cyl leakdown results
11-14-2010, 03:37 PM
#1
cyl leakdown results Hey guys I just finished 6 of.the 8 cyl for the leak down test since the rest of.the pass side is a pita..well want to know what you guys think so far before I try the rest for nothing..
Incase your curious why I'm doing this is I bought a modded car was in the middle of a cam swap and noticed lifter lobe damage. Chipped and worn lobe so before I took off heads wanted to do a leakdown since previous owner was squeezing before well I'm a lil worried here and here's the results so far
I have my compressor set to about 130psi and the tester is set to 90psi..on all the cyl I did I hear the hissing from breather cap and from crank area..
#1..85 psi
#3..68 psi
#4..71 psi
#5..79 psi
#6..73 psi
#7..73 psi
Am I in trouble here? From what I understand its leaking past rings and its a cold engine been sitting for 2 weeks and all cyl were put at tdc before test. Thanks
Incase your curious why I'm doing this is I bought a modded car was in the middle of a cam swap and noticed lifter lobe damage. Chipped and worn lobe so before I took off heads wanted to do a leakdown since previous owner was squeezing before well I'm a lil worried here and here's the results so far
I have my compressor set to about 130psi and the tester is set to 90psi..on all the cyl I did I hear the hissing from breather cap and from crank area..
#1..85 psi
#3..68 psi
#4..71 psi
#5..79 psi
#6..73 psi
#7..73 psi
Am I in trouble here? From what I understand its leaking past rings and its a cold engine been sitting for 2 weeks and all cyl were put at tdc before test. Thanks
Last edited by 408Maro; 11-14-2010 at 03:52 PM.
11-14-2010, 03:49 PM
#2
Set the tester to 100 and turn the engine over a few times before retesting. Then you can easily review your results as follows. If you use 100 psi then anything less then that MINUS the reading is your leakage.
Example 100 psi inserted into cylinder number 1 gives a reading of 85 psi= 100 minus 85=15 15% leakage is the number for that cylinder.
For good readings the engine should be warm and run for a few mins to circulate oil and lube the rings etc. Carbon pasted on the ring lands can drasticly lower the readings.
I would test at TDC and BDC, anything over 10% is alot.
Example 100 psi inserted into cylinder number 1 gives a reading of 85 psi= 100 minus 85=15 15% leakage is the number for that cylinder.
For good readings the engine should be warm and run for a few mins to circulate oil and lube the rings etc. Carbon pasted on the ring lands can drasticly lower the readings.
I would test at TDC and BDC, anything over 10% is alot.
11-14-2010, 04:05 PM
#4
Go by the instructions the tool supplied. It should guide you through the entire procedure including how to figure leakage percentage. 8-12 % for a street engine are good results. The important part of the test is where the air leaks to. If it leaks past the valves you have trouble, It will ALWAYS leak some past the rings.
Don't bother with the BDC testing unless you are really getting fussy.
Don't bother with the BDC testing unless you are really getting fussy.
11-14-2010, 04:12 PM
#6
Thats fine, I'll bet if you cleaned the piston rings it would be lower. Might want to use a top engine cleaner then change the oil to free up the rings good. I use Rislone at every oil change to keep the rings free.
Last edited by O2Form; 11-14-2010 at 04:18 PM.
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11-14-2010, 07:04 PM
#8
Well if you had ALOT of blowby with the oil dip stick popping out leakage you would know when too much is too much. Anything over 20% is starting to push it but hey street cars are not race cars where every possible hp is needed.
Detonation can play hell on the rings and ring lands so be sure your tune is good if you are going to spray.
Most important is how clean the rings and piston ring lands are, If they are dirty with carbon its going to cost you hp. I'd run a good synthetic oil and change it every 6k, that will go a long way in keeping them clean.
Leakage=less HP thats what its all about. As long as its not huffing oil out the pcv hose or blowing the oil dipstick out you are fine.
Detonation can play hell on the rings and ring lands so be sure your tune is good if you are going to spray.
