Regular gas?

[Gith]

Ok so the girlfriend goes out buys a 75 Winnebago Indian.  And it need a bit of work, well a lot of work but first question that really jumps to my mind is what gas does it take.   All of the books and stickers say regular which to me means regular leaded gas so a gas supplement is needed.  She is being told that it can take either leaded or unleaded gas.  Since Winnebago had the engine built so you could use which ever gas was cheapest.  Can anyone give me shed some light on this one? 

Gith

[LJ-TJ]

Well my 318 and 440 take good old normal regular gas. However stay away from the new E-gas it eats all the seals in the engine.

[cosmic]

First off you tell your GF she made a great choice....
second the regular gas no problem with knocking. it will run on 87 octane no problems.
in joy that beautiful peace of vintage American enginering and muscle.
just wait till you see the rubber neckers. you cant imagine.

[ibdilbert01]

I use the cheapest gas I can find in mine, and I have never added a lead additive either.

[ClydesdaleKevin]

You can use the cheapest gas you can find if your engine doesn't knock or ping on it.  In fact, I just recently read that the higher the altitude you are running at in an old carbureted RV, the LOWER the octane you should use.  I think that's why you see a lot of gas stations at high altitude selling regular gas at octanes as low as 86.

Kev

[Elandan2]

In places like Montana and Wyoming, there is 85 octane, but it is more expensive than 87 octane because it has no ethanol in it.  Rick

[PwrWgnWalt]

Rick is 100% correct - living in MT, our regular pump gas is 85 octane.  We are at about 3200 ft ASL here, and my old trucks and the MH run fine on it.  The 87 (mid-grade) is blended with ethanol here.

- Walt

[Gith]

Thanks Ya'll 

[polarman]

 Well the problem with running non leaded gas in an engine that was made for leaded fuel has little to do with how well it runs. The lead was in the earlier fuel as a lubricant. What happens when you run unleaded fuel in and old vehicle that was intended to run "regular" leaded fuel is:
-initially....nothing. It will run and run just fine.
-in the long term is a whole different story. First thing that will happen is that the exhaust valve seats in the cylinder heads will take a severe beating. You see, one of the most important jobs of leaded fuel is to lubricate the valves and seats. These older engine have "soft seats" as opposed to unleaded vehicles that have "hard seats". So, after the exhaust valve seats take a beating for awhile, the exhaust valves will become sunken into the head. Run it some more on unleaded fuel, and the valve will no longer seal on the seat. This will cause a loss of compression. It will happen on all of the exhaust valves and seats and compression will diminish on all cylinders.
-The intake valves and seats will wear as well, but not nearly as fast as the exhaust valves and seats.

There are 2 things you can do to avoid this problem.
1- Remove your cylinder heads and take them to a machine shop so that they can install hard valve seats and do a valve job.
2- Do yourself a favor and dump some additive in your fuel. Lead additive would be best, but anything that can help lube those valves wouldn't hurt(some Marvel Mystery Oil perhaps). I have been known to dump a half quart of outboard oil into my old cars when I could no longer find regular leaded fuel.

[cosmic]

Yes you are correct, but by 1975 they were already using hardened valve seats and this was true for the late 60's and early 70's but by 74 on the 440 ci they were already preparing for no lead gas.

Please correct me if I'm wrong... i thought i read this somewhere.

[polarman]

 Yeah, I think the transition to unleaded fuel happened between 1973 and 1977. Emissions started to become a concern and most cars were equipped with some sort of smog control starting with the EGR valve in 1973. By the end of 1977 all gas powered vehicles were required to have a catalytic converter. So, losing the lead in gas around 1975 sounds about right.

Cool note:
I had a 1977 Chevy Impala station wagon that was an early build for the 77 model year. It had a short pipe bolted into the exhaust where the cat would be on the cars that were built later that season. I just thought that was kind of cool.

[polarman]

 It also should be noted that these changes always took place in regular passenger vehicles first, and often times the changes were not required in medium and heavy duty trucks until years later. That would explain why a 75 Winnebago might be built for regular leaded gasoline.

[Lefty]

There is actually a very simple way to tell if a vehicle is designed for regular leaded fuel or unleaded fuel.
Take your gas cap off, look into the filler pipe. If there is a plate there with a small spring loaded door for the fuel nozzle to go thru, you need unleaded fuel. If there is nothing there, and the pipe is open and unobstructed, you need regular leaded fuel.

The baffle and spring loaded door was installed to prevent people from accidentially using leaded fuel in vehicles designed for unleaded as the lead will damage emission sensors and especially catalytic converters. The old leaded fuel nozzles were larger in diameter than the new (at the time) unleaded nozzles, so a small diameter spring loaded door was used that would allow an unleaded nozzzle to fit thru it, but a leaded nozzle would not.

Note: it is not uncommon to find that prior owners have pried out and removed the blocking plates...mostly because they make siponing fuel from a gas tank extremely difficult. But you should be able to see evidence of its removal in any case, look for signs of broken tack welds, or pry marks inside the filler tube.
Also, it is impossible to know if a prior owner has had the heads reworked for unleaded fuel unless you find a reciept indicating such work, or they can tell you personally. Unless you know for certain, it is best to assume a leaded vehicle requires a lead substitute at each fuel stop, and play it safe.

[ibdilbert01]

On Car Talk (NPR), this question was asked.    According to them the lead was added to help the fuel burn and prevent premature ignition in high compression cars.  As for lubrication, they said this was a myth that put a lot of fear in people during the changeover.   One of them said the myth could of been created from the lead additive companies.    Their advice was to run no additives unless your engine was pinging.   

[Froggy1936]

NOTE: It is very hard to kill a myth or a mythster ! W%

[polarman]

On Car Talk (NPR), this question was asked.    According to them the lead was added to help the fuel burn and prevent premature ignition in high compression cars.  As for lubrication, they said this was a myth that put a lot of fear in people during the changeover.   One of them said the myth could of been created from the lead additive companies.    Their advice was to run no additives unless your engine was pinging.

Tell that to the sunken exhaust valves in my 340 heads from my 68 Dart. When I come up with the money for the machine work I will have them install hard valve seats......
I think I have some pics of them, but I'm not sure I can post them since my membership expired. I'll give it a try....

[Oz]

Everyone can post photos - create galleries and post attachments.

[ibdilbert01]

Tell that to the sunken exhaust valves in my 340 heads from my 68 Dart.

Shhh....   Don't tell the 340 in my Winnie, she doesn't seem to notice....     

[007]

i was told years ago that the lead acts like a cushion , keeps the valve from beating the seats to death , hence hardened seats came into play

[Froggy1936]

Tetraethyl lead (a colorless, oily, poisonous liquid), commonly called "lead," was used as a gasoline additive for automobiles made between the mid-1940s and the end of the 1970s. There were several reasons for adding lead to gasoline. First, lead improved the way that gasoline burned. Second, it reduced or eliminated the "knocking" sound caused by premature ignition in high-performance large engines and in smaller, high-compression engines. Lead also provided lubrication, which prevented the close-fitting parts of the engine from chafing against one another.
New cars (cars made between the 1980s to the present), however, require the use of lead-free gasoline. This is because new cars come with pollution control devices called catalytic converters, and lead destroys the substance used as the catalyst.
Source: Mark's Standard Handbook for Mechanical Engineers, pp.