[RyanGT]

So in cylinder #5 im losing massive amounts of compression. I took it to the dealership (originally to get computer reflashed) and had a diagnostic done and said low power point on #5. I got a new compression gauge, tested #5 and it goes up to about 140-150 but as soon as i stop cranking motor it drops to 40. Think that is the head gasket causing all my troubles? Tested #6 and 7 and they are fine, read a solid 155 and hold compression. I looked inside #5 and its completely fouled up with oil where you cant even see metal. Other cylinders have a thin oil foul, but you can see the metal and shiny spots at least.

If thats what it is whats involved? Does the motor need to be dropped? or can it stay in (its driver side) and just go through the valve covers? Or will the whole intake need to be taken off (kb supercharger). Ill probably end up taking it in if it is anything like dropping the motor or digging too far, not enough time or tools on my hands. Guess on cost?

[mpboy]

no you can change the head gasket in the car... its alot harder, but you dont have to pull the motor, the S/C will have to come off, the timing chain cover, some of the timing componets, valve cover, make sure u mark all the wire with #'s... like put a piece of tape with the #1 on the male and female plugs of every connection, and take pics, and make sure you know where all the bolts go, chiltons or a haynes manuel will give you strp by strp

[RyanGT]

Think thats whats wrong? If timing cover has to come off ill get a new one. The idler is scary. It tweaks like the spring is gone. Had it do that before and it ripped itself out of the cover!

[mpboy]

you will not need a new timing chain cover, you can get a new idler pully, and it could be the rings on that piston are crap.. if your not confedent in cracking a motor open i would take it to a shop, which will cost you im not going to sugar coat it.. when i take my car to ashop i demand to see all the parts they replaced, because some..not all.. but some places will rip you off

[RyanGT]

Motor is only about 5k old. So maybe the rings are bad or was a bad install... This is a fun thing to spend a tax return on...

[mpboy]

Originally Posted by RyanGT Motor is only about 5k old. So maybe the rings are bad or was a bad install... This is a fun thing to spend a tax return on...

was it a rebuild.. was it brokin in properly.. if you hone a cylinder, and drive the shit out of it to hard with new rings.. they will not have proper time to set and they will take a shit and not sit right against the cylinder wall and you will loose compression.... did you break the motor in right?? if not i would tear the motor apart and see what else is broke?

[Trick Tuners]

Have you tried adding a few drops of motor oil into #5 so see if it holds compression better? If it does its probably the rings and not the HG. It would suck to replace a head gasket just to find out that it did not fix the problem and you have to do all the work again. Get one of those testers from an auto shop that looks for hydrocarbons in the coolant. They are cheap and quick and could point to the HG.

[RyanGT]

Brand new forged vt short block. I was very careful and wore it in nice. Did the 3 oil changes before 500 miles and never went WOT till around 750 miles then it was just for a second or two.

[MustangMatt96GT]

Originally Posted by Jgorm Have you tried adding a few drops of motor oil into #5 so see if it holds compression better? If it does its probably the rings and not the HG. It would suck to replace a head gasket just to find out that it did not fix the problem and you have to do all the work again. Get one of those testers from an auto shop that looks for hydrocarbons in the coolant. They are cheap and quick and could point to the HG.

+1

[RyanGT]

Ill try the oil. Just a few drops? Its already so oil fouled im not sure it will help.

[mpboy]

did u do it you self?? the rings have to be gapped diffrent for a supercharger vehical... they will close in around the piston tighter than a stock motor.. i think the stock ring gap is .025 and supercharger is .027 for the ring gap... it could have been to tight and broke the ring land on the piston??

[RyanGT]

I had a shop do the install. No idea what the gap is. They have done some work with supercharged vehicles so i assume it was done right.

[mpboy]

yea try the oil man... it sound like a ring to me

[RyanGT]

um it held compression after i put oil in there... (i also left injector plugged in, didnt last time). It scored a little higher compression than the other cylinders. That point to the rings? And is that good or bad news haha.

[2kGT]

Its bad news! the piston has to come out to fix the ring, and to do that you have to open up the whole engine.

[RyanGT]

Both are bad haha. Now compression is holding in that cylinder... i let it run for about 10 mins to burn off the oil? well its holding compression still... Im so confused.

[mpboy]

ring

[mpboy]

you can also ge to the piston from under the car... but i wouldnt do it.. i would go back to that shop and ask them WTF!!! but u said u waited till about 750 miles on a fresh motor before u floored it... on a S/C car thats prob a little to soon. u really have to make sure that a rebuilt motor is broken in before u floor it.. u might haved shit thaose rings out, and ask the guys at the shop what they gapped the rings to... if the say they gapped it stock then the other rings will prob take a shit to

[RyanGT]

I wasnt tearing on it. Was giving it some throttle while already moving. Not drag racing from light to light hehe. I remember being very careful to 1000 miles got an oil change and then starting playing a bit. Was still mindfull though.

Even though its holding compression now you think its the ring that is bad?

[mpboy]

yes thats what i would go after... a ring will not fix it self... it might hold commp. now but there is a reason it is lossing compresion, and if you tear the ring lands p you will be getting a new piston to.. if your not sure what ur doing take it to the shop, because the clerances in side the mod motors are pretty tight and they have to be right