L98 leakdown test results. New engine! ?
Thread Starter
Race Director
Joined: Feb 2001
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From: Manassas VA
NoVa Events Coordinator
St. Jude Donor '14
L98 leakdown test results. New engine! ?
I performed a leak down test on the problem child L98 here are the results.
88k miles, engine was warm enough not to get burned....
1 - 11%
3 - 12%
5 - 30%
7 - unknown
2 - 32%
4 - 10%
6 - unknown
8 - unknown
I stopped after the second 30+% I can here the air rushing past the rings into the oil pan.
88k miles, engine was warm enough not to get burned....
1 - 11%
3 - 12%
5 - 30%
7 - unknown
2 - 32%
4 - 10%
6 - unknown
8 - unknown
I stopped after the second 30+% I can here the air rushing past the rings into the oil pan.
Last edited by Bluewasp; May 14, 2006 at 09:50 PM.
Melting Slicks
Joined: May 2002
Posts: 2,670
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From: Severna Park MD
Originally Posted by Bluewasp
are you asking what the engine has or what I want to buy ?
Whats in the car now is the 1989 L98 that came from the factory
Whats in the car now is the 1989 L98 that came from the factory
I vote for the L98 to avoid the complications of tuning problems. After all the object is to get track time, not shop time. The 383 miniram can wait until Lilred has outgrown the L98 power.
Thread Starter
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From: Manassas VA
NoVa Events Coordinator
St. Jude Donor '14
Originally Posted by FELNGR8
Is it going to be a L98 crate motor? Or a 383 long block plus a miniram? Depending on price, using a ZZ4 crate and pulling the carb manifold may be the best route.
I vote for the L98 to avoid the complications of tuning problems. After all the object is to get track time, not shop time. The 383 miniram can wait until Lilred has outgrown the L98 power.
I vote for the L98 to avoid the complications of tuning problems. After all the object is to get track time, not shop time. The 383 miniram can wait until Lilred has outgrown the L98 power.
Melting Slicks
Joined: May 2002
Posts: 2,670
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From: Severna Park MD
Originally Posted by Bluewasp
I agree. not sure what she wants to do. In the end its up to how much $$ she wants to spend.
Le Mans Master
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From: In front of C6s.
St: Jude Donor '10
Originally Posted by Bluewasp
Ok... I'll keep that in mind. I don't have time until July to work on a project like this.
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St: Jude Donor '10
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Originally Posted by Bluewasp
I performed a leak down test on the problem child L98 here are the results.
88k miles, COLD engine...
Numbers would be higher (better) if the test was done on a warm engine..
88k miles, COLD engine...
Numbers would be higher (better) if the test was done on a warm engine..
On piston aircraft engines, a delta comp test is standard procedure. The test is always run on a warm/hot engine or otherwise the test is considered invalid. The prop is used to control the piston location and the pressure can be misrepresented if the rings are not in the bottom of the grooves. 80 psi is the standard base pressure and monitored as each cylinder is tested. An 80/75-70 is an average good test pressure. Less than 80/70 is reason to watch closer depending upon total time, aka miles.
Maybe it would be best to run a standard compression test. And then if these results are low, run a delta test.
Racer
Joined: Jan 2006
Posts: 273
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From: Ithaca Michigan
Originally Posted by JrRifleCoach
Why did you run a leakdown (differential compression) test on a cold engine? What was the base pressure? How did you control piston location during the test?
On piston aircraft engines, a delta comp test is standard procedure. The test is always run on a warm/hot engine or otherwise the test is considered invalid. The prop is used to control the piston location and the pressure can be misrepresented if the rings are not in the bottom of the grooves. 80 psi is the standard base pressure and monitored as each cylinder is tested. An 80/75-70 is an average good test pressure. Less than 80/70 is reason to watch closer depending upon total time, aka miles.
Maybe it would be best to run a standard compression test. And then if these results are low, run a delta test.
On piston aircraft engines, a delta comp test is standard procedure. The test is always run on a warm/hot engine or otherwise the test is considered invalid. The prop is used to control the piston location and the pressure can be misrepresented if the rings are not in the bottom of the grooves. 80 psi is the standard base pressure and monitored as each cylinder is tested. An 80/75-70 is an average good test pressure. Less than 80/70 is reason to watch closer depending upon total time, aka miles.
Maybe it would be best to run a standard compression test. And then if these results are low, run a delta test.
Test it warmed up to get better test results. Good luck to ya, Tom
Thread Starter
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Joined: Feb 2001
Posts: 13,911
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From: Manassas VA
NoVa Events Coordinator
St. Jude Donor '14
What is your definition of a "warm engine". 100 ? 200 ? 150? I drove the car into the garage and let it cool down so I didn't burn myself. . I'm not about to pull the plug(s) on an engine at 220 degrees.
I didn't say ICE cold, left over night... I went back a read my first post in this thread and can see how you interpreted my use of the words “cold” and “warm”. I should have said cold enough to touch without getting burned.
I didn't run a "Standard compression test" because I wanted to see where pressure is escaping. A compression test wouldn't tell me that. ie past the rings, the intake valve, or the exhaust valve.
In any case the issue here is the variation between cylinders 10-12% and 32% which is a big difference.
I didn't say ICE cold, left over night... I went back a read my first post in this thread and can see how you interpreted my use of the words “cold” and “warm”. I should have said cold enough to touch without getting burned.
I didn't run a "Standard compression test" because I wanted to see where pressure is escaping. A compression test wouldn't tell me that. ie past the rings, the intake valve, or the exhaust valve.
In any case the issue here is the variation between cylinders 10-12% and 32% which is a big difference.
Last edited by Bluewasp; May 14, 2006 at 08:02 PM.
