Leak down test

Is there a basic way to do a leak down test. The David Brown is not running on all 4 cylinders so before removing the head I thought of doing a leak down test.
I have a compression tester, plus will be redoing all the basics like plugs, leads n timing just in case but deep down I feel I have a sticky valve or 2.

Cobba,

The cylinder in question has to be BDC and valves closed.

Fill it with compressed air, measuring the pressure. Then shut of the compressed air feed and monitor the leakage.

This is a leak down tester I made for RV gas systems. It can give some ideas.
The regulator is to set the system pressure to 2.75kpa.

In your case, the coupling would screw into the head and no regulator would be needed.

I connect the hose to the system. Pressurize via the schroder valve. Shut off the left tap.  Read the pressure. The regulator correctly sets the system pressure.  Over time, the gauge set at say 10psi should not drop.   

Note: the right hand tap is  used to check the test system for leakage. eg. Close and pressurize. There should be no leakage shown on the gauge. When testing the system, the right hand tap remains open.

 
 

Thanks for that. For some odd reason every video clips I've watched say piston at TDC.

The valves are only closed at TDC. I guess you could back the rockers right off to get them closed at BDC.

Jarrod.

You used to get a manifold vacuum tester that would indicate if valves were leaking,late ignition,bad plugs or whatever.

Cobba, a quick easy test is to have the piston at TDC, make an adapter to fit the plug hole, apply compressed air and listen to the inlet and exhaust for a leak.
It's a very basic and simple test but it will give you an idea.

 I was thinking that when at TDC, the pressure can push the piston down and it'll lose pressure.
At BDC, yes, the rockers will need to be loosened.

A compression test might give you the answers more easily. Just remember to have the throttle wide open.

Not if you put it in gear.

JOHN.K. wrote:

You used to get a manifold vacuum tester that would indicate if valves were leaking,late ignition,bad plugs or whatever.


I do have a vacuum gauge but don't understand how it can pon point the trouble
 

This might help

www.onallcylinders.com/2016/03/31/vac-vi...cuum-gauge-readings/