Restoration of BringaTrailer 240z - HLS30-35883

[Captain Obvious]

1 hour ago, inline6 said:

For quite a while today, I tried spraying lubricants and blowing compressed air in the holes of this cap.  But that did nothing.

That is because of the way the valve works. When the piston is sitting static on the bench, the valve is closed. That's why spraying stuff into the holes didn't go anywhere. It's not supposed to. Goes like this...

Valve is held closed by the spring:

When you push on the other end of the little rod (it's actually a hollow tube) it compresses the spring and opens the valve. Fluid flows through the center of this tube and out the two small cross holes that you found all rusty like. Here's a pic of the other end of the tube:

When the master cylinder is assembled, this little screw runs across the bore of the M/C and opens the valve when the cylinder is at rest. It pushes against this tube to open the valve:

So when the cylinder is at rest (and it is important that it IS at rest), that valve will open and allow fluid from the reservoir into the chamber.

So.... All that said. Are you SURE your brake linkage and rod sticking out the front of the brake booster are all adjusted properly such that your M/C was actually at rest when your foot was off the pedal? Because if it's not, that valve will never open and you won't get proper operation of the rear circuit.

[inline6]

Thanks for that info!  So, when I took the cap off, I found that the valve was stuck in an open position (makes sense if that is resting position, as the cylinder likely sat for a very long time and got gummed up/stuck in that position).  The spring couldn't close it.  In fact, there is a hole in the end of the cap, and pressing a flat punch against the valve, it did not move - it was stuck tight.  

Stuck in the open position, fluid just moved freely in both directions.  The rear circuit didn't build any pressure.  

I just got back from the garage - I am done for the night.  This time I was able to bleed the MC rear circuit with no issue.  Then, I was able to bleed all four corners.  I seem to have a solid brake pedal at this point.  Hurrah - I got something done today after all.

Now, I have the clutch circuit to bleed.  And then, I'll try to fire it up and drive it around the neighborhood a bit.

[dutchzcarguy]

@Captain Obvious I thank you too for the explanations of a MC!  I never had a problem with them, did install them but never had to go into them deep.. It sounds completely clear that there is a small valve to shut this piston to make pressure.

Also it sounded logical that the valve was open when it was rusted as the MC was all that time when it rusted solid in rest position.

[Captain Obvious]

10 hours ago, inline6 said:

I found that the valve was stuck in an open position (makes sense if that is resting position, as the cylinder likely sat for a very long time and got gummed up/stuck in that position).  The spring couldn't close it.

Yeah, I should have mentioned that possibility as well. Stuck in the open position will do pretty much the same thing as far as not being able to bleed the rears properly.

Glad you got yours working!!! Now I just need to figure out why I can't get mine to work right.      

[inline6]

So... I ran into the same thing with the clutch master cylinder tonight.  This cylinder was a used part also.  It looked to me like it was replaced by the previous owner as part of the fresh work he did to the car.  Hmmm - actually, I think that was 28 (plus 6 years in my possession) ago!  Anyway, the little valve was stuck in this one also.  For any used cylinder, that valve should be checked and lubricated with a bit of rubber grease before installing the cylinder.  

I was able to get the clutch operational, and the brakes barely so.  I need another person to assist to bleed them properly.  And it is quite possible that the brake booster is not functional.  Anyway, I took it for a brief drive in the neighborhood.  It has been about 9 years now since I drove a Z.  

It's tiny!  Turning around to back up, I was struck by how narrow, and also, how little there is of "car" behind me!  I was reminded again of how awful the throttle linkage is.  It has a lot of initial resistance, so you press a little harder, and then a little more, and then it "let's go", causing more acceleration than intended.  As I recall, I will be able to sort that out by adjusting the linkage and bending the gas pedal arm as necessary.

Oh, and that exhaust stink.  Hahaha!  Even when you get them running well, if you spend much time behind the tail pipe, you stink like you've been running a 2 cycle leaf blower.

While it starts up easily and has good throttle response, it doesn't sound or feel like it is tuned.  When I give it enough throttle to go past 2500 rpm, it acts like it is lean - it doesn't want to rev.  I will need to check timing again (static and dynamic), and check set/mixture screws again, carb sync again, etc. 

Anyway, it runs! 

