Something I did for my car this summer

[David Thomas]

This post is a lot of blab, but I hope sharing what I have experienced and did with my car this summer will be of benefit to some of you.

 Last year (2014) I drove my car up until about mid November; it was running great when I parked it in the garage. The weather turned bad, life took over and the car remained parked without being driven or even started until mid February. We had a pretty day so the wife and I took the car out for a 30 mile run and to fill the tank up with some fresh fuel. Unfortunately, the weather turned worse shortly after that and the car sat again until late April without being run. Late in April it had warmed up considerably, the days were sunny so my thoughts turned to getting the car back out for summer drives again. I cranked it up and was letting it idle in the garage while checking for leaks and in general just listening and observing. After it warmed up, while idling it started acting like it was running out of fuel or loading up and just stalled. It would start right up and run but did not want to idle. I checked timing and idle rpm to be sure all was correct, and then adjusted the idle mixture which seemed to help. I drove the car, it ran great down the road but occasionally it wanted to stall when idling or slowing to turn a corner. I decided the fuel I bought in February must have been bad or a winter mix and decided to just go for a drive and burn that tank up, and then get some current fresh fuel. I did that, it did help some but the car still did not want to idle reliably. I continued to drive the car having to repeatedly readjust the idle mixture over the following months, using several tanks of fuel. The situation improved but I did not have a total cure.

 Around the first of July I found an article on the Carburetor Shop's website about the alcohol laced fuel causing a lean mixture. Thus creating leaner run conditions, idling issues, increased heat soak after shut down and to some degree increased run temperatures. Some of those symptoms were just what I was experiencing this year for the first time. This caused me to think back over the years to when I first started experiencing over heat conditions, and increased heat soak with my car. When I first started driving the car in 91 this area had nothing but straight premium gasoline, I had no heat problems and the car performed great. Slowly our fuel supply started to become saturated with 10% alcohol and I think that is about the time I started having engine heat issues with the car, it just ran hotter, performed great just ran at a higher temperature. Even pulling a long uphill grade would visibly move the heat gauge up. At the time I didn't consider the alcohol causing any issue; I chased perceived cooling system problems, eventually increasing cooling system capacity by installing a new 4 row radiator and high quality thermostat. For years this kept the overheating at bay and the car would usually not get excessively hot unless it was idling for extended periods on a hot day.

 After reading the article on the Carburetor Shop's website, I decided to richen the mixture on my Carter AFB that still had the stock factory jetting. The article suggested richening the mixture by 10% if running 10% alcohol fuel. Several years back I had purchased the Edlebrock Tuning Kit that contained jets, jet needles, springs etc. I decided to increase the primary circuit mixture by 10% and to leave the secondary jetting stock for the time being. The stock primary jetting for the Carter AFB consists of 98 primary jets with 70/57 jet needles. My Edlebrock kit had a jet needle set that was 68/52. By using the 68/52 jet needles in place of the factory 70/57 with the stock 98 jets, I would increase the low throttle high vacuum mixture by slightly less than 10% and the low vacuum wider throttle mixture by about 12%.

 I did this around mid July. After changing the jet needles to the 68/52's, I readjusted the idle mixture and proceeded to drive the car. First impressions were positive, the idle was much more reliable plus the engine performance was much better. The car runs smoother, pulls away from stops with much more torque requiring less throttle application, plus cruising down the road at a steady pace seems to require less throttle to keep the car going. Pulling a hill takes less throttle, heat soak is not as severe and the car starts better hot or cold. This was a simple way to richen the mixture without having to open the carburetor to get to the jets. I may increase the secondary mixture the next time the carburetor needs a kit, but for now I haven't noticed any reason to change the secondary jets. Heavy throttle getting into the secondaries is not often needed and when it is, it is only for a short duration usually to pass. Currently, the transition when the secondaries open is smooth and the car pulls well at full throttle.

 I was somewhat concerned about what richening the mixture would do to the fuel mileage. Back in September the wife and I took the car for a full day's drive. We put about 250 miles on a tank of fuel on roads consisting of freeway, two lane highways and a little city stop and go. I got 15.1 MPG on that tank, which is about what I would have turned prior to rejetting the carburetor. Another tank that had more city driving turned in a little over 14; I can't say that the mileage was hurt at all by richening the mixture. Even if the mileage had decreased some, the performance gain and drivability improvement would have been worth it. At this point, I'm pleased with what seems to be a good improvement.

http://www.thecarburetorshop.com/Ethanoluse.htm 

[David Thomas]

Russ, I hope you have success rejetting your cars carburetor and your car responds like mine did. It was such a small easy change but really made a difference with my car.

Jason, glad to know your jetting was successful, too. Your experience helps to reinforce the theory. I like to keep things stock, but in this instance what we have for fuel today compared to yesterday, requires changing the stock settings to some degree.

 LOL.....Thanks Tony, glad all the blab wasn't too boring!

[Jason Edge]

I ended up going 4% richer on power-up and cruise mode on the primaries on the Edelbrock 1411 by using the 73/42 metering rods (and stock 110 jets).  Like you I didn't touch the secondaries, This seemed to help idle and lower end performance. Good to know the 68/52 metering rods are good substitute for the stock metering rods on the original Carter AFB. If I ever get back into a stock Carter AFB set-up I would have to try that. These are in many of the Edelbrock calibration kits such as the 1479 suggested for the 1406 Carb.