Compression Test Results - Good/Bad ??
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
Compression Test Results - Good/Bad ??
Having some problems with my 418 Iron Block Stroker that is in my 99 VERT. Have signs of coolant leakage under the valve covers and can not seem to troubleshoot an apparant vacuum leak that is causing my short and long term fuel trims to be excessively high.
Decided to perform a compression test across the board to see if my cylinder pressure is where it needs to be. I have no idea where the compression figures should be but here is what I achieved when tested:
2 - 130
4 - 125
6 - 142.5
8 - 142.5
1 - 137.5
3 - 137.5
5 - 142
7 - 137.5
Now I would like to perform a leak down test to check for ring seal. Come someone let me know how to do this.
Any ideas on where you think the water is getting in and why my fuel trims are out of whack is greatly appreciated.
Decided to perform a compression test across the board to see if my cylinder pressure is where it needs to be. I have no idea where the compression figures should be but here is what I achieved when tested:
2 - 130
4 - 125
6 - 142.5
8 - 142.5
1 - 137.5
3 - 137.5
5 - 142
7 - 137.5
Now I would like to perform a leak down test to check for ring seal. Come someone let me know how to do this.
Any ideas on where you think the water is getting in and why my fuel trims are out of whack is greatly appreciated.
Tech Member
Joined: Dec 2005
Posts: 80
Likes: 0
From: Claremont CA
Originally Posted by wheeljo2
Having some problems with my 418 Iron Block Stroker that is in my 99 VERT. Have signs of coolant leakage under the valve covers and can not seem to troubleshoot an apparant vacuum leak that is causing my short and long term fuel trims to be excessively high.
Decided to perform a compression test across the board to see if my cylinder pressure is where it needs to be. I have no idea where the compression figures should be but here is what I achieved when tested:
2 - 130
4 - 125
6 - 142.5
8 - 142.5
1 - 137.5
3 - 137.5
5 - 142
7 - 137.5
Now I would like to perform a leak down test to check for ring seal. Come someone let me know how to do this.
Any ideas on where you think the water is getting in and why my fuel trims are out of whack is greatly appreciated.
Decided to perform a compression test across the board to see if my cylinder pressure is where it needs to be. I have no idea where the compression figures should be but here is what I achieved when tested:
2 - 130
4 - 125
6 - 142.5
8 - 142.5
1 - 137.5
3 - 137.5
5 - 142
7 - 137.5
Now I would like to perform a leak down test to check for ring seal. Come someone let me know how to do this.
Any ideas on where you think the water is getting in and why my fuel trims are out of whack is greatly appreciated.
As far as the water leak... Are you using coolant? Is there water in the oil? If the symptom is a milky residue on the inside of the valve cover roof then this could be caused by an engine that is not reaching operating temperature.
As far as trouble shooting your vacuum leak we need to know what your manifold vacuum is @ idle. If it is 17" + then you probably don't have a leak. If you have an aftermarket air cleaner, dirty MAF or a leak near the MAF then this can cause the FT problems.
Regards,
Scott Brown
Melting Slicks
Joined: May 2000
Posts: 2,498
Likes: 4
From: Brentwood TN
What static compression ratio are you running? If it is 10:1 or higher, I would think the pressure might be more in the 150-155 range. I'm not sure a 13% variation is a good thing. I'd focus on cylinder 2 and 4, specifically the gasket that runs between these two cylinders. Do you have coolant in oil? I have had moisture evidence in rocker covers in the past but if the emulsion in the rocker cover was cafe au lait color I almost always had coolant in the oil pan too. Water/oil emulsions don't lubricate well and your engine is getting ready to start making some REALLY expensive noises if it hasn't already laid the groundwork.
Charlie
Charlie
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
Hello, the compression #'s are roughly within 13% which is OK. If you do not have allot of crankcase pressure then I wouldn't worry too much about the leak-down test. The compression #'s are used for a balance look as the cam profile will affect the cranking compression numbers.
