In accordance with new emission standards beginning in January 2010, California's refineries are increasing the concentration of ethanol in most of the gasoline available from 5.7% to 10% starting at the end of 2009. Several weeks ago after refueling, I noticed a rougher off-idle situation on my daily 235 with dual Carter W-1 intake. Especially before the engine was fully warmed up. Opening the idle mix screws did little improvement and I realized I needed a richer fuel/air mix. The W-1 has a mechanical metering rod and adjusting fuel/air mix is easily done by just replacing the rod, accessible on top of the fuel bowl cover. I always wanted to experiment with different metering rods anyway, because the standard size is not ideal when using two 216 carburetors on a 235. Then I got lucky last week and bought an old collection of various metering rod sizes, very cheaply. The standard metering rod size was 67-46 for the W-1 574s model with .093" main jet. These numbers, stamped into the rod, represent the tapered diameter of the rod going from .067" at idle and part throttle to .046" at WOT. In my collection of metering rods I found a pair of 66-50 size. That seemed just what I was looking for, as I needed a slightly richer mix for off-idle and city driving but a leaner condition at wider open throttle when accelerating. I did a test run yesterday and the engine not only ran smoother, but also had more power and really noticeable quicker acceleration. It was much more responsive when pushing into the pedal, compared to before. I could also accelerate much easier now going up a relatively steep hill on my street, at WOT starting from 1st gear. I did a short freeway run as well and both hard acceleration and driving at higher rpm and higher speed was also improved, with a slightly higher vaccum gauge reading. I have to wait for mileage numbers, but I know they will be higher. If other metering rod sizes aren't available, one could drill out the main jet to .094" or maybe .095" and keep using the standard rod. If the ethanol blend keeps increasing in the future, I will have to do that as well and probably also lower the float level a little. Hope this helps other Chevy 235 owners with dual Carter W-1 carbs and too much ethanol in their fuel.
Just to add on to this, the shop where I am working, we are having real problems with rebuilding carb and fuel pumps to withstand the newer fuel, back in the twentys the carbs were made out of brass and bronz for this reson, so now we do not use the viton tipped flote needles and the same with the fuel pump vavles, hav't to use the bakealite/phnolick ones, as a result, the fuel tends to go back to the tank if the car sits for a couple of days! Nothing for it, just have to live with it.....hope that little bit on info helps....Roach.
The Stromberg bxov-2 carbs on my 261 didn't require any adjustments to the main metering jet, using the very same fuel. However, last summer I tried fuel with more than 10% ethanol and the Strombergs didn't like it at all. The Carter W-1 and 235 combination is apparently more sensitive to the ethanol blend at only 10% already. Both types of carbs use leather as accelerator pump pistons and at least that is not a problem with ethanol. If the blend keeps increasing, I may just separate the ethanol from the gas in a larger fuel canister, adding water, which disolves the ethanol and sinks to the bottom and then could be drained. Since I only use one tank of fuel per month, this may be an option. I would get better gas mileage and power for sure then ...
This is interesting. We have had 10% E for years, actually since they took out the MTBE, which was methanol. Which was also 10%. My old carbs have only needed and idle adjustment and a float lowering. Float lowering because the specific gravity of this fuel is less dense than real 100% gasoline. We also have a winter blend and a summer blend which also needs an idle mix adjustment to keep up on. I read somewhere about there being 50+ different blends of gasoline for the whole country. And it dosen't suprise me that you need to do different adjustments than I do to keep running nice. One of the interesting componants here in NJ is Benzine. A known Cancer causing item. And the distribution yard ADDS it in to every tanker load. Gotta keep the medical profession busy.
I've tried this on a small scale. Do it in a clear container. So you can see the water/ethanol at the bottom. You need to aggitate to blend it all together, then let it rest, and when the mix is clear on top again. it's gasoline. A clear division between the two liquids.
Yes, I tried the ethanol separation using water inside a syringe with a scale to determine the ethanol content. I am thinking about using a 5 gal. glass carboy with a tap to drain the water. We also have summer and winter gasoline in CA, but I never have to adjust the idle mix. Must be our particular mix of other ingredients.
And the next step would be to distill the waste mixture to produce 100% ethanol again. There must be a use for that.
Excellent work, thanks for posting your results. Have you experimented with metering rods from more common 4 bbl. such as the AFB, QJ etc. (which are still available) by soldering the stepped shaft to the "hanger" part of the Carter? Depending on how much room you have some may be joined by a tiny section of brass tubing slid over both. Re: jet sizes. To calculate what effect a change will have, it varies as follows: Main jet ID (not the # size)^2 - metering rod diameter^2. Using your examples: .093^2 = .008649 Power (thin) step .046^2 = .002116 Current area = .006533 New power step .050^2 = .002500 New area = .006149 Change = .006149 ÷ .006533 = 94.1%, or 5.9% leaner. Remember that changing only the main jet changes both power and economy metering - but never in the same percentage, the economy is always affected more. I have an Excel spread-sheet that does this automatically, e-mail me for a copy.
If you do drill the jets... there's no going back... I'd recommend finding the larger jets... You should be able to find them readily available.
Panic - I haven't considered making my own metering rods, using the shaft from the other more readily available Carters. However, with the rods I have, I noticed a great variation in the location where the taper starts down the shaft and not all are usable for the W-1. I was very lucky finding a pair that had the numbers I wanted AND the taper also started on the exact spot as the standard rod. That's why I posted the new improved rod number, saving time and trouble for those who find this post. I haven't worried about the math, until you showed the example - Interesting. I noticed you didn't use the standard formula for area of a circle (p x radius²) I guess, that's to simplify calculation, since the results are close enough. Math and dyno tuning can be fun and insightful, but driving around and often, tells me all I need to know. Nevermind fuel injection and computers....I'd be afraid of falling asleep while driving....haha sdluck - Trying different idle mix and timing settings didn't help, as apparently the fuel/air ratio changed with increasing ethanol. wingnuts - I am not worried about that, as I still have the original jets that came with the carbs, before I swapped everything with new parts of the repair kits. Thanks for all the comments. I am no expert on any of this. Just an every day driver, but proud to have figured this out and my old 235 has come alive.
