment


                              #15
                              Originally posted by TROLLA View Post

                              Yea I get it but it's only to do something to do something, it's not going to be good/awesome, or ever really be done again. Imagine turning up and being like hey boys you know this fucked LS, well let's be fucking sick cunts and make custom liners to fix this up and while we are at it, let's build a stroker crank for it. Also I thought it be good practice to make a gear drive for the cam and billet timing cover.
                              and building a ute car that will be simultaneously the best drag/drift/race/bonneville/autosalon/formula 1 car ever isn't a waste of time? maybe people who live in glass houses shouldn't throw rocks.

                              I'd sooner build a crossplane I4 out of fucked LS bits because I like stupid things but am also quite lazy.

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