dumb question of the day...

My 390 heads came off cuz i was loosing oil. All the valves were way loose in the guides and the seats were sunk. Still ran, and i am surprised cuz i beat the piss out of it.

MarksFastBack said:

So if you have an older engine and it has sunken valves

...it is because of unleaded gas? No other reason?

How about
..hardened seats prevent sunken heads...because the seats are hardened, regardless of gas

How about
...soft seats get sunken valves... because the seats are soft and not because of gas.

I guess I do not go with assumptions.
Perhaps around the time unleaded came out the engines were getting alot of miles on them and that was the reason.

Antique boats do not have the market cornered on the lead gas issue either.
However they do not have the same amount of run time.

Unless I see an actual test from a new soft seat motor and the test shows it had immediate problems leading to sunken valves, then I must contend observations that state examples of sunken heads and point a finger to the gas is presumptuous and hind site with out "actually" knowing.

How about pointing to soft seats and high hard miles? With this scenario it lends a hand towards
"How" the miles were put on, and not
"That" they were put on
...and this seams more logical bases as to why only "Some" engines have this problem.

Because...it would seem logical that if it were the gas "All" would have sunken valves if all were now using the damaging "unleaded" gas.

Click to expand...

Well if all us didn't convince you, by all means go ahead and run unleaded gas with no kind of additive that cushions the valves hammering the seats and when it eventually swallows a valve, let us know. The article you posted sounds like it was written by an enviromentalist trying to fool the public into thinking more bad things about the "evil" oil companies. You're also trying to think in logical terms and that's a mistake when it comes to things like combustion processes and metal on metal wear. Things happen all the time that seemingly defy explanations in engines. The whole process is a vast combination of things happening that do so in a random pattern, you can build two identical engines and run them on the identical fuel at the same time and one will quit before the other. Why is that?

Sheesh, Marksfastback, yer making my head hurt. You have presented a number of questions, and if you are looking for a definitive answer that covers every scenario that has ever happened in the entire free world, you're not gonna find it.

These things happen in trends, it's not empirical. The trend is that since unleaded gas has been introduced, cylinder head builders and machine shops have seen a great increase in the number of sunken valves if pre-unleaded gas heads, as well as have hobbyists like me and Hearne who have been through dozens of heads in the last 20 years.

Does that mean it it true in every case? No, it doesn't.

You are over thinking this. Quit looking for the perfect answer, it doesn't exist.

But the gentleman does make a valid point.

For all we know the valves would have sunk even if led gas had continued to be the norm.

I can easily rule out high rpm race motors and high mileage motors being the issue. My 70 was a 351c 2v motor owned by an elderly woman until the early 90's and a family friend until 2004. It never saw a race, and had 100k miles on it when I got it.

http://www.walshcarlines.com/pdf/mechanicalimplications.d4e.pdf

Yes, it "could" happen. There are no absolutes.

yes I do tend to over think things.

My new roller Engine has new Eddlebrock heads...so I am truly just analizing an issue that has many answers (the more I research the more I learn), my car has hardened heads.
A moment ago I read something here that touched close to what I was thinking.

Perhaps by the time unleaded gas came out, some heads wear starting to wear in already.

Earlier year cars with leaded gas may have worn in as well( I have no way to know) those earlier cars from the 50's tended to be fairly traded in before they would spend money to have them rebuilt (my thought).

Hang in hear for one more thought please. Could the problem be with using a cheaper blend of steel for the making of heads....or do cars from the 50's classic era show sunken heads as well during the unleaded introduction.

If...and I say if...this be the case, time may have taken a toll on these heads with leaded gas, and then started showing its demise in later years, laying it square in the face of unleaded blame as a coincidents.

I guess I feel it may be presumptuous to see sunken heads after cracking open an engine and blaming the fuel. WAIT It may be a possibility as well as leaded gas may be the culprit. As cars got more expensive , people started having them rebuilt. This may have been the case in earlier years if people drove as much as the future cars started being driven in a busier world. People lived in shorter driving distances from work and were still rural. The same people did not abuse muscle machines as much...things were tighter.

hey...I am just saying that there are many variables than just one blame.

ya know it might be the unleaded.

...Everything mechanical is logical...emotions are not logical...if I am wrong about the logic thing, then perhaps the unleaded thing that seams logical ...is not. Thanks for letting me chat and learn.