Using the traditional universal formula, I get a 3.24% difference richer economy and 6.04% difference leaner power settings with the new metering rod. Almost the same results as using the simpler Edelbrock formula.
road runner, In Iowa we have regular,w/87 octane. ethanol,89 octane. or premium, 91-92-92 oc. I thought only the 89 oc has ethanol in it.We use the ethanol most of the time, (knowing the pure gas gives better MPG) also use it in boat motors, weed wacker, lawn mower, ect. I've never had any problem w/ ethanol!!!! ever!!! I do heed warnings about storeing over the winter.... use real gas!! now the problems local people have (and don't understand) is that w/ gas, you buy aload of shit,, water dirt ect. now you buy that tank full of 89 oc ethanol, to try it ....and it takes all that "shit" resting in the tank, and runs it all into the system plugging every thing!! Yes i have pulled many filters, carb full of shit!!! My advise, check your tank, maybe clean it out, add a large filter, and change it !! you may need to clean the carb, I'm not sure about adjusting carbs between tanks of fuel........never heard of it ....ben us'n this ethanol for over 15 years!!!!! Now we have blender pumps! you can choose your % of ethanol! thinking about the power I could get out of my 10.5 to 1 CR rod! maybe a 60/40% blend, set up the timing.....
The change I noticed was after refueling and didn't go away after a few more. And I have been anticipating the increase in ethanol for CA gasoline sometime at the end of 2009. It was not a big change, but since I drive this truck almost every day, I noticed something wasn't right all of a sudden. I opened and inspected the carbs and checked the filter and tank, adjusted the idle mix and timing before I experimented with a richer fuel/air mix. That not only solved the rougher idle and off-idle, but also improved the overall performance noticeably and the spark plugs look great thus far. It tells me that using a pair of Carter W-1 on a 235 requires experimenting with different metering rods to get better burn in the cylinders, regardless of ethanol. What's interesting also is, that I am at 4000 ft. altitude. At sea level, I would want to go with a richer metering rod for sure, especially the more ethanol is in the gasoline.
A note on jet selection: If you drill it out, it's possible to get another choice (but not exactly what you have) by soldering the jet closed and re-drilling it, but the chances of getting the exact flow rate on 2 different jets isn't very good, perhaps within 5%. Jets, even for the same brand carburetor, sometimes differ as to thickness, and also have different countersunk angles at top or bottom. These should all match as they affect how much fuel the jet flows. There are a limited number of threads used to mount jets, and may be the same between not only models but brands (with the above exceptions). The common Holley 122-XX is 1/4-32.
that's to simplify calculation, since the results are close enough. The results are exactly the same down to the last decimal point.
Road Runner - as the metering rod has no function in the idle circuit (unless you have a 1000 + RPM idle), my guess would be some foreign material in the idle circuit which you cleared when you changed the rods. As you have noted, there are MANY different shapes of metering rods for the same type carburetor. There are also different overall length rods for the same style, so having an original to compare overall length and step length is very useful. We have the capability of making rods; but the lathe used is fully manual, thus time-consuming (read - not cheap!). For ethanol mixes, we suggest drilling the idle tubes 0.002 inch oversize. Even if you are somehow able to get real gasoline, this doesn't harm anything, as you can cut the volume by adjusting the idle mixture volume screws. As for the metering rods: Since the effective metering area is the area of the jet less the dynamic area of the rod; drilling the jet will effect both high vacuum (economy) and low vacuum (power) settings IN DIFFERENT PERCENTAGES. Thus changing the rods to maintain a certain percentage change in mixture will give best results. However, since few utilize WOT often, simply tuning the high vacuum step will suffice for these users. And in the "for what its worth" category, the blueprint tolerances on the metering rods are 0.00002 inches. Jon.
And since you posted the altitude at which you live, you might be interested in the following Carter general calibrations: Sea level ~ 4000 feet - standard calibration 4000 ~ 6000 feet - 1 size lean 6000 ~ 7000 feet - 2 sizes lean 7000 ~ 8000 feet - 3 sizes lean Generally, one size lean was done by changing rods only. Two size lean calibration could be rods only; or rods and jets; or rods, jets and vacuum spring. Three size lean calibration virtually always was both rods and jets, often with a spring change as well. We have found that as a general rule; the sea level calibration works well from 4000 ~ 6000 feet when using E-10. Jon.
Thanks for your input, Jon. I rather stay away from drilling the idle tubes by only 0.002 oversize My problem was mostly the off-idle low-speed driving, which just wasn't right anymore, especially before everything was fully warmed up. I remembered your advice from last year, when I was looking for a leaner rod because of my altitude, that if anything I need to go richer, because of the ethanol in the fuel. Update: I did a few more experiments with separating the ethanol and also comparing with the original metering rods. While the off-idle is good now with both rods, there was a noticeable difference in power whenever I drove the richer metering rods, with or without ethanol. Checking the spark plugs shows no difference. Looks like I had a partially plugged idle tube in one carb, but I learned a couple of things from this: I can increase power by changing the metering rods. As the ethanol blend keeps increasing in the future, I will be prepared. Removing the ethanol drops the octane level by about 2-3 points. Engine runs smoother without ethanol, regardless of metering rod size.
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