Restoration of BringaTrailer 240z - HLS30-35883

[Patcon]

I have rebuilt a booster. It takes some special tools which I had to build. I still haven't tried it to see if it works properly. If I were doing it again, I would have Harmon do it for just a few dollars more...

https://harmonclassicbrakes.com/

[Captain Obvious]

21 hours ago, inline6 said:

 Is 20 mm from the bottom of the lid is correct?

Yes, that is the correct spec for 1971.

 Not sure your issue is the same thing I've dealt with, but I've had issues with the floats in the past. I'm sure you've seen some of this? I started getting involved at around page 8:
https://www.classiczcars.com/forums/topic/55190-float-level-advice-please/?page=8

 

[SteveE]

How do you determine if your booster is working?  I am not sure mine is working

[inline6]

I think I recall seeing that thread at one point, but totally didn't remember it.  

So, funny (not so funny actually) thing happened this evening.  I fired the engine up and was doing some brake testing in the driveway.  Went back and forth a few times.  Got out of the car and left the engine running while I walked to the garage to get something.  As I was walking away from the car, the idle dropped quite a bit.  I turned around and came to the open engine bay to inspect, and yet again, fuel was running up and out of the rear carb float vent. 

So... I really don't want this car to catch fire and burn to the ground.  @Captain Obvious, thank you for pointing me to that thread.  I think I'd feel a lot better if I added some weight to my original floats, because I am very confident that the problem is the floats are either hitting on the underside of the float cover, or hitting on the side of the float bowls, or possibly the edge of the cork gasket!  

I don't like the severe angle that they are going to to close the needle and seat.  In this picture, I am holding the float chamber at 90 degrees to the ground, so there is little force of the float against the needle.  This is the position the float is in when it shuts the needle valve as installed on the carb float chamber, and providing me with the 20 mm spec.

 

One thing I have seen in pics as I have been researching through forum posts is that the metal portion of the float (the part with the lever) is sometimes bent as well.  That is, the whole metal part is bent up or down sometimes, such that it is not parallel with the float to surface.  Here is a pic of mine.  I think the metal part is bent slightly down.  The pivot pin hole side is a touch closer to the top of the float than the opposite end.   Bending this can have an impact on the final float position at the correct fuel height specification as well.

I did one more wet set tonight.  This time I went a touch under the 20 mm spec to try to avoid this problem happening again. 

So, @Captain Obvious, what amount of weight should I be looking at adding for 1971 carbs?  Where did you land with your trials?

[inline6]

18 hours ago, SteveE said:

How do you determine if your booster is working?  I am not sure mine is working

My brake pedal effort is excessive.  If you disconnect the hose that goes from the one way valve (attached with a bracket to the firewall on the 240z) and place a piece of masking tape over the open end of the valve (to prevent a big vacuum leak), and then test your brakes, if you feel absolutely no difference in pedal effort (between hose connected and not connected), then the booster is doing nothing.

That is the case with mine.   My one way valve is oriented correctly and functional.  But brake effort is the same with the hose that goes from the valve to the booster disconnected or connected.

Edited October 25 by inline6

[SteveE]

Thanks!   I will try that test.

[Captain Obvious]

22 hours ago, inline6 said:

what amount of weight should I be looking at adding for 1971 carbs?  Where did you land with your trials?

My last incarnation was a 4 gram brass piece threaded into the side of the float. This seemed to work well:

And as for position, I put it into the side of the float over by the hinge pin. That way, it it ever started to unthread, it would tend to hold the float up, not hold the float down. My thinking is it's safer for the float to be held up (thereby cutting off the flow of fuel), than it is for the float to be held down (allowing fuel to flow even when it shouldn't). "Fail-safe". 

You could probably find something generic to use instead of making a custom piece. Maybe a brass wood screw of similar mass?

And as for your hinge integrity, I think maybe yours looks fine. Maybe bent down a couple thousandths, but not enough to worry about.

[inline6]

Something like this perhaps?  
https://belmetric.com/m8-slotted-grub-flat-point-set-screw-brass/?sku=SS8X10SLFLATBRS

or perhaps stainless would be better because it is heavier:
https://belmetric.com/m8x1-25-a2-stainless-iso-4026-flat-point-allen-socket-set-screw/?



And what are your thoughts about drilling and threading up the center of the float on the bottom surface?  Using the same logic you mentioned, if it were to back out, it would either drop out (and lower the fuel when it does), or contact the bottom of the float bowl, and hold the float up higher, dropping the level of the fuel.

Edited October 26 by inline6

[Diseazd]

IMHO, seems to me if you sent those carbs off to Z Therapy to install new floats and valves it would be a cheap fix to know it’s done right. Just kind of sounds tricky to start modifying floats by drilling and screwing stuff in them. Why God created money. Power Brake Exchange built a couple boosters for me…..beautiful work.

 

 

Edited October 26 by Diseazd

[Yarb]

Power Brake Exchange is a great company that has terrific customer service. Thought the booster they rebuilt for me was not working correctly. They had me ship it back at no charge. Checked it out and after it was all said and done I had installed the check valve backwards. On the 78 280 the arrow points towards the intake. I had it backwards. Long story short the booster works perfectly.🤦‍♂️🤦‍♂️🤦‍♂️

 

[inline6]

Does "Power Brake Exchange" only do swaps, with me having to "exchange" my Master vac for another?  I want to hold onto my original one.  

 

[Captain Obvious]

20 hours ago, inline6 said:

Something like this perhaps?  

And what are your thoughts about drilling and threading up the center of the float on the bottom surface?  Using the same logic you mentioned, if it were to back out, it would either drop out (and lower the fuel when it does), or contact the bottom of the float bowl, and hold the float up higher, dropping the level of the fuel.

Yes, I believe a commercial setscrew type of device would work just fine. But as for the material composition... I believe that brass has a higher density than steel. So if your steel on is heavier, that would only because it's longer:
https://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html
https://www.engineersedge.com/materials/density_of_common_engineering_materials__15896.htm

As for screwing it up into the bottom of the float, that would also satisfy the failsafe of closing the valve instead of holding it open. Only reason I didn't do that is I wanted gravity to have as little effect as possible on pulling the insert out of the float. I figured that gravity would have less of a tendency to pull it out if it were stuck into the side. Not that I really expect that gravity could possibly pull it out, but put it on the side just to be sure.