Compression test results

[eds04max]

Compression test's are deceiving.........(if you're looking for short rods).
I ran multiple comp. tests on mine and alway's looked good??????? I didn't see the short rods until we lifted the heads!
You said you are soon-to-be-installing Dual-Fueler's................that'll get-em!!..........Tune conservative
I believe G.M. spec for comp. is 325 psi. (no less than 300).
Ed.

 

[ripmf666]

xTooltipElement

Service Information




2002 Chevrolet Chevy K Silverado - 4WD | Sierra, Silverado (VIN C/K) Service Manual | Engine | Engine Mechanical - 6.6L | Diagnostic Information and Procedures | Document ID: 1233257
Cylinder Leakage Test
Special Tools

• J 35667-A Cylinder Head Leakdown Tester
• J-35667-8 Cylinder Head Leakdown Adapter​

1. 
   
   
   
   
   Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.
   
   Important: A leakage test may be performed to measure cylinder/combustion chamber leakage. High cylinder leakage may indicate one or more of the following:
   • Worn, burnt, or stuck valves
   • Broken valve springs
   • Incorrect valve lash
   • Damaged valve train components
   • Damaged piston
   • Worn piston rings
   • Worn or scored cylinder bore
   • Damaged cylinder head gasket
   • Cracked or damaged cylinder head
   • Cracked or damaged engine block​
   
   <LI type=1>Disconnect the battery ground negative cable. <LI type=1>Remove the glow plugs. <LI type=1>Rotate the crankshaft to place the piston in the cylinder being tested at Top Dead Center (TDC) of the compression stroke. <LI type=1>Install J-35667-8 and J 35667-A . Important: It may be necessary to hold the crankshaft balancer bolt to prevent the engine from rotating.
   <LI type=1>Apply shop air pressure to J 35667-A and adjust according to the manufacturers instructions. <LI type=1>Record the cylinder leakage value. Cylinder leakage that exceeds 25 percent is considered excessive and may require component service. In excessive leakage situations, inspect for the following conditions:
   • Air leakage sounds at the intake manifold tube, may indicate a worn, stuck or burnt intake valve, broken valve spring, incorrect valve lash or damaged valve train components.
   • Air leakage sounds at the exhaust system tailpipe may indicate a worn, burnt, or stuck exhaust valve, broken valve spring, incorrect valve lash or damaged valve train components.
   • Air leakage sounds from the crankcase, oil level indicator tube, or oil fill tube may indicate worn piston rings, a damaged piston, a worn or scored cylinder bore, a damaged engine block or a damaged cylinder head.
   • Air bubbles in the cooling system may indicate a damaged cylinder head or gasket.​
2. Perform the leakage test on the remaining cylinders and record the values.

© 2008 General Motors Corporation. All rights reserved.

 

[ripmf666]

xTooltipElement

Service Information




2002 Chevrolet Chevy K Silverado - 4WD | Sierra, Silverado (VIN C/K) Service Manual | Engine | Engine Mechanical - 6.6L | Diagnostic Information and Procedures | Document ID: 675324
Engine Compression Test
Tools Required

• EN-48694 Compression Gage Adapter
• J 26999 Compression Gage
• J 43244 Relay Puller Pliers​

1. <LI type=1>Ensure that the vehicle's batteries are in good condition, and fully charged. <LI type=1>Operate the vehicle until the engine is at normal operating temperature. <LI type=1>Shut off engine. <LI type=1>Disable fuel delivery system, by removing the EDU/IGN 1 relay with J 43244 . <LI type=1>Disconnect glow plug electrical connectors; remove all 8 glow plugs. All 8 glow plugs must be removed from the engine during each cylinder test to obtain valid test results. <LI type=1>Prior to taking a compression reading, verify the cranking speed is greater than 140 RPM. If the cranking speed is below 140 RPM, repair the slow cranking speed condition before continuing with the compression test. Refer to Engine Cranks Slowly in Engine Electrical. <LI type=1>Install the EN-48694 in the glow plug hole for the cylinder that is being checked.
   
