How do I run a leak down test?
 

Do I need a special gauge or tester or can I use a regular compression tester? I need to run this before I buy new heads, I might go with the 347 instead if i'm having a problem with compression.

Pull the plug, insert the compression tester, and with the coil wire disconnected crank the engine. The tester will show you your compression.

A leak down test is to test the coolant system for leaks I believe.

Actually I think there is a way to test the time it takes for the cylinders to loose pressure but I don't know how to do it either.

Anyone else?

Leak down test
 

To do a leak down test,you have to have a "leak down"
gauge.It has 2 gauges that are attached to each other,
one tells you the in put pressure(you have to have air comp)
and there is a knob to adjust this in put pressure(I think on mine
you adjust to 90psi)The other gauge will just be a dial broken down in to %s,Instructions should tell you how to "interpret"
resuilts,ie 5% leakage ok etc... also used to find sources of cyl.
pressure lost,ie bad rings,head gaskets,valves etc. Sears has these gauges,or you might be able to get one on loan from Auto parts store... :)

Cool, thanks for the info!

Most decent auto parts stores sell leakdown testers for about 80 bucks. You will also need an air compressor to use it.

I recently checked mine and all cylinders were 10-12% leakage. A new just broken in motor usually shows about 5%. I would say if it is 20% or above you have a problem.


Also the testers come with pretty easy instructions.