1977 280z prepup for smog check

[240zadmire]

@Zed Head  thanks for the pointers ! The darn app to convert mov to mp4 didn’t work I guess.  

All the bearings clearance I did check and they are new as well.  I did not check the clearance of the oil pump when I dismantled, clean.., replace the gasket of the oil pump itself and the gasket when mating to the engine.  I didn’t check the oil spring length.... it’s one of those thing “I’ll get to it later” and later is now ?. Sucks but will pull it off and see what’s the problem.  Hopefully still within specs and only need few more $ for the gasket and we’re good! But most likely a new pump seem to be in order! 

Edited September 19, 2020 by 240zadmire

[240zadmire]

Hi all,

I believe I screwed up, again.  Nothing new to me I guess ?

Been reading a lot of threads and I believe Tony D. and many people recommend to use turbo oil pump to get more volume ... apologies if I misquoted. @Zed Head and others in this thread, not that I don’t value your recommendations... I just feel a bit more volume won’t hurt...

 

anyway, as @Zed Head predicted, took the old one apart and seem there are scores on the rotor top and the holder.  However the rotor and holder seem to be pretty flat. My thinest gauge is 0.038mm and won’t slide through.  The clearance of the outer rotor and holder is tight.  Don’t have gauge for it...

what I meant I screw up is that the spring pressure is already out of specs. On top of that, I replaced the washer that is thicker than the stock which make it even less pressure.  Been reading a lot and folks suggest to put a thinner washer inside the bolt to make it more tight/higher pressure.... since I bought the new pump, might as well use it. After all pump is like our heart pumping blood to other organs.

Stock washer

I screwed up and replace with this thicker one 

spring out of specs of 52.5mm

 

it look like when cold start, pressure got to around 45-50 psi.  At idle is roughly 10psi. When the car warm up a big, rev to 2k rpm seem to get pressure to 30psi or so.  I did not see this with my older pump.  I’ll hook up the mechanical gauge tomorrow to see how high it gets.  I’m pretty sure psi would be more higher and more responsive.  

I reduce the movie quality and it’s about 60mb for 3 minutes or so.

 

Stay tune.  I think I’m at ease a bit and ready for the pre smog

[240zadmire]

Old pump on the right and new pump on the left.  As soon as I see the washer. I new I screwed up without open the old pump.

 

experts, please confirm my theory so that anyone read this won’t make mistake as I did.  

[grannyknot]

4 hours ago, 240zadmire said:

what I meant I screw up is that the spring pressure is already out of specs. On top of that, I replaced the washer that is thicker than the stock which make it even less pressure.  Been reading a lot and folks suggest to put a thinner washer inside the bolt to make it more tight/higher pressure.... since I bought the new pump, might as well use it. After all pump is like our heart pumping blood to other organs.

What you are calling the washer is actually the crush washer or seal, the washer that your reading about would go between the spring and the cup that screws into the pump housing.  Find a small washer the same diameter as the spring and place it in the cup that the spring sits in, put the spring in place and put everything back together.  Now that the spring is being compressed more than it was the oil won't get through the bypass valve as easily.

The mechanical gauge will give you a much more accurate reading on what the pressure is, if the pressure is still low with the new pump then as ZH says, the next thing to check is the main bearings and conrod bearings for wear.

The amount of oil your getting while cranking the starter is good,  the head looks very clean, maybe some work was done on it recently?

[Captain Obvious]

Since one end of the spring pushes against the threaded in plug, increasing the thickness of that spring could (under certain circumstances that aren't in play here) reduce the oil pressure. The thicker that washer, the further the inside surface is from the overpressure relief, and the easier it will be to open that bypass.

The only thing that bypass valve does is limit the upper end of the oil pressure. If the oil is thick (cold) and the engine is tight, that bypass will open and limit the pressure to an upper psi. If the oil is thin (hot) or the engine is worn, or the RPM's are low, that bypass valve will be closed and not be doing anything at all.

