carb too rich

C

charlie's 68-6

New member
hi all, i have a 68 mustang with a 200 hedders(thanks mike) 2.25 pipes all the way back with mufler shop turbos.i fabricated an adapter to put a carter/motorcraft 1 barrel from a '77 250,i turned the adapter to have the throttle tip in to the head versus the front of the engine,the car runs great however i can't get the idle down below 1100 rpm at idle,manual transmission in neutral,it runs so rich that its almost not fun to drive. where is the idle jet on this carb and where can i get a leaner size ?the number on the base of the carb is 7287S no other numbers anywhere.
thanks in advance
charlie
charlie's 68-6
 
yes,the mixture screw has an effect on the idle quality but the idle speed adjustment screw isn't even on the stop.still can't get it slowed down.
charlie
 
mpgmustang, no still haven't gotten it leaned out, it runs real good on the road so i know its in the idle ckt. i just don't know what to look for.i'm open for any ideas.
charlie
 
8) first make sure you dont have any vacuum leaks.

second, the idle jet on that carb is not replaceable, but the main jet is. perhaps a call to pony carbs will net you a smaller main jet.
 
Howdy Charlie:

I'm guessing that you are working with a Carter YF. It may be labeled "Motorcraft" some where, but it should be a Carter YF. The YF was the six cylinder carb until 1979.

It will have two screw adjustments. One is the idle speed. The other is a low speed air screw. Changing jets will not have an effect on the idle richness. Put the idle mixture screw back to it's original setting, aproximately 1 1/2 turns out. Until you can get the idle down there is no point in messing with the low speed air screw setting.

My guess is that you are not getting the throttle butterfly to close; either because of a linkage hangup or the butterfly is not properly seated. Try disconnecting all linkage hookups. Find the idle speed screw and turn it to the left all the way. This will to allow the butterfly to close completely. Now manually snap the throttle plate shut, by opening it all the way and letting it snap shut. This may align the butterfly allowing it to seat better.

You may have a hangup with the choke fast idle cam also. Make sure the choke is fully open and that the fast idle cam is not engaged.

One advantage of the YF carb design is that they have a vacuum operated metering rod acting on both the main and power enrichment systems. High vacuum leans the systems, low vacuum enriches them. So changing the jet for your application is typically not necessary. And, the CFM went from 150 on your '68 200 to 195 on a 250. Also all carbs in '79 were designed to run leaner than the downsized 1100 on your '68 Autolite 1100. The YF metering rod system is similiar to Carter's AFB design. The YF design does have a weak accelerator pump system and needs regular rebuilds to avoid a big bog when you step on it.

Check it out an keep us posted on your progress.

Adios, David
 
David,
Thanks, the throttle bindage I have on my 1100v due to the bigger (later) head. and i've seen this as it happens.

Charlie,
Try taking the idle srew out (when engine is off) and see if it's broken, also see if it can help if you screw it in further without the spring... I also think you have a vacuum leak, have you checked your vacuum can for leaks? my old LOM cannister achieved a leak every 6000 miles. extra air with lots fo gas on start up will make it run rough, also reset ur choke, if it's automatic make sure it can get that hot air.

cleaning is also a good thing, while running slean the carb with carb cleaner, try not to spray any down the throat. clean ur idle mixer screw,

GL and keep us posted
 
thanks david and david, i took the carb off thursday evening and cleaned all of the gasket surfaces .while it was on the bench i checked the linkage and saw that the bowlvent lever wouldn't let the throttle go closed all the was ! i got that re adjusted, the choke is all the way lean so that isn't a issue.the throttle is fully closed now! i put new gaskets on with a thin swipe of RTV, let it dry and reassembled it friday nite.saturday evening was the next time i could get to it, the idle mixture screw i set to about 1 and 1half out got it started and had to adjust the idle stop to keep it running, i was really rough so i backed the mixture screw out until it smoothed out ,not quite a nother half a turn.the timing is at 16* at idle no vacumn,the vac port i am using has no vac at idle but increases as i speed up the rpm's.one of the other ports has about 5 in at idle so that port is capped.also the vac advance has been replaced.the advance port that i am using doesn't show vac as soon as i open the throttle , should it? after the engine warmed up i tweeked the timing and the idle mixture to no avail. it is still so rich that even with the garage door open my eyes were starting to sting. so i quit for the evening.i am so frustrated with this,it shouldn't be this difficult to get right. sorry for the long post ,thanks in advance for any more ideas.
charlie
 
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