Compression Test
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
Compression Test
Does anyone know what a healthy reading should be on a LS1 engine with about 42k miles on it... with 25k supercharger miles?
All my cylinders measured between 170-175. The service manual just says anything below 100 is bad... yeah no **** ? It also said to do 4 compression strokes. It was hard to tell so I just ran the starter for about 5 seconds. Running it 6 seconds increased the numbers slightly ( by about 6) and 4 seconds was slightly lower (about 7 or so)...
Well what do you guys say?
All my cylinders measured between 170-175. The service manual just says anything below 100 is bad... yeah no **** ? It also said to do 4 compression strokes. It was hard to tell so I just ran the starter for about 5 seconds. Running it 6 seconds increased the numbers slightly ( by about 6) and 4 seconds was slightly lower (about 7 or so)...
Well what do you guys say?
Intermediate
Joined: Nov 2006
Posts: 41
Likes: 0
From: Knoxville TN
I was always taught to crank the car over until the needle pretty much stops moving. There is always that point where it climbs fast for the first few strokes, and then for the next couple strokes it moves a little slower. Right after that point when it really starts to slow is where I take my numbers. American_HP is right as well. As long as your numbers are consistent you are ok. That is of course unless they are down in the lower 100's. Even maybe once it starts to get much below 150-140psi I would start looking towards a rebuild, but even then as long as they are consistent you should be ok for awhile.
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
Well that's good to hear... a few cylinders I kept cranking it and it maxed out in the 180s... but the manual said 4 compression strokes. Either way I think I'm good to go.
