Jeff, Here’s a video with good info on a 355 engine rebuild, this one is the block, heads and valve guides next in the series. I hope the best for your 355. I saw it last year at Farland Restoration. Beautiful car. Jack is working on my drivers seat this week. Fingers crossed for you!
No smoke and not consuming a lot of oil (more then a 1/2 quart in 2k miles) and a leak down test showed intake valves guides to be worn There can be a possibility they are but I have to ask what did the plugs on the cylinders with the leak look like —- with or with out signs of smoke the plugs will tell if oil is being burnt There is a few ways of testing for guides problems and it sounds like the tech used the easiest one because this is a service at 50 plus miles and so call “ expected” while it’s not a bad call to do but might not have been need now That’s not saying you should put the engine back together with out having the work done It’s out and started on so “it is what it is” and you will have piece of mine knowing it’s done Sent from my iPhone using FerrariChat.com mobile app
My heads are off my 348, every guide is getting done regardless of need. If heads are off I say do them. Sent using FerrariChat.com mobile app
I didn't see anything in the OP's post about rough running or poor power output, I just thought it was in for a routine major... But no thanks on the clapped out Toyota, just not my style.
Mine still felt pretty comparable to my friend's Spider. That said, I was starting to have some stumbling and such. I've been having a lot of issues with my cat ECUs which started giving me slow down lights and even shutting down a bank. In fact that was the original reason I took the car in - and then figured I might as well do the major since it's so hard to get into my mechanic.
Oh yes, I couldn't agree more. My car is running great and I wouldn't want to change a thing! Just wish summer would return....
I just got my car back after a lonnnnngggg visit to the shop. I'll write up a separate post about that ordeal, but I do second a couple things Brian has said. My car ('98 F1 with 67k miles) was running well when I brought it in for a smog check. Failed! So the leak down test showed worn exhaust guides on 2 cylinders. As posters here are, I was skeptical it wasn't just carbon build up on the valves causing a poor seal. But my guy insisted that it was the guides ("a known issue in these cars"). "But, my car should have steel guides, so that can't possibly be the case!" The car was due for a major anyway, at 5 yrs, so I agreed to pull the heads and look at the guides. Because I hadn't seen poor performance or excessive oil consumption, I truly thought it couldn't be the guides. Plus, steel guides never ever fail, right? I was shocked when I saw the heads off the block-- oil residue clearly present on the same 2 cylinders the leak down showed. Front cylinder on one bank, rear cylinder on the other bank (forget how the numbering goes). And yes, steel guides, yet the exhaust guides failed on 2 cylinders. Eventually I got my car back, and I'm very happy to report the car has a LOT more power than it had before! Clearly the 2 cylinders were not contributing much to the power output of the motor, but it had happened over such a long time that it wasn't noticeable. So, to the OP, Brian is correct, it won't necessarily burn a lot of oil. And you won't necessarily notice lost performance until it's back. And I'll add that steel guides can fail (Brian obviously knows that part too, but is choosing not to opine on this part). Swallow hard when paying your major + valve guide bill, but know that once you drive the car again, you'll see it was worth it. Brian, your comment on the vacuum of these motors causing little to no oil consumption when the guides are worn answered the nagging question that has been floating in my brain all this time (I kept meaning to ask the mechanic this question, but there always seems to be twenty things we were discussing and that question kept getting lost). Thank you-- glad to see you back on here again!
How does the 355 engine create more vacuum in the crankcase because it's dry sump? The crankcase is vented to the oil tank where vapors are sucked into the engine by the vacuum in the intake manifolds. Thus the crankcase vacuum would appear to be set by the intake vacuum, just as it is in a wet sump engine. The only difference I can see between the 355 and a wet sump 308, for example, is the lack of and oil/vapor separator on the 355 since the oil tank itself serves this purpose.
How worn were they? What was the valve guide stem clearance of the suspected guides? It’s important because the oil leak from the guides could have been just the valve stem SEALS leaking oil and consequently burning in those cylinders and creating carbon buildup that gave your high leak down numbers. You still have the old valves and guides?
So now I feel uninformed..... I don't know the clearance numbers on the affected cylinders. I saw the heads off the block, there was more than just carbon build up-- lots of oil on the valve seat areas themselves, and not that much carbon. So this was not subtle, which is why I was surprised there was no major oil consumption. The valves themselves were reused, as they appeared to be fine; the guides were replaced but I didn't inspect or receive the old (worn) guides. I will say after having the car out for a long mountain drive, that there was significant power missing in the "before" as compared to the "after". So I tend to believe there was significant loss of compression from the leaking guides. Sorry I'm not more versed in this.
