Normal compression for 1g

[NycDSM11]

I did a compression test the other day and got 140 across the board. Should I be worried and is this normal? Also being that a 1g motor has a low compression ratio does that mean on a compression test the results will be lower?

 

[josh38127]

My car has 130 across all four. Mine ran I like a stabbed rat. You should be ok.

If you can preform a leak down test. That will give you the results need.

 

[604CruisinCroat]

Factory is 165. 130...hmm....losing compression somewhere. Either valves or rings.

 

[slowboy101]

well do you have any modifications

 

[josh38127]

Deleted

 

[92EagleAWD]

Fuel injectors on most gasoline engines are not in the combustion chamber and do not hold compression, they only see vacuum/boost in the IM. So your losing it somewhere else.

 

[El Cuervo]

I don't know if this is true or not but won't you get lower compression numbers if you have more agressive cams? like 272s, 280s, etc. I know I read it some time ago. Can't remeber when.

 

[BogusSVO]

Its the valve seals they are leaky. When I replace them It should go back to 160 like before.

Sorry about jacking the thread man. I know its not cool.

ahhhhh... NO..... valve stem seals have no bearing on a compression test
they are oil seals.

Bothe the valves are closed when on the compression stroke, so with theat, there is no way compression will get to the seals

if the head has been milled a time or 3 before, you change the center line of the cams to the crank , which can cange the cams open and close points allowing for more over lap , That in turn will allow for more compression to bleed off. lowering your compression test.

run a leak down test.

 

[Calan]

His question is two weeks old, but since we're all answering...

http://www.dsmtuners.com/forums/articles-engine-fuel/338152-compression-test-vs-leak-down-test.html

 

[josh38127]

ahhhhh... NO..... valve stem seals have no bearing on a compression test
they are oil seals.

Bothe the valves are closed when on the compression stroke, so with theat, there is no way compression will get to the seals

if the head has been milled a time or 3 before, you change the center line of the cams to the crank , which can cange the cams open and close points allowing for more over lap , That in turn will allow for more compression to bleed off. lowering your compression test.

run a leak down test.

Cool man thanks for the corrections.I'll admit it I am wrong.But I understand now. atleast its not my car with low compression.