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Rebuilding the VG30ET

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  • Rebuilding the VG30ET

    Hi there
    you may have seen my cracked manifold in the media section.
    however, today i have finished pulling apart my Z31 engine this one had done 300,000 kms and it was still running realy nicely. For the crank on the mains and the rods there was NOT a mark or score on it, i couldn't believe it of all the chevs fords toyota's mazda's and rover engines ive helped pull apart and rebuid this vg30 had done the higest mileage and had the least wear in the bores and the crank. The head Gaskets were ready to pop by how easy the head was to lift off but man its so not worn out. I do need a new harmonic balance pully after i used the incorrect puller on it. ( now i have the correct one for next time )
    the timing seems to be one tooth out on the cylinder bank to the right hard to see in that picture.

    Before this thing goes to my engine man is there anything you recomend aside from the usual ( honing,crankshaft polish new rings+bearings,valve seating oh and a head surface and a block deck surface )

    http://www.redz31.com/coppermine/albums ... _marks.JPG

    http://www.redz31.com/coppermine/albums ... _bores.JPG

    http://www.redz31.com/coppermine/albums ... emoval.JPG
    85 Turbo Slick Top
    __________________________________________________ _____

  • #2
    james wrote:
    Before this thing goes to my engine man is there anything you recomend aside from the usual ( honing,crankshaft polish new rings+bearings,valve seating oh and a head surface and a block deck surface )
    well depending on your diagnositcs, you don't have to do any of that "usual" stuff except new rings/bearings and honing

    the heads and block shouldn't be warped

    if the journals aren't scored they don't need a polish

    if your valve seals are not leaking and don't have excessive play then nothing there

    if your leakdown test didn't show improper valve seating, then you likely don't need a valve and seat grind

    but hey it's _your_ engine don't let me stop you

    Comment


    • #3
      Yes i think anybody apart from me would just slap some gaskets on it and away you go

      a crank polish in my view can only help things especially with new bearings being used, and valves seating well it would be a little stupid not to go to the trouble of getting it done while the things apart, its only a fairly baisc freshen up but why not do it properly when your trying to make some hp on stock internals ?
      85 Turbo Slick Top
      __________________________________________________ _____

      Comment


      • #4
        you're supposed to check tolerances before declaring parts bad

        people often find everything is still to spec or within factory limits

        Comment


        • #5
          The timing looks fine to me. The marks on the rear cover don't align perfectly, use use marks on the belt or count teeth.

          That head gasket seal appears fine. The heads are always pretty easy to remove because the stock gaskets tear apart pretty easily once bonded to both surfaces. Your only concern would be checking closely for seepage around the seal ring on both heads and block. Don't have him deck the block or heads unlsss there are some irregularities, and then make sure it's the bare minimum needed (usually .010" max) or you will be throwing your cam timing off.

          The one thing I could do if you have the valves out is smooth the ports around the valve seat insert with any suitable rotary tool. When he does the valve grind, make sure to bring him the FSM or you'll probably end up with seats a mile wide (from most shops).

          Comment


          • #6
            thats a good point about the cam timing im not an engineer and ive mosty played with pushrod engines where doing the works has been fairly necessary.I do have my Nissan Dealership service manual so i will check up on the vavle seating and give him some copies of those pages, the cylinder head castings look pretty good on these heads, certainly not like some of the ones people have described. i might get my engine man to clean up my heads and do the combustion chambers also. thanks for the tips
            85 Turbo Slick Top
            __________________________________________________ _____

            Comment


            • #7
              you're not likely going to end up with an engine in better shape after the rebuild if everything is in good shape on it now. The tolerance ranges most engine rebuilders are satisfied with are far worse than factory.

