What is the prospective test mill?
Again: Unleaded or leaded fuel for mid 70's /6?
- Thread starter SlantedMark4
- Start date
-
Scody21
Just send it
Since you most likely have the thingamjig up and running, I’m motivated to finely pull my mill out. Drink a few ginger ales, run some power pulls and test some fuel on it before we finely put those heads you ported on…
Rat Bastid
Dunamis Metron
LETS GET IT DONE!!!
Rat Bastid
Dunamis Metron
I can’t say but we made two quick pulls and at first glance the AV gas is making the same power as Sunoco 110 and it’s a damn sight cheaper.
Its colder than a well diggers *** outside so in the morning I’ll pull the plugs and get a look.
How exactly do you know how cold a well digger's *** is? .........I recant that. I don't wanna know.
Schyrjajew
Well-Known Member
Never had any problems
slantsixdan
=..=
1972 for V8 engines; 1973 for Slant-6 engines (link is to Chrysler publication on the subject).
In the US and Canada since about 1975, the published octane ratings are AKI, antiknock index, which is the average of the numbers resulting from two different test procedures. One is called the RON (research octane number); the other is MON (motor octane number). The RON is higher than the MON for any given gasoline.
In most of the rest of the world, published octane ratings are RON. So any given gasoline will have a higher octane number outside than inside upper North America. The RON is usually about four to five higher than the AKI, so the gasolines typically available at sea level in North America (87 regular; 89-90 mid-test, and 92-93 high-test) equate to approximately 91 regular; 94-95 mid-test, and 96-98 high-test elsewhere in the world.
With an unhardened exhaust valve and seat, the valve and seat can micro-weld to each other if they get hot enough. Lead halides act as a buffer (a physical cushion/barrier) to prevent this happening. The important thing is that exhaust valve and seat recession only takes place when the valve gets hot enough to undergo localised welding. Then, when the valve opens next, the metal pulls apart like taffy. This roughens the meeting surfaces, and they become quite abrasive. The pounding/turning of a valve with this kind of "pulled" metal on it creates a nice grinding wheel effect on the seat, which is the mechanism behind valve seat recession. In addition, the roughened surfaces no longer seal against each other properly, which eventually allows still-burning combustion gases to flow through the closed valve, causing a blowtorch effect and depriving the valve of its chance to cool while it's on the seat. The blowtorch effect deteriorates the seal further, snowballing the seat recession.
The main thing to remember is that this bad stuff cannot happen If the valve never reaches the crucial temperature. Whether the valve reaches the crucial temperature depends on how the engine is configured (how big is the exhaust valve, how much head metal surrounds it for heat transfer when it's closed, how well is that metal's temperature managed by coolant flow) and how the car is driven and used—towing, drag racing or pedal-on-the-floor hauling will heat up the valves much hotter than driving around town or on the motorway at more or less constant normal speeds.
The Slant-6 has ample exhaust valve seat cooling and stout valve material, and the valve itself is small enough relative to the combustion chamber area that even with a pre-'73 head, without the hardened seats, you'd really have to abuse the engine before things heat up to the danger point.
Very little lead was required to prevent the localised welding effect that leads to seat recession. The majority of the lead was in the fuel as an octane booster, that's all. It was widely used because it was a very cheap and very effective octane booster.
When unleaded fuels were first widely introduced, there was generally only one grade of unleaded available, and the octane was sometimes less than that of leaded regular. We all know that when you use a fuel of insufficient octane, your engine pings. This creates tremendous heat in the combustion chamber, enough to push the exhaust valves to the crucial
temperature.
Because for quite a while only unleaded fuel of subregular octane was available, plenty of people experienced these effects from using unleaded. While many of those engines that suffered under this low-octane unleaded really did need the lead (high load and/or high-RPM engines), the bulk of the failures were due to the low octane increasing combustion chamber temperatures. And so the myth was born that old cars' engines will inevitably die if run on unleaded.
These days we have wide availability of high-octane unleaded fuels, so the insufficient-octane cause of valve heating and subsequent localised welding is no longer a thing.
if you have an old car that is a low-stress application , used in daily-driver service, then just use whichever octane grade of unleaded fuel your car runs well on and drive it for a loooooooonnnnnng time with no valve or seat problem.
The factory's induction hardening was just fine for the original service life of the engine, plus a valve grind/head rebuild or two, but the hardness is about 0.040" (1 mm) deep, so eventually it gets ground through.
The way to eliminate even the possibility of valve heating causing localised welding and subsequent seat recession is to install hard exhaust valve seat inserts and exhaust valves of upgraded material. This is utterly standard practice in the rebuilding of cylinder heads, and has been for years. It is foolhardy to rebuild a "leaded" cylinder head without these upgrades, which are not expensive.
But there's no reason to tear into the engine solely to install hard seats. There is no collateral damage from seat recession. Drive and enjoy until a problem develops (if it ever does), then address the problem.
