so i uh did a compression test...

[sidoze]

I have a '99 GS-T for all you who dont know, and I also have 106,000 miles on it. (yea tell me about it)

Yesterday my curiousity started to outweigh my fear so I checked the compression.

Going from the passenger side to the drivers side I get:

163, 160, 143, 165


i thought 165 was stock compression but anonymous sources state its more like 180.

doing the leak down makes me think the 143 is from a bad headgasket.

so my question is, what should my broke ass do to make it better/make my block last another 40,000 miles. should i do the headgasket? or just wait till i can afford the 6 bolt and not race the living hell out of it.

getting a straight answer on what the normal compression is would help too

i hope im putting this in the right forum

 

[gritsak]

Originally posted by sidoze
I
doing the leak down makes me think the 143 is from a bad headgasket.

did you also do a leak down test, or just compression?....those compression numbers arent horrible....you might try doing it again but adding a little oil down into the lower compression cylinder and see how that effects the numbers...if they go up significantly then you might just have a worn ring

if you havent done a leak down test yet ide get that done...it will e a little better indicator of where exactly the problems is

 

[sidoze]

andy:

thanks a bunch,

i guess my english just sucks, i meant that when i did the leak down test in that cylinder that my compression stayed at 143. thats why im thinking head gasket.

either way im really happy with how long my car has lasted and performed for, i just need another 40,000 out of it so i can get a nice block from magnus or roadrace. if i can get my beater car to work ill get the head ported too

40,000 miles = about 1.5 years if your curious. college brokeness

 

[gritsak]

Originally posted by sidoze
andy:

thanks a bunch,

i guess my english just sucks, i meant that when i did the leak down test in that cylinder that my compression stayed at 143. thats why im thinking head gasket.

either way im really happy with how long my car has lasted and performed for, i just need another 40,000 out of it so i can get a nice block from magnus or roadrace. if i can get my beater car to work ill get the head ported too

40,000 miles = about 1.5 years if your curious. college brokeness

when you say leak down do you mean the oil in the cylinder trick? im assuming you do, what i would do is get an actual leak down test performed if you can...doing this can pinpoint where the air is leaking from so you know whats up with your car.

are you having any symptoms of a bad HG? i.e. loss of coolent, overflow bottle filling up, oil/coolent mix, ect.?

 

[TRBOTSI]

I wouldn't worry about. Drive it on...

 

[sidoze]

i noticed oil in my coolant thats why i checked it.

i just need to calm down and start work on my 6 bolt and take it easy. not like the track i go to is going to be open in the next 5-6 months anyway.

 

[13secGST]

Hey...sup.

I highly doubt there is something wrong with your head gasket. what it is, cyl. 2...the cyl. with lower compression is 90% of the time, the first cylinder to go bad in DSMs. nothing surprising to me...I also did a compression test on my car, a while back...and got similar numbers, with cyl. 2 being the lowest. Then I did a leak down test (you set the cylinder at TDC and fill the cylinder with compressed air, then it measures how much air "leaks" out. When I did that I found I had less than 10% leakage in all four cylinders...which is EXCELLENT. 20% is ok.

My guess to what your problem is, either a slightly more worn ring...possible...or in my opinion, a little more likely would be that at least one of the exhaust valves in that cylinder is a little more worn and probably isn't seating perfectly, or could have a minute crack. But if it was a HG, you would be lucky to have 80psi in that cyl.

And I thought normal compression in 2gs was around 170-180...but I'm not sure either...as long as they are all close, your good...but leak down tests are much more acurate and better to figure out how good an engine is...they are also a lot harder to do.

 

[KRAZYKOREAN]

the compression for a brand new block is 185... for that many miles and such 163 isnt that bad but the 143 hmmm you should do a leak down like everyones else says..

 

[Mike 99GSX]

Stock 2g compression is 178PSI if we want to get really technical

 

[Airpoppoff]

:cough: 6 bolt :cough:

 

[sidoze]

*high fives poppoff* yea dude i'll start that damned 6 bolt. but thats only because i want to run a "big boy" turbo like the rest of ya'll.

13sec: yea people have been saying cylinder 2 is a bastard so that makes me feel good about it. im still going to make it to santa barbara this coming weekend though as long as you guys still wanna meet, 100 miles shouldnt hurt anything.

after talking to 4whlboost then poppoff last night im gonna see how there 2g piston/1g rod setups turn out and probably do my own in the spring.

 

[PSI2HI]

I wouldn't worry about it to much either. As long as its running good i'd just leave it alone.
If you were to dig into it i'd suspect that you have a few leaky exhaust valves. Thats seems to almost always be the case in lower compression. Although it is not always the fix. I have had DSM's w/ as many as 185k miles and the cylinders were still damn near perfect just needed a valve job. As long as you haven't made any drastic mistakes in running the car to hard i'd go for valves if anything. Just my $.02.

Nick

 

[Airpoppoff]

Originally posted by sidoze

after talking to 4whlboost then poppoff last night im gonna see how there 2g piston/1g rod setups turn out and probably do my own in the spring.

good thinkin captian