[78w72]

not trying to be snarky, but why would only the pontiac suffer this problem on an oval track as described but all the other cars didnt have the problem? are fords/chevys/mopars immune to vapor lock or fuel boiling? just curious how the ford was able to pass you under the same circumstances?

[Sirrotica]

Pretty simple, Pontiac rejects more heat through the cooling system than other engines of the same size. The heat coming off the radiator heats the fuel system under a yellow flag. You will occasionally find some other brands that OH on an oval track, but as long as I've been around oval tracks, building, and racing Pontiacs are the toughest to keep cool. My father followed oval track racing since the late 40s, told me that even back then Pontiacs were prone to overheat with straight 8s and sixes.

I had a 455, the ford was a 351 M, most of the chevies were way under 400 cubic inches. To get same the heat rejection in a chevy you have to go to a 454 in a truck normally to find as large of a radiator as a Pontiac 455 in a car. There are very few Pontiac applications that came with a 2 core radiator

I have no idea of why the Pontiac design rejects more heat than other manufactures designs. All you have to do is look at radiator core thicknesses to see that almost any Pontiac of the same cubic inch size required a larger radiator than other GM cars. I've been through the wrecking yards since i was 14 years old, and you will invariably find that say a 350 chevy has a much smaller radiator that a 350 Pontiac, same with 400 inch engines, chevy much smaller than a Pontiac as it was manufactured.

Another GM design that also has problems with having enough cooling system capacity is the Detroit Diesel 6.5 engine. Blown head gaskets in the early engines because of overheat issues. GM redesigned the whole cooling system because of warranty claims.

HO water pump to pump 40% more capacity, water crossover with 2 thermostats for the increased water pump flow, and a super duty thermostatic clutch to engage at lower temps, and reduce slippage, and a 7 blade fan. Those 3 items cut the warranty claims a huge amount.

Comparing same cubic inches for cooling system heat rejection from different manufactures, is always apples and oranges.

My Grand Prix in my signature pics has 2, 3 core radiators back to back. for a total of 6 cores to keep it cool. Fortunately that car had no cooling issues. The car that stumbled was not my own car, it belonged to a friend of mine, so I never worked on it the cure the gas starvation issues, he just didn't want to drive it that night, and I drove it for him. Was leading the feature when the caution came out, and lost the lead on the restart, almost got back by him, but ran out of laps.......

It wasn't the first time I had fuel starvation with Pontiac from fuel overheating on a dirt track, well versed on what happens when you sit on the track idling under caution and the underhood temps creep up.

Anyway, I have no idea of how he had the fuel system setup, as I never drove the car previously. I do know he also had a dual radiator setup copied from my Grand Prix. Routing the lines away from heat sources helps tons on a dirt track. If he had the stock line, they go right next to the thermostat housing, not good.

Oval track racing is totally different that drag racing, street driving, or autocross. 20 laps wide open builds a lot of heat in everything under the hood, so making everything as heat resistant as possible is the way you finish races. Everyone has their own ideas on how to get there. Lots of trial and error on my cars to get the ultimate fuel, and coolant setups.

Vapor lock, or fuel boiling?. I lost because of it.

[PunchT37]

Vapor lock is real, fuel boiling is real. If you don't think so ask someone who has raced an oval track Pontiac, I have, and it happens. I've taken second place while leading a race, because under a yellow flag while you sit idling on the track while they realign the field, then run a lap before they throw the green, you punch it. and the car falls flat, and you get passed by a ford. Second place sucks........

2`nd place is only the 1`st loser.

[Sirrotica]

Originally Posted by PunchT37

2`nd place is only the 1`st loser.

If you look at the picture of the 67 GTO in victory lane, the first loser isn't what I strived for. That car in 2 seasons won 13 races. It was protested 4 times by mostly chevy guys, never found illegal, because it was 100% within the rules.

Chevy guys hate being beaten by a Pontiac.

