[hurryinhoosier62]

Originally Posted by AG

Not sure about this, the heat of combustion for gasoline is 20,400 BTU/lb and ethanol is 12,800 BTU/lb.

Nearly ALL modern gasolines have at least 10% ethanol content. This additional heat source would increase the normal BTU content.

[Jay S]

I am not sure how ethanol got thrown into this topic of hardened seats? Like AG said the density and the energy per lbs of ethanol is quite a bit lower than regular gasoline. To fatten the mixture up to run ethanol should nearly always drop the engine temp. It is why E85 has trouble getting enough heat into the engine. If it is running hot with an ethanol mix it is probably something to do with the tune running lean. I don’t know that the blame should be on the fuel in that case.

The tune running on the lean side over many miles is probably some of the reason why one engine goes forever on a head with stock valves seats, and another has ate the valves into the seats in the same time frame. On something the exhaust valve is running terribly hot, pulling a constant heavy load, it is a good idea to put exhaust seats in to help drop the valve temp down. From what I recall the seat insert help pull heat away from the valve seat, that is why the valves last longer more so than the “hardness”.. On propane engines that we pull hard under constant load, because the fuel is really dry, and often run lean, with hot exh temps, we always have seat inserts done for those reasons. If that is not an option, we have a really wide seat width on the exh to help pull heat from the valve.

I can’t recall that Pontiac really has more issues with seat inserts than other brands. But the coolant is definitely not far away, I have hit it before. If you work on enough heads you will hit coolant installing seats on about any given mfg.

One of my friend’s had seats put in his RA4 heads, the heads were basically new. I thought it was absolutely crazy, since that car will not have more than 3000 miles put on it in it’s lifetime as long as my buddy own’s it. He was shocked when he got them back, he wasn’t really expecting that done. But some builders do it often because they constantly see issues in that area. The builder didn’t know my friend’s RA4 engine was probably not going to see much for miles. If you leave your heads at as shop that does a ton of heads, and tell them to “fix them”, chances are they will come back with new exh seats. I had inserts put in on my 6X-4s with 1.77s, but I planned to drive my car quite a bit, and it has 170 lbs of seat pressure. A lot too this topic, one size doesn’t fit all. I think I read someone’s response that said the same thing. X2

[Formulabruce]

If your engine takes 1,000 Revs to go a 1/4 mile with gasoline with MTBE
Your engine will need roughly 1,100 revs to do that with 10% alcohol.
With E85 , your engine may need 1,500 revs to get the job done, At same speed. This uses MORE fuel, burning More fuel makes More heat.
Regardless of combustion, alcohol has Higher octane.
I mentioned the fuel, because old engines with higher heat may need some mods to help prevent excess heat at the valve seats.
Density of alcohol is pathetic for most ICE applications.

[Schurkey]

Alcohol burns cooler than gasoline.

Alcohol has fewer BTUs of energy per gallon than gasoline.

Running alcohol does not change the vehicle gearing or tire size, therefore it doesn't add a hundred "revs" to go a mile.

Alcohol has higher octane rating than typical gasoline, but octane rating doesn't mean anything in relation to combustion temperature.

Burning more fuel of lower energy-density does not have to create "more" heat. Replacing "high heat" gasoline with some amount of low-heat alcohol REDUCES combustion--and therefore engine--temperature.

The more alcohol you run compared to gasoline, the less heat the engine makes, and the more energy is absorbed trying to vaporize the additional fuel volume.

The only effect that alcohol fuel might have on the valve seats is a lack of lubricity between valve face and valve seat.

I never researched the "calories" in gasoline except to note that "calories" and "Calories" are very different. Captial-C "Calories" is a measure used for food products, and actually represents Kilocalories. The Calories--and carbohydrate content--of alcohol is well-known. Lots of alcoholics are also diabetics as a result of the carb content.

[AG]

Originally Posted by hurryinhoosier62

Nearly ALL modern gasolines have at least 10% ethanol content. This additional heat source would increase the normal BTU content.

Heat content of 10% ethanol and 90% gasoline would be:
(0.1x12,800 BTU) + (0.9x20,400 BTU) = 19,640 BTU/ib.

[Jay S]

Originally Posted by Formulabruce

If your engine takes 1,000 Revs to go a 1/4 mile with gasoline with MTBE
Your engine will need roughly 1,100 revs to do that with 10% alcohol.
With E85 , your engine may need 1,500 revs to get the job done, At same speed. This uses MORE fuel, burning More fuel makes More heat.
Regardless of combustion, alcohol has Higher octane.
I mentioned the fuel, because old engines with higher heat may need some mods to help prevent excess heat at the valve seats.
Density of alcohol is pathetic for most ICE applications.

