what octane?

[gcoll]

I am new to the forum and the new owner of a 1965 AH 3000 BJ8 after selling my first healey a 1961 AH 3000 in 1975. The 1965 Healey has a rebuilt engine but don't know if the valve's or valve seats have been hardened in the rebuild. What is the recommended octane to use in unleaded gas for this engine?

 

[Keoke]

HI, welcome to the forum, Hardened Valves and Seats are good if they were installed. However, if you do not drive your car hard experience has shown that any good high quality unleaded premium fuel will work OK--FWIW-KEOKE--

 

[RAC68]

Welcome to the Forum,

To amplify Keoke’s comments with my experience, I have owned my 64 Healey since new and have never fully rebuilt my engine. I commonly shift at 4,000 to 5,000 RPMs and in 69 had the head off to replace a blown head gasket. During that replacement, no parts were replaced but the head was shaved 60 thousands and resulted in a substantial increased in compression. I have always used unleaded gas since the car was new, and to date, find my compression to be a reasonably consistent 170Lbs across the 6 cylinders.

Although I must use, and do recommend, using 93 Octane, my 46 year usage of unleaded should help calm any use concerns about this gas for enjoyment driving.

All the best,
Ray (64BJ8P1)

 

[Legal Bill]

They had unleaded in 64?

 

[Keoke]

They had unleaded in 64?

Well It started in 1969 but really took effect in 1974 . Consequently, his driving from 1965 to 1969 just coated everything nicely with lead so the transition was unnoticeable---Fwiw--Keoke

 

[RAC68]

As I remember, I was using AMACO Premium that was an unleaded gas. It was rated at 100 Octane and available before 1964.

All the best,
Ray (64BJ8P1)

 

[Legal Bill]

Interesting. I never heard of it in Massachusetts until the 70s.

 

[Donny_L]

Do any of you guys use a lead addative? If so, why? If not, why not?

 

[RAC68]

Hi DonnyL,

Over the years, many have used Lead Additives and some have indicated a preference for it. In most cases, those using lead additives would be hard pressed to prove any benefit from the lead but have experienced an increase in their fuel’s Octane as a result of other components in the additive.

I have used unleaded gas for the past 46 years in my Healey and, as previously mentioned, have not needed to replace any major combustion component other than a head gasket in 1969. I do not race but do drive with enthusiasm. Although I understand that a lead additive is designed to improve valve lubrication, based upon the longevity of my engine and its use, I would only see using a lead additive if I were using my car for competitive events.

Hope this helps,
Ray (64BJ8P1)

 

[Healey 100]

I have been driving my Healey for years with unleaded gas and no additives. My Healey has been driven across the country at high speed several times in very hot weather. No valve damage or recession is evident on this car or any of the other old cars I have -- none have hardened valve seats or special valves either.

The Tetraethyl lead company marketed their product agressively for years, claiming all sorts of benefits many of which were bogus. What lead did was provide higher octane, a definite benefit for high compression engines that ping, knock and diesel on gas with insufficient octane.

Someone pointed out that Amoco sold unleaded "white" gas for years. It was a premium blend with plenty of octane and no lead at all. Some folks swore by it, claiming it increased spark plug life and other benefits. I am sure if it damaged valve gear we would have heard about it.

Drive your Healey and enjoy it. Ethanol is much more of a problem than the lack of lead in today's gas, though my Healey seems to do ok on 10% ethanol.

 

[tahoe healey]

I use only big name high octaine fuel. Costco's has no additives and my Cayanne (now replaced with a turbo Audi) run much smother on Chevron or like gas. I know Healey's have no injectors but I like the way my Healey runs on the good stuff. I'm sure its all in my head but I like to think I'm being good to the old girl.

 

[why]

Read article that gas stations have only two tanks, low and high octane, and the midrange is 50:50 mix, have been using midrange for 35 years in Healeys and when all else is fine they start right up and takes off just fine when I press on pedal. Use to put in a lead additive but after so many articles that not worth bothering with stopped a few months ago. Since a mix, get some cleaner with midrange, although without injectors not sure what is being cleaned otherwise as long as car used a cupla times a month. Short of doing stop-watch testing not sure how could tell difference if I switched to high-test so never did. Not sure how octane boost would add noticeable energy to explosion which is only thing that would make car quicker.
Jay, '65 3000

 

[Bob_Spidell]

...Not sure how octane boost would add noticeable energy to explosion which is only thing that would make car quicker.
Jay, '65 3000

It doesn't. In fact, lower octane gas releases more energy because it burns faster (too fast if the engine pings).

Octane is only a measure of detonation resistance. Higher octane allows higher compression which does increase power and hence efficiency. But, higher octane gas does not make an engine more powerful unless you have a modern engine that senses knock and can adjust the engine parameters (fuel, spark, etc.) to take advantage of the higher octane (or you advance the timing manually). My Mustang will run on regular, but delivers approx. 10ft-lbs. more torque in the mid-range if I run premium (91-octane here in CA).

FWIW, tetra-ethyl lead (TEL) was 'discovered' at the Sloan-Kettering Institute in the late '30s. They did it the old-fashioned way: trial-and-error by testing thousands of additives for detonation resistance. The push for higher-octane fuels was spearheaded by a certain Colonel Jimmy Doolittle, who had a vested interest in higher-performance aviation engines. In a way, TEL helped us win WWII.

