hey guys-- I am wondering why I got 240 in every cylinder on my compression test on a 94 GSR w/ no engine work done-- (that has 160K miles on it)... when I hear about so many other GSRs getting results ranging 195-205. Could my internals be in that great of shape???

The previous owner of my car did not mess w/ engine stuff-- I know that for sure... is 240 abnormally high? I am going to be putting a JRSC on this engine, and I don't want the compression to be higher than stock compression... with good tuning, am I gonna be safe w/ this high of compression??? is there something wrong w/ my engine??? I am very confused about this...

 

how do you do your compression check ?

tell us step by step, on how you prepped it, crank it and etc

stan

 

my friend has done it before plenty of times so I got him to help me...

we unplugged the distributor and took off pulled one spark plug at a time... spun the compression tester in where the spark plug was... made sure it was tight enough-- and then I put the petal to the metal and then I cranked the engine for about 7 or 8 seconds and then took the key out... would put that spark plug back in and move to the next one. my results were 240 on every cylinder

 

are you sure the compression tester was set at zero ?

stan

 

I'd try another tester

 

time for a leak down test
I suspect 110-120%

 

how do you do a leakdown test?

 

I more than likely suspect that the tester is off-- I definately don't think my engine is totally F***ed up because it still pulls fine and doesn't burn oil badly or anything.. no crazy smoke coming out of the exhaust. I'm gonna do the compression test again-- this time using a different compression tester... and then maybe I'll do a leakdown test.... Thanks for the help, guys.

If any of you have any other suggestions, comments, or assumptions in regards to what might be causing my numbers to be high-- drop a post here...

-Zack

 

that is rediculously high

 

why does everyone say its high? Right out of my helms manual it says 270 is normal for GSR. and I think minimum is 140.

I'm scurred cause I did mine and it was only around the 140 range. I think I did the test wrong so I'm gonna do it again.

Also, anyone out there can confirm this, the manual says to take out injector fuse so no fuel squirts in, would this cause the compression to go up or down if I left the fuse in cause now some (I doubt much) fuel is now in the cylinders?

 

No, you shouldn't leave the fuel injectors connected because yes, they will be firing while you crank it and it will boost compression to abnormally high rates.

Unplug the fuel injectors and try again.

 

is 240 abnormally high? i compression tested my friend's GSR engine that he purchased as a complete conversion and we got the same numbers, pretty much.

 

Mine is 226 in all 4, with no fuel. The manual says 240to200 is good fora gsr. 270 to 220 for type R if I remember correctly. That 140 is low and probably burning alot of oil right? My buddies LS is at 140 on 2 cyliders and it burns 1 quart a week.

 

Helms manual says 270psi for gsr is the brand new compression specs, idk why everyone is saying 240 is abnormally high, if u ask me 240 is good, or a little low, but as long as all the cylinders have basically the same numbers u're good, unless all of them are hella low like 100 psi or some ****, anyways trust the helms manual and good luck

 

i don't think that's abnormally high. on my built gsr motor i get 230-225-230-225. the compression is somewhere between 9.5-10.0, i've tested mine with a number of different gauges and they were always in that range.

when i test... i take out all the plugs, screw in the gauge, open the throttle and crank the motor for 6-7 secs with my electronics turned off. w/ the motor hot or cold doesn't seem to make a difference.

most motors i see built by other people usually have anywhere from 175-195 psi. to me that seems on the low side.

 

Damn, you guys make compression tests too difficult

Why dont you just unplug the ECU fuse (this takes care of the fuel that goes in...so you dont have to unclip injecors)

Unplug every spark plug connector from all 4 spark plugs.

Remove 1 spark plug at a time and put the compression tester in the 1 hole (leave the other 3 spark plugs in. )

Crank the engine over WOT for as long as you want i guess, but 2-4 seconds should be good.