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              • #8
                if you see the old valve grinders some of them use.... ugh

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                • #9
                  got boost? wrote: you're not likely going to end up with an engine in better shape after the rebuild if everything is in good shape on it now. The tolerance ranges most engine rebuilders are satisfied with are far worse than factory.
                  To me that just enhances the point that you should have head/block work done by a shop that doesn't slack on the finer details. For example, when I had my heads built about 2 years ago the guy who owned the shop said...'son, this will no be cheap to do, you need to replace everything on those heads that moves'. I smiled and said well you let me know how much all that will cost once you are done and I will pay in cash. He smiled and said, for cash and no BS I will personally grind your valve seats. Then he said...'now son...just so we are clear, I don't buy the cheap parts, this could get up to $1,000, can you handle that?' I say 'do what you would do if this was your car and I will pay you'. I couldn't be happier with the heads he built me.

                  btw- this guy built a several drag cars with various VG engines over the years so he knew what he was doing. (unfortunately this guy retired about a year ago and sold his shop)

                  Also, when I bought my re-man block I talked to the owner and 2 of his mechanics before laying down $850. These guys knew their trade and I could tell that they wouldn't ship out an engine that wouldn't exceed OEM specs. Well that is what I got, a very tight and strong engine that loves to rev quick and long.

                  My point here...choose a shop/mechanic/whatever that has a clue and doesn't take the cheap way out and lets you know right up front what the damage to your pocketbook could really be. If they don't sound like they know their s__t then they don't.

                  show them my motto...
                  Just stand back and throw money.
                  Performance costs money.
                  Reliable performance costs more.

                  Comment


                  • #10
                    OR-Z man
                    having built a couple of engines myself it seemed common sense to get down to the finer details like you said about not slacking off,but also im not the guy who has had a couple of 500hp vg's under his belt, so i didn;t so much know some of the minor things like decking the heads and block can change cam timing however i believe the best information is all the imformation and not just one persons view or thoughts. Im still going to make my mind up get a lot of the work i said done but perhaps as jason said forget about decking the block and heads and perhaps better spending that money/time having valve seats done correctly and the combustion chamber smoothed a little bit aroind the valve seat.

                    man what happened to the days where you had to deck the block on your chev 1 mm and one end and 0.2 mm on the other just to get it parallel to the crank ?
                    85 Turbo Slick Top
                    __________________________________________________ _____

                    Comment


                    • #11
                      that is kind of the point we're all trying to make, an engine builder that knows everything about the shoddy warped domestic motors will know dick about the nissan motors

                      the strength and tolerances of a well maintained high mileage vg30 is seen everytime we tear one down, about the only chronic problem we have is broken exhaust studs, which is partly due to having no flex section at the down pipe

                      it is actually non-unusual to see a vg with 150k that is still within factory/fsm specs... something definately not the case with domestics

                      so when you shop around for a rebuilder you have to find out just how much they know about the imports and nissan engines in particular and aren't just following their 60's wisdom daddy taught them

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                      • #12
                        I certainly hope I'm not the only person who has shown high-milage VG's can still be VERY strong. Almost 400whp on a completely untouched engine with 260K miles on it. Just bolted on my turbo, manifold/injectors and plenum.

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                        • #13
                          my 3 vg's are all between 165-200k km, which you gringos call low to medium mileage, 100-130k miles

                          and the one in the car (87na) I cleaned up that's producing 60psi oil pressure is the worst of the lot, and the lifters show no wear on the bottom, it could use new rockers but it's ok

                          when I took off the valvecovers from the 86na motor, I was greated by very clean dirty golden hued parts with just a hint of oil encrusting some of the valleys on the head.... when I cracked open the 87t motor it was even better still, not a hint of crust, must have been serviced not that long ago as the bypass hose and the coolant hoses under the plenum were new, too bad about all the corrosion on the filler neck and t-stat housing....

                          why is it my least maintained engine has the least aluminum corrosion? and why did I only break one exhaust stud on it, I know the other two motors have several each without taking them off

                          Comment


                          • #14
                            You could prabably drop a VG off a truck on the freeway, and still have it run just fine.
                            Attached Files
                            Drive


                            1975 Datsun 280Z
                            1988 300ZX (NAtoT soon)
                            2006 Kawasaki ZX6R

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                            • #15
                              FreeLanceBum wrote: You could prabably drop a VG off a truck on the freeway, and still have it run just fine.
                              Funny stories!

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