Here's the only picture I have of friends 71, 455 Firebird on dirt, before it was totaled. That's the car that vapor locked, costing me a first place.

[sdbob]

Yes the others go bananas when beaten by a Pontiac. I oftened wondered the psychology behind that!?

[Brentco]

Originally Posted by Schurkey

It wouldn't work to prevent vapor lock,

It likely worked to reduce fuel boiling in the carburetor,

Point being, it could be a valid solution to driveability problems, but not for the problem of vapor lock specifically.

Methinks that the hyper-technical distinction between the two conditions is not particularly helpful and just adds confusion. The term vapor lock is used nearly universally to refer to both conditions. They have the same symptoms and result, and are fixed the same way. Whether fuel is boiling before or after the pump, it’s still fuel boiling in the fuel system causing it to lock up.

I also haven’t seen any formal definitions that make the distinction. “Vapor Lock: partial or complete interruption of flow of a fluid (such as fuel in an internal combustion engine) caused by the formation of bubbles of vapor in the feeding system.” “Vapor lock.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/vapor%20lock. Accessed 15 Aug. 2022.

And of course vapor lock is not a myth. It’s physics.

For those lucky enough to not have experienced vapor lock, you must remember that it’s highly situation dependent. We all live in different climates, at different elevations, and have different fuel grades and qualities in our local stations — and even those vary day to day and station to station.

Especially becomes an issue if you live somewhere without big seasonal changes in temperature. In California, all gas changes from “summer fuel” mix to “winter fuel” mix (more volatile) the same month every year according to the calendar. But the weather, especially in SoCal, doesn’t care about the calendar, and there will be many months during the winter mix time with long stretches of hot weather. That causes all sorts of vapor and fuel related issues.

[Formulajones]

Originally Posted by Brentco

Especially becomes an issue if you live somewhere without big seasonal changes in temperature. In California, all gas changes from “summer fuel” mix to “winter fuel” mix (more volatile) the same month every year according to the calendar. But the weather, especially in SoCal, doesn’t care about the calendar, and there will be many months during the winter mix time with long stretches of hot weather. That causes all sorts of vapor and fuel related issues.

I'm surprised California does that since the winter grade formulation really shouldn't be needed in the warmer climate where you aren't seeing much seasonal change.

We had it in Ohio and it wreaked havoc on our cars. Usually in February or March when we would have those freak warm 70 degree days and they weren't switching to summer grade till April. The car would buck and carry on until the next day when it was 20 degrees again, lol. Once the summer grade came along all was good.

Now living in Arizona, which is basically a similar climate to California, although maybe warmer at times, I haven't noticed any issues with the possible different formulations of winter or summer fuel which has led me to assume Arizona may not be doing that. Even during our colder months we can have 50 during the day, and I can drive down in elevation where it's 70-75 degrees and the car runs fine. No more Ohio symptoms

I may dig more into that and see what Arizona is doing because I'm almost certain we get our fuel supply from the same supplier as California.

[Brentco]

Originally Posted by Formulajones

I'm surprised California does that since the winter grade formulation really shouldn't be needed in the warmer climate where you aren't seeing much seasonal change.

We had it in Ohio and it wreaked havoc on our cars. Usually in February or March when we would have those freak warm 70 degree days and they weren't switching to summer grade till April. The car would buck and carry on until the next day when it was 20 degrees again, lol. Once the summer grade came along all was good.

Now living in Arizona, which is basically a similar climate to California, although maybe warmer at times, I haven't noticed any issues with the possible different formulations of winter or summer fuel which has led me to assume Arizona may not be doing that. Even during our colder months we can have 50 during the day, and I can drive down in elevation where it's 70-75 degrees and the car runs fine. No more Ohio symptoms

I may dig more into that and see what Arizona is doing because I'm almost certain we get our fuel supply from the same supplier as California.

