LS1 compression test numbers low?
07-15-2015, 10:54 AM
#1
Teching In
Thread Starter
Join Date: Dec 2014
Location: Va
Posts: 28
Likes: 0
Received 0 Likes
on
0 Posts
LS1 compression test numbers low? Hello everyone,
I have a rebuilt LS1 with about 7.5k miles. I decided to compression test the motor and my lowest number is 149 and my highest is 162 psi. From what I have found online these seem to be very low numbers.
When I pulled the spark plugs they were covered in oil and had lots of build up on them.
The car is burning some oil too. I have to top it off every 500 miles.
What could possibly be wrong?
I have a rebuilt LS1 with about 7.5k miles. I decided to compression test the motor and my lowest number is 149 and my highest is 162 psi. From what I have found online these seem to be very low numbers.
When I pulled the spark plugs they were covered in oil and had lots of build up on them.
The car is burning some oil too. I have to top it off every 500 miles.
What could possibly be wrong?
07-15-2015, 04:37 PM
#2
TECH Resident
While PSI can vary from gauges, to not doing it properly, engine problems, cold engine, etc. One thing that is important is constancy, Can you post each cylinder and psi reading that you came up with?
General rule is highest PSI reading, in your case 162psi. So you take that, multiply it by .15, then subtract from your reading.
162x.15 = 24.3
24.3-162=145.7
So in theory 145psi is your low end being that your highest is 162psi.
Oil consumption via blow by or oil consumption via leaking valve seals need to be figured out.
General rule is highest PSI reading, in your case 162psi. So you take that, multiply it by .15, then subtract from your reading.
162x.15 = 24.3
24.3-162=145.7
So in theory 145psi is your low end being that your highest is 162psi.
Oil consumption via blow by or oil consumption via leaking valve seals need to be figured out.
07-15-2015, 04:49 PM
#3
Teching In
Thread Starter
Join Date: Dec 2014
Location: Va
Posts: 28
Likes: 0
Received 0 Likes
on
0 Posts
While PSI can vary from gauges, to not doing it properly, engine problems, cold engine, etc. One thing that is important is constancy, Can you post each cylinder and psi reading that you came up with?
General rule is highest PSI reading, in your case 162psi. So you take that, multiply it by .15, then subtract from your reading.
162x.15 = 24.3
24.3-162=145.7
So in theory 145psi is your low end being that your highest is 162psi.
Oil consumption via blow by or oil consumption via leaking valve seals need to be figured out.
General rule is highest PSI reading, in your case 162psi. So you take that, multiply it by .15, then subtract from your reading.
162x.15 = 24.3
24.3-162=145.7
So in theory 145psi is your low end being that your highest is 162psi.
Oil consumption via blow by or oil consumption via leaking valve seals need to be figured out.
1- 152
2- 149
3- 152
4- 160
5- 155
6- 154
7- 162
8- 149
The car does have a 233/239 lsa 113 cam. I was told by the machine shop that the cam will make my numbers lower than the typical 180-220 psi on stock ls1's.
