95 F355 Valve Guides.....Fact vs. Fiction !!!

I always found it odd, bronze guides have been the staple at ferrari since forever. Most American hot roders "upgrade" to bronze guides. Receintly had a 355 that was PPIed by a dealer who said it had bad compression and leak down, thus needed guides. My test should 195 to 200 psi with 11% leak down. Not bad or 23k miles. That being said I had to modify the adaptor to get a good seal. 355 heads have a very small area for plug seal and most tools are too large to seal properly. If you are not paying attention you can be fooled by tool leakage.

 

If it is a later 95 it might never have the issue, but if the valves have never been done in that time on any 95, no guarantees! One of my cars had copper on one bank and steel on the other.... who really knows what came out of the factory?

A later post mentioned oil burning and that is possible for sure, and that coupled with a bad leakdown....is always bad news. A bad leakdown result all by itself, especially on a infrequently driven or slowly driven car is not necessarily a death sentence.

 

Looks to me like your research consisted of reading the ten year old post that started this thread. A friendly suggestion: read more of Rifledriver's posts. That would be research.

I hope this is coming across in the constructive manner it is intended.

 

No one is going to make you drink from the "well" but consider drinking after you consider the source...

 

Thats funny and true.

 

Sorry, no offense, I am not familiar with the source...I am familiar with the fact that there are a lot of myths online about the valve guides. Some much less than a decade old.

Sorry, I won't drink from the well and no kool-aid for me but thanks.

 

I was being a little sarcastic. The masters degree in mechanical engineering and 30 odd years of experience sometimes makes me that way when mechanical things are being discussed and the Ferrari mystique enters the game.

My point was that valve guides that have lasted 27k miles aren't going to go bad over night regardless of which material they are. To make my point further, I just don't know who is replacing all these guide. Over the past 3 years I've looked an a number of cars which had records from Ferrari since day one. Only a single car, a '97, had guides replaced, and that car had a host of other problems to boot.

Right here on this board I read the post from Bradan fixing up a 355 for resale and they took compression and leak down number which were very good. But they found bronze guides so they are replacing them. Is it another case of fixing what ain't broke. "While we're in there spend another $X,000 because the guides might go bad in somebodies lifetime."

As pointed out bad guides usually lead to excessive oil consumption and smoke on throttle off conditions.

Now, let me use my engineering back ground to perhaps make a fool of myself. But when I look at a valve and a valve seat what I see is that the way they are cut the valve should be, or so I would think, self centering in the seat. There is a lot of spring pressure pulling the valve into the seat and if it is misaligned the angles of the seat and valve should make it find the correct position in the seat. No guide has zero clearance so the valve is always going to require this self centering effect as far as I can see.

That said, if correct, then I can not see where a leak down would reveal bad guides. And suppose that the valve did seat incorrectly, would not a couple of rotations of the engine so that the valve opens and closes again give it another opportunity to seat correctly? It seems to me that a bad leak down traced to valve passages would more likely indicate a burnt valve or valve seat, or a bent valve as opposed to bad guides. How would valves get bent? I would suppose that it would be possible to miss a shift and over rev the engine (i.e 5th to 6th ends up being 5th to 4th) , or down shift at too high an rpm, thus floating a couple of valves which then nick the pistons and get bent.

I don't know, I just speculating here. Not to say that some 355s don't have guide issues, but I don't think the idea that if there is no problem in xxk miles that one will turn up over night is sensible.

 

Please help educate me here:

Is it correct to assume that a leak down is done while the valve is open? If the valve is closed, it would seem that the valve/seat integrity would be tested not the valve stem/guide integrity?

And, don't the value guides/valves have a garter spring seal at the top of the guides?

 

A leak down is done with valves closed. And yes, it is the integrity of the valve/seat and piston rings/cylinder that is tested. The idea is that if the guide is warn the valves don't seat correctly.

As for the oil seals, they wear and if the guide is excessively warn then the wobble of the valve stem can lead to excessive wear of the seal resulting in excessive oil consumption. That I buy.

 

It's hard to believe that a worn guide would always cause a poor valve seat. It would seem that the valve would self center on the seat most of the times giving a false test result...

 

Until the sealing surfaces on the valve and seat start to get beat up a little bit from off-center landings (so start to have leaks even when well-centered).

I'd have a completely different opinion on this issue (Does a good leak down test result = all OK?) depending on whether I was a Seller or a Buyer

 

Often it is carbon buildup that causes poor valve seat. This is coming a conversation I had with the owner of the machine shop used for head work by a major east coast authorized Ferrari dealer. The proverbial Italian tune-up and Techron were given as a couple of real-life, low-cost solutions to cars that have not been driven in anger frequently enough.