Most important is how clean the rings and piston ring lands are, If they are dirty with carbon its going to cost you hp. I'd run a good synthetic oil and change it every 6k, that will go a long way in keeping them clean.
Leakage=less HP thats what its all about. As long as its not huffing oil out the pcv hose or blowing the oil dipstick out you are fine.
Last edited by O2Form; 11-14-2010 at 07:10 PM.
11-15-2010, 11:30 PM
#12
Well if you had ALOT of blowby with the oil dip stick popping out leakage you would know when too much is too much. Anything over 20% is starting to push it but hey street cars are not race cars where every possible hp is needed.
Detonation can play hell on the rings and ring lands so be sure your tune is good if you are going to spray.
Most important is how clean the rings and piston ring lands are, If they are dirty with carbon its going to cost you hp. I'd run a good synthetic oil and change it every 6k, that will go a long way in keeping them clean.
Leakage=less HP thats what its all about. As long as its not huffing oil out the pcv hose or blowing the oil dipstick out you are fine.
Detonation can play hell on the rings and ring lands so be sure your tune is good if you are going to spray.
Most important is how clean the rings and piston ring lands are, If they are dirty with carbon its going to cost you hp. I'd run a good synthetic oil and change it every 6k, that will go a long way in keeping them clean.
Leakage=less HP thats what its all about. As long as its not huffing oil out the pcv hose or blowing the oil dipstick out you are fine.
try a good petroleum based oil...NON-SYNTHETIC!!!
even better change to something with a high ZDDP content like Valvoline VR1 or Joe Gibbs Oil.
and change it every 3000 miles....
as far as a leakdown.. its very important to know about how your motor was built..
tight tolerances will leakdown a lot less than a loose turbo motor...
if it was built higher compression with tightly fit rings, leakdown will be considerably less than if you had built a lower compression loose rings forced induction motor.
in my opinion, the results look fine...
and you cant just take a picture of the cylinder walls and tell if theres anything right or wrong with them unless its severely FUBAR.
with cam lobe damage I would be more concerned with the lifters themselves more than anything else.
I would want to replace all of the lifters and all of my valvesprings since it most likely had some pretty hard abuse if it has a destroyed lobe on the cam.
you will also want to do an oil based flush out of you can to get rid of any shavings that may have come off in the engine...
I would get the thing out of the car, on an engine stand and you can do some better inspection and debris removal that way
cut open the oil filter and see whats inside.. its a good visual to see if theres damage before you go pulling every thing apart.
11-15-2010, 11:48 PM
#15
wow.. you've really had the wool pulled over your eyes if you believe the best way to keep an engine clean is to use a synthetic and change it only every 6000 miles...
I dont know you, so I cant make any assumptions about who you are in real life or what your car history has been...
but I can tell you I've raced some big horsepower engines and have built many of my own racecars...big block, small block, FI, NA , and nitrous systems with bigger HP shots than most people have have on motor alone.
I feel fairly qualified by my vast engine experience and having torn apart many of them, the cleanest ones (which also ran the longest)were run with petroleum based oil with a High ZDDP content...not synthetic...
if you dont know what ZDDP is or what it does.. I highly suggest Google searches to find your answers.
I dont know you, so I cant make any assumptions about who you are in real life or what your car history has been...
but I can tell you I've raced some big horsepower engines and have built many of my own racecars...big block, small block, FI, NA , and nitrous systems with bigger HP shots than most people have have on motor alone.
I feel fairly qualified by my vast engine experience and having torn apart many of them, the cleanest ones (which also ran the longest)were run with petroleum based oil with a High ZDDP content...not synthetic...
if you dont know what ZDDP is or what it does.. I highly suggest Google searches to find your answers.