As far as the water leak... Are you using coolant? Is there water in the oil? If the symptom is a milky residue on the inside of the valve cover roof then this could be caused by an engine that is not reaching operating temperature.
As far as trouble shooting your vacuum leak we need to know what your manifold vacuum is @ idle. If it is 17" + then you probably don't have a leak. If you have an aftermarket air cleaner, dirty MAF or a leak near the MAF then this can cause the FT problems.
Car had green coolant mixed with regular water when I got it. Going to flush it out and start over with the pink stuff and distilled water mixed 50/50, thought I would run some coolant sealer through first as I've had good luck in the past sealing up minor coolant leaks which are typical with aluminum heads before the engine reaches operating temperature.
As far as water in the oil, there is no noticeable signs on the tip of the dip stick but the top half of the dip stick is showing light signs of rust. Oil does smell a tinge of fuel due to high trims I guess. Under the valve covers, a white milky substance that looks like white bearing lubricant. I have had to top of the reservoir with a gallon or so every 500 miles or so. Seems to be more moisture than anything that is recurring everytime I start and stop the engine. Engine runs 170 - 185 all the time and I'm sure the thermostat is lower than normal and the fans have been reprogrammed to come on an off sooner than stock.
Vacuum leak and excessive fuel trims are my major concern. I have a Vortex Ram Air Induction made by Breathless Performance Products along with a black Delphi MAF (90mm maybe?). I just had the air assembly apart to clean the filter and to check for leaks but I'll do it again and see if anything rears its ugly head. Also, I'll clean the MAF terminals with carb cleaner in case they are dirty. I'm going to check the manifold pressure next to see what it is showing but I'm running a big cam 244 duration 600 lift so this will likely bring the normal pressure down some.
As far as the water leak... Are you using coolant? Is there water in the oil? If the symptom is a milky residue on the inside of the valve cover roof then this could be caused by an engine that is not reaching operating temperature.
As far as trouble shooting your vacuum leak we need to know what your manifold vacuum is @ idle. If it is 17" + then you probably don't have a leak. If you have an aftermarket air cleaner, dirty MAF or a leak near the MAF then this can cause the FT problems.
Car had green coolant mixed with regular water when I got it. Going to flush it out and start over with the pink stuff and distilled water mixed 50/50, thought I would run some coolant sealer through first as I've had good luck in the past sealing up minor coolant leaks which are typical with aluminum heads before the engine reaches operating temperature.
As far as water in the oil, there is no noticeable signs on the tip of the dip stick but the top half of the dip stick is showing light signs of rust. Oil does smell a tinge of fuel due to high trims I guess. Under the valve covers, a white milky substance that looks like white bearing lubricant. I have had to top of the reservoir with a gallon or so every 500 miles or so. Seems to be more moisture than anything that is recurring everytime I start and stop the engine. Engine runs 170 - 185 all the time and I'm sure the thermostat is lower than normal and the fans have been reprogrammed to come on an off sooner than stock.
Vacuum leak and excessive fuel trims are my major concern. I have a Vortex Ram Air Induction made by Breathless Performance Products along with a black Delphi MAF (90mm maybe?). I just had the air assembly apart to clean the filter and to check for leaks but I'll do it again and see if anything rears its ugly head. Also, I'll clean the MAF terminals with carb cleaner in case they are dirty. I'm going to check the manifold pressure next to see what it is showing but I'm running a big cam 244 duration 600 lift so this will likely bring the normal pressure down some.
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
What static compression ratio are you running? If it is 10:1 or higher, I would think the pressure might be more in the 150-155 range. I'm not sure a 13% variation is a good thing. I'd focus on cylinder 2 and 4, specifically the gasket that runs between these two cylinders. Do you have coolant in oil? I have had moisture evidence in rocker covers in the past but if the emulsion in the rocker cover was cafe au lait color I almost always had coolant in the oil pan too. Water/oil emulsions don't lubricate well and your engine is getting ready to start making some REALLY expensive noises if it hasn't already laid the groundwork.
