Cylinder Leak Tester

[Jim W.]

I need to perform a leak down test on my 64 327/300 4sp. I have been unable to find any one who rents one in the Houston area, so I have two options for purchase of an economical limited use version. One is a Milton #1257 single gauge with regulator for $59.95. The other is a US General dual gauge for 39.99 @ Harbor Freight. Does anyone have experience or recommendation for either of these? It's not much money either way, but I don't want a POC either. Thanks for your input.

[Jack H.]

Re: Cylinder Leak Tester

You just might find a competent auto repair shop can execute the leak-down test for you for LESS money than you can buy the tools + you'll get the experience of a mechanic in controlling and interpreting the test results!

[Jim W.]

Re: Cylinder Leak Tester

You just might find a competent auto repair shop can execute the leak-down test for you for LESS money than you can buy the tools + you'll get the experience of a mechanic in controlling and interpreting the test results!

I probably would have except the car is not currently drivable ( no brakes or steering column ). I just want to check this out before I start a complete tear down for a body off restore. I think i'm up to the task as I just finished a compression test and need to check one low cylinder. Anyway, I like the new experiences and learning. To me, thats half the fun.

[Joe L.]

Re: Cylinder Leak Tester

I probably would have except the car is not currently drivable ( no brakes or steering column ). I just want to check this out before I start a complete tear down for a body off restore. I think i'm up to the task as I just finished a compression test and need to check one low cylinder. Anyway, I like the new experiences and learning. To me, thats half the fun.

Jim-----


I have no experience with either of these but for leak down testers I like only the dual gauge type units, although either type will work ok.

I like the Tavia dual gauge unit, but they cost about $100. If your use is going to be minimal (use it this one time then maybe never again), I think you'll be ok with the Harbor Freight gauge. It'll be made in China, but these leakdown testers are actually pretty simple devices.

[Timothy B.]

Re: Cylinder Leak Tester

Jim, What is the cranking pressure in the low cylinder compared to others?

[Clem Z.]

Re: Cylinder Leak Tester

you need to be very careful doing a leak down test to make sure where the leak is occurring. it could be thru the valves and not the rings. with pressure in the cylinder you should hit the top of the valve stem with a plastic mallet to make sure there is no carbon on the seat causing a false reading. the air pressure will slam the valve shut squeezing out and carbon deposit. on a street driven engine with miles the only thing to look for is that all cylinders have equal leak down. this is not like doing a race engine where you start out with 1-2% leak down as you will see 25% or more on a street driven engine with miles

[Jim W.]

Re: Cylinder Leak Tester

Jim, What is the cranking pressure in the low cylinder compared to others?

Tim,

Here are the results: Cyl/PSI, 1/175 3/175 5/172 7/122 2/160 4/180 6/172 8/170. I anticipated the higher readings due to carbon build up visable through plug holes.. Tested #7 three times, added oil and went to 130 so I'm guessing a valve seat problem. I plan to do the "tap on spring" test as suggested. Car has appx 45,000 miles. What's the best way to decarbon an engine in car that can't be driven and given an "Italian tune up"? I'm hoping I dont need a total rebuild. Thats why Im running these test so you guys can help me interpret the results. Im new to this depth of automechanics but do enjoy it immensely.

[John L.]

Re: Cylinder Leak Tester

Jim & Clem,
What would be considered normal for this engine?
If it is a small block will it be different for a big block?
Since I have both and I am considering doing a leak down test also I would like to know what I should be looking for.
Thanks

[Jack H.]

Re: Cylinder Leak Tester

The norm for atmospheric pressure at sea level is 14.7 lbs/ft2. So, if the compression ratio is actually 10:1, then you'd expect a reading of 147 lbs/ft2, eh?

[John L.]

Re: Cylinder Leak Tester

Now you go and get all techinal on us. What do I know about sea level pressure...I live in the mountains
What would be considered aceptable variances in each cylinders pressure?

[Dick W.]

Re: Cylinder Leak Tester

Find some Wynn's Carbon Blaster, add it to the tank, then drive the car like you stole it for a few miles