here is my setup:

1991 spec b16a
98 gsr cams
nsr-tech ram horn mani, 3" dp
8lbs on a to4b (1.14, .60)
p28 tuned on uberdata
walbro 255lph.
approximate 288whp, traps 114 in a 94 ex.

heres the story. was out railing on it, like I usually do, and held it open in fifth up a decent sized hill, after I pulled off the freeway it sounded kinda like a Subaru and lower rpms under a light load, drove fine, still had good power.

so I took the car down to pac west to do a compression test and it read out 180 185 125 180... the owner said I most likely fried a piston...(not quite sure what all frying a piston includes) also Id like to note that the car didn't smoke and had no other weird sounds besides the light miss. so I took the car back to my house and pulled the head off and didn't see anything obviously wrong with it... I took the head to a local machine shop to get a vacuum test done and everything checked out ok.

the guy at the machine shop told me to do a leak down test with oil, pour it in cyl# 2 and 3 and see if number 3 leaks the oil down. so I did, and they are both at the same level... (I did this yesterday afternoon)


so what I would like to know, is if any one has any ideas or any test I can perform to figure out what is wrong here??? I would like to throw a gsr bottom end in it if it is the pistons, but if it has something to do with the head I don't wanna buy a new bottom end and have to pull it apart.

also this is a dumb question, but can you loose compression in one cylinder because of a head gasket?

any and all help will be much appreciated thank you.

 

crushed ring land?

 

I guess it might be time to pull the pistons out and do something after market in it

usually when you break ring lands it smoke pretty bad?


Modified by K7-1Ktrevor at 11:29 AM 11/16/2008

 

leakdown test, or pull the head.

prob ringland.

 

If the valves aren't leaking and the headgasket is good, then the only thing that can cause a loss in compression are the rings.

Usually, but not always.

 

head is off, nothing is obvious....


can you loose compression on 1 cylinder by just the head gasket????

again. leak down test with oil in cylinder showed no oil draining down.

head was vacuum tested and showed that all valves were seating properly.

 

Just go ahead and pull the piston out and check the rings. If it dont have compression and the head is fine then why not check the rings. Just because oil sits in the cyl walls dont mean the compression ring is ok.

How does the sleeve look? any score marks or scratches

 

MELTED PISTON YOU ARE RUNING LEAN , WHAT WAS YOUR A/R WHEN YOU TUNE IT ?

 

tuned at 11.8 @ wot.


sleeves look good, no scoring marks or anything obvious.... I bet your right about the compression ring.

I think I might just be going the B20 vtec route now.

 

It is possible for a bad headgasket to only effect one cylinder, but i really don't think that is the case here.

A leakdown test is not pouring oil into the combustion chamber and watching to see if it leaks out somewhere. In order to do a proper leakdown test you first need a cylinder leakage tester, the motor needs to be assembled, and then you set the cylinder to TDC and pressurize the cylinder with the leakage tester and it will tell you the % of air leaking out of the combustion chamber. This test is a lot more accurate because it can tell you where its leaking. If you hear air coming out of the exhaust port then its the exhaust valves. If you hear air coming out of the intake ports, then its the intake valves, if you can hear air coming out of the crankcase through the oil cap, its the rings. You get the point.


Basically, since the machine shop ruled out the valves its gonna be the rings.

 

yer the man single cammer.

the guys at the shop told me to do that after I took the head to them when it was disassembled. :/ o well live and learn, this is the first real motor Iv torn apart so Its been a completely new experience for me. I'm still very indecisive on what my plans are for the motor; new forged rods and pistons, or stock b20 or gsr bottom end, but I don't want to run into the same problem again.

I appreciate every ones help for me since Im a rookie. thanks guys.

 

Go forged mane, why not? You'd be able to get more power and have a more reliable bottom end. B20 sleeves are thin and aren't recommended to push hard.

 

Since your motor is apart, use a true bar and a feeler guage to see if your head or block has a low spot near that cylinder. Also, pull out the piston and inspect the ring lands. All you should have to do, since the head is off, just drop the oil pan, rotate the crank so you have easy access to the rod bolts. Just loosen them and pull off the cap, then before you remove the piston from the cylinder, put a sleeve or wrap some tape around the threads of the rod bolt studs to protect them from making contact with the crankshaft, very important to do that!! Also before your remove the piston, make sure you dont have an excessive amount of ring ridge, if you do and you try to pop the piston out, it will destroy your rings, if they are messed up already. If you have ring ridge, your gonna have to remove it before you pull the piston out.

Its too bad you couldnt have done the leakdown test, would have been able to pinpoint the area where you were losing compression. Basically how it works, like said before with that cylinder set to TDC you put pressure into the cylinder through the spark plus hole and a guage will tell you the percentage your losing. If your in the red for percentage lost, next you would listen for air coming through 1 of 4 areas. Out the radiator cap (usually blown head gasket or warped head/block), through the oil filler cap (usually rings), through the intake (intake valve issue), or through the exhaust (exhaust valve issue).

 

broken ringlands for sure...

typically on a b-series ringlands go even before the headgasket lol