Engine making "clackity clack" noises

[bsams]

I learn something new every day. I try not to, but it happens.

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[a64pilot]

Originally Posted by Guy

Nascar sprint cup engines that turn 9500 rpm are using flat tappets. The idle speed is up around 2,000 or so to keep them from digging into the cam. They use very fancy coatings on the parts to make it work at those rpms.

I didn't know that, Formula 1 engine years ago went to pneumatically operating their valves, I assume this means no cams and associated hardware, but don't know, RPM? Who knows.
I like Ducati's Desmo system, elegant but complicated.


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[model 10]

It looks like the rpm of an F-1 engine is about 18,000. If you watch the in car views, it looks like it never drops below about 8,000 rpm.

[a64pilot]

Yeah and I looked up their valve train, seems the only pneumatic thing is they use N2 pressure instead of springs, I though maybe they were pneumatically actuated as that is what I had heard, but guess they aren't.
RPM limit of a engine is limited by piston speed, not crank, so an undersquare engine can turn stupid high RPM.

But engine wear increase exponentially with RPM, so turning the RPM down a little can extend life quite a bit.


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[Cadence]

Originally Posted by a64pilot

Valves do stretch under the right conditions, those being high performance cams demanding very high spring tension to prevent valve float, that along with high temps and they do stretch. Many valves have been pulled in half, often the valve head is a separate piece welded to the stem. Valves if they are floating, the piston head can hit the valve busting the head off too, known as "swallowing a valve", used to use SS valves on budget engine builds as they were one piece valves, and titanium ones on better builds, great thing about Ti valves was if you also used Ti hardware, retainers and keepers, they were so light that almost always stock valve springs was all that was needed to prevent float at even pretty high RPM due to the lower inertia of the lighter valve.
None of this has squat to do with a Marine Diesel, just continuing the engine conversation is all


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Glad you summed it up. I was wondering where it was going.

[model 10]

I am "re-building" our Perkins 107. I noticed it does not have hard valve seats. During the switch from leaded fuel to no lead fuel all the old car engines totally sucked. They needed the lead to lube the valve seats and without the lead the valve would pound itself into the head. I had a 390 ford once that the valves were 1/4" into the head before it finally quit running.
That thing would make some alarming "clackity clack noises" sometimes even with hyd lifters.

[a64pilot]

Car motors years ago went to sodium filled exhaust valves for cooling I think and "Stellite" valve seats as they are apparently very hard.
Now I don't know what stellite actuallyis, maybe a brand name like Plexiglass or band aids?


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[Wotname]

Originally Posted by a64pilot

Car motors years ago went to sodium filled exhaust valves for cooling I think and "Stellite" valve seats as they are apparently very hard.
Now I don't know what stellite actuallyis, maybe a brand name like Plexiglass or band aids?


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Yes sodium for faster heat transfer so I'm told...
Always thought they were crazy expensive and only used in race cars - F1 etc.
Sounds like they have trickled down to road cars - the stuff you learn on CF in a clackity clack thread!

[model 10]

Originally Posted by Wotname

Yes sodium for faster heat transfer so I'm told...
Always thought they were crazy expensive and only used in race cars - F1 etc.
Sounds like they have trickled down to road cars - the stuff you learn on CF in a clackity clack thread!

The exhaust valves stems on some Lycoming aircraft engines are sodium filled. There is a note in the service manual to not nick the valve stem while grinding, as the sodium catches on fire when exposed to air.

[jamhass]

Originally Posted by a64pilot

Now I don't know what stellite actuallyis, maybe a brand name like Plexiglass or band aids?

Stellite is a particular steel alloy, very hard and high temperature resistant. Not worth going into all the details re crystal structure etc etc here ...

[four winds]

Though it is a trademarked name of Deloro Stellite Company.

They produce a range of alloy compositions typically with chromium and cobalt mix.

Stellite Alloys - Chemical Composition, Mechanical Properties and Common Applications