You do not need additives, and won't benefit from them. "lead substitutes" are largely useless. Some of them use a sodium salt and claim to duplicate the buffer effect of lead, but can't substantiate the claim. Some of them use MMT (methylcyclopentadienyl manganese tricarbonyl), which is highly toxic, is of highly questionable benefit in buffering exhaust valves, and tends to foul spark plugs. Other additives are simply octane boosters of varying effectiveness
and varying side effects.
100LL Avgas for racing is fine if thats what the engine likes.
Avgas for the road is not allowed. If you are using it, keep your trap shut or you will lose your supplier. While the EPA may not sniff you out, the revenuers are out looking for shanningans like that.
Race fuels are pretty much the same situation, regardless of the TEL content. Occassionally there are exceptions but its rare.
This why you can fill fuel containers but not pump right into the fuel tank - unless you're at a race track.
Avgas for the road is not allowed. If you are using it, keep your trap shut or you will lose your supplier. While the EPA may not sniff you out, the revenuers are out looking for shanningans like that.
Race fuels are pretty much the same situation, regardless of the TEL content. Occassionally there are exceptions but its rare.
This why you can fill fuel containers but not pump right into the fuel tank - unless you're at a race track.
33IMP
Well-Known Member
I haven't read the whole thread.
Has anybody pointed out that his Switzerland gas is probably rated differently than ours? I'm guessing his 95 and our 87 is about the same.
Has anybody pointed out that his Switzerland gas is probably rated differently than ours? I'm guessing his 95 and our 87 is about the same.
Dartswinger70
Well-Known Member
I dropped off a set of J heads at a machine shop right before new years . I mentioned hardened valve seats the machininst was like "you don't need em..." I said "good , I've seen them drop out of aluminum heads and cause all kinds of problems."
If he waded through slant6dan's post, yes.
Am I gonna have to call your wife and tell her to slap you? Hurry up. lol
Dfr360cuda
Diagnosis... Plum Crazy.
Now the next question is... does the OP's gas have ethanol in it???
MopaR&D
Nerd Member
I could be wrong but I highly doubt it, that's more of an American thing. Europe doesn't have a massive corn industrial complex lobbying the government like we do lmao
I'm a bit confused about what I've read, but I think standard gas (95 or 98 ROZ; called Super 95 or Super 98) can contain up to 5% ethanol. There's also another type of gas, Super 95 E10 or Super 98 E10, with 10% Ethanol.
Ethanol is a problem for carburetor cars. These carbs were designed at a time when they had vented fuel bowls and gas had a bunch of stabilizers in it so that the fuel would evaporate less readily. Once cars all came with sealed fuel injection systems, the gas makers did away with the stabilizers. This is why, if you let the car sit for days it takes a lot of cranking to refill the bowl and start your car. Ethanol is hydrophilic - it attracts and holds on to water. Gasoline evaporates more quickly than ethanol, so in your fuel bowl the concentration of ethanol rises as gas evaporates leaving ethanol. The ethanol and water sit in the bowl and react with the metal of the bowl and develops a gooey mixture of water and corroded metal and when you start the car that ends up in the small passages in the carb. (this is even more prevalent in 2 cycle engines - mowers, chainsaws, etc, which is why you should NEVER use ethanol gas mix in them!!!). There are a number of products to put in your gas tank to change the dynamic so that the ethanol doesn't hold the water. The one I use is called Carb Defender from a company called Driven.
I agree......that is IF you do not drive the car enough to keep fresh gas in it. But cars driven a lot normally don't have issues. At least that's been my experience with E10. Now with higher mixes, I don't have any experience, because I'm not gonna run that chit. All in all though for a car driven regularly, E10 is actually a good thing. Alcohol helps resistance to detonation since it has better octane and cooling properties. That said, don't let one sit up very long with it in the tank and carburetor.
Schyrjajew
Well-Known Member
Aso i ha jetz scho mehreri Slant Six ka u bi aui immer mit Bleifrei 95 gfahre u ha meistens garke Zuesatz drito. Die si so nidrig verdichtet, da meuschder ke Sorge mache. Wenn di dennoch sorgsch, chasch ja Bleiersatz dri tue. Aber Bleifrei 98 bruchsch sicher nid.
Charrlie_S
Well-Known Member
Why not Avgas in your car?
Should you use aviation fuel in your classic car? We asked Sunoco's Zachary J. Santner to find out.
classicmotorsports.com
slantsixdan
=..=
From that link: "ethanol can help gasoline make more power" Bzzt! Opposite of true. That is not what ethanol does.Why not Avgas in your car?
Should you use aviation fuel in your classic car? We asked Sunoco's Zachary J. Santner to find out.
Oha, krass do e Bünzli z finge haha. Danke dir für d Nachricht. Ig bi jetz, weiss nid, so 600km mit 95 ohni Zuesatz gfahre und ha bisher no nüt gmerkt wo nid guet wär. Mitem Bleizuesatz bini chlei vorsichtig, da ig nidemal weiss, ob mine bereits e Kat het
has i dene 15 Monate Besitz nid einisch gschafft das nochezluege. Ab 1974 hets die jo in Kalifornie mit Kat gäh, und mine isch '74 baut worde, aber eventuell nach Schwiizer Vorschrifte... -
