Leak down tester gauge?

[tomkat22]

I'm thinking about making a homemade leak down tester. My question is if I feed a constant 50 psi from the compressor to the spark plug hole,then splice a gauge into the air line the gauge should read 50 psi if there was zero leakage on that cylinder, or 40 psi if there was 20 % air escaping from that cylinder? I admit I'm not real knowledgeable on all things gauge/pressure related.LOL

 

[Linctex]

There's lots of plans online.

The size of the orifice between the two gauges is 100% dependent on cylinder bore size.

A "single gauge" leak-down tester is a stupid idea.

 

[Linctex]

To answer your question specifically,

then YES- 100 psi on the first gauge and 80 psi on the second

(but only if you have the right orifice size!!!!!)

is 80% (or 20% leakdown)

 

[tomkat22]

Thanks.I'm starting to wonder if attaching the air hose directly to spark plug hole,turn on compressor and shut it off when it reaches exactly 100 psi and start a stopwatch and write down how many seconds it takes the 100 lbs to leak out. Maybe not as accurate as a store bought tester but maybe it would tell me if one cylinder is much worse than the others.Rings and head gasket are good but I'm starting to suspect I have a burnt/bent valve.

 

[DONWATERS]

You can just use a compression tester hose and fitting, and run compressed air in with no gauge with both valves closed. Remove all the plugs first, and you can feel or hear the air coming out of ajacent plug holes for blown head gasket or whistling if a bent non sealing valve.. I have done this.

 

[tomkat22]

Oh I'll be listening to those places,tailpipe,throttle opening,etc. Just hope my hearing is good enough.LOL.