Went to Sears and bought a 25.00$ compression checker.
Drove home after 40 minutes of driving, yanked all my wires, yanked all my plugs. Put it in one chamber at a time, and turned over the motor using the key with the gas pedal floored.
1 - 160
2 - 170
3 - 169
4 - 170
How am I lookin? #1 kinda bothered me... But I also did this test before i changed my oil and I was about 1-1.5 quarts low and black (3K miles) So I dunno...
Went to Sears and bought a 25.00$ compression checker.
Drove home after 40 minutes of driving, yanked all my wires, yanked all my plugs. Put it in one chamber at a time, and turned over the motor using the key with the gas pedal floored.
1 - 160
2 - 170
3 - 169
4 - 170
How am I lookin? #1 kinda bothered me... But I also did this test before i changed my oil and I was about 1-1.5 quarts low and black (3K miles) So I dunno...
Looks good to me.
As long as there isn't any more than 25% difference between the high and low you're fine. Absolute #s aren't that important as long as it over 110psi or so.
Dave
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how long did you hold the key/floored it, each time you tested? and is there a peak hold featuer on the gauge or somthing???<--------compression testing newb
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how long did you hold the key/floored it, each time you tested? and is there a peak hold featuer on the gauge or somthing???<--------compression testing newb
10 seconds, and yah it holds the peak pressure till u hit the release valve
Numbers look good dude. 175 being norm and 160 being 6% difference should be fine. Now to get a leak down test and you can be sure that everything is working 100%.
This is my dyno list from earlier today. I also got a compression test done before the dyno and had low results. they were106, 105, 105, 116.
So I went to dyno.
1st-249hp/270tq on 16 psi (tuned for 20 psi....was a mistake, cutout closed)
2nd-270hp/308tq on 20 psi (running lean, cutout closed)
3rd-265hp/303 tq on 20 psi (running great, cutout opened)
poured out white smoke at the end of each of the runs.
had a compression test earlier in the day and got 106, 105, 105, 116. (heard normal was around 150-175ish)
first run was so bad because I forgot to open my boost controller so it was just a mess...
some theories on my low compresion / blowin out white smoke are that my turbo is bad, or I have a bad head gasket...so hopefully I'll get that fixed. I'm gonna take off my ported turbo and replace it with my stock turbo and re-dyno. if that dont work, I'm gonna somehow find a way to go new head gasket, and new piston/rings. but im not looking forward to that!
Oil blowing out could be a sign of seals that are bad in the turbo, but would have no effect on compression, or a compression test. The only things that set compression (for trouble shooting perposes) are valve seats/seals, rings, head gasket. One of those is effecting your compression. Bad news is any and all of them can also leak oil into the chamber and make the car smoke. Do a pressure test on a cyilnder dry and note number, but some oil down the spark plug hole and test again. If the second number raises a bunch chances are you have bad rings. If there is no change your left with valves, or head. Hope this helps.
Randy
Oil blowing out could be a sign of seals that are bad in the turbo, but would have no effect on compression, or a compression test. The only things that set compression (for trouble shooting perposes) are valve seats/seals, rings, head gasket. One of those is effecting your compression. Bad news is any and all of them can also leak oil into the chamber and make the car smoke. Do a pressure test on a cyilnder dry and note number, but some oil down the spark plug hole and test again. If the second number raises a bunch chances are you have bad rings. If there is no change your left with valves, or head. Hope this helps.
Randy
how much oil and what kind?? how do i get it out when i'm done?
Oil blowing out could be a sign of seals that are bad in the turbo, but would have no effect on compression, or a compression test. The only things that set compression (for trouble shooting perposes) are valve seats/seals, rings, head gasket. One of those is effecting your compression. Bad news is any and all of them can also leak oil into the chamber and make the car smoke. Do a pressure test on a cyilnder dry and note number, but some oil down the spark plug hole and test again. If the second number raises a bunch chances are you have bad rings. If there is no change your left with valves, or head. Hope this helps.
Randy
how much oil and what kind?? how do i get it out when i'm done?
A small amount. Just imagine if you had a piston setting in front of you you want to cover the surface and get the rings all the way around oiled, without drownding the piston. lol When your done fire your car up and it will burn off, just like all oil will. You can use the same oil you do for your oil changes and then you don't have to worry about contamination if it blows by the rings. If you use very light weight syntetic it might not work as well as it will not seal up the rings like this test is tring to accomplish. Basicaly it is an old trick to use oil to help seal the rings. If it shows better compression then your rings are bad.
Randy
If an engine was blown once by not having oil in the car, and a second time because of over boost, and the compressions read 150-150-120-150 would this be worth the buy even if the car is highly modded? I'm talking like bored out block, new pistons, etc. etc. The car was wet tested and those are what the numbers are showing. Is this ok for me to buy? How much would changing out the piston rings cost???
.30 overbore, remove the balance shafts, balance rotating assy, new pistons (maybe some cosworth pistons) good rings, ARP that bitch from top to bottom, and you're set
I would steer clear man. Cars that have been beat on will always show there strain. Find a less troubled car. Would cost a grip of time and money to replace everything to where i would trust it. But i am conservative when it comes to my money. lol
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Compression Test Results
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