what is the best fuel to use?

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JamesCalvinIII
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what is the best fuel to use?

Post by JamesCalvinIII »

I remember my dad had a 71 Chevelle SS and he had to put a lead additive into his tank when he filled up

I have a 1967 Corvair 500... will i need to add lead to my tank, or should i use regular gas, or the high grade stuff?

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bbodie52
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Re: what is the best fuel to use?

Post by bbodie52 »

A complex question, but the simple answer is that you should not have to be concerned with adding any kind of "octane booster" or lead additive to modern gasolines for use in a Corvair engine.

Now for the complex answer...

Some Corvair engines run fine on Regular or on a Mid-Grade pump gasoline, while others don't run on anything lower than a Premium Grade fuel with the highest octane rating available. The air-cooled Corvair does tend to run with a fairly high combustion chamber temperature, so they are sensitive to the load they are carrying, outside ambient temperatures, and other factors like long uphill grades -- all of which can increase engine heat and combustion chamber temperatures which could start the engine "pinging" (an indicator of DETONATION in the combustion chambers, which can damage an engine). A Corvair might run fine on Regular gas in the cold winter, but might require an upgrade to Premium on a long trip with four passengers in the hot summer, especially when climbing mountain roads.

12,216 Corvair 500 coupes and sedans were built in 1967, with 95 HP, 110 HP, and 140 HP engines. Very few 1967 Corvairs were actually sold with the 140 HP engine option. (Chevrolet sold 279 of these 140 HP engines in the 1967 model year, 232 with manual transmissions, and 47 with Powerglide transmissions). Some 1967 Corvairs had air conditioning, and some were equipped with AIR (Air Injection Reactors -- Smog Pumps). Some had automatic transmissions, while the others were configured with manual transmissions. You did not specify the engine configuration in your 1967 Corvair 500, but any of these variables can impact the fuel octane rating needed by your Corvair as much as the weight load, terrain and ambient temperature can impact the needs of the engine. The 140 HP and 110 HP engines had a 9:1 compression ratio, while the 95 HP base engine had a lower 8.25:1 compression ratio, which helped it to tolerate lower-octane fuel.
Corvair Underground wrote:The 140 hp engines should probably be discussed separately. They have a generally fair low-end kick, because they share the same cam as the 110 hp's (The 110 hp engine still has slightly better low end power.) They get their boost in power at higher rpms from the larger valves and their extra "booster" secondary carbs. In many ways they are the best rounded Corvair engines-almost. They have one serious weakness, especially under extreme stresses (high heat, high load), and that is they sometimes pop valve seats Considering the high cost of 140 hp heads and engines in general, you may want to think twice about using these engines in high load situations, If you do, however, here is one suggestion-use the engine without the secondary carburetors, The extra boost provided by these is worth about 15 advertised horses, but they guzzle gas and add a strain to the engine. (Remember, we're talking here about "heavy load" applications - passenger car use of 140 engines is just fine.)

Now, as long as we're bad-mouthing these kinds of engines (for heavy load use) , let's bad-mouth some common accessories for basically the same reasons, Center-mounted four barrel carbs, milled heads, and wild cams are ok for "road runners", but keep them off your workhorse. And that brings up the "disclaimer". The options just listed, 140, 102, 150, and 180 engines are great performers for light passenger cars that zip along at respectable rpms, but put them in a "lugger" and they won't last as long as they should, giving you poor gas economy and disappointing performance under many circumstances.

OK, so you're after more power for your workhorse, what should you do? Believe it or not, the best "truck" engines ever put in a Corvair were the 95 hp engines (1964-1969). The 80 hp engines are really very good too, but they lack power in the mid-range and top-end. If you have an 80 hp engine in your van or pickup(80% of them probably do), you will notice a dramatic difference by changing to a 95 hp. Both engines put their best out in lower-end and low-to-midrange and lug around like diesels. Low compression engines also run cooler, longer, and are cheaper on gas.

Now for the real champ. The hands down winner in the Corvair engine field is the 110 hp-probably the best all around performance engine ever offered. You're in luck too, there are a fair number of them running around for relatively reasonable prices. In fact, GM even trusted them to be the first and only high horsepower optional engine officially offered for vans, pickups and Greenbriars. I've driven a number of vans, etc., with 110 hp engines and was really impressed, Even though I personally prefer the 95 hp engine for vans because of lower compression ratios and better gas economy, the 110 would be a very close second.

And what about options for these engines that are best suited for "lower end performance"? A freer flowing exhaust can help some, although I don't advocate headers. The marginally better performance between headers and ordinary glass packs is not worth destroying your lower shrouds, damaging your lower exhaust stacks, and costing twice as much to boot, for 1 ! And the tradeoff for either-they are both loud. Overbored pistons and barrels add cubic inches, an excellent start, The cost scares some people away, though. Larger rejetting of the carbs is good, to and should be done if installing a freer flowing exhaust system anyway. Gas mileage will suffer some, however. Stay away from "center-mounts", milled heads, wild cams, and turbo-charged-unless you plan to race your truck!

