Fantastic, thanks Terry for that extensive write up, and Lach and Kristian for your input as well, the job should (touch wood) be a doodle now. The gaskets have just arrived, will get stuck into it shortly. ------------------- > I agree with this but having done hundreds of these, I suggest that you > loosen the cam gear retaining bolt before you put the wedge down the > chain. Otherwise you will have wasted your time setting up the cam > timing only to have it move when you undo the cam gear. Don't forget the > two 6mm (10mm heads) bolts at the front of the head that go into the > timing case either. I have seen a head wrenched off and these two bolts > and parts of the head stayed behind!! > > Lach > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]] On Behalf Of Terry Rudd > Sent: Friday, 14 February 2003 12:59 AM > To: [EMAIL PROTECTED] > Subject: RE: L6 Head Removal/Refitting > > > Bob, > > The L6 heads are much the same deal as the L4 - I have a feeling that > this is going to turn into an essay, writing about playing with heads > invariable does. It's always a good idea to get hold of a workshop > manual for reference when doing this sort of thing for the first time > too. Good quality tools especially the tension wrench make a rough job > into a good job. > > Here's a bit of a technical guide to pulling a head the correct way, > i.e. make that the way that an SOB like me was taught to do it on a L > engine 30 years ago by one of the best rally teams around. > > Remove the bits and pieces to allow you to remove the rocker cover - > I'll start from there. > > Remove the plugs and rotate the engine by hand to exactly TDC induction > stroke on #1 cylinder; if you go past TDC, then rotate the engine thru > 700 plus degrees i.e. nearly twice more to do it again - it's not nice > to turn an OHC engine backwards, if we got caught doing it in my > learning years it was worth a swift kick up the bum accompanied with a > good verballing. When satisfied it's in the correct position, check that > valves on #1 are both closed, to be sure you can check that the valves > on #6 are open. > > Note the position of the V in the timing wheel in relation to the notch > in the cam thrust plate, the V to the left of the notch is valve timing > retarded (possible stretched chain), in the centre is neutral as in > stock, and to the right indicates the timing is advanced; > > Note which position (i.e. P1, P2 or P3) the dowel in the cam is > positioned on the timing wheel; factory is Pos 1, if it's anywhere else > then it's had the human touch applied to it, i.e. the valve timing has > been advanced for some reason sometime in it's past. > > OK, if the cam dowel is in P1 and notch in centre of the V is as it left > the factory and indicates that the cam chain isn't stretched. You may > wish to consider using P2 when putting it back together for a small > amount of valve timing advance (4 degrees on a L4 anyway, I think the L6 > is the same but I'm not absolutely certain of this). Just a word of > caution with playing with valve timing on the L6, they seem to be a lot > more sensitive to minor advance, if you don't change anything else then > things like heaps more grunt mid revs and then absolutely out of breath > at 5000 rpm can happen - it's happened to me a few times on carbie fed > L26 engines, and by returning the timing to stock it revs to 6000 + as > before - could have been just this engine, jury out on that one and I > haven't had a L6 apart in 20 years to play some more. > > Check the position of the rotor i.e. is it pointing towards the front > (true #1 position) or the rear (180 degrees out) - useful to know when > you're trouble shooting. > > Collecting this information before you pull it apart gives you a good > insight into getting a nicely performing L engine after a head rebuild. > > Use the trusty old solid wooden chock (don't use particle board and the > like) to hold the cam tensioner in place - dimensions are 160mm long, > 32mm high along one end and 45mm high along the other - thickness is > important too - around 10mm is good. A little trick to aid removal after > the wheel and chain is re-installed is to drill a hole in the top of the > 45mm end so you can get the tool out - it's prone to sticking so you can > thread something fairly strong through the hole eg a leather shoe lace > is good (I nearly lifted an engine off its mounts when attempting to get > it out once). The straight edge of the chock goes in along the straight > guide i.e. passenger side; > > As a bit of insurance, you can mark a link and it's position on the > timing wheel, so you know for sure you re-install