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Thread: Cam Chain Tensioner Mystery...

  1. #1
    Registered User rossiz's Avatar
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    Default Cam Chain Tensioner Mystery...

    so after replacing the head and futzing endlessly with the timing chain, i finally got her running. went in to do a valve lash adjust after ~600 miles on the new cam and discovered my cam chain was quite slack. while rotating the cam by the bosses i felt it turn a few degrees as the slack picked up in each direction.

    when i replaced the head, the chain was super tight - so much so that i had to lever the cam sprocket on with a big wrench. it seemed too tight to me, but everything i read stated "zero slack" and that's what it was. the first startup turned over verrrry slowly for a few revolutions, then something clicked and the engine spun free and started. i figured the tensioner was clicking into position or seating itself after being displaced.

    alarmed by the amount of slack i was now seeing, i got my little endoscope cam out and went into the abyss to see what the chain tensioner was doing, and i found it was.... completely missing!!! looks like it got sucked into the hole and i have no idea what to do now. oddly, i couldn't see any parts lying around down there, but they could be hidden in a cavity that i can't see.

    the engine runs pretty well (not perfect, hence my valve check) and doesn't make any crazy noise like i would expect from a loose chain, but i am concerned to say the least. anyone experience this chain tensioner vanishing act??

    a couple videos of the slack chain:





    going in to look for the tensioner:
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    nothing there:
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    just a whole where the oil comes out:
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    am i reading these pics correctly? is the tensioner really rattling around in the bottom end? perhaps this might explain slightly lower oil pressure?
    Last edited by rossiz; 08-21-2014 at 11:08 PM.
    '78 280z - Daily driver/work in progress...

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    It must be down in the oil pan.

    Great photos!
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    Wow, what a handy tool!
    1974 260Z

    Gary

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    Neat to see the sprocket that drives the oil pump and distributor lurking below
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
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  5. #5
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    ok, i get it that the camera is cool and the pics are neat... but what about my L28???
    '78 280z - Daily driver/work in progress...

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    Supporting Member Diseazd's Avatar
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    Don't run it another second......pull the front cover and reinstall the tensioner plunger. You should be able to retreive the plunger with a magnet extender.
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  7. #7
    Registered User siteunseen's Avatar
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Quote Originally Posted by rossiz View Post
    am i reading these pics correctly? is the tensioner really rattling around in the bottom end? perhaps this might explain slightly lower oil pressure?
    Yes, you are reading those pics correctly. The tensioner piston is no longer in the hole in which it is supposed to live. It somehow became dislodged and is probably swimming with the fishes down in the oil pan. And yes, in addition, since this is an unaccounted for unmetered source of oil flow, it could certainly account for slightly lower oil pressure.

    Sorry you're going back in again. Just when things started sounding like you had reached the bottom of the curve? You don't get a break, do ya?

  9. #9
    Registered User EuroDat's Avatar
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    A bit of bad luck. Looks like it was dislodged when you did the head and popped out with the first startup. Probably that click sound you heard.

    Here is a thread over on Ratsun Timing Chain Wedge - Engine - Ratsun Forums. Post #3 has a good photo of what has happened.

    Chas
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    Sorry to hear "the valley of doom" has claimed your tensioner.

    I know your are out of town this weekend, when you return, if you want any assistance, just let me know.

    Many people make one - the tool pictured is 15 bucks from Amazon.
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    1977 280z 06/77

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    Might as well be the Debby Downer, but you would expect some damage to happen as it got levered out of the hole. Either to the tensioner parts or to the cylinder it sat in. Unless you're going to try to rig up a way to reinsert it from the top, with magnets and tape and skinny rods you'll be taking the front cover off, so you'll want to inspect the hole carefully. Should be able to poke around in the oil pan more easily then for the tensioner.

    And I wonder if your timing chain didn't jump a tooth or two. In this case, it's easy to imagine. Might explain why it isn't running quite right.