Well, I guess the point of this whole article is that advertised horsepower versus usable horsepower is a serious consideration. It is always wise to remember the poor quality of gasoline we get these days too. For our own van and pickup we like the 110 hp engine with the low compression 95 hp heads, We get the best of the higher horsepower but can still burn lousy gas.
This question and answer session from another thread may help to answer your question...
iabuell wrote:I have another question too, but I don't feel it would be right to clog up the forum with more threads so I'll just post it here.

When I bought the car the previous owner said that the fuel would have to be mixed with lead since the engine was not made to handle unleaded fuel. I guess I was a little excited to get the car and forgot to ask him what the ratio was for the mix. (I thought about modifying the engine to handle the unleaded fuel but I was told it was quite expensive.) I looked online at different places and the answers were conflicting. Does anyone know the correct ratio for the mix? Also, what would I have to do to modify the engine so it would accept unleaded fuel and how much it would cost?
Don't be concerned about "clogging up the forum with more threads or questions." This is why the Corvair Forum exists! With almost 3000 members, fewer than half who frequent the Corvair Forum post to the forum regularly, and many never post anything at all! That means that many are just "listeners" who frequent the Corvair Forum to find answers and to learn. This is possible because others do ask questions and/or provide answers and information based on their own experiences. So by all means, ask your questions! When your question gets answered, it may benefit many others as well!

I don't know of anyone who adds a lead additive to their Corvair fuel. I never have, and I have been driving Corvairs for decades. My only concern with fuel is ensuring a high-enough octane to avoid harmful preignition and detonation (pinging) that can quickly damage or destroy a Corvair engine, and possibly adding a fuel stabilizer such as Sta-bil to the fuel in the tank if the Corvair is to be driven infrequently. In such cases such stale fuel can be a problem, and the switch to Ethanol makes this problem even worse because Ethanol decays at a faster rate than non-Ethanol blends.

Here is what Clark's Corvair Parts says on this subject:

http://www.corvair.com/user-cgi/catalog ... ge=TECH-12
World's largest Corvair parts supplier since 1973
Image

http://www.corvairunderground.com/news/gas.html
Serving Corvair owners since 1974 - Celebrating 39 years of service!
Corvair Underground wrote:SO WHAT ABOUT GASOLINE?
Almost everyone that owns "older cars" nowadays are worried about getting gasoline that will burn well in their particular car. The lead content is almost gone (it is gone in California) and the octane ratings seem to slip each trip to the pump.

Corvair owners are very fortunate in the respect that Corvairs do not need leaded gasoline. Corvairs are one of the very few cars built prior to the mid-70's already engineered for no-lead gas! Of course that was essentially by accident - the "extreme high operating temperatures (for the time) present in an air-cooled engine forced the Chevrolet engineers to use hardened valve seats and stellite faced valves. So that solves the lack of lead. (If you are still uncomfortable about this let me tell you that we have burned nothing but "super" unleaded in our own vehicles for many years. We have driven them a lot and have experienced no valve or seat failure.) Well, that solves the lead question.

The other question - that of octane rating - is a little more complicated. In their stock forms, the early 102 hp, all turbocharged engines and all 140 hp engines really require "super" unleaded. That means 90+ octane or better. All the other engines can probably run on most "regulars" although the miserable 86 and 87 octane unleaded fuels found around the country may be too cheap. Follow the basic rule if in doubt. If you get constant detonation (pinging) try to slightly retard the timing. If you have to retard the timing so much that it effects the power (and you don't have other mechanical problems) then you will either have to use more expensive gas or "alter" your engine. And just how do you alter your engine?

If you are going to rebuild the engine anyway then this is the best time to plan your "low-octane" modifications. Mostly you will be trying to lower the compression ratio, which can be accomplished the easiest by using extra thick head gaskets and barrel gaskets. If your heads have been "milled" or you have gone to one of the larger overbores (.040 or .060) this is advised anyway. These extra thick copper gaskets are listed on page B-6. Staying away from milled heads, exotic camshafts and the like will help, of course.

If you are not planning to tear the engine apart then there are still some things you can try. Be advised that some of these "add-ons" may or may not allow you to burn trash gas. Dale manufacturing makes "recurved" distributors that are custom-made for each engine. (Because of the complexities involved we do not handle these distributors but you can contact us for information on them). Water injection sometimes work well but they seem to have gotten hard to find and a bit expensive. A last resort is to use octane booster although that is quite expensive and should not be necessary in normal use. We used to carry some octane booster with us in the 180 turbo when we go on a long trip in hot weather because you never know when someone in Gritzl Forks*, New Mexico may slip you 75 octane gas on a 120 degree day!

Anyway, when it comes to the Corvair we have it pretty good. We can burn unleaded, gasohol, whatever, as long as the octane is high enough - this should guarantee that we can keep driving our cars as long as some sort of gas is available.