 

[Donny_L]

Bob Spidell, R U saying that I'll get more power if I use the lower octain?

 

[Bob_Spidell]

Lower octane fuel burns faster than higher octane--and is more disposed to detonation--so more energy is released in a shorter period of time (like an explosive which is actually a fuel which self-oxidizes and burns extremely fast).

You won't get more power with a lower octane, because you'll have to run a lower compression ratio to prevent detonation ('knock' or 'pinging'), which overall reduces power and efficiency more than the greater release of energy. You actually want the fuel to burn slower and more evenly so pressure--known as brake mean effective pressure or BMEP--is exerted on the piston over a greater period of time.

Conversely, you won't get more power running a higher octane fuel than you car requires unless the ECM can adjust injector timing and spark and cam advance. Some engines--older Taurus V6s come to mind--could actually have problems if you ran anything but regular.

Rule of thumb: run the lowest octane fuel that doesn't ping or knock (it should be in your owner's manual).

 

[why]

Bob: Hah, a data based comment at last,thanks for the primer on octane, much appreciated. If your an old guy however you will will know who Henry Manney is, the purveyor of all the cool folklore about cars in the '50s and '60s when it was us in our little dohc 4 cyl alum 1600cc furrin jobs against the cast iron 'Merican V8ers, when Manney gave us the withering cool response: "torque is just a figure of speech."
Jay '65 3000

 

[Bob_Spidell]

Haven't heard of Manney, only been (seriously) into cars for the last 30 years or so (loved them as a kid, got into other things, got back in when I bought my Healey). Horsepower apparently is a better marketing term.

Some racers put it thusly:

Understeer is when the front end hits the wall.

Oversteer is when the back end hits the wall.

Horsepower is how fast you hit the wall.

Torque is how much of the wall you take with you.


More octane trivia:

The octane rating is just a fuel's resistance to detonation as measured against pure octane, which is a hydrogen-carbon molecule with eight--hence the 'oct'--carbon atoms arranged in a straight chain (known as an 'aliphatic hydrocarbon'). For instance, 90-octane means a fuel has 90% of the anti-detonation characteristics of pure octane. The propensity for detonation is measured either in a one-cylinder engine (the 'motor' method) or in a chamber with pressure sensors (the 'research' method). The research method is usually 7-8 pts higher than the motor in the 90-octane range. Pump octane is the average of the two: R+M/2. When a European brags about their 95-octane gas inform them it's measured by the research method, so it's equivalent to our 91-octane pump gas.

Generally speaking, a richer mixture is more detonation resistant (some aviation gas is called '100/110' to indicate lean octane rating (100) vs. rich (110)).

Ethanol has a higher octane rating than most gas, but a lower energy density. That's why some higher-octane fuels blend in ethanol, and also why 'gasahol' gives less MPG.

Diesel fuel has an octane rating of essentially zero, since it is required to self-ignite (detonate) as diesel engines have no ignition system. Mix enough diesel in your gas and your gasoline engine will self-destruct in a few seconds.

Here's an interesting (to me) chart I stumbled across:

https://www.vpracingfuels.com/vp-racing-fuels-master-fuel-table

 

[RAC68]

HI All,

I just commented on another thread that I like these discussions because I learn quite a bit.

If your combustion chamber is relatively original, it is sure to have hot spots and mediocre flow characteristics. Add to this relatively inefficient mix, compression ratios of between 8.5 and (in my case) 10.5 and you are describing a common Healey engine.

As Bob mentioned, high and low octane fuels of the same type deliver the same amount of explosion-released energy. The difference is when the fuel explodes within the combustion cycle. I suspect we all know that if fuel explodes at the wrong time or unevenly, you will loose Engine Power. Octane retards the fuel from exploding until the spark is introduced. Lower octane fuels may be an option for those with lower compression or reworked combustion chambers (no hot spots and good flow), however, in my case I have higher compression with original combustion chambers and would burn more than fuel if I do not use a high octane fuel.

my $.02,
Ray (64BJ8P1)

 

[abarth69]

15% ethanol gas will shut down the old car hobby

Cheers

Mark

 

[57_BN4]

If your combustion chamber is relatively original, it is sure to have hot spots and mediocre flow characteristics.

Hi Ray,

Would you happen to have a pic of an 'improved' healey combustion chamber as I'm in the process of deciding what to do with my 100/6 head wrt running-on and the comparatively poor mpg these cars get.

As a slight aside, the other half of the garage has my Ford Zephyr which is mechanically very similar to the 100/6 and has never experienced running on, nor is it a common issue. The difference in combustion chamber is significant, the Ford has an open bathtub shape that fits almost entirely over the piston, whereas the Healey has the heart-shape which is significantly wider than the bore diameter.

rather average pic of a Zephyr combustion chamber

Hundred six Longbridge chamber vs piston area

You can see at the top of the Healey combustion chamber the peak bit has blueing from getting hot which I'd think is a good source of dieseling ignition so my first thought is to remove it back to a line between the valve pockets and clean up the various other sharp edges. Then CC the chamber and deck the block and head to get the c/r up again.

Thoughts?

Cheers,
Andy.