    There's a 79 ZX in the Arlington yard that you might be able to scavenge from. Row52 | 1979 Datsun 280Z
    1976 280Z, with some minor modifications

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    so i've looked at the pictures of other chain tensioners popped out and squished up between the chain guide and the chain, and it baffles me how mine could have vanished - doesn't look like there's enough space for it to drop between it's housing and the crank gear, and the chain is going "upwards" (traveling clockwise) so it doesn't seem it would drag the tensioner down...

    can i pull the oil pan without pulling the engine? looks like the front pan bolts are obscured by the front crossmember. i already have a new pan gasket (bought to do it "someday" to fix that nagging slow leak). i was hoping maybe with the oil pan off and the valve cover off i'll have access to the tensioner from both top & bottom and maybe i can put humpty together again???
    '78 280z - Daily driver/work in progress...

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    Unfortunately it's down there somewhere:


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    No way in Hell (getting the spring loaded plunger back w/o removing the front cover). IMO. Once you remove the front cover (it ain't that hard), they make an extendable magnet (works like an antenna), you can retrieve the plunger w/o removing the pan, and put it back together the right way!
    Last edited by Diseazd; 08-23-2014 at 06:46 AM.
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    It's hard to get it in the hole with the cover off! I just took one off an L24 and there's no way in hell the plunger could get in the oil pan except in pieces.

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    Last edited by siteunseen; 08-23-2014 at 08:45 AM.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    I just remembered the Zip-Tie around the housing trick Tom Monroe says do.

    I'm wrong, Tom didn't write it. Some clever person on here most likely.
    Last edited by siteunseen; 08-23-2014 at 09:07 AM.
    1972 240Z #918 New Sight Orange
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    1972 240Z #110 Persimmons Red

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    Supporting Member Diseazd's Avatar
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    Good point Siteunseen.......looks like it should be laying on the front edge of the oil pan, however the spring is probably swimming in the oil pan.
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    Registered User siteunseen's Avatar
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    After fooling around with that motor more I think it's possibly able to be seen if you drop the oil pump. He'll have to remove it anyway.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    "can i pull the oil pan without pulling the engine?"

    I'm facing a similar task with my '72, so I feel your pain. From a review of previous posts on this topic:

    1. You can pull & replace the pan without pulling the engine... but it's a tight fit. Things that will help include:

    a) You can jack the engine up ~ 1" by disconnecting the RHS mount. The member who suggested this said, "Remove the two bolts from the passenger-side motor mount rubber. Using a jack, raise the mount arm approx. 1" and then slide a 3/4" block of wood into the gap to hold it. Lower and remove jack". I suspect you will have to disconnect the rad hoses in order to accomplish this (but maybe not?).

    b) Another member suggested undoing both motor mounts, and said that this should be done by removing the single bolt on the isolator that goes through the engine crossmember. I'm not sure who's right, but it sounds easier to try unfastening the RHS mount only to begin with. You can always unfasten the LHS mount too, if the RHS-only strategy doesn't work.

    c) Consider unbolting the sway bar at the frame mounts (and possibly remove the bar completely, to get it fully out of the way?). It appears, though, that this might only be necessary if you're intending to remove the oil pump.

    d) Adjusting the rotational position of the crankshaft might buy you that last bit of clearance needed to get the pan out (or back in).

    Once you've got the pan off (and located that pesky tensioner shoe and spring), check the pan's mounting flange for bending and/or dimpling at the bolt holes. Make sure the flange is flat and clean before you attempt the re-install.

    Re type of gasket, there seem to be varying opinions amongst members re cork-with-rubber vs. rubber-only (is there such a thing?) vs. cork-only. The main caution is not to over-tighten the bolts (see FSM), since this can: a) make the gasket try to squeeze outside the lip of the mounting flange, and; b) dimple the flange.

    There's also a general caution not to be over zealous with the application of gasket compound. For the cork or cork-with-rubber gaskets, I found this recommendation: "a thin film of aviation form-a-gasket".

    I'll be interested to hear what others have to say about this task.

    Looking on the bright side, your recent engine work means that you probably won't have much difficulty removing your harmonic balancer, water pump, and timing cover.

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    looks like i've got a long day (or two) ahead of me...
    the biggest thing i've been dreading is getting the balancer off the shaft (i haven't done this yet) and i'm gonna have to read up on timing the distributor after removal.

    next weekend is a long one... maybe i can clear the decks of obligations and git-r-done. of course i won't know if the tensioner is salvageable till i find it, so may have to order parts and have the car out of commission for a while. booooo.
    '78 280z - Daily driver/work in progress...