I am not following that Bruce? I follow it takes more fuel to do the same work, for sure that is correct, but that doesn’t have to translate to an increase in heat? Isn’t that overlooking the AFR differences for different fuels?

Some AFR examples, Gasoline is ideally 14.7, ethanol is something like 9 or 10, the lower ideal AFR results in a lot less heat from combustion. If you run a blend of ethanol with gasoline the AFR needs to be a bit lower, or for example, jump from a straight gasoline to an ethanol blend, and the engine runs hotter, it is because the AFR is too high. It needs to be richer to lower the AFR. More examples, Propane’s ideal AFR is just over 15, if I recall correct, it’s octane is something just over 110. Octane is much higher than higher than 91 octane gasoline like and at the same time it has lower btu rating than gasoline (more like ethanol), but it needs an AFR if closer to 15. The higher AFR ratio is what make the exhaust hot on propane, and the heat is hard on the valves and seats. Plus it beats ups the valves because it is a dry fuel with no lubrication. Diesel has a lot of lubrication for the valves, and has a higher btu rating than any gasoline, but it’s ideal is AFR starts around 17, and can go as high as 60+. The extreme AFR for some diesel’s is why some people have to have pyrometers on their higher powered turbo charged diesels..

More fuel due to lower density of ethanol and methanol have a big cooling effect on the incoming air charge, and the lower required AFR for ethanol and methanol results in cooler combustion temps also. The density and octane are not the big factors for heat. The issues with ethanol are mostly from the increase in corrosion and absorbing water. As far as I know ethanol and methanol do not have much for issues from a lack of lubrication, if they do the lack of heat offsets it.

[hurryinhoosier62]

Originally Posted by AG

Heat content of 10% ethanol and 90% gasoline would be:
(0.1x12,800 BTU) + (0.9x20,400 BTU) = 19,640 BTU/ib.

And would produce less HP, thus necessitating the engine to work harder which would increase the temp inside the chamber. It’s really not difficult to understand unless you make it so. WHY does running E85 necessitate running much larger carb jets? Because E85 has fewer BTUs to begin with. BTUs equal work; if a fuel has fewer BTUs the engine in question WILL require more fuel( and higher combustion temps) to equal the same amount of work.

[hurryinhoosier62]

Originally Posted by Schurkey

Alcohol burns cooler than gasoline.

Alcohol has fewer BTUs of energy per gallon than gasoline.

Running alcohol does not change the vehicle gearing or tire size, therefore it doesn't add a hundred "revs" to go a mile.

Alcohol has higher octane rating than typical gasoline, but octane rating doesn't mean anything in relation to combustion temperature.

Burning more fuel of lower energy-density does not have to create "more" heat. Replacing "high heat" gasoline with some amount of low-heat alcohol REDUCES combustion--and therefore engine--temperature.

The more alcohol you run compared to gasoline, the less heat the engine makes, and the more energy is absorbed trying to vaporize the additional fuel volume.

The only effect that alcohol fuel might have on the valve seats is a lack of lubricity between valve face and valve seat.

I never researched the "calories" in gasoline except to note that "calories" and "Calories" are very different. Captial-C "Calories" is a measure used for food products, and actually represents Kilocalories. The Calories--and carbohydrate content--of alcohol is well-known. Lots of alcoholics are also diabetics as a result of the carb content.

You’re missing one variable in the equation: lower BTUs equals a lower ability to produce the same amount of work on the same amount of fuel. This necessitates running an engine harder to gain the same amount of work, which would tend to increase combustion chamber temps.

[Formulabruce]

Fact., our CARB V-8s on any alcohol need MORE FUEL to run right...
Any Ideal Ratios for Alcohol OR gasoline don't work when you test drive. 99% of the time, you need to Richen the mixture.
If a New truck on E85 uses 20 gallons to go 250 miles and uses only 15 Gallons of 10% to go 250 Miles, ... its Burning MORE calories....
Sometimes you need to mix some common sense with Science... No Offense to anyone. intended.

[Schurkey]

How can a fuel with lower BTUs per gallon have MORE calories? Both are units of energy. Alcohol is a low-energy fuel compared to gasoline, which is why you need more of it.

Apparently, you're confusing "calories" with "volume".

Because alcohol has less energy per gallon, it takes more gallons of fuel for the engine to work AS HARD (make the same horsepower) as that same engine on gasoline. This may translate to richer jetting, or greater throttle opening, which you're mistaking as "working harder".

