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Alan L Alan L is offline
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Join Date: Apr 2006
Location: New Zealand
Posts: 3,249
leak down test

I tried posting this y/day - so hopefully it does not come up twice.
Made up a leak down tester as in pic. Ideally both gauges would be the same, but I was using my CIS 100 psi test gauge as the inlet side, but could not buy another one same. Setting the inlet pressure at 100 has an advantage with the maths - altho most leak downs seem to be done at 150 psi. It took both my hands to hold the engine steady at 100 psi, and my compressor does not go to 150. I don't think this will make a big difference to the numbers - someone correct me if I am wrong.
I put a small soft metal (not high tensile) blanking plug in between the gauges and drilled a 1 mm hole in it. That is why it is not high tensile. The plug was tapered so would not go fully in, so I recut the thread with a die nut. The hose was a standard grease gun extension hose, and my plug insert used to be a spark plug that had the porcelain ground/punched out. The tube was thin walled 1/2" galv pipe which had the perfect diameter to fit in the plug body and internal diameter to tap with 1/4"BSP for the snap on nipple.
A small regulator valve ($35) controlled the inlet pressure. It may not be the most accurate beast, but I think it worked well enough to tell me if I had any serious internal issues. If you wanted to spend more money, two widescale calibrated gauges would be good. I 'calibrated' mine by putting my finger over the plug end - they should both read 100 - and did within about 2 psi - which I allowed for by correcting my inlet pressure by 2 psi so the leak pressure could be read directly.
My results were all between 96-98% , so I take this to be good news finally.
Finally I have checked something and found it to be OK. They may even be slightly higher in that I am assuming there is no leak at the O ring on the end of the spark plug. Hard to know how much to tighten that.
So, almost there - getting bleed nipple repaired, fixing the 'over length' clutch cable - missing clevis pin bush, chewed out clevis pin and lever, and still waiting for AFR, which must be near.
Thanks for the help guys. May have some AFR Q's depending how that all works out when running. Have EGT installed now.
Old 11-26-2007, 09:37 AM
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