Sodium Valve Replacement

Hey Folks. Unfortunately, my first post here is to ask for help with a substantial problem. I had an exhaust valve break on number 4 in my BB last week and am faced with choosing what replacement to use. I did a search but don't see any consistent recommendations or preferences based on experience with either SI or Ferrea valves. Is there a concensus? I've had the car for three months, Carobu rebuilt it but apparently put the sodium valves back in and now I'm looking at 20 grand in repairs, so I want it done right. Your help and insight would be appreciated.

Regards, Matthew

Unfortunately I've seen this quite often.

I use SI Stainless whenever I have heads off.

From what I understand what happens with sodium valves is they are designed to transfer heat from the valve head down to the valve stem then to the valve guide then into the cyl head which carries away the heat, for the heat transfer to work properly the stem and valve guide must have close tolerences as the guide wears it creates an air gap that causes the heat to remain in the valve stem and causes overheating and the metal is weakened then gets brittle eventually causing the valve head to break off.

As metioned this motor was completely rebuilt by Carobu with new pistons awhile back I can't believe they didn't replace the valves which are a known issue on these cars.

I read Ferrari started using sodium valves on the 308s in 79 which is the same year as Matts BB due to unleaded fuel, do all Boxers are sodium valves starting with the 365BB?

Ferrari started using Sodium Ex Valves in the 246 Series Cars, The Dino 308's from 75 on and all 308 Models until the 4V's. They also used them in the Boxers as early as 76 that I'm aware of.

>>>>>From what I understand what happens with sodium valves is they are designed to transfer heat from the valve head down to the valve stem then to the valve guide then into the cyl head which carries away the heat, for the heat transfer to work properly the stem and valve guide must have close tolerences as the guide wears it creates an air gap that causes the heat to remain in the valve stem and causes overheating and the metal is weakened then gets brittle eventually causing the valve head to break off.<<<<

This is correct and any old Sodium Valve can break without warning, even at idle speed.

Sodium Valves Should NEVER be reused Under Any Circumstances!!!!!

Didn't the Engine Rebuild come with some type of Warranty??

JR,

This was the car on sheehans site ferraris-online that showed a full documentation of a rebuild and restoration by Carobu but it was several years ago and the car has gone though 1 owner since then, you can still see the restoration and engine rebuild dyno info under cars sold on his site.

Regards

Wow - that really is disappointing if they did not address that then. I have heard that this is more common in the 8 cylinder models, but I did not want to take the chance and I had them replaced with stainless in my 512. I also replaced the intakes with stainless and all guides/seals at the same time. Everyone seems to have varying opinions on this and perhaps Carobu maintained they were not an issue and they must not have shown any wear, otherwise one would have thought they would have been replaced during the rebuild. Oh, and the cost of the new stainless valves were around $50 compared to something like triple that for a new sodium valve.

So what are we looking at here, other than the new valves. A new piston, rings and bearing for it, a new liner, and can anything be done for the head? Or is it just headed for the dump?
I'm really sorry you're have to go through this Matt, especially after having the car for such a short period of time.
And as a 79 BB owner, I'm now suddenly finding myself worried about something I didn't realize I needed to worry about!
I suppose the safest route is to change out the valves before I find myself in Matt's position.
Is there anyway to tell a sodium valve from a standad valve without pulling the engine apart?
Anyone care to guess the costs of a valve replacement job?

I'd like to hear from some of the Boxer experts here as well but here's my take on this motor, its just been gone through less than 3 years ago with maybe 3000 miles, correct me if I am wrong Matt, so it shouldn't need much other than a new J&amp;E piston which was what the OE pistons were replaced with, rings and a liner, the head looks fine and of course replacing all the old valves and guides plus the machine work on the heads.
The main and rod bearings probably are not even broken in yet fully.


If this were an old motor it would be time for a full rebuild which runs around $15k or about $13k if you ship just the motor, Carobu charges around $20k for a full rebuild just the motor.

Since this happened with this motor I would be concerned with other mistakes and things not done properly as well from the rebuild.

Their is an old thread on the sodium valves here and the consensus was its very rare for a failure
to happen on a Boxer motor but much more common on the V8s, who knows what they did when they rebuilt this motor which could be the cause of it.

I would like to hear a explanation of this and why they didn't replace the valves from Carobu.

Hello Boxer buddies,

Yes, sodium-filler valves have been used for a long time in Ferrari and other marques. For many years they were thought to be the hot set-up, as in theory, they did help transfer heat away from the exhaust valves to the valve seats. Hence the life of the valves was extended, as their use pulled some heat out of the combustion chambers.

Over time, the valve stems became britle, and without warning, the valve heads would break off and cause severe engine damage. Due to combustion chamber design, or lack of exhaust valve cleanaces, or even poor machine work at the time of a valve job (i.e. the valve face was cut too thin), some engines (designs) were more prone to failure than others. Indeed, a valve failure on a BB is rare, but I have experienced it first-hand.

Sadly, the solution is costly, but far less expensive than repairing the results of a broken valve.

SI makes a nice stainless steel valve for the BB, as well as other valves for Ferraris. Most BBs have loose (out of spec.) vavle guides to begin with...so this is a good time to replace the guides. Typically, I buy my guides from T Rutland's, but there are other vendors that can provide guides. I prefer to buy guides that are undersized on the I.D., as I can them hone them to the precise clearance I desire. Ferrari specifies .0009-.0019" valve to guide clearance. With the clearances set at .001"-.0012", the engines run sweet, wth near zero oil consumption.

Likely, when the engine in question was rebuild, the valves were inspected, found to be "in specs" and re-used. As part of a normal rebuild, the valve faces are often cut (reduced in thickness) and then are re-used. However, with a sodium-filled valve, this often can lead to a even quicker failure, as now, the face of the valve will run even hotter, as there is less material to disipate heat!

As I mentioned earlier, the life (cycles) of the valve, as well as tight exhaust clearances can contribute to a premature, but never the less, eventual failure.

Perhaps a (false) economic decision was made to re-use the existing valves?

Regardless, to replace a piston and/or liner on a BB is a major undertaking... Engine out of the car, transaxle removed...you all know the drill. Yep...and that rod should be checked for straightness. Sometimes the liner is OK...My fear is always "Were did all the debris go?" Should I dis-assemble the entire engine to clean and check everything.

As to my friend Jeff's comments pertaining to the cost of a re-build...I suspect they are possible, but I suspect low at today's current parts and labor prices.

Regards,
David