   
   
   
   Notice: Do not add oil to any cylinder during a compression test as extensive engine damage may result.
   <LI type=1>Connect the J 26999 to the EN-48694 . <LI type=1>Using the vehicle's starter motor, rotate or crank the engine for 6 compression strokes, puffs, for the cylinder being tested. <LI type=1>Observe the J 26999 and note the reading as the compression test is being performed. A normal cylinder reading will be indicated if compression builds up quickly and evenly to the specified level. An abnormal reading will be indicated if compression is low on the first compression stroke, starts increasing on the following compression strokes but does not reach the specified level. <LI type=1>Record the compression reading for the cylinder just tested. <LI type=1>Disconnect the J 26999 from the EN-48694 and remove adapter from the glow plug hole. <LI type=1>Repeat steps 8 through 13 for all remaining cylinders. All 8 cylinders must be tested to obtain valid test results. Record the readings.
2. The minimum compression in any one cylinder is 2069 kPa (300 psi). There should not be more than 345 kPa (50 psi) difference between a suspect cylinder and the average compression of all 8 cylinders.
   • Normal - Compression builds up quickly and evenly to the specified compression for each cylinder.
   • Piston Rings Leaking - Compression is low on the first stroke. Compression builds up with the following strokes but does not reach normal.
   • Valves Leaking - Compression is low on the first stroke. Compression usually does not build up on the following strokes.​

© 2008 General Motors Corporation. All rights reserved.

 

[ripmf666]

Sorry for how big it posted wish it would show up like when we do vin checks

 

[Fingers]

The long hose version of the tester reads lower than those with the short hose or no hose at all. The GM specs are only good for the tool pictured above.

 

[ripmf666]

Thanks thats nice to know Jon , I think most GM tools are Kent moore

 

[LBZ]

The long hose version of the tester reads lower than those with the short hose or no hose at all. The GM specs are only good for the tool pictured above.

Good info-thanks.
Any idea what the volume is in the GM tool and hose?

 

[mytmousemalibu]

Hmmm, cool! I didn't know you could do a compression check with the tool inserted in the bottom valve cover bolt hole :rofl:

Anyone else catch that

 

[Fingers]

I don't know, but I can guess the test gauge volume.

I forget the Stock Chamber size at TDC. Something like 50 cc? So to drop about 100 PSI is has to be about 10cc-15cc.

 

[Fingers]

Hmmm, cool! I didn't know you could do a compression check with the tool inserted in the bottom valve cover bolt hole :rofl:

Anyone else catch that

Missed that, but that is what they are showing in that Picture!

 

[LBZ]

If someone gets there hands on one and fills it with water from a syringe, that would tell us. Unless you like math......

 

[ripmf666]

I have to run by the dealer stealer in afternoon i can look at one of there.

 

[ecc_33]

Test as follows:

piston PSI
1 425
3 415
5 430
7 427

right bank test was

2- 440
4- 415
6- 420
8- 420

I did a quick compression test today after work to see were I was at still. Its been a long time but I think I definately learned one thing

Left Bank Right Bank
1- 400 2- 420
3- 398ish 4- 400
5- 420 6- 395ish
7- 418ish 8- 420

Looks like number 8 is still straight:happy2:

 

[ecc_33]

1 and 6 look to be the worst at 25psi lost. Thats still within the 10% rule if my math is correct but is still looking bad. Guess i wont be getting those bigger injectors installed now. This was with about 5-6 quarter mile passes and probly 55ish pulls with dual fuelers and the gt4088r turbo. I would say about 6 full on runs down the street with the s400. And 1,800 miles with the dual fuelers+ bigger turbo

 

[paint94979]

that still is a lot of use with big h Eric

 

[Stingpuller]

Eric

That's not bad. Was the motor warm when you tested it? It would be down more than that if there was a problem. Spray a little oil in each hole before you test it and I bet the results would be different. Jeff

 

[ecc_33]

Jeff I didnt do any of the above you mentioned(warm engine or ATF) because this is how ive done it in the past, no oil cold engine with battery charger on.

 

[bullfrogjohnson]

What type of compression tester?

I want to do this same type of test. What type of boost are you seeing with the big s400 and 2cp3? with oir without head studs?

 

[ecc_33]

I bought the compression tester from harbor freight. I believe its the same one mcrat has. Bone stock long block and not sure on boost. My guage only reads to 35psi:rofl: I havent logged it yet but guestimating to be around 45ish

 

[S Phinney]

You don't have a problem from your test results. That is pretty good comp numbers. Leak down would give you a better idea of how well your motor is holding up but I think your just fine.