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Discussion Starter #1
My truck has been running like crap since I put in the new motor. I've posted on this a few times but never really got any revelations from it. I know now that it's definately a carb problem. I took the 750 from the mustang and put it on the 390 and after a little adjusting it runs great. W/ the old carb it just really ran funny. w/ the vac adv. hooked up it would run but only w/ full choke. It is'nt really that cold here and the holley would run great w/ no choke. When I unhook the vac adv. and plug the vac. line it ran like crap, it sputtered and missed and then would die. I bought a rebuild kit for it and that didn't help any. I need some help, I don't know much about the intricacys of carbs and need advice.
Thanks,
Jeremy

You can never have too much power, just not enough traction.
 

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Sounds like my truck's 460! I'm having problems with the 4180 Holley, I've been through it a few times and nuthin, put it on the truck and it runs like crap, and it's an oem carb.

I'm not an expert either, but with the vacuum leak the old one has, look at the throttle shaft bores for wear, warped surfaces from p.o.'s overcranking the screws when they've had it apart. That's about the only thing I can offer.

On my truck, I'm throwing in the towl with the old carb. When I put the Edelbrock carb from my coupe on, it ran great. I'm not going to waste the time trying to figuire out what's wrong, it's just not worth the time. I'm going to get a 750 cfm for it.

Tom
You can do anything you want to......ONCE!
aka "my 66 coupe"
 

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Hey, Jeremy, what's the stock carb on your truck?

If I understand right, the truck is running fine with the 750 Holley vac sec carb from your Pony, right?

A picture of how you had all the vacuum stuff hooked up on the old carb would be cool....I'd get a better feel for what's going on...

Did the old carb run better or worse after putting in the rebuild kit?? Or did the problem remain the same?

More details please...*G*

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG
 
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Discussion Starter #4
The engine in the truck is from a 66 Thunderbird. It's a factory Ford Vac. sec. 4bbl carb. As far as vac. I can't send a picture (scanners junk) but I simple plugged all the ports ( I only found one on the passenger side slightly above the primarey throttle blades). It has a very thin plate under the carb w/ a vac. port as well. I plugged that one off too. The problem seems to be the same if not a little worse, and yes it does run good w/ the Holley. It doesn't run perfect but I think a little tuning would cure that (idles too high and stumbles a little at very low RPM, like taking off at idle w/ no or very little throttle)
It's kinda hard to describe what it's doing. w/ the choke all the way shut (on the old carb) and the vac adv. hooked up it'll run at 1700-1800 rpm and sounds fairly smooth but if you open the choke, even w/ the engine at full operating temp, it stumbles and dies. I've also found that pulling the vac line off the vac. adv. (hooked to the one vac port on the carb) promptly kills the engine. I can plug the vac line and it'll start, but it runs terrible and just dies, kinda like a big manifold vac leak. I've tried to adjust the idle mixture screws but w/ limited success. I'm having a really rough time w/ this and need to get it fixed cause I simply can't afford to buy a new carb right now. Thanks for taking the time to try to help
**oh yeah, the tag on the stock carb reads: C4SF B if that helps w/ identification

You can never have too much power, just not enough traction.<P ID="edit"><FONT SIZE=-1>Edited by 69stang_coupe on 03/13/01 09:50 AM (server time).</FONT></P>
 

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Where does the hose from the PCV system hook up to the manifold?....usually, it goes to the port on the plate under the carb...

Is it possible to mount the carb on the manifold without the plate underneath it?.....I'm thinking of eliminating all possibilities of vacuum leaks...

Have you squirt tested for vacuum leaks around the carb with some carb cleaner or similar substance?

Very strange....

Maybe someone else will chime in here since you've added further info...

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG
 
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Discussion Starter #6
This old engine has a very strange PCV setup. There are two vac taps on the intake manifold, one on the front one on the rear w/ a rail connecting the two. In the middle of this rail is a large vac port w/ a line that goes to the PCV valve.
I can hook the carb up w/o the plate underneith and was pondering doing that soon today. I have'nt checked for leaks around the carb either.

You can never have too much power, just not enough traction.
 

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Understand....that should rule out the PCV as a possible source but you might try plugging the port to just see what happens.....that's a pretty good "vacuum leak" put there on purpose...

Keep us posted on your progress...I know my truck gets me around most of the time so I can enjoy my pony....it needs to be reliable...

Pat
http://www.jps.net/binay/webdocs/strtmstng002_sml.JPG
 
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