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    Quote Originally Posted by Namerow View Post
    "can i pull the oil pan without pulling the engine?"

    I'm facing a similar task with my '72, so I feel your pain. From a review of previous posts on this topic:
    I have never done it, but I remember reading in a threw threads that they dropped the pan and remove the oil pick up (two M8 bolts) before they could get the pan off. It seems to make sense because its a lot lower than the crankshaft. You will know soon enough once you dropped the pan.
    You don't need to remove the swaybar unless you plan to remove the oil pump. The steering rack will hit before the swaybar because its a fraction higher than the cross member.

    My experience while changing engine mounts. Things to check while lifting:
    Your top radiator hose and the heater hose to the back of the block will be points to check when lifting the motor. The back heater hose can really strain the fittings in the cabin if its tilted a lot. Its short and makes it less fleaxible compared to the one going to the front of the engine. The bottom radiator hose is generally long enough to move 1".
    The fan shroud on the radiator gets in the way if you move the engine more than 1/2" or more. I had to unbolt the shroud.
    Chas
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    finally got started and making good progress - thanks all for the kind words and encouragement.
    ordered a timing kit from msa (chain, sprockets, tensioner, chain guides, front seal) for the very reasonable price of $135 and sprung another $19 for a new bolt kit. all parts arrived quickly and i set to work saturday morning.

    as posted by others, this job really isn't that bad - there's nothing really complicated or difficult, just a pretty basic disassembly/reassembly. i think i've spent about as much time restoring and cleaning things up as the actual work. of course i had a broken bolt (doesn't even phase me anymore) and a stubborn part or two, but nothing to really worry about.

    i pulled the oil pan first, but neither the chain tensioner nor any ground-up bits were in there. cleaned it up, hammered out all the dimples in the flange from the PO trying to stop a leak by cranking everything down too tight, gave it a new paint job and a new gasket. when i finally got the timing cover off, i found the chain tensioner broken in half (the head sheared off the plunger shaft) and the spring down in the bottom below the crank sprocket. took me a while to find the plunger shaft - it was hidden in a casting hollow in the block. amazingly lucky that those parts didn't get sucked into moving gears - no damage whatsoever to be seen!!

    there have been several others who have posted step-by-step directions (thank you all, i read them over and over) but i did discover a couple of little tips.

    • the oil pan comes off without lifting the engine or removing the pickup - just jiggle and you're good
    • had to remove two bushing pivots for the sway bar to drop it down for oil pump access (easy)
    • removng radiator makes a huge difference
    • there IS a clever way to time the dizzy shaft without a helper!


    the biggie was getting the dizzy shaft timed - a bit of a PITA if you have to install the pump, crawl out from under the car, look in the dizzy adaptor to see how far off the paddle is, crawl back under, adjust and repeat. so i wadded up a paper towel in behind the shaft from below, and used a piece of the old rubber oil pan gasket bridged between a couple bolts in the oil pump mounting surface to act as a stretchy sling under the shaft. then from above, i used a pair of needle nose pliers to push the shaft down, stretching the rubber sling until it cleared the drive gear on the crank, then moved it a tooth and it sprung back up into position - voila! a simple way to move it one tooth at a time until it's in the right position. then i wrapped my pliers with a strip of rubber (from an old motorcycle inner tube i've cut up and keep on hand - very useful material) to make an improvised needlenose clamp, locked it onto the paddle up top to keep the shaft from falling down and was able to pull out the paper towel and mount the oil pump up underneath. of course i put the whole thing together with the paddle 180 degrees out the first time... but it was easy to re-do it.

    oil pan off
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    nothing in it... other than sludge
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    improvised puller setup (nuts, washers, bailing wire) did the trick
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    cover off - goodies inside
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    tensioner was worn anyway
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    find waldo - can you see where the tensioner plunger was hiding?
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    pan all clean
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    new paint
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    Last edited by rossiz; 09-01-2014 at 10:05 AM.
    '78 280z - Daily driver/work in progress...

