Heard a crunching sound and now im waiting for roadside assist.

hey Mike,,,i was not aware of the belt problem you speak of,,,im sure there might be threads on here,,,but can you tell me what the problem was ., and the years,,thx,,,Brett

 

I'm being a little sarcastic...Ferrari used timing belts on the 3x8s and subsequent cars but the 458 Italia uses a chain. I believe the 430 was the first to go "back" to what worked better but I will defer to the real Ferrari experts re that.

The issue is simply that the belt does not have the longevity or the reliability of a chain...as Ferrari finally figured out and "admitted."

 

I am a big fan of the timing belt. As it is, many 308s and mondials are lessons in deferred maintenance. If not for the belt literally forcing many owners to do basic maintenance on their cars and look beyond changing fluids, imagine the condition these cars would be in.

Now sodium valves...not a fan

 

I may be wrong but I read that timing belts have been used to dampen vibration harmonics in high rpm, stressed engines.

Chains tend to transmit and even assist with damage that can be caused be vibrations in an engine at certain rpm ranges.

Chain engines are designed differently to dissipate , dampen or redirect damaging harmonics in the reciprocating masses.

At least this was true in the early-mid 1970's


Things have changed a bit!

ps: How much, real world, cash for :

used QV engines?


used 3.2 engines(328) ?

Just wondering.

 

im no engineer,,but your post sure makes sense,,,,although i agree with mike about the better reliability of a chain,for me,,my last set of belts had apx 28k miles,,and about 7 years,,,i asked the mechanic to save the old belts,,they were a bit worn,,,but in no way shape or form,,,were they ready to break,,,and the tensoner bearings were also in ok shape...

 

Rebuilt QV engine and trans with 2500 miles, EFI, and Electromotive TEC3 - $29,500. Rest of car for free. PM me if interested.
P.S. - 1983 GTS in great shape and is track ready. Turbo components also available. So is trailer.

 

sounds neat, but I bought a 328. - nothing wrong with the 328, but I have always wanted a hot rod 308 GTB, like the Michelotto race cars. ( but for the street)

 

Hi Mark,

I sent you an email with a link to a rebuilt 308 engine with carbs up here in Toronto. 12K for it with 2500 kms on the rebuild.

If thats no good I will keep looking.....

 

Way back when I bought a 246GT with an engine that had dropped a sodium exhaust valve. Fortunately, the valve head stuck in the top of the piston. The owner actually drove it from the Sears Point track to San Jose (75mi.). I was able to save most of it. Did a weld repair and refinishing of the head which was badly nicked but not cracked, replaced all the valves and pistons .. a slight overbore removed the slight damage to the cylinder wall. Balance, reassemble, new timing chain, etc. and it was a very strong motor. So there are alternatives depending on damage .. I was lucky.

 

Ok - so a few questions:
1 - How do you know if you have sodium filled valves? Can you tell by the stem? I.E. without removing the heads?
2 - So if you dont know if you have them, the revs should be kept below 5K?
3 - Is the failure mode from fatigue from high RPM operation, from valve clearances not set correctly / not adjusted?
Thanks

 

all 2v Ferrari engines have sodium filled valves. This includes the BB512i as far as I know.

4 valve engines do not have sodium filled vales, neither do the more modern 5 valve engines.

RPM does not protect you. a dropped valve at idle can damage / destroy as much as one at 7700 rpm, though the small bits scatter farther in the engine at high rpm.

Usually the joint where the head and stem meets cracks and the valve comes loose in the head. The pistons are fragile and there is no extra room in there, so poof goes the piston.

I have been beaching for years that the 2v cars are overpriced as all of them are do for valve jobs due to age at this point. We replace stuff on aircraft due to nitrogen embrittelment fatigue cracks, yet cars are not going to suffer these same effect?

so how about a "original" 1976 308 now? 246 Dino? Aint worth it if they have not had a valve job. Too many other better cars to buy for the money than a Ferrari v8 hand grenade.

25+ year old cars with little highly stressed engines need more than diaper rubbing to be used properly.

 

Actually....... I think they worked too well and out lived their expected life. With the metals of the day, this was a method to build a light weight valve that would endure the heat of a highly strung engine at high RPM. As metallurgy advanced they were able to build a valve capable of dealing with and transmitting the heat effectively to the guide and such the cooling jackets of the head. Transmission of heat from the valve to the cooling jackets is the ultimate goal and the sodium filled valves were high technology in that era.

The timing belts....... those were brilliant and are the reason these engines were able to rev to the limits they are. Carreaper is correct in that their design was very effective at transmitting the rotational requirements to the cams without also transmitting harmonics from the engines lower end while also reducing rotational mass of the components in the system.. It is the generated harmonics from the lower end that limited the valve trains ability to hold the valve seated at high rpm.... well beyond the 308's stated redline.

