C1 Fuel Injection Octane needs.

[Dan H.]

Re: C1 Fuel Injection Octane needs.

Thanks Jim, yep, it fits snug against the top gasket, has a shoulder on it so doesn't go down too far. Ken Hanson shut off valve, works great! Rochester runs fine, love the 380 units!!! Keep em running!
Dan

[G B.]

Re: C1 Fuel Injection Octane needs.

... And I assert, with plenty of available proof, that it's not possible to use modern motor fuel in an early FI engine "without issue".I'd be glad to hear from even one individual who can prove that I'm wrong.

Jim, who accepted your challenge? I'd like to hear from them too.

Jerry

[G B.]

Re: C1 Fuel Injection Octane needs.

The Genesis of my orgional question was based upon a statement by Jerry Bramlett: "WARNING: a 1957-1965 Rochester fuel injection system will NOT always work properly on a stock engine using modern pump gasoline. You must use UNDILUTED 108 or 110 octane racing gasoline in your car after I calibrate your FI unit to get its best preformance. If you're unable or unwilling to buy racing gas, please don't ask me to work on your FI systems"This would seem to say to me that 100 octane Aviation fuel and 100 octane pump Racing fuel are better than ethanol but fall short or 110 octane Racing fuel. And, I am still not clear as to any advantage of a TetraEthyl Lead additive-if any.Again, I have a source for 110 Octane Racing fuel but not 100 octane Aviation fuel and if 110 octane is superior to 100 for FI units, this this would be my first choice.

Richard, I tried very hard to explain why I put the fuel warning on my website. In fact, I even put a link to my explanation at the end of that "warning". In my write-up "Pump Gas Isn't Good Enough", you only need to read the first three paragraphs to understand my perspective. You may not agree with my test results or opinions, but I did post them on my site for FI owners to consider before calling me.

I wish you well in your search for a better fuel solution than 108 - 112 octane racing gasoline. However, I can assure you that it isn't going to be pump gas with magic additives.

Jerry

p.s. - I have no experience with "100 octane racing gas". I've never heard of it. My concern is that if the station can legally pump it directly into your car's tank, then it has boil-off properties similar to ordinary pump gas.

[Duke W.]

Re: C1 Fuel Injection Octane needs.

I'm having trouble parsing your meaning. This reads as if you are saying that fuel perc tendencies are the same with winter and summer fuel. Surely, that's not what you mean to imply.


Must be a carburetor thing. Rochester FI goes full lean when fuel perc sets in.

Jim

The primary difference between winter and summer blends is the low end boiling point. Winter blends are somewhat lower (higher RVP) to aid cold starting. I don't think there is much difference in the 20-50 percent boiling points, so summer fuel doesn't have much more resistance to percolation than winter fuel, but, of course, percolation is more of a problem in warm summer temperatures than cooler winter temperatures in California.

When carburetor bowls percolate the vaporized fuel is vented to the air horn and then drawn into the engine. The resulting mixture is overly rich. The FI fuel meter vents vapors to the atmosphere, so this fuel does not enter the engine, but at idle and on hot restart the fuel pressure in the spider is only a few psi, so percolation in the spider can cause an excessively lean mixture.

Either an overly rich or overly lean mixture can cause rough idle and low speed driveability problems like hesitation and generally poor throttle response until the excess fuel vapors are consumed by the engine (carburetor) or engine load raises fuel spider pressure high enough to keep the fuel in the liquid state.

Duke

[Michael W.]

Re: C1 Fuel Injection Octane needs.

Jim, who accepted your challenge? I'd like to hear from them too.

Jerry

My 57 FI 250 HP Powerglide runs fine on Shell 93 octane with ethanol.
I broke in the engine on 100LL ave gas but found it was a waste of money and if you drive a lot you it's not readily available.
The engine was a fresh rebuild with 9.5 compression and a L-79 cam.
I have put about 4000 miles on the car and runs fine, starts when cold or hot (90 * plus weather) and has never had a percolation problem.
I think the thick 1 piece gasket helps along with a great tuneup by Bob Williams in Sidney, Ohio.

I don't know Bruce personally, but do know others with FI who have had the same positive experience with straight pump gas. None live in/near the swamp, this seems to be a critical factor

[G B.]

Re: C1 Fuel Injection Octane needs.

I don't know Bruce personally, but do know others with FI who have had the same positive experience with straight pump gas. None live in/near the swamp, this seems to be a critical factor

Do you know owners with '57 - '62 Rochester FI units on stock Corvette engines who never have percolation on hot restarts during warm weather when using pump gas?

[Richard S.]

Re: C1 Fuel Injection Octane needs.

Jerry, Thanks for the response. Based upon your input as well as several other NCRS members, I felt the only reasonable choice for me was 110 octane racing fuel.
It will be delivered to my house in two weeks at a cost of $416/54 gallons or $7.70/gal. and there is also a $50 delivery fee and $25 for a pump. My question was an effort to see if others had found success with aviation fuel, or TEL additives and the answer seemed to be-maybe in some situations. Now, as far as storage goes I do not see any problems since I already store 6 vehicles in my garage and drive out basement containing 120 gallons plus. A check with my local fire dept. revealed that it must be stored in a steel container. If there are other consideration please advise me since it is my intention to store this in my garage as a matter of convenience.

[G B.]

Re: C1 Fuel Injection Octane needs.

Richard, that's exactly what I do. I pay $450 for 54 gallons of VP 112 delivered. I personally think the VP brand is better (longer-lasting, better smelling) than Sunoco / CAM2.

Since I go through $3,000 to $4,000 worth of VP a year, I've become used to the hassle.

[Bruce B.]