Not sure about the CR but I would suspect around 11:1 for high performance. I suspect the motor has been abused with nitrous in the past by the looks of the lower numbers on cylinders 2 & 4 which is common for wet systems. Less concerned with ring and coolant seal and more concerned with excessive fuel trims and I do not believe they are correlated but I could be wrong. Trying to decide whether to pull RH cylinder off and inspect the head gasket but a friend of mine thinks they are likely tri-metal and rarely blow out. I was going to try to seal it up first with an coolant sealant before going to all the trouble of pulling the head. I recently replaced the lower base on my FAST intake that was cracked and reattached a manifold vacuum line that was disconnected, also had a baseline tune by PCM4LESS done. No noises in the engine sounds fine and normal.
Not sure about the CR but I would suspect around 11:1 for high performance. I suspect the motor has been abused with nitrous in the past by the looks of the lower numbers on cylinders 2 & 4 which is common for wet systems. Less concerned with ring and coolant seal and more concerned with excessive fuel trims and I do not believe they are correlated but I could be wrong. Trying to decide whether to pull RH cylinder off and inspect the head gasket but a friend of mine thinks they are likely tri-metal and rarely blow out. I was going to try to seal it up first with an coolant sealant before going to all the trouble of pulling the head. I recently replaced the lower base on my FAST intake that was cracked and reattached a manifold vacuum line that was disconnected, also had a baseline tune by PCM4LESS done. No noises in the engine sounds fine and normal.
Drifting
Joined: Oct 2003
Posts: 1,540
Likes: 0
From: bloomfield nj
looks like your problem is on bank 2 and you have a leakage problem between cylinders 2/4.if you are topping off the coolant jug and don't have any external leaks,it's going somewhere[out the tailpipes????].what do the plugs out of 2/4 look like compared to the rest? if they are clean compared to the rest,there is your problem[gasket leak/blown across 2/4].also,iyou may be chasing your tail on the lean condition.if the front o2's are contaminated by the burning coolant they will not sniff right[silicate contamination]
Last edited by dpd; Nov 25, 2006 at 01:56 PM.
Tech Member
Joined: Dec 2005
Posts: 80
Likes: 0
From: Claremont CA
As far as water in the oil, there is no noticeable signs on the tip of the dip stick but the top half of the dip stick is showing light signs of rust. Oil does smell a tinge of fuel due to high trims I guess. Under the valve covers, a white milky substance that looks like white bearing lubricant. I have had to top of the reservoir with a gallon or so every 500 miles or so. Seems to be more moisture than anything that is recurring everytime I start and stop the engine. Engine runs 170 - 185 all the time and I'm sure the thermostat is lower than normal and the fans have been reprogrammed to come on an off sooner than stock.
Regards,
Scott
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
looks like your problem is on bank 2 and you have a leakage problem between cylinders 2/4.if you are topping off the coolant jug and don't have any external leaks,it's going somewhere[out the tailpipes????].what do the plugs out of 2/4 look like compared to the rest? if they are clean compared to the rest,there is your problem[gasket leak/blown across 2/4].also,iyou may be chasing your tail on the lean condition.if the front o2's are contaminated by the burning coolant they will not sniff right[silicate contamination]
Interesting observation but all my plugs look the same with a white to light grey ash look on the L shaped electrodes with carbon on the rims or edges. I replaced the front o2 sensors recently and I have o2 simulators in the front with no cats and rear o2s were eliminated or left unplugged on the rear (could this pose a problem???) If I had a hasket issue between cylinders 2&4 wouldn't the passenger side valve cover have more sludge than the driver and wouldn't some of plugs read differently??
Interesting observation but all my plugs look the same with a white to light grey ash look on the L shaped electrodes with carbon on the rims or edges. I replaced the front o2 sensors recently and I have o2 simulators in the front with no cats and rear o2s were eliminated or left unplugged on the rear (could this pose a problem???) If I had a hasket issue between cylinders 2&4 wouldn't the passenger side valve cover have more sludge than the driver and wouldn't some of plugs read differently??
