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Discussion Starter #1
Our owners manual indicates to use premium gas. I know that back in 66 the gas quality was different.
I have been using Permium and sometimes mid grade gas.

What should I be using. Will it hurt the engine if I use regular unleaded gas?
 

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Depends on your engine, and how you have it set up. Generally, you can get away with regular. I run regular in my son's '65 and daughter's '69. Both are mildly built 302's. The 289 in my '66 is much more radical with it's 10:1 pistons, High rise intake, and nasty cam. I run premium in it.
 

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Yup, I second that, in its mostly stock trim my '71 351C would run just dandy on 87 octane, now with the cam and timing I run I use 93, nitrous requires something with a bit more kick, mixed AV-gas or CAM2.
 

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well back in the day,
my 289 4bbl ran real good on high test, as it was called.
my buddy ran regular, and was never able to keep up with me.
he thought i had a hipo.
it was different gas at the time.
it only cost $.45 per gallon.
regular was about $.38.
wow,
now i run my 73 mach on reg. @ $1.45 per gallon and the wheels still squeel like in the day.
mac
 

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General rule of thumb - anything over 10:1 compression ratio should burn 92+ octane fuel.. Running lower octane fuels will cause detonation, sometimes called pre-ignition, and can damage your engine.
The C-Code challenger V8 was 9.3:1 compression ratio, therefore the 89 octane leaded fuel was OK.
GT's were 10:1 and Hi-po's were 10.5:1. Thats why the air cleaner sticker said 4V premium fuel.. I would recommend 92+ fuel if running a stock 66 GT engine, of course if you are 12:1 or higher, I would recommend nothing but turbo blue or Torco fuel. Looking around 4.00 per gallon but when you have 10K in an engine it's worth it.

You have another option if your engine is 10:1 or so.. Retard the ignition timing a few degrees (like 4BTDC).. You will sacrafice a little power but you will increase the life of your engine. I ran 1 tank in my 66 289, A-Code engine and was getting a bit of pinging at the stock 6 degrees of advance. My engine is 100% stock, although rebuilt, she was pinging. I run Amoco 94 in her all of the time now, no pinging she runs like a champ

Hope this helps, again, just another mechanic's opinion.
 

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General rule of thumb - anything over 10:1 compression ratio should burn 92+ octane fuel.. Running lower octane fuels will cause detonation, sometimes called pre-ignition, and can damage your engine.
The C-Code challenger V8 was 9.3:1 compression ratio, therefore the 89 octane leaded fuel was OK.
GT's were 10:1 and Hi-po's were 10.5:1. Thats why the air cleaner sticker said 4V premium fuel.. I would recommend 92+ fuel if running a stock 66 GT engine, of course if you are 12:1 or higher, I would recommend nothing but turbo blue or Torco fuel. Looking around 4.00 per gallon but when you have 10K in an engine it's worth it.

You have another option if your engine is 10:1 or so.. Retard the ignition timing a few degrees (like 4BTDC).. You will sacrafice a little power but you will increase the life of your engine. I ran 1 tank in my 66 289, A-Code engine and was getting a bit of pinging at the stock 6 degrees of advance. My engine is 100% stock, although rebuilt, she was pinging. I run Amoco 94 in her all of the time now, no pinging she runs like a champ

Hope this helps, again, just another mechanic's opinion.
 

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Discussion Starter #8
where Can I find them?

My car (my son's) is an stock 289 without any modifications. I assume that even regular gasoline should be okay for it, but I will continue with Mid grade anyways.

I like to find out what turbo blue or Torco fuel are so that I can use them on my twin Turbo car.
This 91 Octane California gas is killing my car so I had to lower the boost. I would like to raise it up to 18 psi again. (btw my other car is a 300Zx Twin Turbo)
 

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Discussion Starter #9
They sell 93 octane where you are at?

California's crappy 91 Octane at $1.90 is killing my other car. But for my 289 it should be fine.
 

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Hi GTRTurrrbo,

I would suggest trying to run the lowest octane gas you can without causing the engine to ping. This might be Premium, Mid-grade, or regular. It just depends on how YOUR engine responds to it.

I recently picked up a HIPO fastback and ran Premium at first. I eventually weaned her down to Mid-grade; noticed no lose in performance or pinging. I got brave and went down to regular ( 87 octane here in CA.); guess what? No lose in performance or pinging.

Now your experience may vary based on the type of engine and it's state of tune or modifications done to it.

There's a wide spread belief out there that premium fuels ( or more precisely, high octane fuels) equals higher performance. This is plain and simple incorrect. If you can run an engine with an octane rating of X that does not ping under any conditions, than running a fuel with an octane greater than X will only increase the rate at which your money leaves your wallet. In all actuality, the higher the octane in the fuel, the less available energy in that fuel. The high octane rating is achieved by additives that actually reduce the rate at which energy is released from the fuel, that slower rate of burn (energy releasing) is what keeps high compression engines from pinging.

Bottom line; run the lowest octane rating you can that does not cause the engine to ping. The money saved can be better spent on other goodies. Now once you spend that money on "go fast" goodies for your baby, you may have to turn around and start forking over the big bucks for the premium......it's a cruel trick I know, kind of a circular logic.


Best Regards,

Landmissle 66 GT K-code FB
 

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Discussion Starter #11
My engine is stock and still has the original engine 78K on rebuilt engine with 241K miles. I have used mid grade and didn't feel any difference but never tried regular. I'll give it a shot on the next fill up.

Thanks
Amir
I guess I might have some money by the end of the year for fill my "Go Fast Crack Pipe".
 

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Landmissle is correct. Using higher octane fuel in a car that can run on regular or midgrade is actually less efficient as the fuel doesn't burn as well.

On the other hand my six banger owner's manual says to use 94 Octane "REGULAR". But then octane measurement is different today.

Hey Landmissle, how come you jump out of perfectly good airplanes??
 

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I don't know about California but here in the Motor City, (Detroit Michigan) you can get turbo blue or torco fuel an many gas stations. Right now 87 octane unleaded is running about $1.40/gallon. Torco is like 4.50 a gallon and turbo blue holds at 399 a gallon.. Good luck
 

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"Hey Landmissle, how come you jump out of perfectly good airplanes??"

Well, 66conv6, with pilots like yourself, I"m surprised you have to ask! Just kidding, of course!

This falls under the cataegory of " if you have to ask, you probably wouldn't understand". But since you're a pilot, and not a "whuffo", I know you're asking in jest and don''t need a serious or well thought out answer!

What kind of bird do you fly? Have you piloted any jump ships?

Blue skies,

Landmissle
 

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For the record, detonation and pre-ignition ("pinging") are not the same thing.
Detonation is autoigniton, caused by excessive heat and pressure in the combustion chamber. It is hugely destructive, and to be avoided at all costs. It is characterized by a hard, hammering sort of sound, usually when the engine is being called upon for high horsepower. The second indication of detonation is the tinkling sound of parts coming out of the tailpipe..

Pre-igition is caused by the charge being ignited early by a hot spot in the combustion chamber. It can be quite minor, or can lead to detonation.

The two are related, both can have destructive consequences. Excessive pinging can burn holes in pistons, detonation usually just breaks the top ring land off the piston, seizes the rings, jams the bore, bends the rods.. you get the picture?

So watch the C.R., use whatever octane your engine needs. A teeny bit of pinging isn't fatal in a modern engine, but in our older design "horses", you have to be more careful.
 
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