"Run-on" after shut down, what's going on?

[Zeke]

Well, you don't NEED the 101. And, if it's sold at the race track, it's technically for off-road use. I don't think it will necessarily have any ethanol in it.

I far as I can see, ethanol isn't so bad, it's what it does to older fuel lines, the early metal MFI stacks over time (due to "stand off"), cars with carbs, etc. But, as a fuel, it's OK. A little less performance is to be expected, but it does have its advantages like absorbing water and cleaning the fuel system, the above about system deterioration notwithstanding.

You might not have this problem with better gas, even with some ethanol. We don't have much choice until summer anyway.

[BHerrmann]

Think I'll go ahead with some higher street octane and just see what happens, it might just solve it. I don't want a colder plug as you said, I've always used the 7's and had good luck with them.
Do we lose the ethanol in summer? My main complaint the the ethanol is
loss of mpg in the Toyota 4Runner, don't really notice much difference in mpg with the 73S, or really care for that matter.

[GreenT]

Last year, Conoco took over Union76 and one of the first things they did was get out of the race gas business - Nascar, NHRA, and the stations and auto parts stores that sold their 100 and 110 octane gas. Until then I could buy 110 out of a 55 gallon drum at my local station for about $4.50 a gallon or get 5 gallon cans at the auto parts store. They also used to have a graph on their website that showed you ratios to mix x gallons of 100 or 110 with x gallons of the current 91.5 premium to get an honest 93, 95 or whatever octane you wanted to make your own version of what USED to be hi-test. Somewhere I still have a printout they gave away at hot rod shows at the 76 tent. I'll scan and post it if I can find it. Anyway, VP Fuels has taken up the slack and I can still find 5 gallon cans of it at the parts store. Oddly enough, they charge the same for the 110 NHRA fuel as the 100, so I get the 110 for blending.

Basically, I slug in about a half gallon or so of 110 in each tankful to get a real 93 octane, which is what these cars wanted when they were new and what people can still buy at the pump in 'normal' states. Both Union76 then and VP race gas now are leaded fuels, so I figure the trace amounts of lead can't hurt either, with the valve seats and such. Most gas in the 70's was leaded, and most engines were designed to make use of it.

I can run the 91.5 premium without knocking if I get lazy, but the booster shots I give it make for a much happier engine. Cold starts are much better and especially at high rpms, you can hear and feel seat-of-the-pants wise that the engine is running better. I have S pistons and E cams in a 2.2 and a 9.8 compression ratio which I think was the stock S rating for 1970. None of my cars like Shell, the stuff smells like diesel fuel and every car I have, even my wifes, idles at lower rpms on it. Chevron seems to best the best we have available. Union 76 used to be on a par with it, but I'm not sure that's true anymore since Conoco took them over. Try some better gas, and maybe a good injector/intake cleaner, because carbon buildup will cause the same symptoms.

[BHerrmann]

Good info on 76/Conoco. I did notice I got new gas cards in the mail with
Conoco all over what used to be just a 76 card. I think for now I'll try a better octane Chevron and see what happens.
Speaking of injectors, I suspected that my #6 injector was leaking/developing a poor spray pattern. I was lucky enough to find an old
factory injector testor/cleaner a few years ago and hooked up the injector, sure enough no nice misting of the spray pattern just a few shots that looked like they came out of a bad spray bottle. Also noted a few leeks. The reason I did the check in the first place was after removing the heat exchanger I noted a lot of diluted oil coming out of the number 6 hole. I suspect that the rings have never completely seated, possibly due to this injector. I had some spare injectors lying around and they each gave a much better pattern than the one in the car so I switched it. We'll see if it it helps. BTW, I use lacquer thinner in the injector cleaner/testor, it seems to really clean up the injectors nicely. Could never get the one bad one to clean up at all however...

[BHerrmann]

A brief update, I added some 91 octane Chevron to the tank and checked the
CO on my Gunson testor. I was at 3% at idle so I bumped it up to 5% or so.
No run-on after a few tests. The car has always run well, maybe running a bit better now.
One other thing, I've always used a high-temp paint for my heater boxes and mufflers that is locally available in a flat gray. I've never liked it as an exact color match for the stock color but it worked, retained it's color and stays
on. I ordered from Stoddard the correct factory exhaust gray in spray cans, took off the muffler and heater boxes and sprayed the entire exhaust system.
Very happy with the way it looked, I took it out for a 30 minute drive and when I got back the muffler and header portion of the heater boxes had turned copper color, the sheet metal over the headers stayed the correct color. I've been talking to Stoddard and they are trying to reproduce the
experience I've had, they said they would get back to me. Anybody ever used this stuff??

[pwd72s]

Bruce, I'm thinking it may be as much the age of the fuel as it is the brand. Try to avoid the discount stations who tout "oxyginated". (read ARCO in Orygun) But otherwise? Fresh is best, as I've learned with my "premium" burning mopar v-8. It often runs on, when it has 6 month old fuel in the tank.
For the P-car? I use Sta-bil.

[BHerrmann]

Paul, good point. It is a bit strange that this happened after a visit to
a gas station I've never used before. Probably had a lot to do with it.
So far, no more episodes. I think I'm going to bump the octane up a bit as well, seems to run better.