Cranking Pressure....who's a genius here?
11-24-2004, 09:12 PM
#1
Cranking Pressure....who's a genius here? Does anyone know the stock cranking pressure for an LS1?
Also, what is a good pressure to be at with a cammed LS1 (TR224-114)?
Right now I am at 165 psi, and that is with 7 of the 8 spark plugs still in, so I figure maybe 5 more psi if I take them out. Can I expect any notable differece by advancing the cam 2°?
Mods: TR224, LS6 intake, ported TB, Jet Hot LTs.
Also, what is a good pressure to be at with a cammed LS1 (TR224-114)?
Right now I am at 165 psi, and that is with 7 of the 8 spark plugs still in, so I figure maybe 5 more psi if I take them out. Can I expect any notable differece by advancing the cam 2°?
Mods: TR224, LS6 intake, ported TB, Jet Hot LTs.
11-25-2004, 04:27 AM
#2
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Dont know about the compression with a cam, but you need all the plugs out for sure when checking. Following set procedures is the only way to insure consistancy.
Here’s the lowdown on compression checking from the Service Manual.
1.Charge the battery if the battery is not fully charged.
2. Disable the ignition system.
3. Disable the fuel injection system.
4. Remove all the spark plugs.
5. Block the throttle plate wide open.
6. Start with the compression gauge at zero. Then crank the engine through four compression strokes (four puffs.)
7. Make the compression check for each cylinder. Record the reading.
8. If a cylinder has low compression, inject approximately 15 ml (one tablespoon) of engine oil into the combustion chamber through the spark plug hole. Recheck the compression and record the reading.
9. The minimum compression in any one cylinder should not be less than 70 percent of the highest cylinder. No cylinder should read less than 690 kPa (100 psi). For example, if the highest pressure in any on cylinder is 1035 kPa (150 psi), the lowest allowable pressure for any other cylinder would be 725 kPa (105 psi). (1037 X 70% = 725) (150 X 70% = 105).
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 then 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 two 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.
Here’s the lowdown on compression checking from the Service Manual.
1.Charge the battery if the battery is not fully charged.
2. Disable the ignition system.
3. Disable the fuel injection system.
4. Remove all the spark plugs.
5. Block the throttle plate wide open.
6. Start with the compression gauge at zero. Then crank the engine through four compression strokes (four puffs.)
7. Make the compression check for each cylinder. Record the reading.
8. If a cylinder has low compression, inject approximately 15 ml (one tablespoon) of engine oil into the combustion chamber through the spark plug hole. Recheck the compression and record the reading.
9. The minimum compression in any one cylinder should not be less than 70 percent of the highest cylinder. No cylinder should read less than 690 kPa (100 psi). For example, if the highest pressure in any on cylinder is 1035 kPa (150 psi), the lowest allowable pressure for any other cylinder would be 725 kPa (105 psi). (1037 X 70% = 725) (150 X 70% = 105).
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 then 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 two 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.
Last edited by DaleMX; 11-25-2004 at 04:33 AM.
