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  • KA Rebuild on the cheap?

    So I'm finally motivated to rebuild my spare KA block. Well, the short block anyway. I'd like to keep the costs contained as much as possible so that this has minimal effect on other projects.

    Cheap is obviously relative, if I can do it on my own with good results I will, other things I have no problem taking to a machine shop for the work.

    NA build, high-ish RPM in the 7200 RPM range, or whatever distributor ignition limits me to. Whichever is lower.

    Things I know I'll be using:
    • Existing block w/ hone, or if the condition is too poor, possibly bore it out for added cubes.
    • New pistons will be needed, looking for 10 or 11 to 1 CR. Open to using stock replacement SOHC, or aftermarket. No super-tech though, don't trust them.
    • ARP rod bolts will happen.
    • Stock head gasket
    • Current crank is good to go after being polished.
    • ARP head studs are already on the current motor and will be re-used
    • OEM crank girdle bolts, never pull that off, and don't see the ROI in ARP fasteners there.
    • Stock rods, though I may get a new set or new ones from Rock Auto.
    • ATI or whatever crank damper thing, seems to work well on someone's TTC car.

    Things I'm not sure on:
    • What brand piston, and the benefits of each option. (lower mass / friction / need for valve relief, etc)
    • I don't think I have a matching set of rods and rod bearing caps. Not sure if this is a problem that needs to be machined away, or if I can get away with using them as is.
    • What the hell to do about bearings, who makes good ones?
    • New oil pump? Might as well. Everything I have has significant use / wear on it.


    Other Questions:
    • What's been everyone's experiences with KA rebuilds?
    • What things should I look out for?
    • What do you want to gap the rings to with an NA motor? FSM specs?
    • Anyone have some thoughts on target bearing clearances? 7000rpm reliability being more important than power here.
    '95 240sx

  • #2
    shot peen the rods. have them sized. use ARP bolts. rods are done.

    bearings- Clevite or Nissan are both fine.

    use SOHC pistons- get them coated on top to prevent some cooking, and you'll be fine. use stock/recommended ring gaps for your particular rings.

    oil pump- definitely buy a new one for a performance application. I haven't had one fail, but they're cheap in relation to losing the rest of the engine.

    Set the bearings up a bit loose. they make more power and are more reliable since a tiny amount of non-oiling (suck up an air pocket during hard cornering) can spin a bearing on a tight engine. loose engines are slightly more tolerant to that and there's less friction to deal with anyway so you make more power.

    For not a lot more money, you can have a machine shop put together the bottom end for you- couple hundred bucks and let them worry about gapping rings and mic'ing bearings. gotta find a guy you trust thought.
    Originally posted by SoSideways
    I don't care what color they are as long as they are LONG AND HARD.
    '04 G35 Sedan 6MT- The DD
    '96 240SX- The Track Toy

    Comment


    • #3
      So... Who does one send a box to for the shot peen of rods service? Google failed me on that on.

      I assume when you're talking about the piston coating, we're talking about a swain-tech or similar.

      Does year matter at all with the SOHC pistons? I thought some were higher compression than others when dropped into the DE motors. Trying to be cheap and run 93 octane if i can.

      Is it worth boring out? There's no scoring on the cylinder walls, just some light surface rust from sitting for years and years. I can't imagine 20 or 40 over really amounts to that much in the way of displacement. -- I'm half tempted to use the drill hone I found in my garage on the motor, and take it to the machine shop like that and see what they say as far as go / no-go with it.


      Could you please clarify 'a little loose' on the bearings?
      '95 240sx

      Comment


      • #4
        Originally posted by Sleepy_Steve View Post
        So... Who does one send a box to for the shot peen of rods service? Google failed me on that on.

        I assume when you're talking about the piston coating, we're talking about a swain-tech or similar.

        Does year matter at all with the SOHC pistons? I thought some were higher compression than others when dropped into the DE motors. Trying to be cheap and run 93 octane if i can.

        Is it worth boring out? There's no scoring on the cylinder walls, just some light surface rust from sitting for years and years. I can't imagine 20 or 40 over really amounts to that much in the way of displacement. -- I'm half tempted to use the drill hone I found in my garage on the motor, and take it to the machine shop like that and see what they say as far as go / no-go with it.


        Could you please clarify 'a little loose' on the bearings?
        The machine shop you use should be able to shot peen in house, or at least have a source. Mine did it in house.

        For bearings, Nissan (or Nismo) seems to have the best selection. Their tolerances are the widest range. I think they offer 6 sizes whereas most aftermarket companies offer 3 (although all the aftermarket bearings can still be bought and remain in spec). You could also do the motoiq WPC coating to the bearings which looks pretty awesome, but that is getting to bigger budget territory I would imagine.

        Comment


        • #5
          If you don't have a set of great condition stock rods with matching caps then there is absolutely no way I'd use stock rods. Basically the labor to verify they're good, and any minor resizing is probably close to 1/3 a set of aftermarket nice rods. Shotpeening puts you over 50% a set of aftermarket rods.

          I can help you out with engine stuff at a good price.

          Don't hone the walls yourself, they are likely a bit out of round with a lot of miles, and it's really difficult to get the proper hone finish doing it by hand. A bore and hone costs like $125-175 - I wouldn't skimp out there. Especially on an NA engine. You can easily be adding a few percent displacement there. That's a few percent more power across the whole rev range for like $150ish. Who wouldn't do that if you had a guaranteed say 3-4% power bump for $150 for something you bolted onto the engine? I sure would!

          ACL bearings are nice as well, and typically set a little on the loose side.


          IMO, if I'm paying for labor to go into an engine, I'd get a set of aftermarket rods and pistons. It's not huge $$$ (as you'll see, pm me), and that's going to basically ensure you've got nice, strong, fresh components. All the other stuff after that is a bit of fluff, and probably not that worth it.

