Got Shell 93 Octane and now barely idles 1973 Dart 340

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Here a sample of 93 Shell Octane from about 6-8 weeks in sealed gas can from the garage

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AJ/FormS said:
Hmmmmmmmmmmmmmmmm
No water. Teensy bit yellow.
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Yea, but I'll bet you anything that two cups is off the top of the 8 gallons.
I want to see the bottom of the 8 gallon container.

^^^ Urine Sample? :D
 
Is that the stabilized one?
That's pretty orange on my screen.
When I was still working in the motorsports biz,if a problem unit came in, and I saw that color, out it would come. Fresh went in;drain or ride the carb out; and in many many cases with driveability problems, they magically self-healed. Years ago, I had an 84 Hyundai-Pony. That beast would burn anything I put in the tank.I mean the stalest gas, and even mixed with diesel. Anything except water. I drove an awful lot of miles on free gas; that would not burn in Honda products. All summer long.
yeah water is heavier than gas. I'd like to see what's in the bowls, But I'm about 99% positive it ain't water.
 
AJ/FormS said:
Is that the stabilized one?
That's pretty orange on my screen.
When I was still working in the motorsports biz,if a problem unit came in, and I saw that color, out it would come. Fresh went in;drain or ride the carb out; and in many many cases with driveability problems, they magically self-healed. Years ago, I had an 84 Hyundai-Pony. That beast would burn anything I put in the tank.I mean the stalest gas, and even mixed with diesel. Anything except water. I drove an awful lot of miles on free gas; that would not burn in Honda products. All summer long.
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Yes. This one had stabil added when bought 6-8 weeks ago.
 
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Maybe your American gas ages different than our junk.lol But we haven't had 93 non-oxygenated around here since 99 or so.
Hey I just thought of something; maybe the color-change in 93 differs from the color-change in E10.Maybe that 93 doesn't lose it's potency with color change. Are you using that 93 in a newer weed-whacker by any chance; one with a non-adjustable carb? I wonder how it performs...........

Maybe one can't depend on color-change in stabilized 93, to be a potency indicator
 
When I add 2-4 fresh gallons before starting tomorrow add any stabil y/n?
 
If you're not gonna burn it all out, add just what you need, on Sunday night. That stuff contributes nothing to combustion. It will also not rejuvenate old fuel. Once E10(all I know),goes Orange, it's only good in old lawnmowers and such like, with carbs that have adjustable fuel circuits. Or EFI cars with knock sensors. They will pull out timing to prevent detonation and richen up the injectors to compensate. Unfortunately they seem slow to recover after you put fresh stuff in, if you regularly drive deep into the power.
I have mixed fresh clear stabilized gas with red gas at a ratio to get Orange gas, and that will burn in yard equipment, where the red by itself wouldn't even start the item.

I am so looking ahead to see how this plays out.
 
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AJ/FormS said:
If you're not gonna burn it all out, add just what you need, on Sunday night. That stuff contributes nothing to combustion. It will also not rejuvenate old fuel. Once E10(all I know),goes Orange, it's only good in old lawnmowers and such like, with carbs that have adjustable fuel circuits. Or EFI cars with knock sensors. They will pull out timing to prevent detonation and richen up the injectors to compensate. Unfortunately they seem slow to recover after you put fresh stuff in, if you regularly drive deep into the power.
I have mixed fresh clear stabilized gas with red gas at a ratio to get Orange gas, and that will burn in yard equipment, where the red by itself wouldn't even start the item.

I am so looking ahead to see how this plays out.
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My plan was to change out the carb-manifold gasket/adapter before even trying to start it.
 
Well then if that's gonna be a week from now, I see two options; put the stabilized gas in now, or don't buy gas until you need it. If you read the mixing directions, some of those products claim no potency change in a year.
 
One last question before tackling the gasket/adapter mess. Just use carb cleaner to remove the RTV from the base of the carb?
 
Put on a new a Edelbrock 2696 adapter, but haven't tried starting yet. I am going to a Mobil station that is close to my house for 2-4 gallons of 93 octane.

Here are the pics of the old stuff and manifold along with the new adapter. He used double gaskets cause the adapter to manifold Allen head bolts were too long

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Pulling about 12 to 13" of vacuum a little better, but might be on the rich side now. A little hard starting hot. I will readjust the A/F mixture and check the plugs. I wish on knew what cam was in it. The brake booster has a hiss now. I disconnect and plug its vacuum source and it goes away.
 
So was getting rid of the old gaskets the trick? If so, then the rich settings may have been needed to compensate for vacuum leaks. Idle vacuum may be lower now due to the idle speed being lower....

