Hi Terry, Yeah I was hoping thats what you meant - I didnt really want the hassle/expense of doing valve guides when in your opinion replacing stem seals will suffice.
Andrew > Andrew, > > Thanks for pointing out - yes I did mean to say always change the valve stem > seals. We occasionally went to the considerable trouble of changing the > guides on a few heads in the early days - pretty expensive back then too and > not really worth it for a street engine and cheaper to toss the head and go > downtown to the wreckers and grab another - I guess it really depends on how > much has been put into other mods like big valves and porting etc. I'm not > sure how it's done these days, back then you had to dunk things in a very > hot oil bath, as I said tres exy as it was very labour intensive and no way > to do it without the correct gear. Stem seals seem to be made out of a > better class of materials these days also, I've seen genuine seals totally > stuffed in 70-80K kays, my last set on the old L engine have done 100K kays > and still no signs of anything getting down past them, but the guides are > absolutely kangaroo teds brother, sorry that's probably a 30yo colloquialism > (roo ted). > > regards > Terry > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of GREENBURY, > Andrew Robert > Sent: Saturday, 15 February 2003 4:19 PM > To: [EMAIL PROTECTED] > Subject: RE: L6 Head Removal/Refitting > > > Terry, > > Excellent informative post. > > You mention: > "change the valve guides (always with an old L head as the guides wear)" > Do you mean with every head removal the valve guides should be renewed? Or > just the valve stem seals? If you meant guides, have you got an indicative > price for this work, figuring its not DIY. > > Thanks > Andrew > > > 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]/ ---------------------------------------------------------------------