In other words, if you've got low oil pressure, changing the bypass valve spring won't do anything to help. When the oil pressure is low, that valve is already closed and not having any impact at all on the pressure. So unless that spring is so weak that the bypass is being opened accidently at a very low pressure (unlikely), it's got nothing to do with the oil pressure level.

[Zed Head]

So you're worried about maybe using the wrong washer in the pump?   The video looked good to me.  The pressure is higher, stays up when the engine gets warm, and there's good flow to the cam shaft.  I'd leave it and move on to the next issue.  I think that every Z owner worries about their oil pressure. 

Although, and this might be for someone who's been deeper in to their lubrication system, I notice some bubbles coming from the cam shaft when you stopped cranking.  I don't know where you could suck air in to the system except maybe at the gasket surface. Or the pickup tube in the oil pan.  That would "suck" if it was there.  Not sure how you'd diagnose that.  You might try cranking again with the valve cover off and confirming that the bubbles are constant and not just residual air in the system.  If you don't get bubbles, assume it's fine and just use it.

It might not be worth worrying about though, just an observation.

[240zadmire]

@grannyknot yes, I torn down the entire car, engine, head ...etc and replaced all wear and tear parts.

 

@Captain Obvious Thanks for the great explanation.  I learnt something as always.

@Zed Head you have a keen eye.  I noticed it put didn’t pay much attention as I thought air still in the system as I just replaced the oil pump.... checked the oil dipstick and yes, very loose.  Temporary solution was to wrap around with electronic tape... open valve and crank again and no more bubble.  Thanks

 

so I hooked up the mechanical gauge.  Cold start, psi around 40ish.  It drops down to 10ish PSI as the car warms up and idle.  The PSI is very responsive as I rev up the engine and it could reach up to 60psi.  If I rev up more, might go higher.

I guess as you suggested, leave it alone as the gauge on the dash might not tells the whole thing.  Btw, I have new oil sender unit as well.  Both the old and new one behave the same way.

The Video is 105mb and around 5 minutes long. 

 

[Captain Obvious]

I think the oil pressure on the mechanical gauge looks fine. Seems like an electrical issue with the dash gauge.

[Zed Head]

That's a great video. The pressure seems lower than most at idle but jumps up quick so is probably fine under load.   It's a tough call, I can't think of what you would do about it except a rebuild.  The pump looks fine based on how the pressure jumps when you rev it, but the 10 psi at idle seems low.  I'm only guessing but it looks like you might just have a worn, or loose, engine.   A perfectionist (no offense to those out there) might tear the engine down and rebuild it because it's not "as-new" but it looks like it's supplying oil with back pressure at the higher RPM, so should run fine and last many miles.  Maybe run a thicker oil than standard.

I'd just run it as it is until you hear a rod bearing knocking.  I'm not an expert though, one of the guys who's rebuilt a few might see clues of impending doom there.

 

[240zadmire]

Thanks @Captain Obvious.  That's encouraging!

@Zed Head, don't freak me out 😉 

Let me try to get the smog pretest going on and hopefully pass the smog test as well.  I really want to enjoy it a little while.  I'll keep an eye out for the short block and see if I can do a better "rebuild" next time.  I'm a bit of worry freak myself if I know something is wrong ... though I'm not a perfectionist and I'll never be.  At least in this mechanical/electrical areas.  They are above my brain can comprehends.  Like you say, I have other issues I need to attend to....

 

Say, what should I be looking out for the next rebuild? bearing clearance, piston wall ...

 

regards,

 

[rcb280z]

I can't wait to hear how you make out at the smog station.

Fingers are crossed. 

[240zadmire]

Hi everyone,

After followed all the tips, advices... 
Took the courage and brought the car for the pre smog test.  Unfortunately the car did not pass.  It failed on the too much CO.  

The technician commented the car run a bit rich and need to dial the air/fuel mixture  a bit lower.

as you noticed on other thread and in this thread as well I believe, the car run a bit rich.  I don’t really know how to go about measure the air/fuel mixture after adjusting the air flow meter.

please see the report and any advice you can give.

 

as always, much appreciate all the help.

 

regards