How to do a compression test

mustangLX92 · 06-24-2002, 06:45 AM

What is the correct way to do a compression test. Also what numbers should I be looking for on my car. It has 60,000 miles on it.

cyberstang5.0 · 06-24-2002, 07:18 AM

Well, there is a compression test kit you can buy. You'll have to have access to a compressor inorder to do this. I ran one on mine as well as a leak down test. I pulled 100psi on all 8. That's real good for a stock long block with 100+ miles on it. My friends drag car with 11:1 compression pulled a 130psi.

PKRWUD · 06-24-2002, 07:22 AM

There are two compression tests that you should perform; Wet and dry. Do the dry test first.

For accuracy, you MUST perform the compression tests with the engine as close to operating temp as possible, and have the throttle blocked open. You should also do both tests at the same time, dry first.

You do not need an air compressor to do this.

In short:
1) Warm up the engine
2) Disconnect the coil
3) Block the throttle so that it is wide open
4) Remove all 8 spark plugs
5) Install the tester and crank the engine through 5 revolutions
6) Read and write down the results
7) Repeat steps 5 & 6 for the remaining cylinders
8) Add 3 squirts of engine oil into the spark plug hole of the first cylinder you tested, and test it again
9) Read and write down the results
10) Repeat step 8 & 9 for each of the remaining cylinders, but do not add the oil until you are about to test that specific cylinder. Adding oil to all of the cylinders at the same time won't work correctly.

Your numbers will be higher after the wet test. The numbers themselves aren't as important as the difference between them.

Post your results.

Take care,
-Chris

06-24-2002, 06:45 AM	#1
mustangLX92 Registered Member Join Date: May 2001 Location: Maryland Posts: 138	How to do a compression test What is the correct way to do a compression test. Also what numbers should I be looking for on my car. It has 60,000 miles on it. __________________ Motorsports springs, Lakewood drag struts, Southside rear lower arms. Motorsports upper arms. Lakewood Drag shocks. Southside rear drag springs, sub frames, 3.55 Gears, Cobra intake, 70mm TB, GT40 heads, X Cam, 1.6 Crane RR's, 110lph fuel pump, AFPR, offroad h pipe, Flowmaster catback, 1 5/8" Motorsport headers, under drive pulleys, cold air induction, Black Magic Fan, Pro 5.0, Weld Draglites.

06-24-2002, 07:22 AM	#3
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	There are two compression tests that you should perform; Wet and dry. Do the dry test first. For accuracy, you MUST perform the compression tests with the engine as close to operating temp as possible, and have the throttle blocked open. You should also do both tests at the same time, dry first. You do not need an air compressor to do this. In short: 1) Warm up the engine 2) Disconnect the coil 3) Block the throttle so that it is wide open 4) Remove all 8 spark plugs 5) Install the tester and crank the engine through 5 revolutions 6) Read and write down the results 7) Repeat steps 5 & 6 for the remaining cylinders 8) Add 3 squirts of engine oil into the spark plug hole of the first cylinder you tested, and test it again 9) Read and write down the results 10) Repeat step 8 & 9 for each of the remaining cylinders, but do not add the oil until you are about to test that specific cylinder. Adding oil to all of the cylinders at the same time won't work correctly. Your numbers will be higher after the wet test. The numbers themselves aren't as important as the difference between them. Post your results. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

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06-24-2002, 07:18 AM	#2
cyberstang5.0 347ci of HORSE POWER!!! Join Date: Jul 2001 Location: Houston, TX Posts: 1,416	Well, there is a compression test kit you can buy. You'll have to have access to a compressor inorder to do this. I ran one on mine as well as a leak down test. I pulled 100psi on all 8. That's real good for a stock long block with 100+ miles on it. My friends drag car with 11:1 compression pulled a 130psi.