HF leakdown test is a Piece of Big Steenkeeng SHTUFF but here is

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67Dart273

67Dart273

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..........how I hope to fix it

Bought one of these awhile back thought "how bad can it be.?" Paid what, 40 bucks?

Cylinder Leak-Down Tester

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Looks GREAT, right?

HERE IS the problem. If you look up the developmental history of leakdown testers, they are pretty much based on a regulated (80psi or) 100psi supply and a 40 thousands orifice. A regulator and 100psi gauge, along with a few fittings is all you need

TURNS OUT the HF thing DOES NOT operate at (80 or)100psi. It operates somewhere around >????15 or so psi and the BIG PROBLEM is that the regulator is unstable at that setting IE it "pressure creeps." This means your readings vary, and it's also a PITA to reset

As an added Chineseoated bonus, the instructions are just plain incorrect. Whoever wrote them has "no idea."

Wiki:

Leak-down tester - Wikipedia

So "whut be" de plan? Well easy, I think. The basics are all there.....a gauge(s), fittings, regulator, nice box, etc

You don't REALLY need two gauges, you really only need one on the cylinder side of the orifice. So the plan IS to attempt to duplicate the .040" orifice "somewhat" remove and plug the port for the 100psi gauge and then move THAT gauge to the cylinder side, leaving the "calibrated" gauge on the shelf "somewhere."

Then the 100psi gauge will read "reciprical" IE you set it unconnected for 100, then 80psi would be 20%, 40 psi would be 60% leakeage, etc. Of course it's relative

I actually built one years ago, but the fittings, gauge, and regulator have been used for "other stuff."

I think I'll search around and see if I can BUY an actual orifice, Wiki says:

"In the United States, FAA specifications[1] state that engines up to 1,000 cu in (16 L) engine displacement require an 0.040 in (1.0 mm) orifice diameter, 0.250 in (6.4 mm) long, 60-degree approach angle. The input pressure is set for 80 psi (550 kPa), and 60 psi (410 kPa) minimum cylinder pressure is the accepted standard."

Got that? Neither do I LMAO

From the Wiki page, even tho they mention 80psi, this seems to be set for 100

Leak_down_tester.gif
 
got the same one it is damn near useless . princess auto stopped selling them because they were junk and nearly everyone sold came back says my friend that works there .
 
Youtube is my friend before just about any purchase at HF. Sometimes it's good. Other times it's bad and ain't no third direction past that....

JW
 
I just ordered two of these .040 carb jets. I realize fully they are not "FAA spec" but they are more accurate than a twist drill. If I cannot tap threads for them, I'll ream out the housing and JB one in place. "One for a spare" LOL

NEW OLD STOCK EVINRUDE JOHNSON BRP OMC 327745 .040 DIA. ORIFICE IDLE JET 0327745 | eBay

Just tore it apart. I didn't fuss with it too much but the "orifice" which is part of the main housing, is around .1--.125" Again, this thing does not operate at the recommended 80-100 psi, but rather somewhere around 15
 
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If anybody can make chicken salad outta chicken ****, you can do it.
 
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So you are going to spend money on a big piece of steeekeeng shtuff to make a bigger piece of steeekeeng stuff ?
This ought to be good. Lol
 
You might be able to make that work, but why?
 
jos51700 said:
You might be able to make that work, but why?
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Why not? Most of it is there, all it needs is one 100psi gauge which is there, and the proper orifice. A Matco is 160 bucks

If you have a better idea, "bang for the buck" by all means let's hear it
 
67Dart273 said:
Why not? Most of it is there, all it needs is one 100psi gauge which is there, and the proper orifice. A Matco is 160 bucks

If you have a better idea, "bang for the buck" by all means let's hear it
Click to expand...
This is engineering ..and hot rodding, at it's best...Why spend the money, when you have the necessary tools & knowledge? Not everything works correctly, out of the product box.Open ,your minds....
 
OK I see some improvement.........

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IMG_0914cs.JPG


Top photo you can see the tap sticking out of the body of the unit on the right. The .040 jet I bought off ebay is at far far right. Turns out they have 8-32 threads. The original HF "orifice" is somewhere around 1/8" So all I had to do is ream the "orifice" out to tap drill size, and run an 8-32 tap through it. I used the original HF 0-100 gauge for "inlet" and was going to use one of my compression gauges, but it's 0-300. Then I remembered an old refrigeration manifold, and robbed a low side gauge.

This may not be "completely" accurate. With the plug hole hose plugged in, leaving it "open" and adjusting the inlet gauge for 80psi, the "low" gauge still indicates 8-10 psi. Seems like it should be zero which would be 100% leakage.

Nevertheless it IS a baseline and IS way WAAAAAAYYYY more resettable than the original setup
 
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mopowers said:
-Nice! Would drilling out the 0.040" orifice a little larger lower the 8-10 closer to zero?
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I'm going to wait and see if I can scare up a better gauge for the inlet. They don't track that close, and even though the refrigeration gauge is pretty old, I would trust it over the new HF one. Seems to me that as the blue one climbs past 80 when setting it up, the HF one gets "high" in readings pretty quickly.

The spec for these for 5" bore and smaller is 40 thou. Even thou this is not a "spec" orifice, I'll leave it as is.

The thing is, you cannot really drill out orifices. The drill marks cause turbulence, which disrupts the flow. I would bet that a high velocity system with a drilled orifice might even flow LESS than the original 040
 
Today's "minor improvement" I dug through some of my old HVAC stuff and came up with no less than 5 low side gauges, one of which the needle is fallen off, but could be reglued. I checked them all against the refer gauge on the tester and found one that exactly matched pressure between about 60 and 100. "Last improvement," lol Also the engine head hose for this thing makes a GREAT air fitting to bust stuck heads loose!!1
 
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