[Gary H]

Originally Posted by Gary H

I've had three different Pontiac engines in my shop that had bad recessed exhaust valves. Two engines had 6X heads on them, and other was a mid 60's head. One head had two exhaust valves sunk so bad it couldn't be saved. Too much damage to even put a 1.77 valve in. So, my experience is that although rare, it happens on Pontiac's too.

So, I just posted the above information a few days ago, and then I disassembled a 69' 400 yesterday to for a rebuild. When I removed the heads I found one of the exhaust valves are recessed approximately 1/4". The heads are #62's. Hopefully they can be saved.

[Sirrotica]

Methanol cars run considerably cooler that the same gasoline powered cars do, sprint cars for example need to put heat into the engines with a heating unit even in the summer time before they are fired up initially. The same cooling system that will support a alcohol fired race car, will be inadequate for the same engine run on gasoline.

Hot Rod magazine article:

So, just why does alcohol make more power than gasoline if it has less energy per pound than gasoline? Good question! Obviously, you will have to run more of the alcohol-based fuels to get the same power, how much more will depend on the type of alcohol you're running. With methanol and ethanol it's about 40 percent more than gasoline. Let me espouse some of the good characteristics that alcohol brings to the table.

First, when you burn alcohol one of the byproducts of combustion is oxygen. This helps enhance the combustion process. Another is the cooling effect of alcohol as it "vaporizes" in the inlet track. This helps create denser air as the air/fuel charge enters the engine, another positive. The cooling effect also helps to cool the engine, at least on the inlet side of the equation. Remember, producing horsepower is all about creating and controlling heat.

Another positive feature about alcohol that is seldom discussed is that the incoming fuel charge, the mixture of air and alcohol, is easier to compress than a mixture of gasoline and air. The alcohol doesn't vaporize as well or as completely as gasoline as it comes out of the carburetor or the injector. While gasoline forms a more complete vapor, alcohol forms a "vapor" made up of many very small droplets of fuel suspended in the incoming air/fuel stream entering the engine. Then during the compression stroke, the heat of simply compressing the incoming air/fuel mixture completes the vaporization process.

So, from a mechanical perspective, your engine uses a smaller percentage of the power it's making to sustain continued operation. Long story short, an alcohol mixture takes less energy to compress than a gasoline mixture. And, as an added bonus the last vaporization step also helps to further cool the mixture. Remember, cool, in this case, is a relative term as compared to a gasoline mixture.

Recently I watched an Engine Masters episode where running a blown BBC on alcohol vs gasoline. They had an intercooler on the engine between the blower and the intake, Using gasoline they recorded the highest HP and torque with the intercooler. With alcohol the intercooler made virtually no difference because the alcohol cooled the intake tract without any help from the intercooler. They ran it with and without water in the intercooler with only a tiny amount of difference between the. he difference was less than 5 HP on a 1500 HP pull. They had 2 sets of carbs set for gasoline, and alcohol, other than switching the carbs, everything else stayed the same. In the end alcohol made the most HP and torque due to the cooling effect of alcohol, but of course needed about 30-40% more fuel to do do the same test.

Alcohol by nature cools the entire intake tract as well as carrying O2 in it's mixture into the combustion chamber. The cooling effect, plus the added O2 is how it beats gasoline under the same conditions to maximum power.

The valves will be cooler with alcohol than gasoline, as soon as you start adding alcohol the intake tract is cooler.

Having delivered a ton of E10 and seen it blended, fuel companies use most ethanol to choose what the octane will be in a given blend. The gasoline is low octane as they can make it, and still have a certain specific gravity. The Ethanol is blended to give the octane to whatever the finished product is specified for. Without ethanol, the base gasoline will be more expensive as with pure gasoline, the lighter hydrocarbons are solely used to determine the octane rating.

Alcohol, or alcohol blends, will not run an engine hotter than straight gasoline. It is also a drier fuel that has less lubrication ability, same as propane, it will cause valve, and valve seat recession.

Hopefully this information can settle the dispute.

[mgarblik]

Concerning the valve seat recession issue. I have a student's 1968 400 in class now. Stock rebuild. It had 1 of the 16 valve seats with noticeable valve seat recession. It was an end cylinder exhaust seat. This surprised me a little. Seat area was hammered to a about a .160" wide seat vs. the normal .060-.080" factory width. We re-cut that seat with a 3 angle cutter to the .055" width. It made the stem height about .050" tall on the recessed seat. We adjusted for that and moved on. Pontiac's don't seem to be as bad as other brands for valve recession. Small Block Chevies are the worst. The center 2 side by side exhaust ports will get so bad the entire valve ends up inside the bowl. New seats are the minimum required. Generally, they crack the casting as well and you just throw the junk Chevy heads in the garbage where they belong. That's why they sell thousands of sets of replacement Chevy iron replacement heads every year from dozens of different vendors. By the time you fix 2 recessed valve seats you can have a complete set of bolt on Chevy replacement heads. Pontiac, no decent options.

