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post #1 of 12 (permalink) Old 08-21-2019, 07:23 PM Thread Starter
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New Guy - fuel question for a 1969 GTO

Hi all,

I'm new to the forum and just purchased a 1969 GTO (it's coming from Georgia in about a week). It has a numbers matching recently rebuilt stock 400 engine, 350 hp, rebuilt auto tranny. My question is about the right gas to use (haven't seen anything recent on this in the forums, so please forgive me if this has been discussed ad naseum at some point in the past).

I'm not a mechanic, so the intricacies of what pistons, heads, valves, etc are best are pretty much lost on me. I can change simple things like plugs, belts, hoses, alternators, etc, and that's the extent of my abilities. I'm mainly interested in the experience of others with today's gasoline. I live in Washington state, near Seattle.

I've researched this a bit and there are so many different opinions on this that it's pretty confusing. Some people say theirs runs fine on 92 octane unleaded pump gas. Other say you have to up the octane to 95 or higher by blending in racing fuel. Others say to use additives such as TEL130 (the one most commonly mentioned).

One interesting article said to use the highest octane you can, put in a bottle of StaBil Marine to help with ethanol, then add some lead substitute to help the old valves and seats, and try it. If it pings, add a bottle of Octane 104. This guy must have been a chef in his previous life!

So specifically, here's my questions:

1. Should I start with 92 octane unleaded (which is the highest available here), no other additives, and see what happens?

2.If it pings, try adding an octane booster and if so which has worked well for you?

3. Regardless of anything else, should I always use an additive such as StaBil to counteract the effects of ethanol?

I bought this car as a fun weekend and cruise night driver, so it won't be used for racing and any kind of heavy load except for occasional freeway driving.

I apologize for these amateur questions, but that's exactly what I am - a non mechanic amateur looking to have some fun.

Thanks for any and all advice you may gave for this newbie.

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post #2 of 12 (permalink) Old 08-21-2019, 07:50 PM
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You live near Seattle then you should be able to get non-ethanol fuel. I also live near the water and almost every gas station has non ethanol since that what they put in boats and here most of the non ethanol is high octane. I run that it my 68 with no need for any additives
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post #3 of 12 (permalink) Old 08-21-2019, 07:52 PM Thread Starter
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Thanks, Marshall. What octane do you run - 87,89, or 92?
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post #4 of 12 (permalink) Old 08-21-2019, 09:58 PM
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Hi Tom

Scott here from Lacey Wa

congrats on your purchase !! and welcome here !!

if it were mine .... I would start with some 92 octane from Issaquah ....

Go with your gas cans on Sunday the 1st of September

its our Buick Pontiac OLDS show at the tripple XXX root beer stand right across the street
from the gas station ........

it will be a great show over 200 cars expected ... weather forecast looks great tooooo

Triple XXX Rootbeer Drive-in

Scott T
also a 69 gto owner
2o6 465 9165 and 2 68's and a 57 and a 40
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post #5 of 12 (permalink) Old 08-22-2019, 10:22 AM
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We have ethanol free 93 here.

If you need more octane, Torco Accelerator is supposed to be one of the best octane boosters.

Many say you can lower the timing advance, in order to lower the chance of detonation. But, that also reduces power & can raise coolant temp.

Since the engine has been rebuilt, there is a good chance that it has the dreaded 8-eyebrow cast rebuilder pistons. They do lower compression. But, because of all the sharp edges, and because of the increased quench distance, they are said to increase the chance of detonation.

Last edited by bigD; 08-22-2019 at 10:33 AM.
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post #6 of 12 (permalink) Old 08-22-2019, 02:40 PM Thread Starter
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Thanks, Scott and BigD.

If the car arrives in time I'll definitely try to make it to the show in Issaquah. I can get 92 octane near me, so no problem there.

BigD: thanks for the info on Torco. I'm going to first try some non-ethanol 92 and see how it performs. If I get pinging, I'll try the Torco first. It gets good reviews on Amazon. Boostane and Klotz also get good reviews. I'd be interested in hearing from other classic GTO owners if anyone has used any of these three additives.

And yeah, I've read that lowing the timing advance can help, but at the loss of power and possible increase in coolant temperature I'm reluctant to do it. I know these '60's era GTOs can have overheating issues (I had a '65 389 tri-power when I was in college and boy did it run hot).

There's a classic car repair shop near me in Everett (GP Automotive) that appears to have a very good reputation, so I'm hoping I can make it my go-to shop on an ongoing basis.

Thanks again, all.

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post #7 of 12 (permalink) Old 08-22-2019, 07:28 PM
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I have run the pure gas and the 10% ethanol 93.....the engine can run great on either, but there is a little bit of carb tweaking needed.

I watch the air fuel ratio close on my meters so I can tell the difference. Purse advantage is a higher boiling point or distillation curve....sometimes that will matter to you.

Octane is a chemical mixture with one property only, it reduces knocking which if the fuel igniting by compression and not from the spark plug.
The chemical octane when added to gas reduces that property. Our cars have higher compression ratios. 9 to 11 generally, so what the compression is also effects how much octane you need.

Octane is not power and adds no power. Ethanol gas actually has more octane than pure gas, but ethanol gas has lower energy in the same volume than pure gas. So the easiest way to get octane is with what is available at the pump, ethanol 10% is here 93 and should be easy to get that or 92 where you are.

I would recommend going with one or the other, pure or 10% ethanol and tune in your carb and donít switch back and forth. I have run them both, I now run the 10% pump gas easy to get everywhere at 93. I got tired of chasing down pure stations and frankly some of those had water in their tanks and were off the beaten track.

I drive a bit around and like the ease of pulling in anywhere and getting good fresh gas.

I add Redline S1 as a fuel system cleaner and octane boost, and Stabile 360 Marine for phase separation,....see my other comments in todayís posts on those additives.

I just cleaned my fuellab filter yesterday, but did not have to do anything because it had zero dirt or contamination after thousands of miles. Ethanol is a cleaner in itself...

So a few ways to go!
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post #8 of 12 (permalink) Old 08-23-2019, 05:02 PM Thread Starter
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Thanks, Lemans - good comments. I've read good things about Redline S1, so that's what I think I'll go with. Ditto for Stabile 360 Marine.

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post #9 of 12 (permalink) Old 08-27-2019, 12:15 AM
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I live in CA where gas is crap and the highest you can get is 91 (unless you are lucky enough to find one of those unicorn 100 octane stations that still exist if you can pay $6.00 a gallon). I just don't like octane boosters, whether it is founded or not, I feel like they leave too much crap on the valves.

I put 91 crap from CA in my 69 and it seems fine. I would love some of the options you have mentioned and 92 octane.


Torque (tork), n: 1. The tendency of a force to rotate the body to which it is applied. 2. See also: GTO
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post #10 of 12 (permalink) Old 08-28-2019, 07:13 PM
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I'm here in No Cal and as Leeps states, Gas is crap , costs a lot and only 91. I feel the necessity to boost octain since there is knocking and hesitation with out. We had a cruise night in Castro Valley this last weekend with a tone of classic cars. The stopping and waiting created a bit of vapor lock or something like it. Can was steady under 200 degrees but hesitated on quick starts. That was embarrassing. 1969 GTO Survivor under 60K miles.
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