Leak Down Test questions

How do ya do it? :blush: I have an air compressor but what other tools do I need? Do I need some kind of gauges or something?
It's got 50,000 miles and i'm looking to get some more life out of it.It does run good but smokes a little.. Kinda blackish in color. I installed new Dyna coils, cables, spark plugs, carb rebuild & sync. There is a noticeable "high pitch" ticking sound coming from the top end near the #1 cyl. It's not constant though..Kinda sporadic. It doesn't sound like loose valves or like it needs a valve adjustment. Maybe a wrist pin?
I pulled the exhaust, noticed the exhaust gaskets were gone. I looked into the exhaust ports they are all carboned up but the #1 also had wet oil around where the valve comes through. Seal?

I wanna do the right thing and not just throw money at it.
Sometime in the future i'd like to do a big bore kit on a different engine.

Any advice on what to do first?

Thanks

Leakdown test is basically pumping air through the spark plug hole into the combustion chamber, then stopping and listening to where it leaks out, such as from exhaust, carb, crankcase breather, and/or head gasket.

It's real easy to miss seeing an old sooty flattened gasket crusted up inside the exhaust port. And sometimes there are two old gaskets in there.

Good Luck!

a leak down tester and a half inch breaker bar with the proper sized socket to fit on the rotor side crank bolt dont use the ignition advancer bolt. you should be able to find a leakdown tester at harbour freight of places like that.also some auto parts places.

Would inquire to local auto supply store such as Auto-Zone about possibily borrowing a leakdown tester to take and use at home.

Some of these places are pretty decent about having on hand an assortment of test tools for loaning out to customers.

Good Luck!

If not already done, would first check valve clearances and assure the gaps are adjusted to specs.

That alone might improve the compression and engine performance.

Good Luck!

Wasn't getting compression in 2 of my cylinders and I knew I should be seeing at least something. I was able to use my air compressor and my compression guage as a "poor man's" leak down tester fairly successfully recently. I took the gauge off the compression tester and took out the one way valve. Running compressed air into the cylinder immediately gave me a clue as to what was happening. I had the cams holders overtorked and they were barely pressing on the intake buckets just enough to cause zero compression. Can't take credit for the idea on the leak down tester - I think I got it off this forum.

that will work but there is no way of measuring how much leakage there is andalso you have noway of regulating the air pressure going into the engine or gauge but it would definetly tell you where the problems where

Are you saying the bolts were stripped out and not holding the cams down ?

Thanks guys.
I have the service manual and i'll start checking the valve clearances tonight. Will a leak down test tell me something that a compession test will not?

To use a leakdown tester u aply 100 psi to 1 gauge and the air will pass through into the motor at 100psi. as the air leaks past the rings or valves the psi on gauge 2 will drop . this shows u the pesentage of air loss. Eg, if u start with 100psi and end up with 90psi u have lost 10psi or 10%.
if u do this on a fresh motor u will have a baseline # (say 5%)as your motor wares u can monitor its presure loss.I made my own. u just need to epoxy the pathway from gauge#1 to #2 closed, then drill it out again @ .040".
Here is a pic of a factory made unit.

cnyl wrote:

Thanks guys.
Will a leak down test tell me something that a compession test will not?

Yes, if you have leakage it will be audible where it's coming from.

What Mark said. Mac offers a "pressure differential tester" for @ $140.00 it has 2 guages as Marks' and a manual presure regulator for input air. when in use you can calculate pressure loss, and by listening at airbox/exhaust/oil filler, determine roughly where air is escaping IE intake/exhaust valves-rings.& by removing adjacent plugs, can track head gaskets blown between cyl's. what it won't show is if a wrist pin has escaped and eaten cyl wall, tho comparing compression #'s & leakdown points a finger. Most shops will perform a test for @ an hour's labor, maybe less since plugs on our' pets are readily accessible.G