Cylinder #3 down - Heads coming off!

Sorry, but an engine with a spun bearing could still have compression. You do a compression check and a cylinder leakage test before removing the head from any engine. That's standard practice.

He should try and get to the root cause of the issue before removing the head.

 

Well, a spun bearing will drop the piston down probably .010 or .020" which will kill the compression, whereas just doing a leak down test wouldn't really highlight the difference in compression in that cylinder. So it all depends on what you are trying to find out. Also, a leak down test could "leak down", while having zero to do with the cylinder head (for example a broken ring). But saying a compression test is useless without a leak down test isn't true. Each test is designed to address different problems in a motor. Of course, they work best when used together.

And yes, a motor with a spun bearing will still have "some" compression. The point is the drastic reduction seen in the compression when compared to the rest of the cylinders. If you spin a bearing, the compression in that hole is going to be probably 50 to 100 psi, vs probably 180 to 200+ (depending on the compression ratio) in the rest of the holes. You're trying to tell me a motor with a spun bearing will "still have compression". Yeah, when compared to zero psi it will.

Ray

 

I'm still curious what the final word will be on this issue - but I don't think pulling the head will be required to find it

Ray

 

I don't believe a cylinder would never fire if it had good compression, but failed a leak down test. Miss at some RPMs maybe, but not just stop firing. I always view the results of a leak-down test with caution and skepticism. I had a Honda Accord that consistently failed a leak down test, but ran strong and smooth for another 100,000 miles.

You haven't finished tracking down the problem until you've gone all the way back to where ignition begins. Have you done the above?

 

Well you could read and study the implications of post 8 and post 15. Otherwise you can keep replacing parts until you get lucky. If anyone does not know who these posters are do a search.

 

I'm sure you've heard that joke about the guy who had a car that wouldn't start. No gas getting to the carb. Just be the fuel filter, so they replace that. No luck. Probably the carb.. maybe something wrong in the float bowl or something. So they replace that. Still nothing. Hmm.. defective fuel pump? Replace that. Then they notice the car is out of gas...

Let's hope they aren't over there pulling the heads right now. I always try very, very hard to actually isolate the problem before tearing into (or replacing) anything. It worries me when the subject line of the thread is "heads coming off"

Ray

 

I have seen that before.

Show good close up pictures of the combustion chamber and piston.

PM me if you want details of what to look for.

 

What is your diagnosis and how did you arrive at your conclusion?

 

Broken valve spring.

 

I think you just wanted a good excuse to pull the head off.

Seriously, keep the pics coming and let us know what you find. I love these types of threads.

 

what does the #3 intake runner look like?

head torque 74nm+38* min 104nm+131*max
varitor/bushing 196 nm

 

Do you have the header out of the car?

 

Another cracked manifold eh...?

 

If cracked header, I'd guess it's another one just starting to show up, as the 360's are starting to get mileage on them. I'd also guess we're going to see more problems like this in the next year...maybe the 355 reputation will be passed on.

Brian, I believe you have run into bad headers on alot of 360's already, right?

Check the liners with a dial bore gage- more than likely the OEM p!ss thin coating is worn away too.

 

Did the pre-cat in the manifold meltdown(during the cherry red exhaust) and pieces of it get sucked into the cylinder breaking a ring or scratching the cylinder?

Does the engine have to come out to remove a piston/rod assembly?

This is gonna be expensive..

Maybe you will get lucky and it will be a valve problem.

If the headers breaking down do cause this problem then I guess the Fabspeed headers would be a good idea.. Right?

 

I was thinking broken up precat getting ingested. BTDT. But it was a broken spring. That is unusual but good news......cheap fix.

 

Have you changed the springs with the heads on? (not sure if there is enough room or if there is a good spring tool available that will fit?) Also, what cost does a matched set of springs for the top-end run on a 360? Thanks for any opinion, Scott

 

That's what I was thinking "indigestion". I've heard about broken springs never seen one on a ferrari. The op never did do leakdown. you can buy a leakdown tester for 30 bucks and if you can get the new spring in there insitu I'd leak it down to make sure the valve is ok from getting kissed by the piston. Its hard to determine concentricity too with head on. It would be a shame to put the car back together only to find now you got a sticking valve or other damage.

RD,
Is a spring breakage likely to be such a random event as to not worry or would you suspect the rest of the springs and replace all either because "conditions of use" or bad metalurgy of a spring batch?

 

No. There was actually a factory tool to do it for a 4 valve motor. Don't know if it will work on a 5 valve. Wouldn't be hard to make. Ferrari actually uses pretty good springs. Broken springs or spring problems are pretty unusual in my experience. If you chose to do just the one I would get OE. If not get a pair out and see what Isky has to offer. Ron Isky is or at least was pretty up to speed on European cars.

 

Like you and I both said Ferrari springs have had a pretty good history. Things do change though and the 360 fleet is getting older so we shall see. At this point if it were mine I would leak it down, replace the broken one and see how it goes. If on the other hand that car has a history of high miles and bouncing off the rev limiter I might rethink that.