Hi,
Here's da deal. 69-F250-360 (I assume)-C6-2 barrel autolite-single exhaust. I rebuilt the carb and when I set it with a vacuum guage it runs well except that when holding a steady speed and just ever so slightly trying to accelerate it feel like it wants to bog a little bit until you give it a little more throttle.I then richened up the mixture screws about 1/4 turn and it runs fantastic, only problem is that it "stinks" like a chebbie with a quadrajet. Really Rich,even if I lean it back out a little and mileage is 7-8 MPG. Initial timing is at 8 to 10 degrees BTDC at specified idle with vacuum advance disconnected/plugged. I get no spark knock and it starts without even barely turning over. Where should I look to get a little improvement in mileage and help the richness problem? Should I try advancing the timing until I get spark knock under load and then back it off just enough to eliminate the knock? Will that help me get a more complete burn/combustion? The engine uses no oil and does not smoke a bit. It appears to be a fairly fresh "Parts Store" rebuilt and even though the block casting numbers show that it could be anything from 360 to 428 (numbers come up as a service block common to 360-390-410-428) I'm assuming a 360 as it doesn't seem that the previous owners would have spent any extra $$, and it has no guts,seeming to be low compression. Any and all thoughts appreciated
Thanks,
Gene

 

is it just fouling the plugs or can you actually smell it down by the exhaust? do you get black smoke if its at idle in your driveway and you stomp on it to 3500 rpms?
if it was rebuilt then maybe the jets that are in it are not the right size. idle mixture is important, especially if you spend alot of time idleing and this will affect the driveability around town if it fouls the plugs, but no need to go crazy with it, as long as its close then its good enough. vacuum gauges are nice, you can pick them up for about 10 bucks at harbor freight, because i'm a picky lunatic with everything on my truck, but as long as you get it to where it bogs down and then out 1/4 turn you should be good.

 

Check the power valve, and make sure you have the same range as the one removed during the rebuild. There should be a number on it some where like 6.5. These numbers are where the power valve opens. Could also be the source of the richness. But recheck the float levels.

You may need to adj on the accelerator pump rod to get rid of the bog. Make sure when you touch the throttle the pump squirts. Sometimes you need to go to a different hole to make the pump squirt quicker. Their should be 4 holes on the throttle and 2 different positions on the pump end of the rod. Try dropping down to make it squirt quicker.

 

No plug fouling, no smoke, black or otherwise, even if idled for 10 or more minutes. "Smell it down by the exhaust?" Heck, if I got that close it would probably knock me out!! If idling, you can smell the richness anywhere within 50 feet of the truck and even while driving slowly at like 15-25 MPH. Smells like the choke is 1/2-3/4 closed. Except for the stench, the truck runs as close to perfectly as I could hope for. Even if I lean it out enough to bog, it still stinks. As previously mentioned I do have a vacuum guage and used it to set the mixture. As for the accelerator pump, at all throttle positions, any slight movement towards acceleration gives a pretty good squirt. The carb is not the original, as I had to find a replacement because the one that came on the truck leaked due to stripped screw holes for attaching the accelerator pump. I'm not sure what it is from (maybe an earlier Bronco) but it has a manual choke and the rebuild kit covered a very wide range of years/models. Power valve could be the issue, I guess I can check the one from the old carb (although, who knows if that was original) against the one that came in the kit. As for the jets, I used the ones that came on truck, as they were missing on the replacement. I'll pull a couple plugs and see what they look like. Is there a chance that the outer ring on the crank vibration damper has spun a little bit to give me an inaccurate timing reading and could the timing being off create a rich running condition? I've been playing with older Fords and Chebbies since the mid 1960's and am usually pretty good at these kinds of things, but this little nuance has me stumped. I realize that I can't expect economy car fuel mileage but 7-8 MPG is at least 15-20 % lower than it should be and the stench is embarrassing. I drive like there is an egg between my shoe and the accelerator pedal and follow all other "good fuel mileage" techniques.
Thanks Again Folks,
Gene

 

My 68 in 1971 only got 10mpg with 97 octane fuel. If I was lucky and did mainly highway and kept the speed under 60 it could get up to 12mpg. And it has a 3.25 diff.

 

+1 i have a 3.25 diff and i use 92 octane and get 12mpg.

68horses if you suspect something is up with the timing you can inspect your timing chain and gears. the stock cam sprocket has plastic teeth that chip and the chain can also be worn. if that is the case the truck will run like crap. but i dont know about it running rich due to that. the harmonic balancer is probably fine as long as its tight. the only ring i know of is an oil splash coffee saucer on the inside which is held in place by a rectangular key. do you have a friend with an exhaust analyzer?