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Discussion Starter #1
I was playing around with the main jet in my 1100 today (200 6 cyl). I have been running a #69. According to the Ford manual, it is supposed to be a #67. I installed a 67 and the car would hardly run while driving. It idled well but bucked and snorted while driving. Needless to say, I went back to the 69. I would not have thought a .002" difference would have made that much difference. Ive been chasing poor fuel mileage. I get 16 mpg average. It runs good and the spark plug color looks good so, the chase continues. ... Sure has me wanting to try a little larger jet size just to see how it runs though :) Unfortunately, 69 is the largest i have in the parts bin.
 

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The tolerance on jets in that age range is greater than u think. I remember an article where they said moving one number was pointless. Holley used to sell close tolerance jets but today they are probably all much better
 

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I've been thinking about trying the same thing (for the same reason) I just didn't have any other jets laying around. So thanks for posting this.

I am kinda disappointed to hear that it didn't work. I was hoping that'd be an easy solution.
 

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Discussion Starter #4
Im not sure whats going on with mine. Like I said, it runs great. Bump the key, and it fires right up and idles smooth. I bumped the timing to 12 degrees from its base of 6. Any higher than that, it surges at low speeds and pings. Manifold vacuum is 19 hg and steady. Compression is excellent on all cylinders. Dwell is set to 38 degrees. I will add that I drive it 70-75 mph quite a bit and of course, she's wound tight at those speeds so, 16 mpg may be the best she can do.
 

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When addressing fuel mileage issues on early sixes that seem to run decently I always start looking at three things. First is any sign of external fuel leaks that might not show up as drips on the ground. Does it smell "gassy"? Are there signs of fuel stains around the carburetor/manifolds or fuel pump? The next is checking the vacuum signal from the carburetor when equipped with a spark control valve (SCV). The vacuum signal range is VERY small, from near zero to around 4"hg and is ENTIRELY responsible for controlling ALL spark advance on SCV engines. Lastly, is the condition and calibration of the distributor. The Load-O-Matic distributor, used in conjunction with the SCV-equipped carburetor, needs to be in good condition and respond to those small changes in vacuum signal. Non-LOM distributors that have both mechanical (centrifugal) and vacuum advance mechanisms need to be accurately adjusted to provide optimal performance and fuel economy.

Another two things to look at on the 1100 that can have an effect on fuel economy are the power valve and vent valve. The power valve must move freely and can be adjusted by adding and removing calibration shims that pre-load the spring on the power valve rod. The vent valve adjustment will prevent pressure building in the fuel bowl which will force excess fuel into circuits that would ordinarily rely solely on suction to draw fuel.

You might want to consider giving these things a look and sending off your distributor to Dan Nolan at The Mustang Barn to have him go through it and bring it back to specs.
 

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Discussion Starter #6
Bart, Ive looked at and addressed all of those issues with the exception of the distributor. Im currently searching for a distributor to send off to Dan for a rebuild now so that I can continue to drive my car while its being rebuilt. Thanks for the suggestions!
 

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Discussion Starter #7
Just found a distributor and will be shipping it to Dan next week.
 
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