One has to study chain design to appreciate the belts. Roller chains transmit the rotational forces very well but do very little to dampen harmonics and generate their own as they turn. Morse type chains as used in the F50's are less susceptible to transmitting harmonics but are gear eaters by design, thus limiting their useful life. Chrysler (foggy memory?) used the Morse designed chain on the slant 6 (ultra low rpm) but had to use plastic gears because all of the metal ones would crumble as soon as the case hardening wore through.

Resilient, economical, lighter weight with less rotational mass and easy on related parts. Careful what you wish for, the belts were used in an era when disposable technology was only being considered for lesser cars. Today planned obsolescence is a design requirement. Gripe about having to replace the belts but appreciate why they came about... chains predated the car by some 500 years. Ferrari choose to change to belts from chains and job security had little to do with the decision.

 

Sodium valves were fine for race cars/airplanes where the maintenance schedule pretty much takes care of the downside. Street cars do not get that maintenance. What works great in an engine that is serviced every outing or every few hundred hours and operates in a relatively narrow range of RPM/temperatures is vastly different than what will survive for 20+ years in a street car.

The same is true of belts; the belt superiority theory sounds great but in practice chains/gears are far more reliable and longer lived. There are tons of stories about broken cam belts and darned few about broken chains.

 

I have a Daytona Competition engine on the stand that suffered a separated valve head at redline. The head dropped onto the piston and was turned 90 degrees and pushed back into the seat sideways. The result was a cracked seat and a dent in the piston. Considering the value of a factory Competition engine for a Daytona.... some folks are very fortunate, others... not so.

I also have my 77GTB engine on the stand that suffered the same fate leading to me buying the car as a project. Upon removal of the head what was found was a Connecting Rod with the wrist pin still in place but no piston ( (s), two were affected) to be seen. With no piston to guide the rod up the cylinder...... it flopped about where ever it wanted to.

Every failure of this nature I have seen over the years occurred while at, or moments after a high RPM rev of the engine.... thus my suggestions to limit the RPM's until the valves are replaced. Given today's value of the 2V cars this replacement is difficult to justify if logic is used in the decision process. Given I have a non justifiable passion for the Carbed 308's.... I figured if the job had to be done then it was the perfect time to find a way to update this lump with more power. As with the never to be matched style/sound of the 355, I rather doubt an equal of the early 308's sound and style will ever be made. A justifiable exercise? No way, just a passionate one and only history will be the judge on the value of the effort.

This thread ought to start a shlt storm debate of the 2V vs 4V cars, their value, the sound and style..... At least we need not involve logic or reason in those discussions as those went out the window the day the car was purchased.

 

Longevity was quite a ways down the design requirement list when the 308's came to be, ultimate performance and style drove the design and raised the bar in the day.

I have to agree and disagree. "Stories" is an accurate term as to date I have yet to see a belt fail on its own and I have been working on the Ferrari's since the 308's were new. I have seen "caused failures" from other components failing but not a belt on its own. CORRECTION: I remember a few that pulled the teeth off the belt around the drive gear now that I think of it. OLD and brittle those belts were! Owners gripe about belts because there is a risk to not performing routine scheduled maintenance. As an owner of a number of belt driven Ferrari's, I too agree with the pain but appreciate why they are there and what that allows.

If the debate is on Longevity and Reliability.... we are in full agreement. There isn't a slant 6 Dodge ever made that wouldn't break 250,000 miles with the original chain in place. Aircraft, and Chrysler for that matter, run sub 4K redlines.... a whole different design. In no way am I defending Ferrari's designs, they did some pretty meat headed things and played CYA on many designs. I just happen to think the belts were a well thought out idea for a high RPM engine.

 

We're repairing one of our race car heads from a dropped Ti valve. The motor was fresh (under 16 laps at sub 5K rpms) from a rebuild, and it looks like the exhaust valve seat popped out. The exhaust valve struck the intake valve, and the valve heads were broken off and lodged in the chamber. The piston head was chewed entirely through. The chamber itself was pretty beat up, too. All re-welded and re-machined. New valves were ordered, and many were returned. It seems even new, out-of-the-box valves are looking suspect. The biggest issue was that the oiling galley was punctured. However, it's been repaired and pressure tested (@ 2x the normal psi), and it's holding fine.

Moral of the story? It's amazing what can be repaired. Or, maybe re-builds are a bad idea?

CW

 

... have other valves than the 308, yes smaller. Are they also of sodium type?
/Pero