If it is cranking a lot before firing when hot, then it could well be too hot fuel boiling in the carb. High ethanol content is worse. May be time to add a heat shield under the carb, like this one: Holley 108-51, Holley Insulating Carb Gasket Heat Shield | Holley

Double check to see if this one fits your AFB. There are other types out there.
 
nm9stheham said:
So was getting rid of the old gaskets the trick? If so, then the rich settings may have been needed to compensate for vacuum leaks. Idle vacuum may be lower now due to the idle speed being lower....

If it is cranking a lot before firing when hot, then it could well be too hot fuel boiling in the carb. High ethanol content is worse. May be time to add a heat shield under the carb, like this one: Holley 108-51, Holley Insulating Carb Gasket Heat Shield | Holley

Double check to see if this one fits your AFB. There are other types out there.
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Idling 850 rpm in park. I adjust the timing to advance it to just above the visible marks since someone said 2.5 BTC is not enough. I hate ethanol. Is 12-13" of vacuum acceptable supposedly the engine was rebuilt 3,000 miles ago, but I don't know its history or the cam specs.
 
It'll vary all over the map with different cams so it is hard to say. Stone stock cam would be up at 18" or more; a moderate cam would be around 13-15"; radical cam 10", maybe less.

So where do the visible timing marks end? 10 degrees? 20 degrees? If 20 degrees and you went beyond that, then total initial timing (what you just set) plus stock mechanical advance will go beyond what you should have.

BTW, did you plug the hose to the vacuum advance module on the distributor when you set the timing?

You can profile the cam to see what it is. Requires some tools and knowledge but can be done.
 
You can set the idle timing almost anywhere. But there's only a tiny window that is correct, and only you can find it. see below,heehee

Manifold vacuum can vary several inches with timing changes.
 
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I can get close to just shy of 15" but seems to be a different reading every time I cannot it. Idle seems to a little rough shaking a little more than before all this: console and door panels rattle. It will only start warm if I hold the accelerate part way. Timing set to just above top mark of the timing marks.
What just started is a hissing that appears to be coming from brake power booster, which was not happening before I disconnected the manifold line to the check valve and plug the manifold connection and the hissing goes away, but a hard brake pedal. The brake pedal seems very low. Check braking linings are good. Fluid a tad low maybe 1/2" in rear reservoir of the master cylinder. No leaking at the wheel cylinders and front brake hoses were changed recently.

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Solve the engine problem first
later the hissing booster connection.
Manifold vacuum can vary several inches with timing changes.and rpm plays a big role too

Here's the deal; with no vacuum leaks and vacuum numbers from 12 to 15 and an 850 idle, your cam is "not very big". This should be an easy tune.Prove, prove that there are no vacuum leaks.Prove externally, prove internally, prove the intake, the carb, lines, the PCV hose,everything. Blow out the low-speed circuit including the idle-bleeds.Then
I'll say it one more time;check and adjust your T-port sync. By doing this,the timing will settle itself/no more guessing.
I suggest to target an in-gear idle of 650, with neutral jumping up no more than about 100.

A bad shake at those vacuum numbers, would lead me to suspect a bad cylinder. Put the IR gun on the exhaust ports, and find a bad one, then check it's compression.There could be more than 1. Could just be a bad plug or wire. That would also explain your unstable idle vacuum, and why you need the high idle.
Unless the M-rods are not seated down at idle.
I think you're gonna need a timing tape, or a DB-timing lite.
 
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AJ/FormS said:
Solve the engine problem first
later the hissing booster connection.
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I was just wondering if the brake booster having a vacuum leak might be affecting the engine issue.

Not sure what else to do, other than a possible internal carb issue. It's an older Carter competition series AFB 9635SA from the early 90s
 
Yes it absolutely will; the booster vacuum IS the intake manifold vacuum. A leak at the booster is a leak into the manifold. With the booster line disconnected and plugged, a hard pedal is normal... YOU have become the power booster LOL.

The timing sounds OK at just over 10 degrees; maybe not optimum, but at least not in an unsafe range.

So did you adjust the idle mixture screws while looking for maximum vacuum readings? You generally have to go back and forth and back and forth on each side a few times.
 
nm9stheham said:
Yes it absolutely will; the booster vacuum IS the intake manifold vacuum. A leak at the booster is a leak into the manifold. With the booster line disconnected and plugged, a hard pedal is normal... YOU have become the power booster LOL.

The timing sounds OK at just over 10 degrees; maybe not optimum, but at least not in an unsafe range.

So did you adjust the idle mixture screws while looking for maximum vacuum readings? You generally have to go back and forth and back and forth on each side a few times.
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Yes, I went back and forth. After enriching it getting the highest reading about 15" vacuum, but seems rough and will only start pressing the accelerator part way while cranking.

What is the optimum timing setting?
 
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