Re: C1 Fuel Injection Octane needs.

My 250 HP 4360 #136 runs fine on Shell 93 octane diluted with ethanol.
My question to the 110 fuel or 100LL users is, what do you do on a trip over 225 miles? Assuming you get 15 MPG.

[Jim L.]

Re: C1 Fuel Injection Octane needs.

The primary difference between winter and summer blends is the low end boiling point. Winter blends are somewhat lower (higher RVP) to aid cold starting. I don't think there is much difference in the 20-50 percent boiling points, so summer fuel doesn't have much more resistance to percolation than winter fuel, but, of course, percolation is more of a problem in warm summer temperatures than cooler winter temperatures in California.

Hmmmm, well, how much is "much"?

With the winter fuel we've been getting and seem to be still getting, I can see fuel perc happening when outside ambient is anything greater than 65 - 70. However, with summer fuel, temperatures have to be greater than 80 - 85 before fuel perc again rears its head.

For my money, that's a meaningful difference.

The FI fuel meter vents vapors to the atmosphere, so this fuel does not enter the engine,

Yes and no.

With the engine off, fuel vapors will vent to the atmosphere. However, when the engine is running, manifold vacuum (operating through a restriction) pulls bowl vapors directly into the doghouse. The vapors which get pulled into the doghouse don't significantly mitigate the effects of fuel perc in the spider, though.

but at idle and on hot restart the fuel pressure in the spider is only a few psi, so percolation in the spider can cause an excessively lean mixture.

A few tenths of a psi, actually.

or engine load raises fuel spider pressure high enough to keep the fuel in the liquid state.

A "trick" which will instantly stop fuel perc is to start driving. By that I mean that as soon as the engine starts, let out the clutch and go.

The engine will stumble a bit in the brief interval between engine start and clutch engagement, but will immediately smooth out once the vehicle starts moving. Works every time.

[G B.]

Re: C1 Fuel Injection Octane needs.

My 250 HP 4360 #136 runs fine on Shell 93 octane diluted with ethanol.My question to the 110 fuel or 100LL users is, what do you do on a trip over 225 miles? Assuming you get 15 MPG.

Bruce, your definition of "runs fine" might differ from mine. Yes, all four of my test cars will "run fine" on pump gas.... well, except when I try to idle a '57 - '62 unit at 800 rpm for extended periods in hot weather over 90 degrees, or I've just started a unit up after a brief period of heat soak, or I hold my foot near the floor while driving for minutes at a time. What are your results under those conditions?

I get about 20 mpg on the highway with my 3.70 rear cars. The 4.11's get about 17. My cars "run fine" on the highway using pump gas, but they won't idle worth a crap in hot weather for long. And no way would I test my top end with pump gas in the tank.

Jerry

Clarification: The design of the spider feed tubing was changed in '63 to combat percolation. This factory improvement actually helped, so the '63 - '65 models don't percolate as much during extended idling on pump gas.

[Joe L.]

Re: C1 Fuel Injection Octane needs.

All-------


A lot of these problems with FI that are discussed in this thread were prevalent back in the 50's and 60's using the "old time" gasoline formulations that a lot of folks today think were the greatest ever. In fact, that's why a LOT of these FI systems were unceremoniously separated from the cars they were originally installed on. I did one of these conversions myself to a 1964 FI that my brother owned back in the mid-60's. Neither myself nor anyone else could make that thing run right. Finally, my brother, who really didn't give a hoot about FI anyway, had me swap out the system for a manifold and carburetor. He was then quite happy with the car for several years.

It's possible that today's gasoline formulations, and especially E10, might somewhat exacerbate 57-65 FI problems. However, I don't see how octane rating has anything to do with it. As far as octane is concerned, it should be sufficient in today's fuel for any 57-60 FI. It might be marginal for 61-65 but I still think it should be sufficient.

To me, the the logistical problems created by having to use alternative fuels (e.g. aviation fuel, racing gasoline) would be FAR too much of a constraint on the operation and enjoyment of a car. There's not only the expense involved but the problem of accessing the fuel when you need it. I want to be able to pull into any gas station and get fuel and not have to plan my driving around obtaining fuel. In addition, the idea of storing relatively large quantities of gasoline in drums in my garage or otherwise on my property is something I would have no intention, at all, in getting involved with. In fact, in many areas such storage would be illegal.

So, I'd have to say that if I owned any 57-65 Corvette FI and I had to use alternative fuels in it, I'd probably do the same thing I did for my brother way-back-when.

[Michael W.]

Re: C1 Fuel Injection Octane needs.

Do you know owners with '57 - '62 Rochester FI units on stock Corvette engines who never have percolation on hot restarts during warm weather when using pump gas?

The answer from each of them is 'it's no worse that back when 'gas was gas'. I took that to mean it's the nature of the beast.

[Jim L.]

Re: C1 Fuel Injection Octane needs.

The answer from each of them is 'it's no worse that back when 'gas was gas'.

I disagree with that conclusion.

I've been driving fuelies for 35 years. My perception of the fuel perc problem is that it is significantly worse now than it was back in the day.

With the winter fuel I've been using, I've seen fuel perc with spider temperatures as low as 105F.

[Michael H.]

Re: C1 Fuel Injection Octane needs.

I've been driving fuelies for 35 years. My perception of the fuel perc problem is that it is significantly worse now than it was back in the day.

.

Jim

I agree with you. Again.

I've been driving fuelies for just about 50 years. (57 FI BelAir in 1963, then Corvettes since) They all had some minor hot restart/idle issues but not as bad as with today's E10 fuel.

Fortunately for me, there is ethanol free fuel about two miles from my house.