Well I am stumped, please help me!

OK, so I am having this problem. My engine is a freshly rebuilt Ford FE 360. Stock intake manifold, stock cams, stock everything. It's in an 1976 F-150 truck. The carburetor I put on there is practically brand new but I think it might be the wrong one because the engine won't run well. Someone purchased this carb and threw away the one that originally came on the engine. It is a Motocraft 2150 carb. It says AN2 1.21 on the side. My homework says that means the venturi size is 1.21 and it is a 351 CFM carb.

My vehicle has an EGR valve which mounts on a spacer underneath the carb and is turned on by spark vacuum only when the engine is heated up. A ported vacuum switch keeps EGR from engaging until the engine is warm.

My vehicle also has a PCV valve system. The PCV valve is on the passenger side valve cover and then there is a breather on the driver side which has a hose to bring in fresh air from the air filter body. There is a breather filter there.

The vehicle does NOT have a smog pump. It also doesn't have a charcoal canister or whatever that is. Only PCV and EGR.

The carburetor has a fat connection on the back (where I have PCV connected), then it has a small connection on the back (don't know what it is, probably manifold vacuum), then it has the "spark" connection on the side underneath the choke (I have EGR and timing advance hooked here). Then it has the "air horn" connection, on the top, and then on the front underside, on the driver side, there is a connection that is not used. I read somewhere that this connection was for some kind of charcoal canister system.

What is happening is, when I try to set the timing to around 10 degrees BTDC, the engine practically won't run. It just kind of wants to stumble and die. I have to set it at 15 degrees BTDC for it to stay running at idle. It also won't start unless I have it around 15 degrees BTDC. Even then it is hard to start and I have to feather the gas pedal.

When the engine is at normal operating temp, I try to set the idle mixture screws, using a vacuum gauge. I can not get more than 15 on the vacuum gauge, no matter how far I turn out the screws, and if I turn them in too far the engine starts to die.

So, if I set timing around 15 degrees BTDC, then when I try to start going from a stop, the sudden accelleration makes the engine backfire out the carb and die. Also if I am going along with the engine at high revs, then let go of the accellerator, the engine wants to stumble and die.

I checked the vacuum system very carefully and I can't find any vacuum leaks. Everything seems fine with the vacuum connections.

So, my little brain is thinking, maybe the engine is running way too lean all the time? I checked the fuel filter and it's fine. The fuel pump was also replaced recently.

So what I'm thinking is, what if the person who bought the new carb didn't know exactly which one to buy, and got the wrong one? Maybe they got a carb that had the wrong jets for this setup? If the jets are too small wouldn't this cause a lean condition all the time, forcing me to run timing that is advanced too far?

On a motocraft 2150 can I find out what jets are in there? Can anyone tell me what jets this particular engine and vacuum setup call for?

Or do you have other ideas? I have a vacuum gauge, a tachometer, and a timing light. I have followed the directions for setting timing, idle mixture, and idle speed. I just can't seem to make this engine run right, it acts like it is always going to die.

The thing that makes me suspect the carb is, this carb was purchased before the engine was replaced with a new longblock. The old carb was damaged so they just bought a new carb from Autozone. They weren't sure which carb to get so maybe they got the wrong one? Anyway, the OLD engine was running like this too. They had a mechanic adjust the timing and it ended up advanced way far like close to 20 degreees BTDC. The mechanic also plugged off the vacuum timing advance even though the advance works. I think he did that because the timing was already so advanced it couldn't go farther. The engine was overheating and it had bad valves and rings so I swapped in a rebuilt longblock, and the carb was so new I just rebuilt it and swapped it over... and now the new engine is acting the way the old one was acting. BING this makes me think carb problem!


Anways please share your wisdom...

 

Sounds more like an EGR problem. I always make a block off plate for them because of allthe problems they cause. Also I don't think the EGR belongs on the ported vacuum port. The timing job the mechanic did was wrong. Initial timing should be 8° to 12° depending on your advance curve. Usually back fires out he carb are caused by a valve problem or timing issue, such as the vacuum hooked to a manifold vacuum port instead of the ported vacuum. Ported vacuum port should have no vacuum at idle.

