F355 on FerrariAD and Compression numbers found...

Almost every thread here in the past has said grouping is more important than absolute numbers because the test method and equipment calibration and atmospheric will not always be the same - imposing therefore your 200 plus requirement (which I do not agree as being described in these threads as normal) could result in a car with good grouping having its test compromised unneccessarily - caveat : non-owner of 355 but active contextual thread follower

 

seem like decent numbers to me..

 

In my experience - owning 355's and paying for 5 failed PPI's...those numbers are just ok... with some question as to high leak down numbers.

 

Recently had mine done and heres what I had

left front
220
200
220
210

Right front
210
205
200
200

Didnt do a leak down so I dont have those numbers.

Juyst posting this for comparison purposes..I was told my numbers were very good. Not saying numbers have to be 200+

J

 

Those are spectacular!!

I believe there are a few factors that can affect ones results (for better or worse).

Here are some:

Weight grade of oil.

Test done after car was sitting overnight and cold.

Elelvation. Atmospheric pressure.

Humidity in the air injected into the cylinder. If the engine is hot/warmer the humidity will expand (at higher rate than dry air) inside the cylinder as the engine heat convects into the humid air. Giving better readings.

I am sure there are other factors...its early...need caffine

 

The #s are fine. The leakdown percentage is far more important than say 150 psi or 200 psi. There are many good sites that explain leakdown tests and compression tests as well as explaining how to use the data. You shoudl really do a little research on this before getting PPIs done IMHO. All of the figures are way under 20%. The engine is in good health according to the #s. So if your concern is whether or not the engine is low compression then your fear is unfounded. Buy the car.

 

Yeah, I second that!
gordon

 

I would have to agree, I normally would be hesitant to encourage a reluctant purchaser. (here it comes) BUUUUUUT if I were looking at this car and the price was right among other things, The #'s above would not bother me whatsoever! I would agree that they are satisfactory and the engine has plenty of life in it!

 

Those leakdown %s are somewhat high. Here are the results on a 1995 F355 I purchased last year with 11,000 miles (test performed by Ron Tonkin dealership):


1) 11.5 bar, 2%
2) 12.0 bar, 2%
3) 11.5 bar, 2%
4) 11.5 bar, 2%
5) 12.0 bar, 2%
6) 12.0 bar, 2%
7) 11.2 bar, 3%
8) 12.5 bar, 2%

 

11.5 bar = 169.5psi
12.0 bar = 176.4psi
12.5 bar = 183.8psi

 

Just out of Curiousity; What was your Mileage ?
As a Point of reference, mine were 195-205 @ 17K.

 

About 13.6k

 

Here is one I just took apart.

95 355 34k miles Owner is ex SCCA National Champion and he and his son drive the wheels off it at track events.

Still has bronze guides.
Compression
225
165
195
200
230
220
220
220

Leak down

1
42
5
3
0
3
4
1


Leak down with heads off

1
41
1
1
0
0
1
1


The first photo shows the tool used for checking leak down with the head off.
The second shows one of the good cylinders. This should show that 355s can normally hold 99-100 percent even cold. This is one of my mechanics brand new tools. The one I have of a different brand that I have been using for 20 years routinely shows the same results.
The next photo is pretty good proof that there is a compression problem outside of the valves and guides.

Also to support Daves and my suspicions #2 had a burned out header pipe.

We did not go out and cherry pick cars after the last debate on the topic. This was the very next 355 in the shop.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

This seems to support one of my opinions.

I am really starting to think that is a good idea to perform a warm compression check, at a minimum, before pulling the motor out.

You can decide from there, whether to then do a warm leakdown, cold leakdown (after the motor is out). And from there, pull heads or whatever.

I mean, you need to pull the plugs and wires anyway, might as well do it before the motor comes out, and while the battery is still hooked up.

If you invite me down to see the "Ancient Ceremony of the Maranellan Cam Dialing", I will tell you the story of an Olds 455 that was started up while laying on the ground.

JM

 

wonderful pics above ... thanks Brian.

.

