I filled the 81 Z28 up this morning at the BP with the usual Amoco Ultimate gas and instatly experienced a problem before I even got out of the parking lot.. I had smelled a slight smell of gas on the way there, but nothing really out-of-the-ordinary, especially for this old car.

After filling up....Missing on 3,5, and 2, stalling at idle, constantly have to pedal it to keep it running, and hesitation on acceleration, little power as compared to before. All classic signs of either a severe vacuum leak or bad gas.
Its doing the exact same thing it did when I wasn't thinking one day and put 87 in it. I'm thinking they got the Ultimate and Regular mixed up on the dump.

I put some seafoam in the gas to see if it would help and its now running better, still missing, still not idling, but just not as bad. Something just has to give. Anyone know of a product that I can get off the shelf that will give me more than .6 more octane points like regular octane booster?

Even with more octane, I'll still have the missing problem to contend with, so I'll probably buy new plugs.

 

For a couple seconds there I thought this was a question about a Chili recipe...

On a more serious note, they used to have an octane booster called "Outlaw 107" that the guys used to take racing on Friday nights. Fuel line antifreeze will help, but it melts rubber fuel lines if you use too much, causing a leak.

What probably happened is the higher priced gas sat and got stale. It's happened to me before. Run it on the highway till you burn out 3/4 of a tank, then look for a place where the gas is cheap, the station is busy,and the gas will usually be fresh.

 

I saw that outlaw stuff at PepBoys the other day. They had other brands as well , one had a 108 octane label on it. I am not a big believer in a mechanic in a bottle but in your case this is understandable. I did seafoam my intake last week, I think it helped alot as well. I still have a pending fuel problem, but I will repost that story when I get it repaired.

Good luck, I hope its just a bunk tank of gas in your case.

 

Last time I used OUTLAW 107 was about 1983- I had this 1972 Olds 98 with a 455 Cube "Rocket" engine. That car was too awesome,power everything, and I've had smaller apartments. The engine was no slouch either, but I have to be fair and say that given the weight of the vehicle, and the power of the engine, the suspension was, to be kind, minimalistic.

 

Find someone with that can get you on an air field and fill up with some aviation fuel (not Jet fuel, that's Kerosene) AvGas is about 150-170 octane....

 

Probably soaked the plugs and some are dead. Fuel filter too, particulates, replace. Is the fire in the old coil up to par? Don't take much to upset an old cars stomach.

 

rivereye, you never cease to crack me up! LMAO

A little more background on this engine...It has a 650 holley, moderate cams, bored .030 over on the rebuild, and is equipped with high compression pistons. Its especially tempermental.

I didn't get a chance to run it or work on it today, but I'm definately going to find a bottle of outlaw. And don't hold back the suggestions on the additives. I don't care in the slightest if they have road-illegal dyes!

The ignition coil has been on since November. Its an MSD. I'll check it to make sure, but I'm almost sure its not the problem. I'm also going to check out the distributor to make sure theres no wear on the points.

Putting a new fuel filter in soon. Results when I get it done!

 

Fuel filter changed, ignition checked good. As of now, I have adjusted the idle a little so it doesn't cut off and I'm gonna drive the tank gas out of it and re-fill.
If that doesn't work, screw it. I'm gonna buy a few gallons of 102.

 

That seams a bit high to me so I looked it up, I thought AV gas was 110 but I found this info.

In the past, there were many different grades of aviation gasoline in general use e.g. 80/87, 91/96, 100/130,108/135 and 115/145. However, with decreasing demand these have been rationalised down to one principle grade, Avgas 100/130. (To avoid confusion and to attempt to eliminate errors in handling aviation gasoline, it is common practice to designate the grade by just the lean mixture performance, i.e. Avgas 100/130 becomes Avgas 100). More recently, an additional grade was introduced to allow one fuel to be used in engines originally designed for grades with lower lead contents: this grade is called Avgas 100LL, the LL standing for 'low lead'.

 

Yeah, I, ah, need a half tankful of aviation gas to ah,... ...flush out the rest of a tank of bad gas, yeah, that's the ticket...