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Drifting
Joined: Oct 2003
Posts: 1,540
Likes: 0
From: bloomfield nj
Originally Posted by wheeljo2
looks like your problem is on bank 2 and you have a leakage problem between cylinders 2/4.if you are topping off the coolant jug and don't have any external leaks,it's going somewhere[out the tailpipes????].what do the plugs out of 2/4 look like compared to the rest? if they are clean compared to the rest,there is your problem[gasket leak/blown across 2/4].also,iyou may be chasing your tail on the lean condition.if the front o2's are contaminated by the burning coolant they will not sniff right[silicate contamination]
Interesting observation but all my plugs look the same with a white to light grey ash look on the L shaped electrodes with carbon on the rims or edges. I replaced the front o2 sensors recently and I have o2 simulators in the front with no cats and rear o2s were eliminated or left unplugged on the rear (could this pose a problem???) If I had a hasket issue between cylinders 2&4 wouldn't the passenger side valve cover have more sludge than the driver and wouldn't some of plugs read differently??
Interesting observation but all my plugs look the same with a white to light grey ash look on the L shaped electrodes with carbon on the rims or edges. I replaced the front o2 sensors recently and I have o2 simulators in the front with no cats and rear o2s were eliminated or left unplugged on the rear (could this pose a problem???) If I had a hasket issue between cylinders 2&4 wouldn't the passenger side valve cover have more sludge than the driver and wouldn't some of plugs read differently??
o2 simulators in the front?????? not a good idea.simms in the back,yes,but not in the front. from your compression readings i still say you have a issue on the right bank with cylinders 2 & 4.
you are using coolant,that means it's going somewhere[if not on the ground,out the pipes??].you want to look at the center electrode ceramic and compare it to the others.
you also want to get front o2's into the collectors,you can't diagnose diddley squat with simms in the collectors.there is also no way you could possibly get any type of a/f readings with simms[they don't sniff anything!!!!!!].
right now you are just wasting your time looking for lean conditions.
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
I have front o2 in the collectors plugged in. What do o2 simulators look like because I have two black module looking pieces about 2" x "1 in size that have a flashing red tiny round light that seems to be integrated into the front o2 wiring harness somehow.
Do you suggest I pull the head off or try to seal it with some radiator stop leak and conditioner? If it were blown out I would suspect much lover compression numbers?
Do you suggest I pull the head off or try to seal it with some radiator stop leak and conditioner? If it were blown out I would suspect much lover compression numbers?
Drifting
Joined: Oct 2003
Posts: 1,540
Likes: 0
From: bloomfield nj
Originally Posted by wheeljo2
I have front o2 in the collectors plugged in. What do o2 simulators look like because I have two black module looking pieces about 2" x "1 in size that have a flashing red tiny round light that seems to be integrated into the front o2 wiring harness somehow.
Do you suggest I pull the head off or try to seal it with some radiator stop leak and conditioner? If it were blown out I would suspect much lover compression numbers?
Do you suggest I pull the head off or try to seal it with some radiator stop leak and conditioner? If it were blown out I would suspect much lover compression numbers?
you just said you didn't have front o2's. for me to try and help you,you need to tell me the right stuff.YES or NO.do you have o2 sensors in the collectors? yes,the things with the light are the simms.they will plug in up in front along the frame rails.the plugs for the fronts are up there too,but the plugs between the front and rears are different.
did you put the headers in or did someone do it for you???
your highest compression readings are 142,your lowest are 130/125 on 2 cylinders next to each other,IT SOUNDS like that can be where your problem is,but unless you give me the correct info i can't help.honesly i would expect yor motor to have between 150-155 pds of cylinder pressure.
