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noob valve adjusting on 1978 280z


argniest

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I suppose it depends on which brand you buy! ROFL I don't think Yoplait is large enough. Maybe Yotastic or Danon, which comes in the squattier cup. But it doesn't really have to be a yogurt cup. Just find something that will plug up the boot. Maybe a rubber ball or a juice glass?

And yes, you've got it all right (in the picture). You don't have to plug the hose up. You can just leave it hanging.

Edited by FastWoman
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I suppose it depends on which brand you buy! ROFL I don't think Yoplait is large enough. Maybe Yotastic or Danon, which comes in the squattier cup. But it doesn't really have to be a yogurt cup. Just find something that will plug up the boot. Maybe a rubber ball or a juice glass?

And yes, you've got it all right (in the picture). You don't have to plug the hose up. You can just leave it hanging.

DING DING DING we hhhhhhhhhhhhhave a winner :)

OK, but what about this question. I will find a 'something' to plug up the hole...but when I start blowing into that hose, isnt it going to make the yogurt cup go flying out of its hole? Should I slap some tape over the yogurt cup to make sure it stays in there while doing this pressure test?

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Sure, you can fortify with some tape or simply hold it in place with your hand. In my experience, if you wedge the cup in there pretty well, you have to blow quite hard before the thing pops out, but with a bit of lung power, you can do it. ;)

Incidentally, I save my squatty yogurt cups for mixing epoxy and other odd uses, so I always have a stack of them in the garage. That's why this test famously became my "yogurt cup" test. ;)

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Well thanks! I just wanted to make sure I was understanding how to do this test. I think I do now. So once its decided if I should/can just leave valves alone for now...I would rather do other things that dont involved internal engine parts. I cant stress that enough :o

Things like yogurt cup test, removing HVAC vacuum lines out of the engine vacuum loop by temporarily disconnecting them, by removing spark plugs and Fuel injector connectors, one by one and listening to what happens. I can always adjust valves later. After doing a bunch of other things.

Edited by argniest
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PS I have the 1978 280z 5 spd. Just as a reminder.

I did this with engine stone cold

So here are the numbers. I will number them from 1 to 12...starting at the front of the engine for cylinder #1, valve 1. (I)ntake valve and (E)xhaust valve.

1(E) - .012

2(I) - .007

3(I) - .008

4(E) - .012

5(I) - .008

6(E) - .012

7(E) - .011

8(I) - .007

9(E) - .011

10(I)- .007

11(I)- .007

12(E)-.012

Can anyone tell me if these numbers are OK, bad, really bad?? I dont know what tolerance the engine has to run with these numbers, and if they are bad enough to warrant causing my vacuum to be lowered a little, medicore, or a lot.

THANKS

For a cold engine your intakes tends towards a little tight and exhausts loose. Clearances should be:

Cold:

Intake .008

Exhaust .010

Hot:

Intake .010

Exhaust .012

Every manual that I've read that makes note of the difference between cold and hot strongly suggests adjusting the valves only when the engine is hot. In an ideal world, the only time you adjust valves cold is after a rebuild. And then after getting the engine installed and running, adjust them again while hot. You seem willing to put in the time so I'd suggest doing them twice. Once, cold to get them close (and for practice) and then after driving around for at least 15, preferably 30 minutes, do'em again while hot.

The tight intake valves could lower your vacuum as they are effectively being held open to long and the compression stroke could be pushing the charge back into the intake manifold. The exhaust valves, I'm almost willing to bet, is the cause of your lousy gas mileage. They are not opening deep enough or long enough to allow the burnt gases to escape. Your injectors are sending in the gas expecting it to burn with X amount of air but effectively you only have X-Y, where Y is the volume of burnt gases, of air to combust.

Since you have a manual, you don't have to bother with giant sockets or remote starters. Just put it 5th and push. If that's a little too difficult, loosen a few plugs (mark the wires first, please!) and you could push it to Kansas.

Don't sweat it. You far more ambitious than I have been and about the worst that can happen is getting a nasty cut/bruise on a finger when loosening a nut. Just be sure to write down which one's you've done and tighten the, whatever the hell the bigger nut is called, the securing nut will do, back after turning the other nut to adjust the clearances and you'll be fine.

Chris

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well, what I would like to do as soon as I can, is to run the car around for 20 minutes get it warm, and bring it home. Pop off valve cover, and take measurements when they are still warm/hot. I think it will be good to have that data too. And see what kind of differences I spot between the clearances between cold and hot. And then comes the fun of adjusting them. Now that I have removed and put back on valve cover, and also closely inspected everything in the valve train of the engine, I mean it all looks in good shape. Everything seems consistent, and no loose pieces laying around like some people found in their own Z car engines. It was fun spinning the camshaft around (i used a big wrench on the alternator nut) and I could watch the valves opening and closing and rocker arms moving. I mean this is the first time I have ever seen any of this, so while that seems silly and trivial, it was really neat to see it all first hand for the first time. It taught me a lot. Now I know what the cam lobes are, the rocker arms, the intake and exhaust valves and springs, the lash pad. And the spring clips on the rocker arms. :)

I still dont know if I will adjust them myself or not. I would rather do it myself, but I might ask these local mechanics I met, who seem pretty knowledgeable, and are nice to me, patient with all my stupid ignorant questions. But then again, I did offer to pay them to put up with my questions. I am on the clock when I am there, even if we are just talking. I figure its only fair to pay them for their advice. ANd they dont mind if I hang out with them while we were doing all that other smoke testing, scope testing etc. SO they might let me even do some of the adjustments myself. Like have them do one, and me do one, have them dbl check while I work, etc. I would feel a lot better the first time, to have a pro there. This is not something to take lightly. One mistake and I just cost myself inummerable heartaches of money and wasted time waiting to get a blown up engine fixed.