          I would definitely get a good valve job done, and pay for some light porting (blend the bowls, unshroud valves, clean up casting marks) if you don't want to do it yourself. That's worth quite a bit of NA power there too.

          Want some cams too?
          '18 Chevrolet Volt - Electric fun hatch for DD duty!


          DefSport Koni Sleeve and Spring Perch Buy!!!
          http://www.nissanroadracing.com/showthread.php?t=5902

          Comment


          • #6
            Holly crap, the KA crank damper things are expensive. Not doing that.

            Thanks, but I've already got some crappy cams in the motor, and the head was refreshed a couple seasons ago. It's fine for now, I'm keeping my focus on the spare bottom end here.

            I think all the required precise measuring equipment is in a fancy box at my dad's place. I'm inclined to do the assembly myself.

            I see your statement not as its only double the cost to go with aftermarket rods, but more like it's still half the cost to re-use old rods than it is to get new aftermarket. Buying another set of used rods to have matching caps probably makes it cheaper still.
            '95 240sx

            Comment


            • #7
              You can definitely save some money by doing your own assembly. I think my piston ring compressor was from Sears and it worked fine. I borrowed a nice ring filer from a friend, and also bought a series of feeler gauges and bore gauges to double check things. All the machining - boring/honing I left up to the shop. The shop also spec'ed my bearings for me. I simply double checked their work.

              If you plan on getting a matching set of used rods, have the machine shop check them for roundness torqued with the caps, then shot peen them. If you're using ARP rod bolts (you should) they will deflect differently than stock rod bolts anyway. I read somewhere that some nissan rods are already shot peened. May want to double check that as well.

              Like Def says, don't skimp on a bore/hone. The hone is super delicate too from what I have learned. I never tested it and always errored on the side of caution. One of the tips I was told was to cover the rod bolts with some rubber/silicone hose when pushing the piston/rod into the block to keep the rod bolts from nicking your fresh hone in case the rods swing into the cylinder wall.

              Comment


              • #8
                Originally posted by Sleepy_Steve View Post
                Holly crap, the KA crank damper things are expensive. Not doing that.

                Thanks, but I've already got some crappy cams in the motor, and the head was refreshed a couple seasons ago. It's fine for now, I'm keeping my focus on the spare bottom end here.

                I think all the required precise measuring equipment is in a fancy box at my dad's place. I'm inclined to do the assembly myself.

                I see your statement not as its only double the cost to go with aftermarket rods, but more like it's still half the cost to re-use old rods than it is to get new aftermarket. Buying another set of used rods to have matching caps probably makes it cheaper still.
                That's basically what I was getting at on the rods. Why pay money to have a set of old stock rods when you're most of the way towards a set of new aftermarket rods you really shouldn't have to worry about?
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

                Comment


                • #9
                  Originally posted by Sleepy_Steve View Post
                  Holly crap, the KA crank damper things are expensive. Not doing that.
                  How high are you planning to rev the engine, and how long do you want it to last?
                  Above 7200rpm, you need one to make the engine last. it's not a "If I can afford it, I'll do it" It's a "If I want my engine to last, I need this".
                  Originally posted by SoSideways
                  I don't care what color they are as long as they are LONG AND HARD.
                  '04 G35 Sedan 6MT- The DD
                  '96 240SX- The Track Toy

                  Comment


                  • #10
                    KA24DE will not last long at 7200rpm w/o an ATI Damper. Also a super light clutch/flywheel combo improves durability.

                    I'm selling my QuarterMaster 5.5" 2-disc setup. Just haven't taken photos yet to put in For Sale section. Let me know if you're interested.
                    NASA Time Trials TT3


                    BTW I work for Garrett

                    Comment


                    • #11
                      OK then, where's the best place to source an ATI damper? Best I see is Summit at like $445... Is it the kind of thing you generally buy new?

                      How high can you spin the motor reliably without a fancy lightweight clutch and damper? 6800? 7000?
                      '95 240sx

                      Comment


                      • #12
                        Are you building this to a class? What are you trying to accomplish with the engine?

                        Trying to get an NA KA to spin up high and last a long time is pretty $$$, and by the time you start making good power you're going to drop the engine life by quite a bit.


                        You already have a Bikirom right? Have you looked at what a T28 turbo setup would run? You could do a stock SR manifold with a KA flange welded on for dirt cheap, reliable stuff. Then cheap eBay parts around the T28. Put in some STi 525 cc injectors - a reliable ~250 rwhp with tons of torque.
                        '18 Chevrolet Volt - Electric fun hatch for DD duty!


                        DefSport Koni Sleeve and Spring Perch Buy!!!
                        http://www.nissanroadracing.com/showthread.php?t=5902

                        Comment


                        • #13
                          The thought is to build it for TTE with NASA.

                          I know... there is a hoosier shod super charged miata, but it's the cheapest class to run with people actually running in my region.

                          2700 lbs, tune for 158hp over the widest possible range, pull timing where needed to be compliant like the guy with the supercharged miata does.
                          '95 240sx

                          Comment


                          • #14
                            See if powerbond makes one for your motor. I got a new harmonic balancer for the sr 20% reduction for ~$200.

                            Comment


                            • #15
                              Can you run a turbo and stay in TTE if you keep it at 150ish rwhp over a huge range? No reason for RPMs on a KA at that power level. It will be a lot of work to keep power up that high at higher rpm.
                              '18 Chevrolet Volt - Electric fun hatch for DD duty!


                              DefSport Koni Sleeve and Spring Perch Buy!!!
                              http://www.nissanroadracing.com/showthread.php?t=5902

                              Comment

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