Did a Leakdown Test and...
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
Did a Leakdown Test and...
I'm not sure how to read the results. The instructions state to do it on a slightly warm engine with the piston is at TDC. Well my heads are on, but no pushrods or rockers are installed so I have no clue where TDC is. At least I know the valves are closed. Is it critical to do it at TDC?
Some things to consider:
Engine is ice cold
Pistons could anywhere.
Brand new heads, never run. Do valves really need time to "seat"?
I tested where the crank was at for test 1:
1. 18% 2. 28%
3. 29% 4. 28%
5. 28% 6. 25%
7. 24% 8. 21%
For test 2 I rotated the crank roughly 360* degrees.
1. 24% 2. 30%
3. 32% 4. 32%
5. 25% 6. 20%
7. 24% 8. 40%
From those number I would take a stab and guess that the lower numbers indicate the piston was higher in the bore and the higher numbers mean it was further down. And the number that are same mean the piston was close to same location? The car was put in gear so they wouldn't move.
FYI - A few months back I did a compression test and all the cylinder consistently came in the 170-180 range. Hardly any oil the catch can, maybe a tablespoon. I didn't notice any oil usage over a 3k mile oil run.
I'll do a retest at TDC (when I find it) and see what I get... I hope the numbers get better.
Some things to consider:
Engine is ice cold
Pistons could anywhere.
Brand new heads, never run. Do valves really need time to "seat"?
I tested where the crank was at for test 1:
1. 18% 2. 28%
3. 29% 4. 28%
5. 28% 6. 25%
7. 24% 8. 21%
For test 2 I rotated the crank roughly 360* degrees.
1. 24% 2. 30%
3. 32% 4. 32%
5. 25% 6. 20%
7. 24% 8. 40%
From those number I would take a stab and guess that the lower numbers indicate the piston was higher in the bore and the higher numbers mean it was further down. And the number that are same mean the piston was close to same location? The car was put in gear so they wouldn't move.
FYI - A few months back I did a compression test and all the cylinder consistently came in the 170-180 range. Hardly any oil the catch can, maybe a tablespoon. I didn't notice any oil usage over a 3k mile oil run.
I'll do a retest at TDC (when I find it) and see what I get... I hope the numbers get better.
Melting Slicks
Joined: Nov 2004
Posts: 2,715
Likes: 0
From: Tinker till it blows... then back it off a notch, maybe!!
St. Jude Donor '08
OUCH
Not good results, but has car been sitting a long time?
That could be your low power problem that you've had for a while.
Your call, but if you have or are close to firing it up, do so and check another day.
Normally wear happens at the top of the cylinder, so even if some pistons were low, they may test better.
I think that you found your low power problem.
40% on number 8? You do mean last hole on passemger's side, yes?
If it was 7, I would say that you are suffering from the broken ring/land disease. Could stillbe the case.
How many miles on engine...are you the orignal owner?
Sorry to hear about your latest findings...keep the faith.
Not good results, but has car been sitting a long time?
That could be your low power problem that you've had for a while.
Your call, but if you have or are close to firing it up, do so and check another day.
Normally wear happens at the top of the cylinder, so even if some pistons were low, they may test better.
I think that you found your low power problem.
40% on number 8? You do mean last hole on passemger's side, yes?
If it was 7, I would say that you are suffering from the broken ring/land disease. Could stillbe the case.
How many miles on engine...are you the orignal owner?
Sorry to hear about your latest findings...keep the faith.
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
Yeah, it's probably been sitting for at least 2 months. Probably dry as bone. Yes, number 8 rear passenger side. I'm thinking maybe it's at BDC or something.
42k on engine. Probably about 23k with the Maggie. I got it with right around 38k.
I'm the second owner. It looked like he took average care of it. But you never know. Like I said before I've analyzed the oil a few times and it's always come back with below average values. Nothing exciting when I pulled the heads or the front cover. Hardly any discoloration - wiped right off. We'll see.
42k on engine. Probably about 23k with the Maggie. I got it with right around 38k.
I'm the second owner. It looked like he took average care of it. But you never know. Like I said before I've analyzed the oil a few times and it's always come back with below average values. Nothing exciting when I pulled the heads or the front cover. Hardly any discoloration - wiped right off. We'll see.
Melting Slicks
Joined: Nov 2004
Posts: 2,715
Likes: 0
From: Tinker till it blows... then back it off a notch, maybe!!
St. Jude Donor '08
That's why leadown tests have to be made and should eb made before teardown and when diagnosing engine problems.
With a compression test, you can turn the engine over until it comes up high, unless it's really bad.
When I do a comp test, I let the engine turn maybe 4 or 5 turns for every cylinder. When you do it again after some miles, do the same thing to get relative results.
I guess I'm closing the barn doors after the horses already got out..
How close are you to firing it up?
Some cheapo Diamond pistons and compstar rods will fix it quick, fast and in a hurry
With a compression test, you can turn the engine over until it comes up high, unless it's really bad.
When I do a comp test, I let the engine turn maybe 4 or 5 turns for every cylinder. When you do it again after some miles, do the same thing to get relative results.
I guess I'm closing the barn doors after the horses already got out..
How close are you to firing it up?
Some cheapo Diamond pistons and compstar rods will fix it quick, fast and in a hurry
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
eh... well I have to put the headers on, sparkplugs, adjust the valves, put the supercharger on and heat exchanger assembly... reconnect everything - radiator, fan assembly, etc. Still a ways, but not too far away.
I just have to go for broke now... I'm not about the replace the bottom end...
FWIW: when I did the compression test I would crank each cylinder for 3 seconds. That was my system. It would go higher if I kept cranking it, but that probably defeats the purpose.
I just have to go for broke now... I'm not about the replace the bottom end...
FWIW: when I did the compression test I would crank each cylinder for 3 seconds. That was my system. It would go higher if I kept cranking it, but that probably defeats the purpose.
Last edited by Third Gear; Jun 8, 2007 at 02:59 AM.
