Sodium Exhaust Valves

Hi,

How risky is it to keep the original sodium-filled valves in a carbed 308? I vow to always make sure they are adjusted properly (i.e. not too tight so as to transfer excess heat to the heads). How much would it cost to have them replaced (approx.)? I have a '76 308 with 21K on it that runs extremely strong and is smooth as silk right now.

If an older engine is running fine I really try to avoid scaring the owner when possible, however when they just come out and ask as you have I think it's best to give the facts that the sodioum valves are certianly capable of breaking off without warning or reason.

IMO the guide to stem rocking that occurs, along with the embrittlement of the stem to head area is as much or more of the culprit than valve adjustment.

Sorry.

Thanks..

How much would this cost to have done (for preventative mantainence)? $3K, $4K?

Hi Anthony,

by yourself as a DIY project or in a shop?

Either way it's a pretty large job. While it may be possible to get the front head off in the car, on the early cars I pull the engine. Steam Clean the heck out of it, then pull the heads, send out to the machine shop for new guides and SI Stainless valves, plane the Intake Manifolds bottoms to head surfaces (if the slightest warping is found), all the misc. servicing, like new hoses, water & fuel, Carbs, Carb Bases & Gaskits, Distribs, etc., then back in the car. I think realistically one could spend 40-60 hours on the job depending on conditions plus the machine work, plus the parts, Gaskit Set, Ex. Valves, all guides, belts, tensioner bearings (if needed), hoses as necc., valve adj. shims, etc.

I think parts & machine work could easily run $3K alone.

HTH's

Regards, JRV

Hi, I have visited this great board very frequently and now it is time to register. When I see the level of expertise here I will probably be more on the "information receiver" side than on the "information provider" side. Some years ago I have studied some automotive engineering in college, so maybe I can contribute with some theory, if this helps.

Back to the thread:
I plan a major inspection with my '75 GT4 this winter and it looks like it is a good idea to replace the valves. My engine needs about 2 litres oil per 1000 km, so I guess the valve guides/seals are worn/hardened anyhow. Is there any special type of valve you can recommend? And do you use the OEM valve seals or are there better ones?

Regards
Harry

Hi Harald, Welcome Aboard !! I hope you will feel as free to help us from your experiences as we do sharing ours.

To your valve question:

When the heads come off an older Ferrari Engine that used sodium valves they should be replaced with Stainless Steel Valves.

SI Valves seems to be a good source for Stainless Ex. Valves as well as guides and seals.

There web addy is www.sivalves.com

As to the seal question, the debate rages whether rubber or teflon is the best, my personal preference is the teflon as they allow a little oil in while causing little friction on the stem. There are many arguments that can be made for either type, so truthfully on a street engine it's hard to say one is best or better, because a head is rarely if ever taken off due to simply seal issues, unless they were improperly installed somewhere along the way. When someone says their guide seals are causing oil consumption what I see generally is a fair amount of guide wear that is more likely the culprit imo.

You reminded me I need to put the SI Valve link in the Resource Area..thanks.

Glad you like the atmosphere here and hope you'll hang around.

Regards, JRV

Do the 79 308's have the sodium valves?
Thanks,
Jim

yes, they do...all carbed cars I believe...


Anthony

JRV

Are sodium valves a real issue for BB512 Boxers? Several people have mentioned to factor this cost into the purchase price if buying a Boxer. What is a ball park figure to replace the sodium valves in a Boxer?

Ken,
Sodium valves can be an issue for most, if not for all cars that use them. Virtually all Italian cars of the late 60s, 70s and early 80s used them. Personally, I had been running sodium valves in my 365BB for almost 20 years without any problems...as well as countless race-preped Alfa motors.

During a recent rebuild, we did change them out to conventional SS valves, as well as guides, seals...and all the other worn components.

Factor the cost (of replacement) into the purchase of the car? Sorry, but that doesn't make alot of sense to me, as the market has already determined the fair value of these cars...potential engine issues aside.

Ball park:
Remove engine for typical 30K service
Remove heads
Replace all guides and exhaust valve
Check heads for line-hone
Check cams-repair lobes/replace cams as needed

$5,000-12,000, if doing a complete service

Would I personally pull the heads off a known solid engine BB because I suspected sodium valves...likely not (and I didn't)

Regards,
David