Yeah apparently summer blends are more expensive to manufacture, and that has the greatest effect in California, because California has the strictest standards for reformulated gasoline. So I’m sure the oil companies want to keep the summer period as short as possible, regardless of whether a winter blend is actually needed in the winter months.

Map showing the federal requirements, and an interesting read at the link below. States and counties impose their own requirements on top of these, so the picture becomes even more complicated.

https://www.eia.gov/todayinenergy/detail.php?id=11031

[Formulajones]

Originally Posted by Brentco

Yeah apparently summer blends are more expensive to manufacture, and that has the greatest effect in California, because California has the strictest standards for reformulated gasoline. So I’m sure the oil companies want to keep the summer period as short as possible, regardless of whether a winter blend is actually needed in the winter months.

Map showing the federal requirements, and an interesting read at the link below. States and counties impose their own requirements on top of these, so the picture becomes even more complicated.

https://www.eia.gov/todayinenergy/detail.php?id=11031

That's interesting thanks for that. That's really surprising the entire state of California is stuck with that. Well maybe not so surprising

Appears Arizona isn't doing that which makes sense based off what I explained before.

[Brentco]

Originally Posted by Formulajones

I haven't noticed any issues with the possible different formulations of winter or summer fuel which has led me to assume Arizona may not be doing that. Even during our colder months we can have 50 during the day, and I can drive down in elevation where it's 70-75 degrees and the car runs fine. No more Ohio symptoms .

It looks like seasonal blends are used only in the Phoenix metro area and to some extent the Tucson metro area.

Posted this before seeing your response — yeah your experience seems spot on.

[Formulajones]

Originally Posted by Brentco

It looks like seasonal blends are used only in the Phoenix metro area and to some extent the Tucson metro area.

Posted this before seeing your response — yeah your experience seems spot on.

Doesn't that seem strange when Phoenix and Tucson really don't have seasons?

I mean in the sense that it's pretty much warm year round.

We have what everyone refers to as mild seasons up here in Prescott where it's 50's during the day in the winter, but teens and 20's at night. Summer is over 100 during the day that tapers off to 90's then 80's as the fall gets closer. Seems the blended fuel for colder climate would make more sense up here.

Not that I'm complaining, that crap don't work very well when it warms up outside.

[Brentco]

Originally Posted by Formulajones

Doesn't that seem strange when Phoenix and Tucson really don't have seasons?

I mean in the sense that it's pretty much warm year round.

We have what everyone refers to as mild seasons up here in Prescott where it's 50's during the day in the winter, but teens and 20's at night. Summer is over 100 during the day that tapers off to 90's then 80's as the fall gets closer. Seems the blended fuel for colder climate would make more sense up here.

Not that I'm complaining, that crap don't work very well when it warms up outside.

Yeah it doesn’t make sense functionally. My understanding is the regulations come from emissions requirements — the metro areas have stricter emissions requirements, so they have to use summer blends which evaporate less VOCs.

As you say, you can just thank the gas gods whatever you get seems to be good stuff (I’m sure your attention to tuning helps a great deal as well).

[Sirrotica]

Originally Posted by Formulajones

Doesn't that seem strange when Phoenix and Tucson really don't have seasons?

I mean in the sense that it's pretty much warm year round.

We have what everyone refers to as mild seasons up here in Prescott where it's 50's during the day in the winter, but teens and 20's at night. Summer is over 100 during the day that tapers off to 90's then 80's as the fall gets closer. Seems the blended fuel for colder climate would make more sense up here.

Not that I'm complaining, that crap don't work very well when it warms up outside.

The blend is for meeting air pollution standards, it's not just for drivability, the winter air pollution standard is relaxed because fuel usage drops off beginning in the fall.

