Hi,
I have a problem I am trying to trace down. In short I think my valves are burnt, so I decided to pump air into the cylinder. I do not have a true leak down tester, but I have a hose I can screw into the spark plug hole and pump in compressed air. First, I screwed the hose into the number seven cylinder and decided to blow into the cylinder with my own mouth. I was able to continue blowing through the cylinder and it would not hold much pressure; with 30psi going into the hose I could hear a hiss from the motor. My question is dose this confirm I have a problem or is it normal for a cylinder not to hold very much pressure? I am trying to avoid pulling the heads if there is no problem. Thanks

 

There is no substitute for doing a real leakdown test without a tester. The valves have to be closed for you to do the test.

 

Pull the rockers off the cylinder you just tested....that'll insure the valves are closed. Then repeat your air pressure test. If you can hear air escaping at 30 psi then you can be sure you need work......

 

Pulled the rockers off and I continue to have a leak. At 30 psi I can hear a hiss; I can even here it when I blow with my mouth. I am going to pull the intake and see if it is coming out of the intake port; it is not coming out of the exhaust port. I wish I had a leak down tester to do it the correct way.

 

If memory serves, the actual pressure a leakdown tester uses is much more than 30 pounds. And the leakage is measured as a percent of that higher pressure. It could be that a low pressure will not get as much resistance to leakage as a high pressure.

If you have a leakage issue, you should not have to pull anything apart to find where it's coming from. If it is an intake valve, it will be audible from the throttle body with the plates held open. If from the ex valve, it will be heard at the tail pipe and if the rings, from the oil fill cap.

However, I would not jump to conclusions until you actually use a leak down tester. They are not expensive and you could even purchase one through a local mower shop from either Briggs or Kohler. They are that easy to find.

Why are you looking into this an issue? What sort of problem have you had?

 

Why are you looking into this an issue? What sort of problem have you had?[/QUOTE]

My car has just been running bad; (8mpg), I have checked and rechecked all issues that could arise in the fuel and ignition system. I am 100% sure my ignition and fuel systems are working correctly, so that made me think about the internals. I did install the cam way off timing when I first installed it. The headers were glowing red/orange and I continued to drive the car for a few thousand miles; I even melted a few holes in the headers before I figured out I screwed up. I think this is when I caused some damage to the internals.