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rossiz

Valve Seals Done

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the z is running well, but using a little oil and showing some oil-fouling around the perimeter of the plugs. compression is acceptable, so i figured i'd check the valve seals. thanks to blue's tech tips, i had the tools, parts and process sorted and went at it saturday morning.

couldn't wait to try out my new spring compressor :)

couple things i discovered:

  1. i didn't have to mess w/my lash adjustment, just used the spring compressor to pull out the rocker arms and never touched the adjustors. easy-peasy, and the clearances checked out just fine when i was all done and put back together.
  2. the collets/retainers were very stuck inside the spring cap - so much so, that when the first set popped loose, they shot out of the top of the retainer like pellets - one of them hit me in the forehead and landed on the intake manifold, the other flew off and landed with a "clink" somewhere... after a few minutes of feverish searching, i found it: sitting on the very edge of the "cliff of doom" - the edge of the hole down into the timing chain!! i grabbed my magnet and rescued it from causing untold damage.

so the lesson learned: put a finger on top of the keepers when breaking them free!! some of them were so stuck, i had to really push on the spring compressor - i was afraid i might bend a valve, with it pushing against the wadded up rope in the cylinder. but they all eventually came out.

i used an egg carton to keep my parts organized by cylinder and worked my way from 1-6, doing the full job on each cylinder before moving on to the next. with the plugs out and the car in neutral, it was easy to turn the cam with a wrench on the sprocket nut to get the lobes up and cylinder at tdc for each one.

the valve seals were crusty, hard and definitely past their prime. i wiggled all the valves when they were free, and fortunately the guides felt good - no excessive play, so i'm hoping the new seals will do the trick.

put her all back together, oiled the top end liberally before closing the cover, and she fired right up WITHOUT the little puff of smoke i was previously accustomed to. whole job was done in about 2 hrs - a good portion of that was figuring out how to do the first one, then it went pretty quickly.

put in a new set of freshly gapped plugs, and i'll be checking them in a few days to see if the oil is staying in the cases now...

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Nice job.

I found that a few taps with a hammer around the perimeter of the spring caps before using the compressor, will loosen the collets.

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yup - tdc required, or else a LOT of rope...

tip: after it's at tdc, put trans in gear , otherwise when you're pushing down on the valve it will move the piston and you have to start all over again.

job is easy - just takes time to do carefully. caution while pushing rope into cylinders: really easy to drag your screwdriver/poker across the plug threads, which are soft aluminum.

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Two things...

ALWAYS stuff a rag into the timing chain hole so you don't lose anything down there

When you stuff the rope into the cylinder, do it with the piston a bit before TDC. Once the rope is all in, raise the piston via the crank damper bolt to compress the rope and put some pressure on the valve. Otherwise, the valve will open a bit when you use the spring compressor.

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The only thing I see is the end of the mousetrap spring should be coming out of the center of the anchor spring not down through the center and a little wear on the timing chain. I give Blue....fill us in.

Edited by Diseazd

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On my 71 the "clothespin" springs, at the base, are not hooked in the loop. They are hooked on the back side. I really don't know which is right. As far as I know the head has never been apart. Is that a collet or piece of one on the right rocker?

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The backside is correct.....probably works either way, but FSM has it hooked on the back so the little short end comes up in the center of the loop....IMO

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yup - easy to mix that one up.

and you can bet i'll have a rag handy to protect from things going over the "cliff of doom" next time i open the valve cover - too scary!!

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well, after a week of driving i checked the plugs and i'm happy to report a great improvement.

plugs before seals were replaced: lots of oil around the perimeter, and the threads would literally be wet w/oil when i took plugs out

post-30163-14150828727382_thumb.jpg

after seals replaced: looking good. i still seem to have a little bit of unhappiness on #3 and #4, but definitely an improvement. the odd thing is that those two clinders also seem to run rich - i'm thinking i've got unbalanced injectors, probably time to change them out...

post-30163-14150828727833_thumb.jpg

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About 20 years ago, I sent my injectors into Marren Motorsports for cleaning and they told me they were beyond saving. They found me new Ram brand injectors and when they flow tested them, they were all over the map, so they ordered something like 18 more injectors and flow tested them all to finally get a matched set within spec. They were shocked at how much variation they were seeing with the new injectors. The bottom line is that injectors new or old can and will have very different flow rates.

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I've heard that reading plugs isn't what it used to be. From what I gather, it's OK for plugs to look leaner than they used to in the past. Ten years ago, the white insulators on 1,2,5, and 6 would be called lean. Some people have cited gas formulation changes that have "shifted" the norm?

My highlander for example, the plugs come out looking scary lean, but everyone tells me they look perfect. Scary lean...

P1050146_zpsda63740a.jpg

BTW - Did you know you're running the "wrong" plugs for your year?

http://www.classiczcars.com/forums/electrical-s30/47495-spark-plugs-projected-tips-vs-standard.html

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@Jeff: understood - on my bikes (ducati twins) i've always had injectors matched and it makes a noticeable difference when tuning for afr - the shop keeps about a half dozen new injectors on hand and when they order a new set they flow test to find a matching pair. too bad you can't adjust them...

@Cap'n: yes, i did a bit of research on plugs and the projected tops seem to run fine so i'm happy with them.

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Did your research turn up any info as to why Nissan moved away from the projected tips from 75 to 79 only to go back to them in 80? Any ideas? I've continued to wonder.

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P79 came in '81 though, so if they reverted in '80, it would still be the N47 head.

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It's not a big deal or anything. I'm just curious. I've had both projected and non-projected styles in my 77 and didn't notice any difference. It could be anything from slightly better emissions test numbers during those years to a typo in the manual.

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Denso/NGK price brakes to Nissan? LOL

CO, for experimental fun, I would try to pick a day where you can advance the distributor to just get the projected plugs to ping going up a hill... then swap in the regular plugs and see if the ping stops...this may prove the flame front theory.

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