Also the fuel is the same at it comes from the refinery no matter what the season is, it's blended with additives as it's loaded in the tankers (loading racks) to go to the retailers. That is where the fuel is changed to different seasonal blends. That way it can be changed in a day. If the base fuel was changed, it would become obsolete sitting in storage tanks. That is also when ethanol is blended into the base fuel, as its loaded into tankers. It starts deteriorating as soon as the ethanol is blended, and the mixture is exposed to air. The pure gas can be stored, much longer than ethanol blends can be.

I drove tanker for Kenan Advantage tank lines, so that is real time experience, not from the net.

[Formulajones]

The emissions part makes sense since we don't have anything of the sort up here in Yavapai county.

[78w72]

strange about the ohio winter gas causing running issues like engine bucking, ive been in iowa my entire 30+ driving years & have never noticed much difference in how my daily or classic cars drive come warm spring days. the summer blend isnt used until may1, plenty of very warm days by then. winter blend starts sept1, still plenty of warm days into mid sept in my area, it can be in the lower 90's till mid sept.
my pontiac engines are stock, mild built, & 10.75:1 500+hp, none of them act much different in starting or running with either winter or summer blend fuel. worst thing i get on the hottest summer days after hard drives with summer blend premium fuel is a occasional slight run on when shutting off the 500hp engine, but that is more due to carb throttle plates being open a little too far, i adjusted idle speed down & its almost gone.

im sure different blends can act different for some engines, but just like vapor lock or overheating, storing fuel issues, etc, ive been lucky enough to never deal with that on any cars ive had from SBCs to carb'd foreign or classic pontiac v8's.

[Formulajones]

Depends on the car for me.

The Camaro, Chevelle, and Firebird don't do it. They just don't care. My 79 454 1 ton truck cares however.

On the truck, if I run the aluminum intake and block the heat cross over, it's perfectly fine. When it came time to sell and put back to stock, I installed the iron intake and opened the heat cross over, it became a vapor locker under certain circumstances and was damn near predictable. It especially didn't like winter grade fuels on warm days.

Cars in the stable now don't exhibit any problems.

[78w72]

yeah i dont claim have some magical powers when it comes to that stuff, just been lucky ive never had to deal with it, well im sure some of its not luck & has to do with the tune of the engine or parts i select like proven parts from guys that know what they are doing like cliff built carbs or a sun tuned hei. but the 2 other cars i have now & the ones ive owned in the past are all stock parts & built/tuned myself & advice/assistance from others that also know what they are doing.

the one thing i do notice with winter blend fuel is slightly lower MPG, checked myself or going by my current daily computer MPG, drops by .5-1 MPG every winter season then goes up in the summer.

[Brentco]

Originally Posted by 78w72

the one thing i do notice with winter blend fuel is slightly lower MPG, checked myself or going by my current daily computer MPG, drops by .5-1 MPG every winter season then goes up in the summer.

That is some diligent monitoring of fuel consumption. Summer blends are supposed to be just a smidge more energy dense with a few percentage points better MPG, so it’s impressive you picked up on the small difference.

[78w72]

Originally Posted by Brentco

That is some diligent monitoring of fuel consumption. Summer blends are supposed to be just a smidge more energy dense with a few percentage points better MPG, so it’s impressive you picked up on the small difference.

yes its very noticeable when the change happens or when i use 10% ethanol vs straight gas, nothing else changes on the vehicle & i know to increase tire psi when temps drop. i noticed it on the gauge of my previous daily, but when i got a newer daily a couple years ago i seem to watch the mpg monitor closely even though its not 100% accurate it provides a baseline that will show changes in fuel, tire psi, driving habits etc.

with gas prices so crazy it makes you aware of how you drive & i find myself getting passed by all the soccer moms & people in the rat race that are in such a hurry to race up to the red lights... then i just coast by them knowing how to time traffic lights.

[Spaceman Spiff]

Has a stalling issue like this. Was chasing my tail until I happened to touch the coil and it was red hot.
It was overheating, causing the car to stall. Had to wait for it to cool down, before it would refire.
Really surprised that it didn’t just give up altogether the first time.