 

like Bear said, I would definatly eliminate the egr out of the system unless they are working right they can cause big problems, make sure the vacuum advance is hooked to a port that has no vacuum at idle, just unhook it for now until you get it timed decent, make sure the pcv valve is working properly, closing at low vacuum, maybe use some starting fluid and spray around the intake to find vacuum leaks,,it sounds like a vacuum issue to me,,,also just for jokes and giggles recheck your spark plug wires to be sure they are right,,,have you checked the distributor to see if it is working right? good luck,,,Neil

 

As for the seemingly high initial timing, that might be due to a slipped ring on the harmonic dampner. It will show 15° but might really be only 5°, or whatever. Did your rebuild include a NEW dampner? Or did you re-use the old one?
This could all be related to your other post in which you question the Duraspark...I think I would run that issue down before you start chasing tail (uh, your own, that is)!

 

Checking the damper for slippage is pretty simple and I always do it while the engine is on the stand before install. Just TDC the motor and look to see if the pointer is correct.

 

what every one said is correct.this is what I would do,recheck wires,advance none at idle,pulls with accelleation.if ok then set points.all this is JMO.points set 20tho. feeler guage or dwell at 22.with this done go to timing.put timinglight under the seat,back off dist. bolt just enough to turn dist.let her run till she is warm.Push dist.back and forth until she sounds bad both ways.find the spot that it sounds smooth.you may have to idle down the carb.just play with the dist. and carb idle only ,until tou feel like it is good trust your ears and it will be very close.drive it ,if it sprark knocks,back off dist. towards drivers side just a very tiny bit at atime antill it does not.if it is hard to turn starting,back off the same way.at this point it sould run good .adjust carb mix. if she don't run great ,let us know.hope this is of some help

 

And if he does the timing your way he will end up with the timing to far advanced, like it is already. Unless you have a very short advance curve, like on a race motor or a recurved dist., you can't set initial timing that way without being to far advanced.

 

Everyone's different, for me to time by ear I end up 6 degrees over advanced about everytime on average. To leave it over advanced you'll notice a reduction in fuel mileage and if your lucky not encounter detonation.
You can run a high total advance for a short duration to get a maximum HP number on the dyno but not pulling a load up a long grade in the heat.
.....=o&o>.....

 

Hey guys, just an update, tell me what you think about this!

I got the engine running the best it has ran so far... but with the idle mixture screws only about 1/2 turn out!

It even runs OK with the screws turned in ALL the way. Not great but OK.

I messed with it for hours and from what I was seeing, adjusting things and seeing what effect it had, I am thinking that it seems to act like it is running rich all the time. Then, even with the accellerator pump on the lowest hole, it seems to flood out when I start off the line. I could be wrong but that seems to be the main cause of my problems off the line, TOO rich of a mixture.

Now, this seems strange, so I am wondering if maybe my float bowl level isn't correct. I did not adjust the float level, I thought it would be set OK from the carb before I rebuilt it. Who knows maybe the needle valve is leaking or the bowl is just set too high or something, it seems like something is feeding more gas into the engine than I can deal with using the adjustments.

So, I will run the engine with the top plate off the carb tomorrow and see what I can find out, unless you guys have a better idea.

FYI, with the accellerator pump on the bottom hole (I have 4 holes on mine) and with the mixture screws turned out only 1/2 inch, I am able to squeal the tires off the line for the first time ever since I started working on this truck. I also drove it on the freeway up to 80 miles per hour and it was just smooth sailing. I was able to accellerate easily without having to floor it to make the auto tranny down shift. Usually the only way I can speed up much is to make it down shift but now, with it WAY leaned out more, it would just take off. It ran so buttery smooth. It's like the leaner I can make it, the better it runs. That is why I think there is a problem with my carb!

 

bear45/70 I have been working on Fords for 30 years for myself, my family members, friends, and other people and setting motors like that has worked for me. I got good gas mileage, very good power, no spark knocks and they did'nt over heat. It can be done this way you just have to play with it to tweak it.

 

Troubleinnc2, The problem with your way is that the average guy out there can't tell from the way the engine runs or sounds that it makes whether the timing is to high or not and that's why I say don't tell people on the internet to use this method. They will damage their engine and not have anyone around to prevent that from happening. It's a bad deal all around. If your buddy is at your house and you walk him through it and show him the signs of trouble and the sounds that are bad, that's a totally different deal.