 

Yup, been there, got the T shirt. Pretty hard to argue photos. How long was it driven with the exhaust leak present? A good one to add to my data log / spread sheet.
Damn, I would like to see compression numbers above 200! Help, send some air up this way, we are a bit short at this altitude.


jm3,

"Ancient Ceremony of the Maranellan Cam Dialing"

Your a brave man! Did Brian discuss with you the initiation rights one must go through prior to watching him do this? Shame, we have lost many virgins over the years. High point is a few have survived, scared for life but still have a pulse.

Dave

 

Having owned a 355 for a very long time - and looking for mine (going through many many many cars). I went through about 5 ppi's when I finally bought my 355 Spider.

There are many factors as has been mentioned that will contribute to the numbers. However those numbers posted by JoelP look good... I would not be worried with those numbers in themselves. The numbers on these cars will vary depending on conditions, warm, cold, etc. These numbers are not bad by any means - imo.

I would be more interested if a good mechanic or shop has been looking after the car. Call them and talk to them, find out what they think.

If it is a private shop - more the better you will more likely get a straight answer. If it is just a dealer or broker that has the car but did not do the work - that is more the concern point in my mind.

What other work has been done, belt service, etc. etc. That will cost you more in the next several years as opposed to those compression numbers numbers.

Good luck in your search.

Rich Wallace
F-Chat Consultant

 

Sorry, I ignored the question and got side tracked. Very poor form indeed.
Rich answered the question quite accurately.

Dave

 

Don't know. Breach in the manifold is quite small. Not nearly as big as most you see by the time they come off, No insulating debris in the area, could not really even hear it. The rough running at idle was pronounced but who can tell which was more responsible, the manifold or the cylinder? The other 7 cylinders have no discernable ring ridge but just running your finger up and down #2 has a good ridge. I'll run a gauge in it when the piston is out and if there is something to look at I'll get ring pictures also. I think because these are dry sump motors and as such have huge vacuum in the crank case the rings get pretty bad before oil passes around them. With 41% leakage the piston looks little different from the others. On the motors I have had bad cylinders and rings the pistons are often like new. Little land wear and skirts have zero really. It is just the rings and liners that go away.

 

So, the last pick with the 40 something leakdown was caused by the burned out header?? Looking at the #s with head on/off, it apears the rings got damaged by the burned header and not the exhaust valves. Am I reading this correctly??

 

It has never been officially admitted to but Dave and I have long believed due to observing a number of cars that there was a link between burned out headers and burned valves. It has been hard to get good info though when we were not directly involved because many cars have header replacements but which pipe that had the failure is generally not noted. In a few he and I have done in the last few years where there was a burned valve and a burned pipe on cars we did they are the same cylinder. #2,3,6+7 all run hotter and we know that. It is almost always one those 4 that fails both in the header, the valves and the rings/cylinder. But we have been trying to develop data that really proves our suspicion it is always a cylinder that has a header fail and then a valve problem.

I noted on a previous thread that I have repaired quite a few motors with rapid ring /cylinder wear. Of course many here told me I was wrong and it does not happen but here is a good example. I have been involved with quite a few just like this one, several while the cars were still in warranty. Ferrari paid in a number of the cases. They even replaced the motor in one we did and they sent us a rebuild that was done in New Jersey. When I made a few inquiries it turned out ours was not the only one rebuilt there. This just happens to be the very first I have taken apart with a good history that can be traced that has a burned out manifold and serious ring and cylinder wear on the same cylinder.

Is one car proof? You tell me.

I never meant to make a connection between exhaust valve failure and ring/cylinder failure other than to just state that they both happen and happen sooner than they should.

None of this really has any thing to do with the valve guide issue. With the exception that some materials chosen for this motor do not last well in the heat developed it is a separate issue.

 

After reading my post, I don't think I communicated my thoughts correctly.

What I meant to say was:

In this example, the bad header did not seem to affect the valve sealing. Since the rings are the primary reason for the bad leakdown #s in that cylinder.

Out of curiosity, have you ever installed Total-Seal rings on the compression land? I have used them quite a bit with very good results. The engines I've used them in almost always see increases in power over the stock rings along with higher compression #s.