Why such strange Leakdown Results?

[larry47us]

Grady, thanks for the comments.

My problem right now is that we are going to meet a bunch of early 911 nuts this weekend in IN, and after driving nearly 2,000 miles in Kermit, I think that I am best off getting it adjusted before I hit the highway again.

So, even though I could do the Valve adjustment myself - Chris taught me a few weeks ago - I need tools, and a bit of help for the first one, and it is tough to ask weekend mechanics on the other side of the world (naperville is the other side) to "come on to my house, to my house come on." to have a valve adjustment party.

Do you think that another 500 miles this weekend would do anything harmful? I was thinking that any more miles than necessary on the car after burning off the carbon would just add premature wear to the valves. I can wait a bit on the MFI. I have the book, just not the knowhow.

Grady, Souk - whatcha think?

larry

[Grady Clay]

Larry,

“after driving nearly 2,000 miles in Kermit, I think that I am best off getting it adjusted before I hit the highway again .”

Yes, you are best off but that isn’t to say it is absolutely necessary. Pull the valve covers and verify you have equal clearance on all the valves. You just need to know there isn’t a valve with little or no clearance. Clearance of 0.003” is OK, 0.005” is slightly noisy hot, and 0.007” sounds as if something is wrong.
It wouldn’t hurt to do an oil change and check the sump plate.

It seems the MFI is running acceptably on the highway for now. If everything is in good condition, you eventually may be able to get in the 20 MPG range or better. How does it start and run cold?
Before you touch anything in the MFI, you need a good repeatable baseline. That includes valve adjustment, ignition timing, compression & cylinder leak tests, and the rest of CMA. This is all best done in conjunction with spirited highway driving.

BTW, I’m trying to organize a Pelican gathering in Indianapolis on the Friday afternoon –> evening after Thanksgiving. I’ll start a thread when things are firmer. Where in Illinois are you?

Best,
Grady
gradyclay@hotmail.com

[Jim Richards]

Originally posted by larry47us
I know what you mean, when I was with Souk and Chris a couple of weeks ago, I asked them about MFI, and their response was . . . . .

Carbs are easier to adjust.

Those boys need to be schooled. MFI is not hard and stays in tune longer than carbs. Souk, Chris, whassup?

[Jim Richards]

Originally posted by Souk
Hey! Jim, I could learn MFI faster than you can do one lap at Road America!

Hehehe. We'll see you in May.

Originally posted by Souk
...maybe I should just go buy an MFI car and learn...

Now you're talking. You'll never go back to [insert other induction here]

[larry47us]

This afternoon I picked up Kermit at the Mechanic's. He adjusted the valves (two were a bit loose, two were a bit tight - no biggie), replaced the spark plugs (they were all covered in carbon - the MFI was running too rich), adjusted the dwell and timing, adjusted the MFI (leaned it down a bit) and did a leakdown test.

Now is where I get really confused. I have now had three leakdown tests done on this engine.

Mike did a test last fall, and the results were:

1: 19%
2: 18%
3: 18%
4: 9%
5: 10%
6: 10%

Then I had another leakdown done two weeks ago, at Speedsport Tuning in Westport, CT after the engine was re-installed, and the car was run a bit.

1: 8%
2: 22%
3: 5%
4: 4%
5: 1%
6: 20%

I picked the car up and ran it for 2,000 miles coming home, and then had the valves adjusted, and another leakdown test run, so that I would have a solid baseline to work with. Here are the results from today.

1: 25%
2: 25%
3: 23%
4: 23%
5: 23%
6: 20%

Jeff, my local mechanic, said that it is good that these results are consistent, and that the numbers really don't matter. (obviously a high leakdown number at ANY pressure is bad.) He said that he was doing the test at 100 PSI, and that his leakdown equipment works a bit different from others. Even a new engine would have some leakdown, and that there isn't such a thing as Zero leakdown. He said that I should feel very good about the engine, that it's solid.

I drove it home. It idles very smoothly (after it warms up) and drives like a champ.

So the questions are,

1. If there is greater pressure used in the test, aren't the numbers going to be higher?

2. What is the standard pressure used to measure leakdown?"

3. Do you agree that the results of this test are positive, and I should just relax and enjoy Kermit before the snow flies?

TIA.

larry

[HarryD]

Larry,

Like many tests, I think you need to consider the leakdown in context with other tests and observations. What is the compression? How is your oil consumption? Does the car smoke on acceleration (possible failing rings), decelleration (possible valve guides), all the time, only on startup?

Relax and enjoy the car. Unless, you enjoy worrying instead .

[larry47us]

Harry:

OK, you're right. I guess that I was looking for definitive information on the condition of the engine. Everyone says "leakdown reigns." I guess that the numbers don't mean as much as the other things you mention.

So, in light of that, here are the other answers. Compression is between 145 and 150 on all cylinders. The car doesn't use ANY oil. I ran it for 2000 miles, and maybe it was down 1/2 quart - Maybe - the dipstick still showed full. No smoking unless I really stress it while it is really cold. (I did a hard acceleration with a cold engine once on the trip, and left everyone else in a cloud of smoke.) Doesn't smoke noticeably on start-up or otherwise, after its warm - either on accelleration or decelleration. The engine doesn't backfire, and pulls strongly.

OK, done with this issue. I'll stop agonizing about it.

larry

[golfnow]

Originally posted by larry47us


OK, done with this issue. I'll stop agonizing about it.

larry

when is the car party

[larry47us]

I'm gone this weekend, but I'll try to find a date.

Soon, grasshopper, soon.

larry