Speedo / Tach / Gauges: 63/64 Avanti Pressure/Vacuum Gauge

[studebaker-R2-4-me]

I just received a 63/64 Avanti pressure/vacuum gauge in the Mail that I would like to hook up in my Hawk. I thought it would be an easy hook up but not so. There is a special fitting on the rear of the gauge for the line. Anyone know where I can acquire the pressure/vacuum line?

Allen

[WCP]

I don't think that there should be a special fitting. Usually a piece of rubber tubing slips over the gauge port and connects to a steel line that passes thru the firewall where a similar piece of tubing connects to a manifold port. Before installing, apply vacuum to the gauge to make sure that it moves freely. These gauges have a habit of becoming sticky or seizing after almost 50 years, even NOS ones. If that proves to be the case, it can be disassembled and freed up and lubed, preferably with clock oil.

[Stan.Gundry]

I freed up my vacuum guage by dripping some lubricant with teflon into the vacuum inlet and let it soak that way for several days. I did that two or three times. After soaking it that way each time, I carefully blew compressed air over the vacuum inlet and the lower pressure (the venturi principle if I remember my high school physics correctly) moved the inner mechanism back and forth, breaking up the crud inside. This also sucked out the lubricant so I could treat it again with fresh lubricant. That must have been 10 years ago. It is still very responsive to vacuum changes and works like a charm.

[Adamsavanti]

Hi Stan, I was just using your book yesterday while working on my Avanti. This description of how to free up a gauge is brilliant! Haven't noticed lubricants with teflon. Any particular brand?

[WCP]

Stan, I'm not sure why your method would free up a vac/pressure gauge, although you can't argue with the result. The curved vacuum/pressure tube inside the instrument is completely sealed from the mechanism that translates tube arc movement into needle movement. It's the lubricant on this mechanism that hardens and freezes the gauge. You have to take the unit apart to correct this.

[JER]

WCP, How do you get these gauges apart with out ruining the case or face?

[WCP]

JER, you carefully pry up the back side of the bezel. In order to do this without distorting the front of the bezel, I set the gauge face down and into a hole in a piece of 3/8" plywood. The hole should be sized to give a firm fit to the inner protrusion of the bezel. The prying of the back lip of the bezel should be done in many steps around the bezel and several rotations until the gauge can be lifted from the bezel. Once repaired or restored, reverse the procedure by slowly bending or rolling the bezel lip inward again gradually with many rotations while firmly pressing the gauge downward into the bezel supported as before in the plywood hole.

[Stan.Gundry]

I used Tri-Flow Superior Lubricant (http://www.triflowlubricants.com/Sup...rior_drip.html). It is available on amazon.com. No, I did not disassemle the unit. I treated it just as described. As they say, "It may not work in theory, but it worked in experience." Even it it was not possible for the lubricant to reach the moving parts of the gauge, it could have dissolved 30 years of deposits left by fumes reaching it from the intake manifold--perhaps a clogged orifice. It had a very sluggish response before I treated it. After treatment it has responded instantly to changes in vacuum.

[studebaker-R2-4-me]

I just hooked up my vacuum/ pressure gauge to my Hawk,... and low and behold it does not work. I've taken apart quite a few gauges and successfully put them back together but this one is a really nice NOS one and don't want to go there yet. Think I will try Stan method before taking it apart. Now to find some sewing machine oil. I will let you know my results.

Update One Hour Later:

I not the most patient guy when I think I can fix something. I took it apart. Tried the oil in the inlet blew compressed air into the inlet and lost patience after about 40 minutes.

I have NO Idea how putting oil in the vacuum/ pressure outlet would ever repair this gauge. As WCP states the inlet of this gauge is TOTALLY independent of the needle mechanism.

I could not find any oil around my house but went next door and my neighbor had some. I lubricated all the pivot points within the gauge (there are a few) and it broke free. Hooked it up and get a very good response on the gauge at idle, runs about 15 and up to about 20 when I increase RPM's, then drops off to about 0 at 4500 RPM with the supercharger puts pressure on the manifold.

Question to Avanti R2 owners: What pressure reading should I expect out of this gauge? The pressure scale on the gauge reads 0-10 psi. Under boost what reading do you get?

Allen

[41 Frank]

If all the pulleys are the proper size and no belt slip is present you should see about 5# @ 5000 rpm Allen.

[studebaker-R2-4-me]

If all the pulleys are the proper size and no belt slip is present you should see about 5# @ 5000 rpm Allen.

Hi Frank, how's Arizona or are you back home now? We had a great holiday down there, spent a few days down in Tucson horseback riding at a ranch. Great scenery.

I'm not seeing 5# on the gauge. I doubt I have belt slippage with a brand new short S/C belt for good wrap around the pulley and a new pulley I just media blasted to roughen it up. I've taken the vacuum/pressure line off the rear intake manifold, same place as the hydrovac and throttle kicker, hoping that is where it should come from. Best I have seen is 0 on the gauge. It's too last to start revving the engine in my shop... don't think my neighbors would be too happy with that, but there is always tomorrow.

Allen

[studebaker-R2-4-me]

I just had my Hawk out this morning, only seeing vacuum on this gauge. Is this what I should expect?

At 2500 Rpm I'm reading about 10-12 at idle 18-20. When I step on it the gauge goes down to 0. Have not seen it go into the positive range.

What does this all mean?

Thanks,

Allen

[WCP]

I don't think you should see any positive reading below 3500 rpm. Try a sustained 5000 rpm on the road at load, not in neutral! Your SN92 should be putting out 5+ psi if you have the high efficiency impeller. Talk to KoolR2 for his experience. The SN92 needs to be shimmed to get the drive into the 25-30 in.lb. torque range. As I recall, without checking my notes, after approx. 18 in.lbs., the shim pack behind the belleville washer must be increased 0.001" for each 1 in.lb. gain, or some 0.012" to achieve 30 in.lbs.
BTW, the SN92 is not easy to take apart, due to the single fat O-ring. It takes a lot of care and ingenuity to accomplish that without damaging the housings.

[studebaker-R2-4-me]

I don't think you should see any positive reading below 3500 rpm. Try a sustained 5000 rpm on the road at load, not in neutral! Your SN92 should be putting out 5+ psi if you have the high efficiency impeller. Talk to KoolR2 for his experience. The SN92 needs to be shimmed to get the drive into the 25-30 in.lb. torque range. As I recall, without checking my notes, after approx. 18 in.lbs., the shim pack behind the belleville washer must be increased 0.001" for each 1 in.lb. gain, or some 0.012" to achieve 30 in.lbs.
BTW, the SN92 is not easy to take apart, due to the single fat O-ring. It takes a lot of care and ingenuity to accomplish that without damaging the housings.

I have not done a sustained 5000 RPM under load yet, just a quick spurt on city streets and city limits trying not to attract too much attention. Mike Myers rebuilt my Supercharger a few years ago when it seized up going to his house after a South Bend meet. Mike shimmed it up pretty close to the back plate. Jon got a little upset with the tolerances Mike was trying to achieve. Interesting job rebuilding that Supercharger well into the night.

Sounds like I am on track then with this gauge

Allen.

[Gunslinger]

I'm far from all that knowledgeable on blowers, but has your engine been rebuilt? Bored out cylinders, improperly adjusted valves, and even a thicker than stock head gasket can all affect boost. If the cubic inches have gone up slightly due to an overbore or the compression slightly reduced, then the boost is somewhat less at the same rpm's and load if nothing less has changed with the supercharger or pulley itself. It would take higher rpm's to achieve the same boost level.

At least that seems reasonable to me.