HELP! super low compression test

[WILOWNU]

did a warm compression test on my 6bolt block and got the following results 151,145,135,148. the totally shitty thing is that the motor is BUILT... and only has about 10k on it. the car has overheated a few times due to when I got it the temp sensor wasnt even hooked up. car used to go through about a pint of coolant a week, but now it goes through about a gallon every few days.... any ideas? I am thinking warped head/head gasket.... any other ideas? thanks guys.

 

[peypey's ride]

I would maybe do a cylinder leak test to see if you can pinpoint any leakage. Have the head checked for warpage too, and get a new head gasket. If the head is warped then have it decked. Once you put it all back together, run the car for a bit then let it cool off and do another compression test.

 

[fwdmaster]

I would maybe do a cylinder leak test to see if you can pinpoint any leakage. Have the head checked for warpage too, and get a new head gasket. If the head is warped then have it decked. Once you put it all back together, run the car for a bit then let it cool off and do another compression test.

peypey's ride, has a very good point, maybe overheating a couple times caused you you to blow your head gasket causing you to have low compression

 

[WILOWNU]

but would the hg have to be blown on all 4 cyl's for it to be low across the whole engine? would it be better to have it decked or to find another 1g head that is in good shape? im just baffled because it has arp studs and a cometic hg in it. also does anyone have an Idea as to how much I am looking at if I have a shop do this for me?

also....could I maybe check and see if my head studs are loose? and if they are tighten them to spec and check my compression again? what are the specs for head studs on a 1g?

 

[kahl23]

1st off, cometics are apparently not that great.

Beyond The Dyno All Head Gaskets are Not Created Equal

However, that test was on Evo gaskets and done by Cosworth, so take it with a grain of salt.

Second, what compression/manufacturer are your pistons? What kind of break in did you use? I've heard of improper break in leading to troubles with the rings mating to the cylinder wall, but then again after 10k it should be broken in no matter what.

 

[WILOWNU]

mahle 8.5:1, not sure about the ring brand. the car runs GREAT it just loses water. I dont see steam out the exhaust, the plugs look good, no water puddles....im just like WTF.

 

[peypey's ride]

but would the hg have to be blown on all 4 cyl's for it to be low across the whole engine? would it be better to have it decked or to find another 1g head that is in good shape? im just baffled because it has arp studs and a cometic hg in it. also does anyone have an Idea as to how much I am looking at if I have a shop do this for me?

also....could I maybe check and see if my head studs are loose? and if they are tighten them to spec and check my compression again? what are the specs for head studs on a 1g?

To answer your question, NO. With you overheating your engine a couple of times its very possible that the head is very slightly warped. You can check the head yourself with a 2ft long straightedge and a feelergauge. The Hanes Manual gives specs for head warpage. Also, fix your overheating issue! The other guy is right when he stated that all headgaskets are not created equal. The OEM Evo3 MLS headgasket is very well proven. I have had Cosmetic headgaskets leak from around waterjackets before. The ARP studs should be replaced if you have more then 2 torques on them. Just like oem studs they do stretch too.

 

[1gDSM4g63]

Having a rebuilt engine doesn't mean you're going to have a higher compression. Compression in the 130-170 range is fine with all cylinders consisted. But I may do a leak down test on the 135. It is over 10 psi off all the others so they maybe a chance of a blown head gasket or your stud aren't torque enough since you're losing coolant. Is there a sweet smell along with white come out of your exhaust?

 

[WILOWNU]

Also, fix your overheating issue!

I havent over heated since I fixed the coolant sensor right when I bought the car, the only thing now is that I am loosing coolant and have to keep adding it or I will overheat.


Also 1gDSM4g63 I dont smoke at all out the exhaust other than the nice black soot from unburned fuel when I crank on it, but I do smell the sweet nasty anti-freeze when I lay into it a bit and then let off of the throttle.....