New Motor Shot???

[Cablefed]

Last night I did a compression check on my motor. Well the numbers did not come out to good:

Cyl #1 130
Cyl #2 100
Cyl #3 140
Cyl #4 140

I added some oil in on 1 & 2 then performed the check again and gained about 15 more on top of each number for #1 and #2. That said I assume my rings are shot on #1 & #2. The motor is newly rebuilt with about 5000 miles on the motor. I had put in wiseco pistons with Eagle rods and had the block bored out .20 over.

My question is can I pull the head and remove the oil pan and get the pistons out and re-ring the pistons again? I also assume I need to rehone the cyl. walls? Is there anything else I need to do here? I can do the actual work I just don't want to run into another case of bad rings. Any input would be appreciated. Cheers.

 

[Cablefed]

So I'm reading a thread on here with a guy that has a similar problem but has more compression than I do. I too have a metal head gasket as well as the bored out block so I would assume my compression readings of 140 to be OK since compression has been lowered with my new components. I am going to try a few things that are recommended in his post by some of the engine guru's on this board.

The car seems to run fine with some smoke at WOT, but very little. The car does idle a bit rough, but I thought that was because of the cams 264 HKS Intake, 272 Exhuast. I just think that 100 on piston #2 does not seem right. I just figured since we added oil to #2 and saw an increase in my reading that the piston rings are worn or did not seat right. Before I go pouring any comet in my motor I will check the timing, valve seals, and other obvious items before I go pulling the pistons.

Anything else I might need to check while I'm in there? I just don't see how a loose or bad valve seal would net me a loss of 30 on my compression checks, or could I be wrong? I put new valve seals on the head prior to putting the head back on the car as well as seat the valves. I'm new to troubleshooting motor problems but am very willing to learn and open to any educated suggestions.

 

[IllEagl]

you can re-hone the cylinders from the oil pan...

 

[ajinvista]

Yes you can re-ring and hone the cylinders(I did it from the top) w/o pulling the motor or the crank. Trick? to getting the oil pan off is to loosen the half shaft bracket bolted to the car, I had to slap myself for that one duh.
I had to do all 4 cylinders becuase the guy who did the motor gave me the wrong set of rings(standard bore) I didn't gape them in the cylinders before I put the pistons in and payed for it, total redo. You can make your own ring squaring tool. I just cut down a roll of 3M masking tape to 85.5mm for mine.
I broke it in per MotoMans instructions and it worked perfect. Until........
I F'ed it up. Drove it for a few days maybe 100 miles, not a bit of smoke kept the boost to 10 lbs. ran great, decided to race an EVO and a 911 on the Interstate. I think I lost a ring maybe an oil ring, anyway I will be doing this again at least to one cyl. I replaced the valve stem seals on the one cylinder, no good. Mine smoked from idle all the way up and one plug was still covered in oil.
Check the plug wear for different signs of whats going on in there.
You can check to see if a seal popped up a little, some one else here had that happen I think I read. But the compression #'s leads me to believe it's the rings.
The whole deal is a pain in the ass but I did it alone with a minor amount of tools and time.
Good Luck
Can I ask a question, I pulled a plug from a good cylinder after running it and smoke came pouring out the plug hole like a train stack only blueish white. WTF?

 

[InvaderGSX]

Are the pistons 9:1? Is the compression check done when the motor is warm and really cold? It makes a little difference. Basically your rings are definitely bad. No way should the compression be that low. On my 8.5:1 JE forged pistons I had 180 in each cylinder and I had a 4 layer metal head gasket. Another thing you would notice with bad rings is your oil is getting burned. On a new motor you shouldn't burn any oil after 3000 miles. Question is why the rings went bad. Did you use regular oil when breaking in the motor? I would use regular cheap oil for at least 3000 miles before switching to synthetic. I usually run 10w30 valvoline and after 300 miles I change the oil again and then change it again after 2000 miles and so on. Then after 3000 miles I go to synthetic. Using synthetic right away does not allow the rings to seat.

 

[Defiant]

you can re-hone the cylinders from the oil pan...

That may be the dumbest idea I've read this week. You can't get the pistons out with the head on, so why bother doing it the almost-impossible way?

