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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
I put two 100psi gauges on my leak down tester. One on each side of the orifice inside the body of the tester.
The tester has an air pressure regulator on the air inlet side so you can set that where you want it.
With a 100psi gauge 1 psi of air lower on the right side gauge downstream from the orifice is 1% leakdown, or if the right side gauge is 10 pounds lower then the left side gauge than it's showing 10% leakdown.

100psi works well at true TDC because the piston will stay there and not turn the crank.
At pressures lower than 100psi while the piston is somewhere between the top or bottom of the cylinder it's much easier to hold the crank from turning with a wrench on the crank pulley nut.

Originally Posted by boosted79 View Post
Good numbers for a zero hour engine. My tester is a two gauge with an .040 orifice, both gauges read the same with it dead-headed. These were taken with 80 psi inlet. I check a little before TDC so the rings are against the bottom of the lands. Sometimes at TDC the piston will rock and that can upset the rings giving a bad reading.

#1 75 6%
#6 75 6%
#2 74 7-8%
#4 70 12%
#3 76 6%
#5 75 6%

I squirted a little WD into #4 and it went up to 76-77. That one had the highest ovality of all of them at 8-9 tenths of a thou.
Old 03-26-2017, 02:19 PM
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