Jetaway: do you really think if my valve clearances are only that much off, that it could wreak that much havoc on my engine? And do you think my valve clearances as stated, could be making engine vaccum only 11 IN when idling at 900 rpm, and 14 IN when I set idle at 1500 rpms? Again since I dont know how tolerant the engine is for .001 off the mark or .002 off the mark on exhaust, it didnt seem like they were in bad shape to me. But I am only about as smart as a 2 watt light bulb right now.

Edited by argniest
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argniest, yes my Z is a '78 and 510 Blue (to answer your earlier question). Sorry I did not respond earlier as I have been lurking - no need to post when you have been getting all of this great advice! When you get done adjusting the valves, you can come to Houston and do mine - after all of this I think I could certainly trust you.;)

For the HVAC vacuum question way back on post #18, The fitting you marked as #1 is the one to block off. #2 is for the AC Fast Idle and is controlled by one of the Mag Valves.

Did you check ALL of the little EGR related vacuum hoses?? Just had to ask.

BTW - When I was young and just learning to work on cars and something or some task would be kicking my Arse, my father would remind me not to get frustrated and angry, but to put my tools down and take a break. Walk away for a while, get a drink, rest your hands and clear your head. It was hard sometimes because I wanted to resolve the issue. :beer: Just a reminder.

Finally, Why were you posting at 1:14 in the morning?! Go to bed!LOL

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Im a late nighter, always have been since the day I was born. My software programming work can keep me up until 2 and 3 am, so 1:14 is actually early for me. And yes, while I get frustrated, I have never been actually mad about any of this project. Its just like the best carrot I can ever imagine, dangling just out of my reach. Every day it taunts me and teases me. And in order to get it, I have to do so many new things, and learn so many new things, things that take a lot of time, and then finally someday I can just walk over and grab the carrot and devour it :-) Its good advice what you gave tho. Thanks.

Yes, I have checked all vacuum lines, hoses, etc. And the smoke tester we used too, would have shown any important leaks. Im still going to find out if they can put dye in it. My todo list is huge again. :o And the HVAC system has been temporarily removed from the vacuum loop in the engine by dosconnecting said hoses and plugging off the port hole in the intake manifold either with a vacuum guage or a hose with a plug in the end of it. I also removed brake booster vacuum line too, just to make sure that wasnt effecting anything. And nope didnt make any difference in engine vacuum. I know I need to break out the multimeter and do some serious testing of things, especially related to FI connectors 6,5,4. I feel like a spinning top, I got to stop spinning around and take some more things off my list

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Right now, you have some of the best advisors available from this site, watching over you and providing insight,suggestions and experience. IMO, they are here and responsive to you because you do your homework and you follow instructions (usually). I say usually, because if you don't adjust your valves as your next step, well, I may just stop following this thread! Damn, son! Just go for it!

Chris (Jetaway) couldn't have said it better as to why you can't put it off (valve adjust) any longer...

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Jetaway: do you really think if my valve clearances are only that much off, that it could wreak that much havoc on my engine? And do you think my valve clearances as stated, could be making engine vaccum only 11 IN when idling at 900 rpm, and 14 IN when I set idle at 1500 rpms? Again since I dont know how tolerant the engine is for .001 off the mark or .002 off the mark on exhaust, it didnt seem like they were in bad shape to me. But I am only about as smart as a 2 watt light bulb right now.

In a word, yes. I was very busy with work when I bought my Z and a student (college) whose family built race engines (American, not a Z's) offered to adjust the valves for $30. I said, OK as he could do it while I was at school. Clattered all the way home. I parked the Z for a couple of weeks and when I did adjust the valves it had a lot more power. Do I know for an absolute fact that tight intake valves cause low vacuum? Nope. But they could. You shouldn't think just in terms of the absolute measure -- .001 or .002, but in terms of percent. Your intakes are 1/8th or 12.5% tight and the exhaust somewhere between 20% and 25% loose.

Bit more ominous, isn't it?

Your engine may have other problems but until you get the valves adjusted correctly, your diagnostics are as likely to lead you down a blind alley as solve any problems.

Chris

Chris

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Chris, dunno... I'm a bit skeptical these errors could make THAT much of a difference, but I don't know for certain. I mean 11 is a pretty low vacuum reading, and three of his cylinders are essentially nonfunctional. (Perhaps the last part about nonfunctional cylinders is in another thread.) FAIW, when I bought my car, two of my exhaust valves had almost no clearance at all. I'm somewhat amazed they weren't burnt. I can't say the engine was running great then, but I can say my putting the valves in proper adjustment did little more than to quiet the valve train just a bit.

But Argneist, just do it! We're all rooting for you! You're our rock star! You have in your hands the collective karma of the Z universe, so nothing can go wrong! ;)

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