We continue to have problems with our '61 fuelie. Engine was rebuilt along with the F/I unit. Ran great when cold but once warmed up, it is difficult to start and runs very rough. I was advised to try racing fuel. Bought 5 gallons at $18/gallons (110 octane, no ethanol), drained out the California gas and added the new fuel. Runs like a top, cold or warm! I guess the ethanol was causing havoc in the system. I guess this serves me right for living in California. I clearly can't continue to buy $18/gallon. I will try to buy some aviation gas but I've heard it's frowned on by most small airports. Is there anything I can do with our premium gas to offset the ethanol? I'm sure this isn't a new question to the forum. I apologize for bringing it up again but I'm new to the forum.

 

Your FI unit could be experiencing fuel percolation, a common problem under the right circumstances. More information would be helpful to know for sure:

What is the ambient temperature when the engine runs roughly?
When it runs roughly, is the engine idling or are you under way? If under way and engine runs roughly, you've got other problems.
Describe in detail your hot start procedure..... if done correctly, the hot engine will re-fire instantly, even if it subsequently runs roughly.
When the FI was rebuilt, how was the air/fuel ratio calibrated?

If fuel percolation is the issue, postings #5 and #7 in this thread detail the most effective solutions known:

curing FI fuel perc, click here

Regarding premium fuel, no, there is nothing you can do to it to reduce its tendency to percolate in an FI engine. Fuel percolation in Rochester FI is a byproduct of engineering decisions made 67 years ago.

 

I have been running a mix of Sunoco 100 and Chevron 91. The engine runs better in all weather conditions. As Jim says percolation is just part of the game with the FI.
The 100 octane costs 9.99 a gal.
Google it for a station near you.

 

It is illegal to dispense avgas directly into a car but legal to put it into 5 gallon cans, etc then put it in your car (preferably somewhere else).

 

I have the exact same problems running my fuel injected 55 here in California in warm conditions. I've tried insulating the fuel lines, using nylon bolts on the spider blocks and a cooling fan, but nothing worked satisfactory. I recently purchased racing fuel at $18 a gallon, and it runs like a champ. However, that is not a practical (nor economically feasible) solution. I called a local airport who will sell 100LL Avgas to pump into containers, but haven't tried it yet. Just this morning, I found a gas station not too far from me that sells 100 octane pump gas. I'll try that next to see if it helps.

By the way, I also removed ethanol from 91 octane pump gas (its a pretty easy process) and it didn't seem to help much. I spoke to a Sunoco technician who said that removing ethanol would probably have only a minor effect on the vaporization pressure since it comprises only 10% of the volume of the pump gas.

Finally, you should talk to Jim Lockwood about the modifications he can make to your system to alleviate the percolation issues.

 

I have owned a fuel injected SWC since 1979, and probably haven’t driven it 2,000 miles u because of exactly the issues described above. I got tired of having hot start and subsequent rough running issues, and on 95 degree plus Texas days that I just quit driving it. I have decided to pull the engine and let the next owner have the joy of dealing with that. I am installing a 395” AFR head equipped with a Ramjet EFI that Craig fabbed up for me. I would still like to have every one of those I saw for sale for a hundred bucks though.

 

Jim, I'm grateful for your input. Prior to putting in the 110 octane racing fuel, it was my mechanic who experienced the issues with rough starts and underway when the car heated up. He indicated that it occurred when the engine temp was in the 180-190 range. With regard to your inquiry on whether it occurred only when starting or if he also experienced it underway, he confirmed it was both once the engine reached normal temps. He indicated that he opened the throttle to 3/4 when trying to start.

I will bring the beast back to Ed at Corvette Services on Monday to see if he can do some additional magic but I think it will be limited to adding nylon bolts to help insulate the spiders and perhaps some additional tuning. He sourced the new F/I unit for me so he might be the best person to address the setting for the air/fuel mixture.

Is there anything else you can suggest? Did your modifications to recirculate fuel like the later Stingray F/Is and replacing the copper fuel line with steel help. If so, would you be willing to make these modifications to the beast? We're in California so I could drive/transport the car to you. I will try feeding it AV gas once I run through the rest of the racing gas to see if it continues to run better

Many thanks for your help!

