Found this while I've been researching ways to troubleshoot the ills on my 74 Bird with a 70 383. http://vmaxoutlaw.com/tech/leakdown_tester.htm This is a helluva tool and though it needs a compressor, it can really help alot of people with doing the basics rather than 37 posts of "my car doesnt run good?" If you have a compression tester, you are half-way there as far as costs. Use the hose and remove the schrader valve, and use the gauge on the manifold you just made! My cost, $0, had a comp tester, and told the pipefitter at work that it was a "government project". Haha, we all know what that is!! By lunch I had my tool! But really, a cool and useful tool that just using the basics and a little homework can tell you alot about the health of your motor.

 

Thanks! I now have plans for Sunday! That is great info. I've done the compression test thing but have never tried the "leak down".

 

Just make sure to make the "damper"! useless without it. Sorry, didnt mean to shoot your day in the ***!

 

Nah, I love this kind of stuff.

 

Thanks for the great info. I have one I made years ago but this is nicer. I use mine once a year on my engines to determin its health. LOL I keep the first test I do as a base line. After that its something to compair the new readinds to. Lawn tractor's car's truck's they all get checked. Your right its a great tool for our members to help with those not sure questions.

 

Wow, where did the time go? It is now 8:30 I just got done dinner and spent all day in the garage. I had no time to make the leak down tool. I rebuilt the two carbs on the Hemi, (removed the counterballanced "butterflies") replaced metering rods, bumped the base timing to 15* (yep that much, this cam likes it) total timing to 40*. These numbers are from the laptop MSD program read out right from the engine computer, not a defective timming light, so I know they are correct. tightened the conections on the fuel pump, adjusted the shift linkage (twice), rebuilt the vacuum pump... I guess that is about it. I still plan to make the leak down tool maybe this week or this coming weekend. Oh hell maybe I'll just buy one.

 

Leakdown testers are the bomb, the only thing I would add to this is technique.
I use a piece of rubber fuel line to listen through. If you listen to your carb while the cylinder is pressurized and hear air escaping you know you have intake valve problems, listen to the oil filler or dipstick tube and if you hear air it's a ring problem and if you listen to the exhaust pipe and hear air its an exhaust valve problem. This gives you a good idea to where your probs are.
Cheers

 

Also heard online that the "harbor freight" ones just dont work, or are defective. I finally got the toolmaker at work to drill the 1mm or .040 hole in the epoxy plug for mine. Its sunday tomorrow and i hope to have some feedback to you all about a cheap homemade tool. I'll get a pic of it when I can find the camera/computer cable.

 

Finally got around to using the leakdown tester I made. Turns out the motor isnt in too bad a shape. Here's the results.

Cyl.
1 - 7% leakdown
8 - 18%
4 - 16%
3 - 6%
6 - 16%
5 - 14%
7 - 10%
2 - 19%

Not too bad considering the motor is cold and dry, hasn't run in a month. a squirt of oil in each cyl. lowered the rate about 2% from these numbers. I could detect no leakage past the exhaust or intake valves. So the motor may be a bit worn, it is still in good health.
Since I had the front of the motor apart to check the timing chain, I had time to play with the balancer. I used a timing tape to lay-out the marks on the damper and used a cold chisel and number punches to degree the damper. Since the motor fires every 90Deg, I also marked it at 90, 180, and 270 deg so that finding tdc on each cyl. would be easier. Hope this helps someone. I'll try to get some pics tonight.

 

 

do you know the mileage on the motor?