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2100 motorcraft advice needed.

SKOOTER

Jr. Member
Joined
Nov 6, 2007
Messages
84
Loc.
Sacramento,Ca.
I have re-built carb, and the problem i have is the cars rpms are not high enough in drive, 1,2 , rev. It almost's dies unless im not messing with pedal. If I adjust the idle screw to be ok in drive, 1, 2 , rev; then when its in neutral or park it is way, way to high. I cant get a happy medium. I have also messed with both carb adjusting screws. There is no dash pot on this carb. I have stock points disributor with no vacuum advance. Its a 289. New tank, electrick fuel pump, filter, lines. Is this just a normal 2 barrel occurence? any help is appreciated.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
X2 on the vacuum leaks. how high is the idle in park when its set so it doesnt die in Drive? It sould be around 200 rpm higher maybe a bit more. Also timing can affect the idle speed/quality you may want ot recheck the timing. Points wear constantly and the timing changes as they wear.
 
OP
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SKOOTER

Jr. Member
Joined
Nov 6, 2007
Messages
84
Loc.
Sacramento,Ca.
about 1200 rpm at park and neutral. about 550-650 in all other gears. When you say it should be around 200 I cant imagine my rig even running at that rpm. Thanks for reply
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Idle speed is not 200 but it should only drop about 200 when put into gear. idle speed in gear should be about 650 rpm the idle speed when in park will allays be high although yours sounds to high so maybe theres a vacuum leak as stated.
 

Justafordguy

Contributor
Bronco Guru
Joined
Sep 26, 2009
Messages
6,253
Vacuum leaks will cause higher RPM. That's really what it sounds like to me. Have you adjusted the idle mixture screws? That could also cause it to be lean at idle.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Yep vacuum leaks cause higher rpms and when a slight load is put on the engine it will cause issues like you are having. One way to tell if you have vacuum leak is usually your idle mixture screw adjustments will have little effect on idle quality. Doesnt matter if the dizzy has vacuum advance or not as long as the vacuum port it was supposed to be hooked to is plugged off at the carb.
 
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SKOOTER

Jr. Member
Joined
Nov 6, 2007
Messages
84
Loc.
Sacramento,Ca.
A key thing you said was idle screws will not be affected by adjustments if there is a leak. That desribes my scenario. Got new can of starter fluid and sprayed the base of carb. There was a difference in rpms while doing that. Last time i barely sprayed carb and didnt really notice anything. I re-tightened carb and that did make a difference and idle screws now responded to adjustments; but I still have leak at base of carb. Im afraid of overtightning and snapping those studs. Like I said, i just re-built this and put new gaskets betwween spacers. Maybe i should try some sealant also?
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
either double up the gasket or get one of the 1/4" thick gaskets that are availible they will help. Also make sure the spacer block or egr plate under the carb is not cracked especailly if its plastic. Did you replace the gasket under the spacer block/egr plate?
 
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SKOOTER

Jr. Member
Joined
Nov 6, 2007
Messages
84
Loc.
Sacramento,Ca.
Replaced new gaskets with some thick new gaskets. I also put sealant on and now no more leaks. What a difference. now I was able to time it at lower rpms and do some final adjustments with idle screws. I can't believe the difference. It purs at about 700 rpms. I didnt understand the relationship with timing, and carb but Im gettting it. Im able to put it in gear without it dying or consantly feathering gas pedal . Next Im gonna try to figure out how to use my vacuum gauge for final adjustments. Thanks all for input
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
You want highest steady vacuum you can achieve with the adjustments it might take doing each side a couple of times.
 
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