11-15-2010, 11:51 PM
#16
I'm not going to debate... I'm just going to leave it as what I mentioned above...
the original poster can do his own research on the web
but he's going to find out that pro racers and engine builders suggest exactly what I mentioned above.
and I've done high 6's at 200mph in the 1'4 mile
the original poster can do his own research on the web
but he's going to find out that pro racers and engine builders suggest exactly what I mentioned above.
and I've done high 6's at 200mph in the 1'4 mile
11-15-2010, 11:57 PM
#17
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haha Im sorry for instigating. I swear a few weeks ago I read a thread a couple pages long on this subject. I definitely agree soundengineer just thought it was funny. the phrase that came to mind was, "here we go again"
11-15-2010, 11:58 PM
#18
I've seen leakdown results being a bit over the place when the rings aren't sitting against the proper side of the piston groove. Once pressurized, a slight tap turning the crank in its proper direction can make the ring sealing way better.
A little oil in the cylinder can help determine if a leak is valve seat related if its difficult to hear where the air is going. Since you're planning on pulling the heads anyway, check the valve seats for sealing. If its got some miles to her, and you do have some cam issues, I'm guessing they're not in perfect shape anymore.
As for non-synthetic being cleaner than synthetic, thats hilarious. Same with the ZDDP. It's to help wear on high pressure contact surfaces. Detergents in the oil are what help keep everything clean.
EDIT:wow this thread moved fast. Soundengineer, I'm guessing most of the oils you've used have a decent additive package (aka good detergents among other things) in them along with the ZDDP. The best oil and change intervals will be hugely affected by the max oil temp and blowby. There won't be a real good answer to synthetic vs non vs semi for a while I think, since they all have their place, along with certain additives. And using advertising from just about any oil brand can't be a good idea. Just look at the E3 plugs to see what real marketing can do!
A little oil in the cylinder can help determine if a leak is valve seat related if its difficult to hear where the air is going. Since you're planning on pulling the heads anyway, check the valve seats for sealing. If its got some miles to her, and you do have some cam issues, I'm guessing they're not in perfect shape anymore.
As for non-synthetic being cleaner than synthetic, thats hilarious. Same with the ZDDP. It's to help wear on high pressure contact surfaces. Detergents in the oil are what help keep everything clean.
EDIT:wow this thread moved fast. Soundengineer, I'm guessing most of the oils you've used have a decent additive package (aka good detergents among other things) in them along with the ZDDP. The best oil and change intervals will be hugely affected by the max oil temp and blowby. There won't be a real good answer to synthetic vs non vs semi for a while I think, since they all have their place, along with certain additives. And using advertising from just about any oil brand can't be a good idea. Just look at the E3 plugs to see what real marketing can do!
Last edited by The_Rizzle; 11-16-2010 at 12:08 AM.
11-16-2010, 01:10 AM
#20
petroleum based oils are better at collecting the dirt.. why do you think they are dirtier at shorter oil change intervals..
the ZDDP is a lubricant made with Zinc, it also helps keep dirt from sticking...so that the oil can collect the dirt and sludge
between the two, you will have an extremely clean engine assuming you keep up with a regular maintainence oil and filter change schedule
as far as the detergents in oils, they have gotten better over the years, but they are also counter productive to the lubrication process. too many detergents and your oil is not a very good oil at all and it cant do what it is supposed to do.
synthetic oils are typically designed to be slicker than petroleum oils, it does not mean they do a good job at trapping the dirt and sludge so that it doesnt collect on the engine parts..it typically does not do a very good job at collecting the dirt and sludge.
I wish I had pictures of all the petroleum oil engine tear-downs vs all the synthetic oil tear-downs I have seen or done... the petroleum oil engines are always cleaner
the ZDDP is a lubricant made with Zinc, it also helps keep dirt from sticking...so that the oil can collect the dirt and sludge
between the two, you will have an extremely clean engine assuming you keep up with a regular maintainence oil and filter change schedule
as far as the detergents in oils, they have gotten better over the years, but they are also counter productive to the lubrication process. too many detergents and your oil is not a very good oil at all and it cant do what it is supposed to do.
synthetic oils are typically designed to be slicker than petroleum oils, it does not mean they do a good job at trapping the dirt and sludge so that it doesnt collect on the engine parts..it typically does not do a very good job at collecting the dirt and sludge.
I wish I had pictures of all the petroleum oil engine tear-downs vs all the synthetic oil tear-downs I have seen or done... the petroleum oil engines are always cleaner
