losing compression....

lppro

lppro

LP Performance & off road
Apr 21, 2007
895
0
0
35
Sugar Hill, Georgia, United States
so i did another compression test for the heck of it...

heres what my last 2 test results were

test # 1

1=180
2=178
3=181
4=180
5=179
6=180


test #2

1=170
2=169
3=179
4=180
5=179
6=180



and the last one i just did like 5 min ago..

test #3

1= 160
2= 155
3= 170
4= 175
5= 170
6= 170

so what do you guys think?

the motor is liss than 2 thousand miles old, rebuilt head with 3 angle valve job, decked, 1.4mm MHG decked block with .40 over JE pistons and eagle rods...

I'm thinking either there is a hair line crack in the HG or the head... i guess there is only one way to find out... time to pull the head... oh joy...
 
I

IJ.

Grumpy Old Man
Mar 30, 2005
38,728
0
0
62
I come from a land down under
It pulls the cylinder wall making a spot about the size of a 1/4 that the rings can't touch losing compression and causing blowby (take the oil cap off and hold your hand on it idling to feel if there's pressure)
 
zachm611

zachm611

Beauty In Disguise
Apr 15, 2006
543
0
16
38
new mexico
its not the 7ms fault... but then again if its already 40 over then it might be the last straw... good luck with whatever you decide to do... and im glad i saw this thread so i can make sure i torque it down to 36 ft/lbs and not more.
 
buldozr

buldozr

New Member
Jan 9, 2007
362
0
0
North Texas
lppro said:
i believe so. :still looking for a 1j:.....
Click to expand...
Dont get too crazy, I just tore down a 3000gt motor cause the owner of the car had someone do a COLD compression test on it(a BIG no no, gotta let those rings/pistons get warm so they can seat) with erratic results, come to find out, it most likely had a cam timing issue(dohc v6's are notorious, the timing belt alone is probably 13 ft long if it was cut so lots of room for error)... Anywho, what im trying to say is dont get too crazy, I just tore down a perfectly good block due to a bad diag...:3d_frown: get a buddy with experience to do a second opinion, it may save you from making an expensive mistake. Just my .02 cents.
 
buldozr

buldozr

New Member
Jan 9, 2007
362
0
0
North Texas
here is some tips, make sure you have a hot battery(this will keep everything equal if the motor is spinning the same speed all the time), if you think you have a ring problem, shoot some oil down the cylinder and see if the compression number comes back up, if it comes up, 95% its a ring issue, if it doesnt come up, most likely a valve timing/warped valve issue or possible head gasket. MAKE SURE THE MOTOR IS WARM AND INTAKE PIPE OFF BEFORE THE THROTTLE BODY with the throttle wide open. Good luck with it.
 
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