3.6 Alloytec VZ compression?

[dharry]

Hi all,

Can anyone tell me what the compression should be in the cylinders on a VZ Alloytec?

Dean

 

[2005vzute]

Record the compression readings from all of the cylinders.
• The lowest reading should not be less than 70 percent of the highest reading.

• No cylinder reading should be less than 965 kPa (140 psi).

If a cylinder has low compression, inject approximately 15 ml (1 tablespoon) of engine oil into the combustion chamber through the spark plug hole. Measure the compression again and record the reading.
• 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. Compression improves considerably when you add oil.

• Valves Leaking -- Compression is low on the first stroke. Compression usually does not build up on the following strokes. Compression does not improve much when you add oil.

• If 2 adjacent cylinders have lower than normal compression, and injecting oil into the cylinders does not increase the compression, the cause may be a head gasket leaking between the cylinders.


well there ya go...thats for a VE alloytec..should be the same for the VZ's

 

[impulsive]

someone was telling me that the compression figures are higher then most V6's..

 

[2005vzute]

who knows...that info above is straight off the GM service manual for VE's so i doubt this information is arguable...

 

[impulsive]

no one is arguing dude.. was stating something i was told.. i dunno anything bout compression.. dont get ya knickers in a twist

 

[2005vzute]

hahaha i tried to say it as nicely as i could..i was just saying that's from the holden mechanics service manual and those figures can't be argued against no matter what anyone says ...i know **** all about compression too..except that combustion pressures can get up to 7000kpa
oh and i said it was from the GM service manual so he could believe it was a straight answer and no dicking around with 20 different answers
sorry if it sounded like i was havin a go at ya or something

 

[dharry]

Thanks guys... with a compression on all cylinders between 65-75psi i'm guessing that's pretty stuffed then

Now it's just a matter of finding out why...

cheers

 

[2005vzute]

gimme a minute..i'll try find the possibilites from my information sources...shoulda rememebered this stuff in the other thread you posted

 

[2005vzute]

Important: A leakage test may be performed in order to measure cylinder/combustion chamber leakage. High cylinder leakage may indicate one or more of the following:

• Worn or burnt valves.

• Broken valve springs.

• Stuck valve lifters.

• Incorrect valve lash.

• Damaged piston.

• Worn piston rings.

• Worn or scored cylinder bore.

• Damaged cylinder head gasket.

• Cracked or damaged cylinder head.

• Cracked or damaged cylinder block.

 

[2005vzute]

Apply air pressure to the J 35667-A J 35667-A and adjust according to the manufacturers instructions.
Record the cylinder leakage value. Cylinder leakage that exceeds 25 percent is considered above acceptable and may require component service. In above acceptable leakage situations, inspect for the following conditions:
• Air leakage sounds at the throttle body or air inlet hose may indicate a worn or burnt intake valve or a broken valve spring.

• Air leakage sounds at the exhaust extension pipe may indicate a worn or burnt exhaust valve or a broken valve spring.

• 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 cylinder block or a damaged cylinder head.

• Air bubbles in the cooling system may indicate a damaged cylinder head or a damaged cylinder head gasket.

Perform the leakage test on the remaining cylinders and record the values.