390 engine running rough - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 08-01-10, 06:53 PM Thread Starter
Registered User
 
Join Date: Aug 2010
Posts: 4
390 engine running rough

I little background first, I bought this truck from a guy, whom didn't known much about it. So I have been shooting in the dark for a couple of weeks now.

Information to known, I live at 5000 feet. I have tested this engine from top to bottom, on the basic stuff. Vacuum lines, steading reading on the gage at 15 pounds. It idles pretty good, but if you put the throttle down, it hasitates, or will die out. If you put in gear, it dies out. Idle set at 950 RPM's.

The timing is set at the best vacuum and hearing idle, 30 degree's, from the timing light. It has an accel breakerless points thing on it, with the correct 8140 coil.

I am out the point of reaching out, I messed with the holly double pump carb, don't known the model, it reads 3532 on the throttle body? I turn in the mix screws all the way, and turn out, and it doesn't react??

Suggestions???

FENNER74 is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 08-01-10, 09:28 PM
Registered User
 
kdtrucker's Avatar
 
Join Date: Jan 2007
Location: New Mexico
Posts: 278
Re: 390 engine running rough

Sounds like too much CFM (carb) for the motor. A stock 390 shoud run just fine with a 600 cfm carb single pump, vacuum secondaries. 15 inches of vacuum at idle is pretty much stock.

You can never really trust the harmonic balancer (if stock and is the original) to accuratly read true when you time your engine. A new balancer should read true, but if it don't, you'll have to find Top Dead Center by finding where number one piston is up at the top of the compression stroke, and mark your balancer, because it may be off a degree or two, or more.

Check your plugs and wiresand make sure you are getting a spark. Blue is a good color for spark.
kdtrucker is offline  
post #3 of 8 (permalink) Old 08-01-10, 11:58 PM Thread Starter
Registered User
 
Join Date: Aug 2010
Posts: 4
Re: 390 engine running rough

I have TDC'd it, by using a plug in #1 on the compression stroke, then taking a stick and following it to the top. It does read acurrate on the balancer....

I keep coming back to the carb too, I took it apart, it has number 62 jet's in the front, and 2.5 on the power valve....
FENNER74 is offline  
Sponsored Links
Advertisement
 
post #4 of 8 (permalink) Old 08-02-10, 07:15 PM
Registered User
 
kdtrucker's Avatar
 
Join Date: Jan 2007
Location: New Mexico
Posts: 278
Re: 390 engine running rough

With 15 imches of vacuum you should have at least a 6.5 power valve.
Change your PV first and then, being that your at 5000 ft up you check your plugs, if they are clean and light brown, leave the 62's in. If they are dark try a a lower number jet untill they become light. If they look like they are clean and brand new, go higher on the jets.

Start with the Power Valve and go from there.
kdtrucker is offline  
post #5 of 8 (permalink) Old 08-03-10, 10:25 PM Thread Starter
Registered User
 
Join Date: Aug 2010
Posts: 4
Re: 390 engine running rough

I installed the 6.5 power valve and put some 61's in.. The truck runs much better, with a little hesitation now. But I haven't messed with the adjustment screws, or plunger spring..
FENNER74 is offline  
post #6 of 8 (permalink) Old 08-04-10, 03:19 PM
Registered User
 
kdtrucker's Avatar
 
Join Date: Jan 2007
Location: New Mexico
Posts: 278
Re: 390 engine running rough

You said the timing is at 30 Deg. ?? Set the timing to about 6 and then adjust the idle.

You also said you are running a double pumper Holley....There is a rear metering block on that carb with jets in it also, so you'll need to down size those jets
kdtrucker is offline  
post #7 of 8 (permalink) Old 08-04-10, 04:42 PM
Registered User
 
72Ford250's Avatar
 
Join Date: Jul 2010
Posts: 10
Re: 390 engine running rough

Quote:
Originally Posted by kdtrucker View Post
You said the timing is at 30 Deg. ?? Set the timing to about 6 and then adjust the idle.
i have my timing at 16 degrees of timing i am about 5700 ft in elevation and my 390 runs great?

1972 250 6.4L(390 FE.) (edelbrock intake manifold-edelbrock 600 cfm carb-headers-dual pipes cherry bomb mufflers-engine bored 30 over)
72Ford250 is offline  
post #8 of 8 (permalink) Old 08-04-10, 08:14 PM
Registered User
 
kdtrucker's Avatar
 
Join Date: Jan 2007
Location: New Mexico
Posts: 278
Re: 390 engine running rough

Without knowing exactly where TDC is....(when the piston is all the way up and the connecting rod is purpendicular to the piston)You'll never know where to time it. Unless you installed a brand new balancer....if your like me and reused the old stock balancer the timing marks are off because the outer part of the balancer has slipped on the rubber between the outer and inner parts of the balancer.

I'm at 4300 ft and My 428 is timed at "O" TDC. So you can't always trust those old stock balancers.
kdtrucker is offline  
Sponsored Links
Advertisement
 
Reply

  Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars > The Garage - Tech Forums > Engine Specific Tech > FE (330-428) Tech


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome