Quick check --- sodium valves only on exhaust on 308 carb/2v, not on the inlet side. Right ?
I don't own one Project is on hold, maybe I will ask you in the future where you got your fiber panels to make my 308 more or less original again...
also 2v injected, My personal comment is that the fear of sodium valves is without validity! I changed mine out on our 82 and after inspecting all I think it is a witch hunt!! lost
Any Tech here can give you documented failures of sodium valves. In the same breath one I greatly admire said, 'stay well under the Red Line and chances are you will be fine for many years to come. Push or exceed it, and we'll probably meet under unhappy circumstances sooner or later.' Take that as you will.
Hey Lost, how goes it I don't know much on the fear factor, but my personal run-in with the witch... It turned out to be a good thing. Got my fingers in all the holes Image Unavailable, Please Login
Forwhat it is worth I tried breaking the EX valves by throwing them against the concrete and aslo holding in a vice and hitting with a hammer. My point is how many failures are caused by an interference issue and how many have failed due to fatigue? I can only wonder and as the PP said keep her below the redline and all will be well. just sayin, Lost
For anyone not quite up to speed on issues of metallurgy and engineering principles, FWIW here's my take: the point of filling the hollowed-out critical part of the valves with sodium (a very volatile metal!) is this: at high temperatures, the sodium melts and travels up/down the interior of the valve by heat convection, like water in a heating system, acting like a very primitive cooling system, transporting heat in one area to another, (slightly) cooler area, where it cools down that part of the valve stem and so becomes a heat exchange cycle. This removes some heat from the hottest part of the valve, where it's also the weakest. Keep in mind that the hotter metal becomes, the weaker it is,and less able to resist stress. Fine so far, but of course valve stem metal had to be removed to do this, and at some point the heat exchange process no longer compensates for the reduced strength of the valve stem due to there being less of it. At some point this crude cooling system cannot keep up with excessive exhaust heat, the valve stem cannot take it anymore, having reached the metal's temperature failure point, and there goes the valve. Sodium filled valves have since been replaced by better valve materials, and also- I assume- by controlling combustion cylinder temperatures somewhat by cylinder head redesign. Having 4 valves per cylinder rather than two contributes to valve longevity, there being more valves, and so valve stem metal surface- to cope with the combustion heat. Another factor is the metal fatigue cycle, meaning metal can only undergo so many cycles of stress and temperature changes before failure occurs, like the structural elements of high-performance aircraft and airliners, especially pressurized ones. It's like bending a metal rod a lot, until it finally fails and breaks at the bending point. So that easily explains why the valve fail in some cars, not in others. It's all a matter of how far one pushes the vehicle to its particular limits, and for how long a period. No stress, no failure. Lots of stress.... Hope this helps. Sorry for the lengthy discourse but not everyone has been exposed to detailed explanations that would help them to understand the engineering principles involved. No voodoo, believe me! BTW nice photos, E-Dino & carl888! Cheers, Rich
Hey Rich, thanks for the good write up. For my case the most probable catalyst was a plugged cooling passage in the head. The water jacket was a chocolate mess. Change your antifreeze on a regular basis boys.
I hear you! They are still using them. Just my opinion and I think there is room for discussion. Lost
There are no 100% probabilities in the world of predictive failure analysis. I think a good approach --- at least this is the one I advise folks when they ask --- is not to tear an engine down just to pro-actively replace the Na valves, but if you already are tearing it down for another good reason, and the engine has a good amount of wear on it, then it is a good idea to do it ---- it won't be adding a lot more cost to the job at that point. IIRC, you can get a set of SS valves (exhaust only) for around $500-600 (less if you shop around). Of course, you will also likely want to replace the guides, too.
Rich, the only problem with sodium filled exhaust valves in Ferrari engines is Porsche, Mercedes-Benz, Audi, Lamborghini, BMW and countless others have used sodium filled exhaust valves without issue since WW2. Not to mention numerous competition and aviation engines for over 50 years. I think the problem with the Ferrari valves is not the fact they're sodium filled. But rather how they are assbembled. In the picture I posted you can see the break is just proud of the tulip. Every failure I have seen has been in this area. Further investigation reveals the tulip is actually spun onto the stem. A Mercedes-Benz exhaust valve for example is one piece except for the very top of the stem which is welded. It's some 10mm away from the collet grove. There seems no rhyme nor reason to the Ferrari failures. That valve of mine failed on the bench, I just tapped it lightly holding the stem and the head snapped off (along with a small pyrotechnics display courtesy of the sodium). In my own engine, it ran fine, about 70,000 miles. My friend has a 308 GT/4 that's used in anger with the original valves. Yet other engines can have failures just turning the engine over by hand. Chances are if your engine hasn't blown up by now it's possibly fine for the life of the engine. My personal opinion is that using possibly and Ferrari in the one sentence doesn't really bode well for the long term enjoyment of the vehicle. It's also important to remember that it's not just 308 engines that suffer this problem, it's 246, all 308, all 365 series, Boxer, 400, 412 all the way up to the introduction of the Quattrovalvole engines.
Good responses, but I must say that I never meant to imply that sodium filled valves couldn't work or were always to be held to be troublesome, but rather to point out the issues involved, regardless of who made them for or for which particular application they were intended. Another way to look at the issue might be this: Porsches, for example, have had the reputation of being very fast cornering vehicles, right up to the limit of adhesion- at which point the rear tended to come around, very very quickly, with nearly no warning at all. True or not, the point is that the tradeoff was to provide higher ultimate limits of cornering, at the sacrifice of warning the driver of impending loss of control. So in the case of valve design, there it is- possibly higher limits of valve failure, but very COMPLETE, immediate failure at the limit point. I have no data at all to support this idea (perhaps others do, either way?) but anyway that's the idea I suggest here. Regardless there seems to be somewhat less controversy when non-sodium filled valves are employed, for whatever reason. Yes..no??? Cheers, Rich
My GT4 will be 40 years old next month. I was stressing so much about the exhaust valves I decided to pull the engine and change them out. The engine came out last August. There is a thread about my progress. http://www.ferrarichat.com/forum/308-328/458208-observations-gt4-engine-pull.htm In the process I've found several problems: two cracked valve thimbals, worse than bad fuel filler hose, and who knows what other problems lurk in there before we turn the corner and begin reassembly. I have the time, I'm an old retired guy and I still have a passion for this car, and I want to be able to depend on it until I pass it on to one of my sons (if either one wants it).
@ Rich --- Everything you say is very true. Also, worth noting is that not every application is the same in terms of how a valve may be stressed / loaded. The overall configuration Ferrari used on the 308 valve train obviously is not ideal in this regard ---- because failures have indeed happened. The fact other makes / other engines with Na valves have been robust is not all that relevant. Not really apples and oranges, but definitely "green apples" and "red apples". Also, the exact design and manufacture of the specific valves Ferrari put in the 308 could be unique. There could be weaknesses in baseline design or in the manufacturing process that makes these particular valves less robust than others.
We changed the sodium valves out while we had it apart. There is a new sodium valve being made now apparently to very high standards and also very high price. We went with the standard steel.
Apologies for resurrection of this thread . I took my 42 year old ( new ish to me ) GT 4 208 to a highly regarded U.K. independent . I enquired about the alleged sodium 2v Ferrari myth Issue . The response that came back was the principal has only seen 1 in 40 years and the senior mechanic of over 30 years never seen any .Nor any of the 1/2 dozen or so younger techs . They race prepare cars and generally have 20 + in the shop at any one time and book 3/12 ahead for routine work . They are F40 specialist and owners ship cars from all over the World for service and work such is there F car authority. I mentioned the armchair forum favourite banded about on the Internet, of worn valve stems leading to a bit of shake = stress concentration. They replayed nope ! They think Ferrari unlike 70.,s Porches/ BMW ,s etc had issues because of a very slight miss alignment at the cam belt change , basically folks not quite following the factory method , taking short cuts and there verdict was it’s critical to check and recheck the timing any thing that may alter that at a belt change could in theory be so slight it does not cause catastrophic failure straight away . Instead steadily just by a gnats whisker over stressing the valve stem . This might explain and join up the dots of the various posts ^^^^^ ?
I think several things contributed to the failure of some valves: 1) The weld is at the bottom near the head, one of the hottest parts, 2) this is where air was injected for the catalytic converter cars (further heating the weld area, 3) the valve guides are soft, wear prematurely and allow eccentric valve closing which induces bending moments in the weld area leading to fatigue, 4) valve springs are stiffer than they need to be (higher rate before anyone gets their knickers in a knot) so the eccentric closing is exacerbated. With good guides and/or no air injection they are probably good for the life of the car... if you're lucky and the engine has been looked after Expensive servicing has probably meant deferred maintenance for many cars which adds to the problem.
totally unscientific but when I stripped my 2v engine for a rebuild I put a few valves in the vice and gave them a tap with a baby sledge. Here is the result. Note how the valve seemed to already have a crack around the join. This from a tired 65000mile 2v engine. I'm passing no judgement but when I rebuilt it it was stainless steel valves all around.
I admit to being an overly cautious person. I wasn’t enjoying my 2 valve car worrying that a missed shift, a few too many redline escapades or bad luck would end up in turning my expensive toy into a parts car. I now have a 4 valve car without those pesky valves, I sleep better and rev it with less worry. I think it all depends on your ability to “BE HAPPY, DON’T WORRY” and “DO YOU FEEL LUCKY” Now I just worry about timing belts, texters, police, gawkers, etc Just my .02
Thanks for sharing Guy. Supports what I've seen and read-- clear signs of fatigue propagation. Were you guides also loose?