 

Edited October 22 by inline6

[inline6]

Took another look at the carburetors tonight.  Neither piston was dropping to a "clunk" in the carb bodies.  The needles were touching the nozzles, and that was keeping the pistons from going to their correct locations when doing the "piston drop" test.  I was wondering why my idle speed kept moving around!  

I loosened the nut holding jet bridge and centered it properly on the rear carburetor.  Firing it up briefly, the idle is MUCH improved.  I will do the same for the front carb and give it another little test drive.

Edited October 23 by inline6

[inline6]

Ok.  Front and rear carburetor nozzles are properly aligned.  Both carb pistons pass the drop test.  Carbs sync'd again.  Initial timing adjusted to 17 degrees before top dead center (euro distributor) at 750 RPM.  Idle is staying exactly in one place.  

I drove a couple of blocks again.  I haven't hit more than 20 miles an hour.  However, the driveline seems quiet.  No noises coming from the transmission or the differential.   

At two turns out on the mixture adjustment screws, it is lean.  It idles nicely, but try to give it some gas and it is like you popped up a sail catching a headwind - the engine doesn't want to put out 🙂.  When I pull the starter circuit a bit, the power kicks in.  

So, it appears that my engine mods may have altered the fuel needs a bit from stock.  I ran my track car on SU's for a couple of decades... That engine had "some porting", 1 mm bigger intake valves and a header and dual 2" exhaust.  If I recall correctly, the SM needles didn't work as well as the original N27 stock needles when I finally got everything dialed in.  This engine has similar mods but a "stage 1" Isky cam.  It is really quite mild, just has bit more lift.

I guess I will play with unscrewing the mixture nuts a bit to experiment with determining what the engine wants.  The manual calls for 2.2 turns out.  I have them out exactly 2 right now.

[Captain Obvious]

10 hours ago, inline6 said:

It idles nicely, but try to give it some gas and it is like you popped up a sail catching a headwind

In addition to running the nozzles down a little more, maybe try some thicker oil in the dampers. What do you have in there now?

[inline6]

I put 20 weight in.  I think I used to run just 10W-30 in the Su's on the track car.  This time, I paid attention to the factory workshop manual.

[inline6]

Unscrewed the mixture screws one half a turn and fired the car up tonight.  Backing out of the garage, I notice liquid on the ground.  It was fuel coming from the rear carburetor.  Float seems operative.  My rear carb needle and seat appear to no longer be sealing.  I took it out and blew compressed air to clean everything out.  I examined the needle rubber tip and the seat with a magnifying glass.  They look new, but when I put everything back together and fired it up again - same thing.  Fuel overflowed out of the vent in the top of the chamber.   

Looking online... and I am not finding needle valves available.

Edited October 24 by inline6

[inline6]

Not finding needle valves readily available was probably a good thing.  I probably would have ordered them, however, I went out to the garage and took the float cover off again and inspected everything again.  This time I used about 10 psi of compressed air and checked to sealing.  The float was turning quite a bit angled in order to get it to seal.  That doesn't make sense to me.  I don't get why the floats aren't more level at the point where the needle seals against the seat.  In this case, the bottom edge of the float appeared to be crossing over where the side of the float bowl would be (if the cover was on the bowl).  Perhaps the side of the float was interfering with the side of the float bowl and not able to rise more to seal the needle against the seat. 

Though I used the clear tube method to set float levels previously, I repeated that process tonight with this carburetor bowl, and again set the float level so gas came up to a mark I set at 20 mm from the bottom edge of the float cover.  Is 20 mm from the bottom of the lid is correct?

The needle and seat is working properly again now.  I took the car for a another brief 3/4 mile drive.  It was not fully warmed up, but it ran a bit better than before at 2.5 turns out on the mixture screws.  Assuming I don't run into another issue, I will get it up to temp and try another brief road test tomorrow to see if I will be able to get the mixture close by backing out the mixture nuts a bit more.  

Perhaps I will need to switch to different needles.  I don't know.

Edited October 24 by inline6

[inline6]

I bled the brakes and clutch again today.  Brakes function, but the booster is not boosting 😉.  This 7" kit is available from Zcardepot: https://zcardepot.com/products/power-brake-booster-rebuild-kit-7-inch-240z 

It looks like the right one to me.  Anyone buy and install one of these? 

My booster looks like to be the rebuildable type that they mention (note red circled area):



They are in Missouri, so stuff from them usually shows up where I am in Georgia within a few days.