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    today i hope to get it all finished - will post the results

    broken bolt... lovely
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    old bolts vs. new set
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    cover all cleaned up, new seal & gaskets
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    new parts installed
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    holding dizzy shaft in place
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    holding paddle from up top
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    paddle 180 degrees out - it's offset so it makes a difference...
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    refreshed pan in place
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    front buttoned up
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    '78 280z - Daily driver/work in progress...

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    Supporting Member Diseazd's Avatar
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    2 questions.....1) Did you make sure you were on TDC (compression stroke, not exhaust stroke) before installing distributor drive shaft? 2) How did you make sure that the bottom tang of the distributor drive shaft fit into the oil pump correctly? If it didn't engage properly, you'll have no oil pressure.
    Last edited by Diseazd; 09-01-2014 at 10:19 AM.
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    90 300zx and a 1996 Acura NSX.....but who's counting?

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    @ Diseazd:
    first thing i did was to set tdc comp before taking anything apart. timing mark on pulley pinned to 0 degrees, cam lobes off the rockers, kept it there the whole time. so when i took out the pump it was already set to receive the dizzy shaft tang correctly. just slid it right back in after timing the shaft - piece of cake.

    so i got her back together, all buttoned up, filled w/fluids, checked that everything was put back together and torqued up.
    fired her up and am quite pleased with the results. i'm guessing the old cam chain was stretched, because there's a huge difference in the way she runs & revs. up at around 4,500 she just sings and pulls like crazy. even sounds different, more growly than before. took her out for a test spin and wow, very nice - responsive and i must admit the sound of the motor led me down a rather childish path - all done on a closed course...

    '78 280z - Daily driver/work in progress...

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    Nice result.

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    Excellent. Glad you got it back together and that the tensioner didn't take out any other parts when it snapped.

    Quote Originally Posted by rossiz View Post
    when i replaced the head, the chain was super tight - so much so that i had to lever the cam sprocket on with a big wrench. it seemed too tight to me, but everything i read stated "zero slack" and that's what it was. the first startup turned over verrrry slowly for a few revolutions, then something clicked and the engine spun free and started. i figured the tensioner was clicking into position or seating itself after being displaced.
    Your tensioner clicked into position all right. Into position at the bottom of the front cover that is!!

    Impossible to go back at this time, but I wonder what happened. You think you didn't get the tensioner plunger into position correctly at the very beginning? My guess is that it slipped out and was wedged on an angle from the very beginning and that's why you had such a hard time getting the cam chain on. And it went from there.

    I liked your shot holding the distributor drive shaft from the top. I did the same thing when I was changing my oil pump and didn't want to mess with the timing. Looked like this:

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    yes cap'n, i believe you are right - it was out of the housing and at an angle, i'm guessing the "click" was when the head sheared off the plunger and the pieces fell down into the bottom. the two things that blow my mind are that the pieces never made any trouble with all the other moving parts in the immediate vicinity, and that the engine ran for 600+ miles with no tensioner whatsoever without skipping a tooth. i'll call it a great deal of luck!!

    the other side benefit from this whole exercise is that i've now rebuilt most of the engine - all that's left is the block
    '78 280z - Daily driver/work in progress...

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    rossiz, you were able to "wiggle" the oil pan free but was there a struggle re-installing? What did you use for gasket and sealant?

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    the pan wiggled out quite easily, went back in with no drama. i bought the gasket from msa - they had two versions, i bought the more expensive one which they told me is a bit thicker... it's a green gasket material - neither cork nor rubber, installed with no sealant. seems to work just fine (no leaks yet!)
    '78 280z - Daily driver/work in progress...

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    Nice write-up and pix. Thanks for taking the time (during and after). It's good to see that the cautions about 'jack-up-the-engine-and-remove-the-oil-pickup' were unnecessary. I'm curious to hear more details about two components of the work that you say much about (and which have earned commentary in write-ups by others):

    1. What tool(s) and procedures did you use to loosen harmonic balancer securing bolt? Degree-of-difficulty rating? Did you just put the car in gear rely on wheel chocks to keep the crank stationary, or did you remove the starter and wedge the flywheel ring gear?

    2. Any drama in loosening the 3 long bolts that secure the water pump & timing cover (esp. the skinny 10mm bolt located at the 11:00 position on the pump body)? Tips/techniques... or did they all give up without a fight?