[geeteeohguy]

Originally Posted by Sirrotica

Castor oil isn't really a solution to any 4 cycle engine in the crankcase. Early dirt track racers used it as it is a high quality oil before it's heated. After being heated in an engine it must be drained immediately before it solidifies into a molasses like semi solid.

It may be fine as top end oil, but knowing how it acts to thermal cycles I would be leery of it sticking rings.

I got back into flying vintage control line airplanes about 10 years ago. These are large balsa and silkspan covered planes with 50+ inch wingspans, and run the old Fox .35 Stunt and Torpedo .29 and McCoy Red Head engines from the 1950's. The oil is pure castor bean oil mixed with nitro. What a great smell! Brings me back to my pre-teen and early teen days! That said, the engines must be cleaned after use or the castor sets up like glue and will stick the piston in the bore. They can be freed up, but what a mess. I have friends who race pre WW1 cars, and use it for exhibit runs, etc. Messy stuff indeed.

[Half-Inch Stud]

Originally Posted by Gary H

So, I just posted the above information a few days ago, and then I disassembled a 69' 400 yesterday to for a rebuild. When I removed the heads I found one of the exhaust valves are recessed approximately 1/4". The heads are #62's. Hopefully they can be saved.

Worthless without a photo. 1/4" recessed !! Sounds like really bad rocker geometry would indicate a problem.

[Sirrotica]

When valve guides get loose the loose valve is able to only hit on a small portion of the edge of both the valve face, and seat. Loose guides are going to hasten recession of both seat faces.

There is no doubt that removing lead from the fuel added to wear of the guides, and valve faces since the early 70 in all brands. The early Pontiac heads never wore out guides at under 100,000 miles unless the owner ignored oil changes.

In 1977 I had a customer that had just bought a 1977 Impala with a 305, I serviced the car regularly, and at 17,000 miles the guides in 2 cylinders were junk. The owner wasn't happy, and chevy dealer was of little help. the guides were so loose that it sounded like it needed the valves adjusted, they were slapping around so badly, constant ticking was the stem rocking in the guide.

[Formulajones]

There is really no brand of engine immune to this stuff. It's just typical engine wear and engine rebuilding 101. If you want to save a set of 50 year old iron heads, then new seats, guides, valves, are pretty much the norm and you'll have to start warming up to the fact of spending about $1500 to do it right. Any good competent machinist can put seats in your heads if need be.

If spending that kind of money rebuilding 50 year old iron heads doesn't sound appealing, then you have to start looking at aftermarket aluminum options. That's just the way it is.

[scott70]

That's why I like to throw in a mix of AV fuel...for the lead. Its called lowlead but airplane mechanics say there's plenty of lead in it. I'm lucky enough to have a small airport nearby.

[Steve Shively]

From what I have heard, Pontiac engine & heads were cast with a higher Nickle content, making it a harder steel. Conversely, Chevy stuff is cast with a softer steel. Porting Chevy stuff is so mush easier than Pontiac.

[Sirrotica]

Originally Posted by Steve Shively

From what I have heard, Pontiac engine & heads were cast with a higher Nickle content, making it a harder steel. Conversely, Chevy stuff is cast with a softer steel. Porting Chevy stuff is so mush easier than Pontiac.

That was true until 1977, when the bean counters started cheapening the castings in all GM brands. In an effort to improve the bottom line the nickel content was cut from the remaining 400, 301 and the 2.5 Iron Duke engines.

I've taken the heads off of 301 with 60,000 miles, the ridge was so bad you couldn't get the pistons out without a ridge reamer. The Iron Duke engines wore the bores out so quickly you could pull up to a GM car at a stop light with a 2.5 engine, and determine what engine it had just from the piston slap coming from it. The air cleaner had oil in the bottom of it due to the blowby being so excessive it couldn't be handled by the PCV system.

One of GMs bone headed moves that made people swear off GM cars by saving a dollar, or two. by cheapening the alloy in the cast iron. In retrospect, cheating customers to improve the profit margin made money for a few years, until people quit buying their cars. Then the government (John Q Public, paid the bill) saved their butt with the bailout. One of the reasons I will never buy another new GM car. Looks like GM is going to hit the skids again in the near future, hopefully they just go out of business for good, no more bailouts.

Mary Barra doesn't have as much sense as my dog has.