Tom

 

Tom,

You may be having a fuel perc issue but my interpretation of your symptoms is that something else is also happening. The reason being that fuel perc stops instantly once the engine has a load applied. Instantly. Like flipping a switch. So since roughness continues after the car is moving, it isn't percolation.

As to how much my modifications help, in the thread I previously linked, see posting #231.

I'm more than happy to modify your FI unit if you want me to. And if you are willing to deliver the unit to me, that would be far better than shipping it. Going forward, we should probably take this off line.

Jim

 

Thanks Jim, my email address is tsanborn@pacbell.net.

 

I drive in Miami with 90+ degrees and awful stop and go traffic. Works like a charm. Zero percolation problems. Two Sundays ago, drove all over Miami at 90 degrees and heavy traffic. Not one cough. My Corvette has zero rough starts. Sometimes I do not drive it for several weeks and it starts right up. Then it runs great and idles at 900 RPM. 1959 Corvette fuel injection and solid lifter and high lift cam all original.
I completely rebuilt my Rochester about three years ago with the help from Jim. He walked me through the calibration which came out awesome.

So what do I attribute my successful taming of the Rochester FI. Well number one to having most of the parts replaced with new ones and the very successful tuning. But the number one contributor, IMHO, is the marine blower that I have cooling the spider and secondly the non-ethanol 90 octane gas I use. Two simple thing that tamed the beast completely.

Jim I already installed the coil over suspension on the 1935 Ford and tomorrow we are starting to install the engine and the transmission. SBC 350 ci/354 hp/416 ft-lb Dyno tested.

 

Thanks Rdelvalle. It sounds like you, with a bit of Jim Lockwood's help, have found the magic formula for creating reliability in a C1 F/I under very adverse conditions. What type of gas are you running? I just picked up 10 gallons of AV gas from our local airport. It's the only none ethanol gas available in CA. If AV gas is the only way to get our beast to settle down and run properly, it would mean that I would always be tethered to the nearest airport and always carry gas containers to transfer it from the pump to the car. Jim was nice enough to offer to take on our F/I issues and hopefully get us to where you are. Just waiting for him to respond to my email address.

 

Thanks for the "wake up call", Tom. I needed it! Check your email.

Sleepy Jim

 

That's because you stayed up to late last night.

 

It was more than a little of Jim's help. He held my hand throughout the entire rebuilt and calibration process. Mi FI is in perfect running condition thanks to him. I use Rec-90 gasoline. That is a 90 octane non-ethanol gas which is named Rec-90 in Florida for recreational vehicle 90 octane. It is readily available in South Florida.
You can make your own non-ethanol gas from the ethanol gas. It is fairly easy once you have the set up. There are several postings on how to do it. If I would live in California I would most certainly would make my own non-ethanol gas, or better yet move to Florida. If you are interested let me know and I will post the link to the posting. I did a lot of work trying to solve the percolation problem and like I said the blower is the number one followed by the non-ethanol gas.
I am not saying this because I red it or someone told. It was my thorough testing that yielded the results I achieved. The non-ethanol gas is a most. But you need to cool the spider and the non-ethanol gas both.
Regarding the blower it is a very simple set up that can be reversed in not more than 10 minutes. If you want to show your engine and not have the blower showing; it can be removed in not more than 10 minutes.
Good luck

Roberto

 

Thanks Roberto, I'm envious of anyone that lives in Florida. Here on the Left Coast, it is almost impossible to find non-ethanol fuel unless you buy AV gas at $6.70/ gallon or racing fuel at $18/gallon. Given that limitation, it would be challenging to take an extended "Buzz and Todd" road trip unless you wanted to shlep along a few gas cans and keep track of where the local airports are. I think I've seen the ethanol distillation method of adding a little water to a container of gas. The water bonds with the ethanol and settles to the bottom of the vessel. Then you syphon off the good stuff on top or drain bad water mixture from the bottom. I'm not sure my wife is up for seeing me trying to crack petroleum in the garage. Besides, you would still be tethered to where you store the good gas. Might be easier to get one of the 32 gallon wheeled gas carts with an integral hand pump and keep it filled with AV gas. AV gas is the same price as premium around here and you don't have to pay for the ethanol that you're throwing away with the distillation method.