Incidentally, I've ridden in the OP's Challenge car and I have to say that car spent most of its life in the high RPM range. The fact that a race car that is pushed so hard can have such good leakdown #'s could be a testament to the carbon theory.

Moral of the story: warm your 355 up properly and then drive it as intended.

 

And I agree with that although that would mean changing the valves seats (and maybe valves too) when doing guides and I've read this is not the norm.

 

Fab, think of it more as a matter of "when" as opposed to " if"

Like a timing belt service, it's a matter of "when" you have to do it, not "if" you have to do one.

There are many 355s here that have gone through this process because of necessity.

 

Totally disagree. Timing belts and oil changes are preventive maintainence. Things like valve guides are corrective maintainence, to be done when necessary, if necessary.

 

The valves may or may not need to be replaced. If only one or two cylinders have really worn guides, you may only have to replace a few valves, if any. I'm looking at the receipt for mine right now and it says:

"Performed inspection on runability of car before performing service: Vehicle idle is not running smoothly, performed emissions test. 1170ppm H.C. on right bank of engine, 118ppm on left bank of engine. Engine right side has possible compression issue."

"Performed compression test on vehicle, found that the compression ranges from 16.0 bar to 14.0 bar on the right bank. Recommend that since this vehicle is prior to 1998 and sintered valve guides aren't in this engine, heads should be removed and rebuilt."

Later it says: "Inspected combustion chambers once heads were removed from engine. Cylinders have a lot of carbon on pistons. Tech cleaned all carbon off tops of pistons, cleaned all surfaces on engine for heads to come back from sublet for reassembly."

"Valves were ground and cleaned, no valves were necessary for replacement."

So, this car either had carboned up valves or bad guides (or the guides caused the carbon) but in either case the heads had to come off and it was the right choice (imo) to go ahead and install the sintered guides.

 

My '97 355 spider had a build date of July '96. In its maintenance history, there is an invoice from the local Ferrari dealer recommending valve guide replacement in '06 at 12k miles. The previous, original, owner declined. When I took it in for a major last January, I therefore budgeted for guides. Somehow they had healed themselves. Either that or the Ferrari dealer lied in '06. It makes me wonder how many of our 355s actually needed the guides done, versus Ferrari dealers needing to pad their bottom line.

 

There are many bronze alloys. Ferrari used greater and lesser amounts of copper for the purpose of heat transfer to the head. In fact the F50 guides, many of which Ferrari under took to just proactively replace because they were so bad were not even called bronze. They just referred to them as copper. But in all those years you speak of Ferrari did get a long standing reputation for guide problems. The 355 was a major leap in specific power output and the combination of the 5 valve head having very little coolant space around the valve and in the head to keep things cool and the high exhaust temps the guide material that had worked just OK for so long was no longer good enough. Neither were the exhaust manifolds for very much the same reason.

There are a variety of good silicon bronze and manganese bronze alloys that if used would probably not been an issue. Likewise there are a number of stainless alloys that if used in the manifolds would not have been an issue either but all that comes under the heading of "what if", not "what is".


No question, bad diagnosis and over selling play a part, just as they play a part in medicine, plumbing and insurance sales but it in no way changes the facts, the guides are junk and many really have failed. Ferrari after seeing the problem and experiencing unacceptable warranty costs made a well documented change to sintered iron in mid year 98.

 

I have replaced guides on low mile 355's of all years. I had one customer say the engine went bad sitting in the garage.

 

The seals are quite good quality and generally outlast the guides. Also the 355 is a dry sump motor. For the people that do not understand the import of that in this discussion I will explain.

The oil pump that sucks the oil from the motor and returns it to the tank is very high capacity. In fact it is double the capacity of the oil supply pump. There are several reasons but the important one here is it is intended to create a vacuum in the crankcase. Under vacuum the motor will make a little more horsepower. That vacuum also, coincidently works to keep the oil inside the motor. If the valve seals were removed completely little oil would be burned for this reason. We have seen in some motors large pieces of gasket missing with no oil leak because with so much air being drawn in oil could not escape. The chance of oil loss obviously depends on the location of the leak but due to the head design the valve stem is in a location that has little oil to start with. The intake valves have vacuum on both sides but they are not subject to nearly the degree of wear that the exhausts are.


Again, people can deny this all they want but it was a problem accepted as such by Ferrari and they took expensive steps to repair cars and eliminate the problem.

 

My car is a Jan 98 build date. When I do the major 4 years from now, I'll pull a head and see what I have.

I wonder if this could be seen with a fiber bore scope?

 

An eyeball works just fine.

 

Really? No xxxx I was talking about looking now without taking apart the engine.

 

Brian, have you ever come across any bronze guides in the mid year 98's or 99's?

There was a discussion that I read awhile ago where bronze guides were found on the 99's posted by another reliable source.

 

Is that mid 98 model year or build date? I've never seen this clarified.