No worries. The technicians working on it are just soo very close to answering the root cause. I wished more people measured. Measurements are a huge key to proving if all the consequential problems (leak down numbers, oil passing though valve seals, carbon build up) was either caused by just worn/aged valve stem seals OR valve guide clearances being too loose. The problem with not measuring is that we will never know what was the root cause. Obviously, replacing everything with just FIX it. As it’s possible you only needed valve stem seals and a valve angle job(machining valve face and seat) to restore your power. Here is a video that Dave Lelonek(StickyRX) made about valve clearance on a F355. He used guide pins, but there are other ways to measure it (small bore gauge, dial indicator, etc). It’s a great reference.
Wondering if anyone knows the real source of poor leakdown numbers on 355's. Is it carbon buildup from oil consumption, or that worn guides allow valve heads to beat up valve seats, resulting in poor sealing? I would imagine the latter -- especially since it appears that worn guides in 355's don't show themselves via excessive oil consumption. I come from the 911 world, where worn guides show themselves via oil consumption but not poor leakdown unless they're really far gone. 355's seem to reveal the problem via LD test, and I wonder if this is why the problem always seems to be caught so late.
Everyone started to do leakdown testing because the fear their model had the Notorious valve guides that Ferrari put in the early models. Since Ferrari didn’t have a range of assembly numbers that were affected, owners feared they may have them. One way owners knew they were in the clear was having a build date that had sintered steel guides in them, so called Ferraris updated part. For the ones that still feared, they asked “how do I find out?!”. Someone answered “leakdown testing!” Though REALLY worn guides COULD show high leakdown numbers. High leakdown numbers is not directly related to valve guides. Porsche, BMW, Ferrari… no matter what car. You measure guides to determine fault. How people are using leakdown testing is a joke, it’s not the end all say all. It’s just the initial test… I’ll make it simple. when you get high leakdown numbers, the technician needs listens to where the leak is coming from. Intake valves, exhaust valves, piston rings. If he confirmed it’s from the valves. He should recommend fuel cleaner like f355spider did on post 5. Drive the damn car, then retest. If there is leak down improvement, it’s carbon buildup, if no improvement, valve sealing issue but not necessary valve guides are worn, could still be carbon that can’t be cleaned with fuel cleaner or just needs a basic valve seat and face machined. If leak down is large enough and needs to be addressed, engine heads get removed. Gets inspected, GUIDES AND VALVE STEMS MEASURED not assumed, you can check if it’s off center, conical/oval or flared/tapered, THEN and only THEN you can answer if the guides caused the valve seat to valve face to wear or just needs a basic valve seat/face machining work. it’s okay if a lot of people here have deep pockets for their peace of mind. That’s not my concern, I only care about correct diagnosis. which is turn can save many owners money. It’s funny, because valve guides are simply a damn hole that needs a few thousandths of an inch clearance from a stem. If you have 20k miles or even more and you measure your guides to be perfect, those guides will stay like that. High leakdown numbers WILL eventually show on any engine in some point, as early as 10k miles. It may just need fuel cleaner, It may need the head off to address, not necessarily the guides to be replaced. The reason valve guide replacements became notorious is because everyone is correlating high leakdown numbers with valve guide wear without measuring. And now hundreds if not thousands of f355s are just getting them replaced without fact. Just the fact that everyone else is doing it. If in fact JSBMD post 36 had steel guides and were MEASURED worn, a lot of owners should be concerned right now. The answer I want to hear is, “I replaced my guides because I measured and know that it is so and so thousandth of an inch loose” NOT “I replaced my guides because my leakdown numbers were high”. here is another thread of this issue https://www.ferrarichat.com/forum/threads/95-f355-valve-guides-fact-vs-fiction.5554/
It obvious that both worn valve guides, and carbon build up can be causes (maybe a combination of both). One cannot dismiss the guides can be bad, as it is clearly obvious from many noted mechanics that have diagnosed the problem. But worth trying GM Top Engine Cleaner introduced into the intake system, as one inexpensive attempt for better numbers before tearing down the top end. ACDelco 10-3015 Top Engine and Fuel Injector Cleaner 32 oz. – PartLimit I am uncertain any product added to the gas tank would help much. But during my ownership (knowing what was done prior to my purchase) I did add Lubro Moly Ventil Sauber to my tank once or twice a year. Now called "Valve Clean" Liqui-Moly - lm2001KT - Valve Clean - 150mL (ecstuning.com)
And here is a data point: If you think that factory steel valve guides are free from this problem ... I have a bridge to sell you.
I've actually been surprised at the number of those that ended up having issues. In fact I read or heard somewhere they can even cause additional wear to the valve stems in some instances? I have an acquaintance with a late 98 that had to have a top end rebuild.
Happened many times, read many posts where this is mentioned in passing, no thread about it just mentioned in an unrelated post. I would say not uncommon. 355s can be expensive to maintain it seems.