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    very cool, I forgot about the competition oil pan gasket from MSA.

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    Quote Originally Posted by rossiz View Post
    the two things that blow my mind are that the pieces never made any trouble with all the other moving parts in the immediate vicinity, and that the engine ran for 600+ miles with no tensioner whatsoever without skipping a tooth.
    Agreed... It's simply astounding that you didn't jump a tooth or run a chunky bit through the chain.

    Murphy must have been off doing something else. You might want to watch your back.

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    Quote Originally Posted by Namerow View Post
    2. Any drama in loosening the 3 long bolts that secure the water pump & timing cover (esp. the skinny 10mm bolt located at the 11:00 position on the pump body)? Tips/techniques... or did they all give up without a fight?
    Those water pump bolts are notorious for rusting and breaking. Soak them for days with a combo of ATF/Acetone and you might get lucky. I only broke one when I did my water pump.
    Kelly R. Johnson
    1978 280Z...yes it's automatic...but I'm fat.

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    Quote Originally Posted by Namerow View Post

    1. What tool(s) and procedures did you use to loosen harmonic balancer securing bolt? Degree-of-difficulty rating? Did you just put the car in gear rely on wheel chocks to keep the crank stationary, or did you remove the starter and wedge the flywheel ring gear?
    thanks for the kind words - always fun to give back a little, especially with all the help this forum has given me. no special tools - i took off the oil pan first, then simply wedged a block of wood between the crank and the side of the block and used an 18" breaker bar to loosen the pulley bolt. it gave in pretty easily, no drama. getting the pully off was a pain, primarily because the two threaded holes for the puller were filled with crud and i couldn't get them clean enough to get the puller bolts in, so i made a Rube Goldberg by putting nuts and large washers on 3 bolts and wrapping the whole mess in bailing wire to grab the outside of the pulley (i guess it would properly be called the "pullee" in this case). fortunately it wasn't suck on too bad and came off with little fuss.

    Quote Originally Posted by Namerow View Post
    2. Any drama in loosening the 3 long bolts that secure the water pump & timing cover (esp. the skinny 10mm bolt located at the 11:00 position on the pump body)? Tips/techniques... or did they all give up without a fight?
    HA!! drama for sure. i had already broken one of the long bolts when replacing the water pump and had drilled & re-tapped it all the way through the timing cover a while back (i left the water pump on the timing cover for this whole exercise - why create a leak, eh?) and fortunately none of the other long bolts broke. i did replace them all and chased all the threads clean with a tap. the heater hose connector bolt to the timing cover broke and had to be drilled out, i replaced both of those with some leftover manifold studs i had laying around.
    '78 280z - Daily driver/work in progress...

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    You got a lot done in a short time. Impressive. I like the bailing wire puller trick, I did similar with an adjustable pipe clamp on a two jaw puller, to break a bearing loose and pull it. I think I took a picture for the record just because it looked so bad.

    Found it...
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    1976 280Z, with some minor modifications

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    Hey mate

    I do have one question. For my understanding the tensioner is not supposed to have ANY slack during the first install. Looking at your picture with the chain I can see there's a bit of room there. Was this the way you finally installed it? Am I wrong here guys?

    Thanks
    Jan
    1976 280Z
    HLS30288273

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    with the new chain guides, tensioner, chain & sprockets in place there is no slack - not horribly tight, just firm. i was able to lift the cam sprocket into place with no drama, then i adjusted the slack-side guide to get the top tangent with the chain, then installed the tensioner and it's basically right up against its housing - not jammed in, just set to provide full travel against the chain as things wear in.
    '78 280z - Daily driver/work in progress...

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    Looks perfect rossiz ........you did good!
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    aw shucks.

    funny thing is, my original plan was to buy a spare engine, rebuild it over time in my garage on a stand, then do a weekend swap.
    at this point though, i've done everything but the block while it's in the car! down the road i might prep a block with a set of big-bore flat tops and lightened rods, then swap it out with all the new stuff that's on my current engine.

    but that's down the road... i'm really loving what i've got right now, can't believe how much fun this thing is to drive! it makes a fantastic sound above 4K and pulls hard all the way up to 5,500K plus.
    i'm happy.
    '78 280z - Daily driver/work in progress...

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