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2006 DTS Performance
141 Posts
Discussion Starter · #1 ·
Well I Just couldn't help myself. I just had to know what I have. At first I was a little dissapointed, but after ferther research and my Dad bopping me in the head for not factoring certain things into my compression results, I think my N* has some squeeze still. Ill let you guys tell me what you think.

First thing I need to note is the compression results below are 3 pumps. Not 7 like Cadillac specs require or any other compression test procedure I looked up. I always did old school 3 pumps for some reason. Now I wish I did at least 6. The next thing that must be noted is the engine was cold cold. The car had beed sitting for well over 36 hours and the outside temp was about 55 degrees. Last but not least the test was a DRY test. I sprayed some brake-cleen in the intake ports(manifold off)to test the valve seal. So the cylinders were not oiled.

The ONLY reason I did this is because I have a new intake manifold, injector set, ignition coil cassettes(right and left), ICM's, and 02 sensors coming from Northstar Performance. I spent the weekend in the gerage taking my time disassembling everything. Cleaning everything up getting ready for the new stuff. The motor has just cracked 100K miles so all this stuff should be replaced anyway. Everything looks like it has seen their better days. I just finished doing a head gasket job and those Sure Grip Studs and MLS Gaskets from Northstar performance really sealed those heads up great. I have absolutely no cylinder or coolant issues and the engine runs 202 degrees in traffic.

Compression Results

1-120 2-120
3-120 4-120
5-120 6-120
7-120 8-120

Leak Down Results

1-30% 2-30%
3-32% 4-30%
5-30% 6-30%
7-32% 8-30%

Also while observing cam timing (again this is a well running engine with proper cam timing) I noticed the intake valves start to open exactly when the piston starts to travel down on the intake stroke. I also noticed GM engineers allow the piston to reach BDC on the intake stroke, and allow the piston to just barely start on the compression stroke before fully closing the intake valves. They are just about closed at rod dwell at BDC. But dont fully seal until the piston just starts up on the compression stroke. This is just an observation.

Let me know what you guys think about those compression/leak down numbers. I think I still have some squeeze. This motor was not re-ringed and the heads were not revalved. Just pressure tested, vacuum tested and surfaced. Sealed up with Sure Grip Studs and MLS gaskets. Work performed on my own vehicle.


I have been told by a local respected engine builder (mostly chevy stuff) that a warm engine with well oiled cylinders will (not can) raise my compression results substantially
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