MYBLKSS

iTrader: (1)

Before I make any major repairs to my motor I want to make sure the bottom end is in good shape. What are the proper procedures to perform these tests?
Should the Car be warm? Which should I do first? If I have good compression do I have to do the Leak down.

KGSloan

i would just do the leakdown. it will tell you a lot more.

to do the leakdown test:
1.warm up car
2.pull all spark plugs
3.loosen the rockers (gotta have the valves shut)
4.hook up leakdown guage to air compressor
5.screw air hose into a cylinder
6.connect guage to air hose in motor (make sure you have the motor locked up and the e-brake on)
7.check PSI on both guages and find the percentage leakage
8.move on to the next cylinder

if one of the cylinders is losing a lot of pressure, you'll be able to hear where it is escaping. into the intake is a bad seal with the intake valve (maybe bent), into the exhaust is a bad exhaust valve seal (maybe bent), or into the crankcase is a bad ring or piston.

good luck to you

MYBLKSS

iTrader: (1)

this might be a stupid question but how do you work on a hot car? Won't you get different readings as the car cools. It is going to take a while to get the car up in the air, remove valve cover, Ign, starter, and plugs. How will my motor hold the heat that long?

KGSloan

it won't be "hot" but it will still be warm. i just did a leakdown on my motor this past weekend and it took about 2 hours. the motor was still warm when i finished and the readings i got were the the same from the time i started to the time i finished (i redid the first cylinder just for that reason, i wanted to see if it showed anything different after the 2 hours of cooling). i think the main idea is to not be working on a cold engine.

PREDATOR-Z

You will need 100 psi.

DenzSS

I did a leakdown on a 427 this weekend that ended up with an 18% leak on a warm motor. We checked 3 cylinders and then said the hell with it, the engine is junk. No use putting more effort into it.

8 out of 8 plugs had a dark band on the ceramic, 6 out of 8 had burnt through the ceramic in the same band. Nothing like an engine that burns 3 quarts of oil/1000 miles.

MYBLKSS

iTrader: (1)

thanks for the replys what's the maxium % leak down? my motor has about 72,000 miles on it. My heads are fairly new but who knows what shape their in I got them from JPR. So I might have any number of problems.

DenzSS

Look for about 8%. A well built engine should hit 5%, a good engine will hit 2-3%.