* A fellow from New Mexico asked me where Gritzl Forks was. I told him I didn't have the slightest idea. You get the picture.
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

JamesCalvinIII
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Re: what is the best fuel to use?

Post by JamesCalvinIII »

Thanks for the response, I will be printing this out to read through.


I am not sure what size engine i have... I am looking up the vin (10137 7w121 679) and it says
1 Mfgr 1 Chevrolet
2-3 Series 01 Corvair F6
4-5 Body Type 37 2dr Coupe/Hardtop
6 Year 7 1967
7 Plant W Willow Run MI
8-13 Sequential Serial # 121679 121679

I am picking up the car thursday so its not here with me now... but as for usage..

I will only use the car a few times a month, maybe a long trip once a year, It would sit in a parking lot at the beach few times this summer.

I am in Long Island so the climate is moderate,

I would prefer to use the best fuel regardless of the price, and add the additives if needed, I am all about doing things the right way or better.

also the car has been sitting being started here and there, Im sure there is something that this car could use.

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bbodie52
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Re: what is the best fuel to use?

Post by bbodie52 »

The engine serial number is located on the engine cases, to the right of the alternator and in front of the oil filter adapter, between the oil filter adapter and the main top engine shroud. It is a seven character number that starts with a "T" (Tonawanda, NY, the GM engine manufacturing plant). The next four numbers tell the month and day of engine manufacture. The final two letters will tell us the most about your engine. It may be obscured by oil and accumulated dirt, but if you can provide the two-letter suffix code at the end of the serial number, we might be able to identify the engine for you. (If you can take a picture of the metal body tag in the engine compartment, we can decode it and tell you more about your Corvair's origins. The tag is riveted to the rear frame in the engine compartment, near the distributor.

I know that we have previously passed a lot of information and suggestions to you in earlier posts since last October. I would recommend changing the fluids in the car, such as oil and filter, transmission fluid, flush and replace the brake fluid, etc. Examine everything that is rubber: Tire condition and age, flexible brake lines, fan belt, etc. Check the condition of the brake shoes and brake drums, and look for fluid leaks, including around the shock absorbers, brake master cylinder, brake wheel cylinders, etc. Lube all grease fittings in the suspension, and if the universal joints in the rear driveline halfshafts have grease fittings, get those too. Check the horn, lights, windshield wipers and washers and all other electrical functions for proper operation. Look at the front and rear tire tread wear patterns. If they are uneven, cupping, or otherwise showing abnormal wear patterns, determine the cause and have it corrected. A good test drive may also reveal any problem areas. Basically you are establishing a baseline for the condition of your car, so that you can establish a basic knowledge of the condition of the car and a maintenance and service schedule.

Check the tire sidewalls for a DOT age code. Information on tire age codes and locations can be found on the Internet. If the tires are excessively old, have sidewall cracking, etc., consider replacing them.

The Corvair has a 14 gallon fuel tank and will probably get 20-24 mpg. You should try to drive it enough so that the fuel will not grow more than a few months old in the tank. If you will drive it less than that, consider adding Sta-bil fuel stabilizer to the fuel to slow the rate of decay. Ethanol blended fuel deteriorates faster than non-Ethanol fuel.

Try to minimize driving the Corvair in the winter where the unibody Corvair will be exposed to road salt. This will help to minimize rust and body rot problems, which can be a serious issue -- especially in the northeast. If you find existing signs of rust, corrosion, and body rot, it might be wise to have the body evaluated by a trained body shop technician.

If you can post detailed pictures of the car on the Corvair Forum, we can help to evaluate the condition of the car. Include detailed pictures of the engine compartment, trunk, interior, and any ares of concern you might have.
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

JDGriggs
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Re: what is the best fuel to use?

Post by JDGriggs »

This was really helpful! Answered nearly all my questions about fuel. The guy I bought my Corvair from recently had been using and said to use the lead additive. I'd rather not.

What about non-ethanol fuel? Would that be better to run than E10/ E15 fuels?
JD
'66 Corvair 500
'66 Corvair Monza

"[...] we have to go on record and say that the Corvair is in our opinion [...] the most beautiful car to appear in this country since before World War II." - Car and Driver (October 1964 issue)

joelsplace
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Re: what is the best fuel to use?

Post by joelsplace »

Yes. Non-ethanol fuel is much better. The only additive you might need is some green Stabil if it is going to sit for long periods. If you run it several times a year nothing is needed. Brad's octane explanation is excellent. Some of my Corvairs are happy with 89 and the turbo cars all need 93.
114 Corvairs, 5 Ultravans and counting
Northlake, TX

JDGriggs
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Re: what is the best fuel to use?

Post by JDGriggs »

Thanks! I'll probably run non-ethanol primarily with Marvel Mystery Oil on occasion then. I like to at least think it's helpful with carbs.
JD
'66 Corvair 500
'66 Corvair Monza

"[...] we have to go on record and say that the Corvair is in our opinion [...] the most beautiful car to appear in this country since before World War II." - Car and Driver (October 1964 issue)

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