I plan on isolating the F/I from as much heat as possible with the nylon bolts idea and installing an electric fuel pump. My next step will be to add your idea for the fan and ducting to cool the spider hub. Finally, I'll try to Shanghai Jim Lockwood to dial in the unit. My cleaver plan is to convince Jim that he needs to take an extended vacation to Santa Barbara. If that fails, I'll resort to the old "Hey Jim, does this handkerchief smell like ether to you"? Then it's just a matter of popping him in the trunk and .... I may be revealing too much.

I did hit the local cars and coffee this morning to catch up with a guy that has been running same '58 C1 with F/I since 1964. He says that the car works perfectly with the local 91 octane gas with ethanol, but has apparently made numerous modifications to the system. At least there's hope.

 

Hi Roberto,

I have removed ethanol from our California 91 octane fuel using the water method. It’s an easy process, but I found it did not solve my percolation issues. I have not tried it in conjunction with a cooling fan as of yet. Have you tried running ethanol fuel with your blower and does it still have issues? Curious to know how much of a difference it makes.

 

Good process of elimination Ktholin. I'd like to hear if Roberto's setup works with ethanol fuels as well.

 

I would love to see a pic of this marine blower or a link to purchase.

 

Here is the link to the posting of how to remove the ethanol. As far as storing you just make 10 or fifteen gallons and keep it in 5 gallon containers. I buy the REC-90 and store it in my garage in 5 gallon containers. When I need it I just fill it up at home. It is just convenience I could go to the gas station and pour it there.

I did a complete restoration of my Vette as it was sitting for about 5 years and had deteriorated to a very bad condition. I did not have to do the paint as it has the original in excellent shape. But every thing else was fair game including the FI. We experimented with many things to address the percolation issue and did it methodically, I bought, I believe it was 100+ Octane racing gas to no avail. Only when we installed the blower and I used the REC-90 did it completely got fixed. We tried the blower by itself using E10 gas and it improved tremendously but once in a while threw a tantrum. When I switched to REC-90 mission accomplished.
So if you do the blower alone you will get a very significant improvement but if you want 100% then you need non-ethanol gas. I am a retired engineer so I was very methodically experimenting with the different solutions changing one variable at a time. You need to cool the spider and use non-ethanol gas. Cooling the spider means using forced convection to cool it i.e. a 120 cfm blower. Insulation IMHO will not do it.

California Recipe try it you'll like it - CorvetteForum - Chevrolet Corvette Forum Discussion

 

Here is the posting where this problem is discussed at nauseum. Jim and I are contributors to this posting. Is long but all the information is there. I explain in detail how to fabricate and install the blower. I do understand that some forum members want to keep the engine looking original and the blower detracts from that wish. I respect their wishes.

I personally do not care to show my car. I had it almost five years and I am yet to be asked to see the engine. To me showing the car means driving it around town and enjoy all the people honking and giving me the thumbs up. I do not have the patience to sit the entire day showing the car. Besides I am super busy right know Hot Rodding a 1935 Ford Convertible. I hardly have time to take the vette out for a ride.
My blower set up is very reversible and you can take it out in abut 10 minutes with no trace of its existence. So if you go to a show to show your car and you are driving the car, when you get there open the hood and take out the blower set up. Before you depart put it back on.
My car is all original including the mufflers, except the blower. If someone is looking at the engine and asks what that is, the answer is that there were a handful of vette that had an experimental set up to address the percolation problem, Mine is the only one left with that option.
By the way do not be fooled with the concept of how simple the set up is and thinking that it is amateur cheap looking. I used Home Depot parts and a West Marine blower and fabricated the set up that looks very professional. It works and it is simple. If the blower fails it will cost me about $30 to replace and about 10 minutes to change.

Fuel Injection Percolation Issue Improvements - CorvetteForum - Chevrolet Corvette Forum Discussion

Regards

Roberto