I have an old 81 F250 with a 400 and C6. I rebuilt the original carb. It runs great on choke but idles real fast (no its not the fast idle setting) then when the choke FINALLY opens it won't idle unless you cover the carb with your hand or turn the idle setting way up which of course causes it to idle way to fast. Even on chok when you cover the carb with youor hand it speeds up the engine.

I have all the vacuum plugged off. I am running points ignition (swapping to HEI style if I can be sure the engine is in good shape machanicaly and I can make it run). I was about ready to pull intake off and see if it was leaking when I put a friends older 2100 carb on and it idles smooth and slow. So I am almost certain its a carb issue.

My carb is missing the lever on the throttle shaft between the throttle plates that moves the metering rods, but I really don't think that should come into play at an idle. Before I rebuilt the carb it would not idle but it would put rubber down well into second gear. NOw my trans is out so I can't try it out on the road since rebuild till I get the trans fixed.

I also tried another 2150 that idles pretty good till it stumbles then smooths out. Doees this a few times then dies. I tried another 2100 and it seems to idle pretty well. Could my issue be weak spark from points causing my issues? I of course replaced and gapped the points. New plugs, wires, cap, rotor. Fresh gas.

Timing is at 3 degrees. It runs much better advanced a ways but then it wont start when it gets warm. Has normal vacuum reading when idling with choke on and VERY little vacuum as it slobers to its death when choke opens.

Question 1: What is my carbs problem?
Question 2: Can I run the 2100 with no kickdown linkage without causing trans problems?

 

Obviously there is something wrong with your carb. It could be anything, a wrong gasket, something forgotten during the rebuild, etc. There is no way of knowing, you will just have to go through it again or get another carb.

You do not have to run the kickdown linkage. Just make sure it doesn't lay around somewhere on the engine and get accidentally activated all the time, which will mess the tranny up when it shifts. But if it lays in there in the relaxed un-activated mode, the tranny will shift fine, it just won't downshift when you nail the throttle.

 

I suppose I knew this abut the carb but was hoping for a magic fix Also thanks for the reassurance on kickdown.

 

Must spread reps around before giving it to Franklin. I thought I recognized avi. I am not onmuch but it seems when I am you are there to answer my questions. Thanks again

 

An old, curb-side type of quick check for vacuum leaks was to cover the air horn on the carb. If idle increased, it also increased the possibility of a vacuum leak somewhere in the circuit.

 

That is kinda what I thought, but I have ALL the vacuum plugged off and when another carb is plopped on it idles great. I am not sure where a carb could leak vacuum internally but I am sure its possible.

 

I took carb apart again and found I had used the same shape gasket as I took out for the "enrichment valve". BUt on closer inspection the new valve had a bit different shape. I put a perfect circle gasket on instead of the circular outside and three hump inside like I had originaly put on. I thought it seemed to be better but I had not had a chance to get it good and warm. When I went to back it on my trailer it sputtered and ddid not have the power to get up the ramps. I rolled down and tried again. This time it died like you shut the key off. I had just put 5 gallon in it which isn't much but I am assuming my float is off as well GRRRR.

Do you all set the float by the paper from the bottom or on the vehicle full of gas with the top off?

 

If you have the 'wet' float level spec for your carb, you measure from the top edge of the float bowl directly to the gas.....with the top off, & the engine idling.
I use vernier calipers because there's a bit less tendency for the fuel to 'jump up' & give a false reading, like it does with a ruler.
If you only have the 'dry' spec, you still measure from the top edge of the float bowl, but to the top surface of the float with it in the 'up' (needle valve closed) position. If the carb is off the engine, you can turn it upside down to get this measurement more easily.

Some kits give both measurements, some only give the dry one.
I recently rebuilt a 2150; the wet & dry levels given in the kit didn't correspond.....so I went with the wet level, which is what counts.
The Chiltons manual has both measurements if you have your carb tag number.

The power valve gaskets have that 3-lobe shape so that regardless of how the valve seats, fuel can still get through. A round gasket could block the flow, depending on how the power valve sits.

With the lift cam for the air metering rods missing, you'll be running a bit leaner at wider throttle openings.

 

I took my limping F250 to a trans shop to get the C6 rebuilt. I didn't feel like cleaning it and I like a warranty so I use a trans shop. Anyway, They are also racers. They heard it limp of the trailer and immediately said "Float set right?" I thought it was but hey....I been wrong before. He said he would look at it.

When I went to pick it up the truck still ran like crap. He said he tried to help the carb but had no luck. So now I feel better about not being able to make it run. I took the new parts out of it and put in another 2150 and it seems to be doing just fine. Not sure what that carbs problem is, but its life is over. It will now get hammered so I never try to rebuild it again

But I did learn some things from the experience so thanks for the tips guys!

 

My old bronco did this. Cover the carb with your hand and it would run smooth, It was a tear in the intake/block gasket!(by EGR). When covering the throat of the carb with your hand, the correct volume of air was being consumed. Spray brake cleaner around the whole block-intake surface, if it suddenly races, there's you leak!