250 inline 6 Stalling issue, new to me truck!

[89Suburban]

I miss playing with those old school in line 6's.

 

[Bextreme04]

Ok sweet! I just wanted to make sure! Yea I knew they would drop, it just seems like it’s a bit too much still. Just gotta figure out how to adjust that

The fast idle screw will be the last thing you adjust. When you go to start a totally cold engine, you should press the throttle pedal all the way to the floor once and then let it up. This should allow the choke to pull shut and the fast idle screw will then rest on the fast idle cam as shown in the diagram. That is when you adjust that screw to achieve ~900RPM when it first starts, which will then climb to ~1200-144RPM as it fully warms. Once fully warmed, a quick tap of the throttle will let the fast idle cam drop down and the throttle will then be resting on the regular idle screw.

I highly recommend tuning the carb with a tachometer and timing light rather than a vacuum gauge if you can find one. You tune the carb for peak RPM and then lean it 50-150RPM from peak for best idle mixture. That will correlate pretty close to peak vacuum as well.

 

[South90]

The fast idle screw will be the last thing you adjust. When you go to start a totally cold engine, you should press the throttle pedal all the way to the floor once and then let it up. This should allow the choke to pull shut and the fast idle screw will then rest on the fast idle cam as shown in the diagram. That is when you adjust that screw to achieve ~900RPM when it first starts, which will then climb to ~1200-144RPM as it fully warms. Once fully warmed, a quick tap of the throttle will let the fast idle cam drop down and the throttle will then be resting on the regular idle screw.

I highly recommend tuning the carb with a tachometer and timing light rather than a vacuum gauge if you can find one. You tune the carb for peak RPM and then lean it 50-150RPM from peak for best idle mixture. That will correlate pretty close to peak vacuum as well.

That makes total sense! Thank you! Yea I didn’t want to mess with it just happened to notice when I took the picture! I need to get a tach, got the timing light though! Making sure this carb is dialed in is my next step!

 

[Old Guy Bill]

My first real drivable car, a cherry '71 Nova with a 250.. I'll always have a sweet spot in my memories for it.
I had it bored, added a cam & header and a two carb intake.. it would out run any of the common V6 cars of that era, still got smoked by any 350

 

[89Suburban]

My first real drivable car, a cherry '71 Nova with a 250.. I'll always have a sweet spot in my memories for it.
I had it bored, added a header and a two carb intake.. it would out run any of the common V6 cars of that era, still got smoked by any 350

Yup my first was a slant six in a Dodge p/u with 5 on the floor. I put clifford intake on headers on that as well.

I'm not a Ford guy but my high school buddy had a F-250 with the 300 IL6. That was a tourqey tank of a truck. Later on he got a brick nose F-150 with the FI 300 IL6 and 5 speed manual. That didn't seem to have the grunt the older truck had. I am guessing because of the axle gearing.

 

[South90]

I’m not gonna lie, I’ve never seen one of these engines I thought about keeping it and building it up some, but the amount of money it takes vs a used turnkey 350. I might just end up doing that lol

 

[pinballlarry1]

Good job! If your truck still has the emission decal by the radiator, please take a picture of it and post it. There are others looking for that model emission diagram. thanks.

 

[South90]

Good job! If your truck still has the emission decal by the radiator, please take a picture of it and post it. There are others looking for that model emission diagram. thanks.

 

[DoubleDingo]

Did you post it up in the thread with the labels. If not, please do, and make sure to tag a moderator so they can add a link to the first post, showing it in the list.

 

[pinballlarry1]

thanks for posting that XMR emissions diagram. I stand corrected, yours is twice as complicated as my '81, you even have an air injector pump.

 

[JBswth]

Just picked up an 84 c10 with the 250ci inline 6 yesterday (automatic)! As far as I can tell everything is completely stock! Looks to have the varajet 2se in it. (Previous owner told me about this issue before I purchased, not a big deal just looking for guidance as I’m not too familiar with carbs!)

Truck starts right up, drives great! Really loves old country back roads 45-55 cruising!

Issue is….

If you put it in reverse and not giving it enough throttle, she stalls. Doesn’t matter if the truck is cold or fully warmed up.

Also as your slowing down to a stop light or stopped traffic, most of the time as soon as you come to a stop it’ll stall out. Only once on the way home it stalled as I was coming to a stop.

Previous owner had the truck since 2019, and he told me as he coming to a stop he would just pop it in neutral and feather the throttle to keep it from stalling, or just keep it in drive and do the ol 2 foot action of holding the break and feathering the throttle to keep it from stalling!

All of my research has proven to show me it could be as simple as carb adjustment, vacuum leak, to rebuilding the carb, etc. I noticed there is like 100 vacuum lines (exaggeration) but it’s like a spaghetti of them and drives my ocd crazy! Would like to simplify and clean the engine bay up if possible to! Just looking for some advice and pointers or if someone has had this same issue!!

Thanks everyone!

Does this carb have an idle stop solenoid? If so, is it working? It should be extended when the engine is running. When you shut it off, it de-energizes and the plunger retracts. The purpose is to prevent dieseling/running on after you have shut it off - when the plunger retracts, throttle plates shut.

J. B.