P.S. I am not an environmentalist...I shoot deer every year...I cut down trees cause they regrow (and they are a good source of heat)...I have never hugged a tree...The polar areas were warmer in the 30's than they are now.

Your Edelbrock heads need hardened steel inserts because the heads are made of aluminum. But wait, since the heads are aluminum, why use steel valves? Why not aluminum valves? You get the point? Stck heads aren't made from steel. They're a cast iron alloy. Steel valves are harder than the head's iron. This was the two materials used for decades before the 70's introduction of unleaded fuel. The lead additive had two functions, seat wear cushion and octane booster (it's Tetra-ethyl lead, not just lead) It was a compound that combined two products (perhaps more, I ain't a chemical engineer) to serve at least two needs in an engine. It was discontinued for two reasons as well. Lead was found to be hazardous, and with the smog controls and engine detuning going on in the 70's (you had to have lived it, in case you were too young to be there) Their wasn't a need for the octane booster either. Wasn't till the mid 80's came around that the auto makers found their way back to performance oriented cars and by that time the computer controled engine has been able to perform with a lower octane rating (like my 2006 GT Stang,it's tuned to produce 300 hp with 87 octane gas ) so there's still no need for the earlier additives (I'm sure they came up with better alternatives since too anyway) If you want an answer to seat wear "back in the day", hunt up a couple of "old timer" machinists and ask them. I'm sure there was some seat wear then too, just not as much. People then tended to run engines into the ground in some places, some rebuilt, some traded them off, it all depended on their personal finances just as it does today. You're searching for a definate answer to an indefinate question, you may never know the total truth. Just the mere facts of the use of hardened seats in iron heads coupled with the introduction of unleaded fuel should give you an answer to your question. The author of that article sounded to me like he was making a case for the use of lead additives in motor fuel, some sort of conspiracy by evil corporations, instead of an intelligent explanation for something.

Very well said.

Well said or I'm a very good bull ****ter ? I ain't got all the answers (yet ) But I try.

Supposedly there are potassium and sodium compounds that can be added to gas to serve the same exhaust seat lubrication that tetra-ethyl and alkyl lead did. However, that seems to be of less importance now probably every engine built anymore has hard seats. Also worth noting is the emergence of catalytic convertors meant that lead just had to go or they clog up.

Ethyl-tertiary butyl ether and methyl tertiary butyl ethers are used as both octane boosters and oxygenators. They have more energy per molecule than the ethanols and methanols they are made from, so it is added to gas in order to reduce emissions and increase octane. Now that MTBE is being phased out, everyone is looking to gasahols.

If you want a few hours reading, check out this ~49 page Automotive Gasoline FAQ. I found it by researching using diethyl ether as a high-octane fuel like alcohol. Ether is impractical, but I did find outt hat toluene has an average octane of something like 148!

I used to think that higher octane (associated to faster performance) ment higher flamable type fuel.

In reality it actualy means less flamable...or requiring a higher compression to ignite.

Is this correct

...

No, it's just as flammable as low octane and usually burns just as fast. It is just more resistant to breaking down into knock-prone compounts at lower temperatures(lower being ~400*C/750*F). That means that the heating of compression has to reach higher temps(over 600*C/1100*F+) before the fuel will autoignite, translating into far greater tolerace of high compression ratios and/or boost before autoignition is a risk.

There is a ton of chemistry going on inside a cylinder.

hard seats/leaded gas

I am not an old timer machinist(started in 74) but I do see old heads and they tend to have sunken/eroded seats also. I don't see as many as 70 and yes 80+90s heads but that is because there not as many and they don't get driven as far or as hard. My understanding is that the lead reduced the micro welding of the valves to the unhardened seats (valves dont tend to wear as they are much better material than cast seats).you see it more often in trucks (high load) or cars that are driven at high loads (towing ).I also read an article in a machinists publication that (memory fading ) implied that once a car was run with lead the seats were treated /impregnated and unless reground or abused as in subjected to high load they should hold up well. I have no training as a chemist but i also seem to remember my Father who was a chemist telling me that the tetra ethelene was for octane boost and the lead for lubrication (may be wrong word) of the seats. last but not least if you do go to a machine shop for seat inserts make sure that the shop installs hardened alloy seats as I just removed cast iron inserts from a 68 302 that were sunken (yes they actually sold cast iron inserts )