I'M NOT PICKING ON YOU,BUT WITHOUT THE CORRECT INFO I CAN'T HELP
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
Yes I have front O2s and I replaced them new a few weeks ago. However, also up front sandwiched in between the O2 connector and the wiring harness is the flashy red module which I guess is an O2 simulator but not sure, buddy of mine said it could be some type of O2 interceptor. Also, the part # on my MAF sensor is #25168491 black delphi but there is a personal engraving on the bottom (someone placed it there with an ice pick or something and it shows ZV524, the paperwork I received with the car shows an 85 MM GM unit but not sure if it has been recalibrated or not. I'm about to go unhook the flashing red modues up front and put it all back together add the coolant sealant and see if I can break it. Headers are TPIS and they were on the car already but I've had the RH side on off when I replaced the starter (another issue in itself that is now cured).
Last edited by wheeljo2; Nov 25, 2006 at 08:14 PM.
Drifting
Joined: Oct 2003
Posts: 1,540
Likes: 0
From: bloomfield nj
don't unhook the simms!!! STOP!!!!!! first,let's back up to the beginning!!! i still feel your coolant issue has to do with cylinders 2 & 4.
but first!!!!!! look at your maf,if it says granatelli on it that's your lean problem.even it doesn't,it can still be your lean problem.
clear your faults,turn the key off,unplug your maf,start the car[you will have a maf fault],if your lean faults are now gone,you have a bad maf.
redo your compression test,dry.then redo it again,but put a couple of squirts of oil in the cylinder your testing,if the numbers come up,you have ring sealing probles in that hole.
you probably have a head gasket sealing problem on the right side that gets worse when the head expands when it gets hot.
your call,but i would get to the bottom of the problem instead of throwing stuff in it and trying to launch the motor.
up to you-----
but first!!!!!! look at your maf,if it says granatelli on it that's your lean problem.even it doesn't,it can still be your lean problem.
clear your faults,turn the key off,unplug your maf,start the car[you will have a maf fault],if your lean faults are now gone,you have a bad maf.
redo your compression test,dry.then redo it again,but put a couple of squirts of oil in the cylinder your testing,if the numbers come up,you have ring sealing probles in that hole.
you probably have a head gasket sealing problem on the right side that gets worse when the head expands when it gets hot.
your call,but i would get to the bottom of the problem instead of throwing stuff in it and trying to launch the motor.
up to you-----
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
Ok I'm now under my vette again, the front O2s are in tact and hooked up. The rear O2s connectors are up front near the frame rails next to the front O2 connectors but they were unplugged and simms plugged in. I still have the original rear o2 jumper harness that extends out to the rear where the rear o2s used to be. I know this does not help much but it does clarify we I have.
Drifting
Joined: Oct 2003
Posts: 1,540
Likes: 0
From: bloomfield nj
Originally Posted by wheeljo2
Do you all agree that the coolant issue has nothing to do with my lean condition and that they are two separate issues?
possibly,but without the car in front of me,well......
BTW,you never mentioned pressure testing the coolant system.have you done that??????????
if not,i suggest you do it.do it with the plugs out and let it sit overnight. if you do have a leaking gasket,you may be able to see the coolant on top of the piston[s].
if you don't have a pressure tester or don't know how to use one,i will explain it to you.
another way is,if you have access to a emmission analyzer,you can hold the probe over the coolant jug[with the cap off],if you see the unit showing HC/CO,you have combustion gas getting into the coolant system
another way is with a block tester,you stick it in the top of the coolant reservoir and run the car,if the fluid in the tester goes from blue to yellow,you have combustion gas in the coolant system.
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
compression readings
excellent points i'll try that stuff too. by the way, I'm going to retest my compression but an charging my battery first as I know it needed to be charged, would this have impacted my test in that the starter was turning less rapidly?
Drifting
Joined: Oct 2003
Posts: 1,540
Likes: 0
From: bloomfield nj
Originally Posted by wheeljo2
excellent points i'll try that stuff too. by the way, I'm going to retest my compression but an charging my battery first as I know it needed to be charged, would this have impacted my test in that the starter was turning less rapidly?
yes