it in the same place, > providing you don't change the location of the cam dowel in a different > P number. Undo the cam retaining bolt and remove the timing wheel from > the chain. It's important to keep track of where you remove bits from as > everything should be returned to where it came from - this really only > applies to head bolts, valve springs and seating washers, collets, > rockers etc. Bits like mani bolts etc are not important. Make sure that > you know the head bolt removal sequence, on most engines it is the > reverse of the tightening sequence as shown on the VRS set. > > Once you've removed the head then remove each valve, (remember to label > or use some method to identify where it belongs), check the valves > aren't bent i.e. slide in the guides easily, change the valve guides > (always with an old L head as the guides wear), de-coke the valves, > check the seats for blow by and correct as required, check that the head > is flat and serviceable, by serviceable L series head has all of the > letters in "NISSAN" along the lower edge towards the front cylinder > visible, if it's on the limit and you need to shave it further to true, > then it's head saver time, or better you will need to source another > head. > > Don't forget check that the cam dowel is tight in the end of the cam, > grab hold of it with a pair of pliers and check that it's tight i.e. it > wont rotate in it's hole and there's no sign of cracking around it where > it locates in the end of the camshaft. It's not usually a major problem > in a Datto L but none the less they'll grenade real bad if that dowel > comes adrift. > > Re-installation is pretty much the reverse, make sure the surfaces are > as clean as you can get them. After the head is torqued down, pay > particular attention to relocating the cam timing wheel in the correct > or chosen position, as this is the part that ppl find difficult - it's > not really that hard if you follow the tear down tips. If it's not in > the correct position on an L engine it's going to show up as the engine > is turned over during the valve adjustment process. I recommend that the > crankshaft is turned over by hand thru a further 720 degrees after > completing the rocker adjustments to be sure before the starter is hit > for the first time. If you changed the dowel position to adjust the > valve timing, it is quite normal to have to rotate the cam a fraction > (around 4 degrees for each number) to refit the timing wheel. > > I would only recommend that you get stuck into the inlet ports if you > have had some experience - we practiced this sort of stuff on a stuffed > as in cracked or something head to explore the limits and perfect > technique. The novice can fairly safely use a dremel and some fine wet & > dry to polish the ports, but that's all I'd do unless you are > comfortable with delving further. > > if you're still reading this you will have a bit of an insight into a > routine L series head service. > > Have fun with it, > > regards > Terry > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of Bob > Sent: Monday, 10 February 2003 9:57 PM > To: [EMAIL PROTECTED] > Subject: L6 Head Removal/Refitting > > > Hi All, > > Ive ordered in my VRS kit and will be changing the head gasket shortly. > I have only taken a head off once before, are there any special tricks > with the L series that I should do? I looked throught the archives and > saw plenty of trouble with the chain tensioner slipping, how can I try > to avoid that? Also, is it worth cleaning up an E88 head at home with a > die grinder, is there anything worthwhile that can be achieved by a > backyarder? > > Regards, > Bob > > > > --membersozdat------------------------------------------------------- > OZDAT Mailing List Please Note:- > Send (un)subscribe requests to [EMAIL PROTECTED] Send > submissions to [EMAIL PROTECTED] No unauthorised > redistribution of this email http://www.ozdat.com/ozdatonline/index.htm > http://www.ozdat.com/ozdatonline/listindex.html > http://www.mail-archive.com/[email protected]/ > --------------------------------------------------------------------- > > --membersozdat------------------------------------------------------- > OZDAT Mailing List Please Note:- > Send (un)subscribe requests to [EMAIL PROTECTED] > Send submissions to [EMAIL PROTECTED] > No unauthorised redistribution of this email > http://www.ozdat.com/ozdatonline/index.htm > http://www.ozdat.com/ozdatonline/listindex.html > http://www.mail-archive.com/[email protected]/ > --------------------------------------------------------------------- >
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