 

[Big Woo]

Basicily if you are getting low compression numbers it is comming from one or a combonation of the following places.

1: Head gasket / head bolt / stud problem
2: Intake and or exhaust valves
3: Pistons and or piston rings
4: cracked cylinder head and or engine block
5: no spark plug (don't laugh I have seem it before)

Valve seals can't really cause a cranking cylinder pressure loss, since for them to have any effect on cranking cylinder pressure, there must first be a leaking intake or exhaust valve, otherwise there would be no cranking pressure getting to the seal in the first place.

100 psi is defiantly below the book specified low service limit, so you defiantly have a problem there. A leak down test may help you determine where the leak is comming from. You can do a simple test without buying a leak down tester. Basicily it would work like this. However you will need a few things, or at least access to them.
1: air compressor
2: adjustable air pressure regulator
3: pressure Gage
4: air lines and fittings
5: some basic hand tools
6: a good ear.

REGULATE YOUR AIR PRESSURE TO 5 to 10 PSI !!!
THEN REGULATE YOUR AIR PRESSURE TO 5 TO 10 PSI !!!

Remove the spark plugs, and rotate the engine to TDC (top dead center) of the compression stroke, for the cylinder to be tested in this case cylinder number 2. Basicily you want the piston at the top, and both the intake and exhaust valves closed. Then you will need a connector that will screw into the spark plug hole and adapt or connect to your REGULATED LOW PRESSURE air line. You can make one from an old spark plug, a pipe nipple, and the correct air connector for the air hose you are using. Or you can use the screw in portion of your compression tester, and again the correct connector, if you have this type of compression tester. NOTE if you are using the compression tester piece method make sure to remove the shrader valve from it first. MAKE SURE YOUR PRESSURE IS REGULATED TO 5 to 10 PSI and connect to the engine. If you can hear or feel air leaking back through the intake, then you have a leaking intake valve or valves. If you can hear or feel air leaking out of the exhaust, then you have leaking exhaust valves. If you hear or feel air leaking out of the crank case, and or out of the breather fitting in the valve cover, then you have a piston or ring problem.

A few notes here.

The leak down testers you buy, have Gage's that allow you to measure the persentage of leakage, in this case you know you have a leak, and you just want to know where it is comming from, so presentage of loss is not really a factor here.

For safety make certain that you have a adjustable air pressure regulator in order to reduce the pressure used for testing. I have seen people connect to line pressure, and break things, fingers, and move cars by pressurizing a cylinder with 150 psi.

If you don't get the cylinder right at TDC, then when you pressurize it, it will push the piston down the cylinder. Find a good safe way to maintain engine position while testing. Such as manual trans in gear, parking brake on, wheels chocked, and LOW PRESSURE.

This seem fairly long winded, but it is a simple test that will verify where the leak is comming from, that way you will know what has to be done.

If you do end up pulling the motor down, check for broken rings, verify ring end gaps, piston ring land condition, cylinder wall condition.

Also of note many people tend to use standard bore pistons, and re-hone the cylinders, although there is no basic problem with this as long as the correct tolerances and surface finishes are maintained, there is one thing that many tend to overlook. A block that is standard bore for X number of miles has a ridge near the top of the cylinder, where the top compression ring stops and changes direction. On the stock piston from the factory that ring is X distance from the top of the piston, then people install a set of aftermarket forged pistons, and NOT all of these pistons have the top compression ring located the same distance down from the top of the piston. If the pistons you use move the top ring closer top the top of the engine block deck surface, and there is a ridge present there, you can have a dramatic and abrupt change in cylinder diameter, and may break the top piston ring. Especially if you set the ring end gap at a point below the ridge.

 

[Cablefed]

I ran the test cold and hot and still got the same numbers. Bigwoo, thanks for your input, I plan on trying your advice on doing a leak down test as you described. If I do have to pull the pistons I will pull the head and pan and remove the pistons from the top of the motor. I am running 9:1 compresssion with the block bored out .020 over stock.

Now my next question is once I run the test and lets say it is the pistons can I buy just the ring set for my wisco's and if so can any wisco dealer get them?

I will post my results to this thread once I perform the test this weekend. Thanks for all your help guys, its much appreciated.