Edelbrock 1407 - vacuum advance hhok-up?

[The_Handier_Man1]

From: jddrivfour  (Original Message)
Sent: 1/30/2005 6:27 PM

I installed this carb years ago. In trying to find out why my engine loses power under load I looked at the distributor as well as the fuel system. I completely took distributor apart and found out one of the centrifigal advance springs was slack alowing some advance at low rpm. When I reinstalled I discovered the vaccuum advance was movingall the way at idle. The 1407 has a ported and unported vaccuum. This is only shown in the exploded view in the manual. Since the thermoquad used the "drivers side" port-thats what I hooked up to on the 1407 -this is the unported vaccuum one. Have not been able to road test- 4inches of snow west of Denver.



From: HeavyHaulTrucker
Sent: 1/30/2005 8:47 PM

jd, disregard what port the vacuum advance was hooked to on the ThermoQuad -- the Edelbrock requires unported vacuum (yes, driver's side port).  But the slack in your distributor's mechanical advance spring means that it is shot -- just had this problem a couple of months ago.  Luckily, it  is easy to cure... a new distributor for the 413 & 440 is only $50 at O'reiley's.  And you can change it right there in the parking lot, without even getting underneath.

John



From: jddrivfour
Sent: 1/31/2005 12:56 AM

When the distributor was connected to the unported side, the advance was about 10 degrees at idle. Was the 440-3 set-up for unported vaccuum advance? I closed the spring end to take out the slack-for some reason the end of spring was modified. Although the spring may be fatigued, I put it back in for now.
My EGR has been disconnected since I owned the vehicle. It always passed emmisions. I believe the EGR puts exhaust gas back into the combustion chambers to lower nitrogen oxides.



From: HeavyHaulTrucker
Sent: 1/31/2005 8:22 PM

Been there, done that -- barring a stretched timing chain, you probably need to replace the distributor and hook the vacuum advance line to unported vacuum.  First of all, the additional advance is being thrown in by the weak spring in the mechanical advance; lets put it this way:

When the vacuum advance is disconnected and plugged, your engine should be timed to either 4, 5 or 8 degrees Before Top Dead Center -- whatever your valve cover decal says.  With the weak mechanical advance spring, you are playing catch up because of the extra advance thrown in by tne weak spring allowing the counterweight to fly early .  Then when the vacuum advance kicks in, there is not enough plate travel to allow it to provide all of the vacuum advance required.  You will never get your timing right because of this.  The only cure is to replace the weak spring -- but they don't sell them individually, or even in a set, and the ones from the GM HEI Advance Tuning Kit sold in the parts stores won't work.  The only way to replace the mechanical advance springs in your distributor is to replace the distributor -- period.  Now, I am going to throw a small fly into the ointment here.

Have you checked timing chain slack?  There is a distinct possibility that your timing chain has either stretched or jumped a tooth.  Checking timing chain slack is pretty simple, and should be done before changing out the distributor just to rule it out if nothing else.  Check the Message Search to find a description of how this is done, ok?

Now, with the Dodge 440 and 413, the distributor is a "half shaft" design.  The shaft ends in a flat tang that fits into the slot on the distributor drive gear -- which is a trapped part of the camshaft gear train.  As I said in my first post, you can change it in 15 minutes with a 1/2" box end wrench and a timing light -- it is probably the simplest engine part the Dodge has when it comes to replacement!  While it is not a humongous job, you can't say the same about the timing chain & gears.

The added vacuum advance at idle doesn't hurt anything.  What matters with the 440 truck engine is advance under load.  When load is applied in these old Winnies, vacuum drops alot -- under full load, vacuum should be at or near zero.  And under full load, up to about 3000 rpm, the mechanical advance provides all the advance the engine needs.  When you come out of acceleration mode, and level off to cruise mode, the vacuum advance provides enough advance to improve fuel consumption and driveability.  Also, Edelbrock themselves told me that the 1407 Performer on a 440 needs to be hooked up using the unported port.  But I will tell you, the old ThermoQuad I replaced had the vacuum advance hooked up to the unported vacuum port (front driver's side) originally.

John



From: denison
Sent: 2/1/2005 7:11 AM

    I dislike spending big bucks, and have so far been able to avoid buying new distributors.   I am willing to spend time in junkyards though, and I agree that you shouldnt expect advance springs to last forever.
    I would try to get a set of springs from another mopar distributor, whose springs had the same appearance, and same feel when you tug on them, as the original good spring from your existing distributor, and then try them out.  I have gotten such springs from junkyards on several occasions, and I since I was buying larger items at the same time, I cant even say they charged me for them.
    The real test to me is whether I am happy with the performance, if my spark plugs stay a light beige, if there is no detonation, and my mpg is acceptable.  Of course learning the mpg can take several hundred miles of driving to find out.
   I bought a mopar big block distributor from ebay, which seemed to have the identical springs, but had more "travel" for the centrifugal advance, maybe 20 or 25 degrees: It probably came from a passenger car or pickup truck motor.    I also got one from the Magic Junkyard that came off the same type 413-1 RV engine my Winny has.  It had the same limited centrifugal advance travel - about 15 degrees I think, but different springs - thicker.  Perhaps thats why it ended up in the junkyard?
     My untested theory is that passenger car distributors allowed more high rpm advance than those in truck engines, to give the passenger car engine that extra horsepower for passing on hills and getting speeding tickets.  By contrast, the distributors on truck engines had a limited centrifugal advance range to keep from melting the pistons due to detonation if you were climbing a long upgrade in hot weather.   Anyway, thats what I suppose.
   And the service manual says to time the ignition with the vacuum advance hose disconnected and capped off. 
    There are automotive distributors where the two advance weights arent identical, and the springs are also different, and arent supposed to be swapped.  I think the 356 Porsches were all this way, and so is my old motorcycle.



From: Liv42dayOK
Sent: 2/15/2005 8:11 AM

Original message posted by: jddrivfour  (Original Message) Sent: 2/15/2005 12:27 AM
I finally resolved the Carb/fuel pump problem- my spark plug wires were burnt at the headers! The symptoms of lack of power going up hill with that sound of running out of fuel made me believe it was all fuel pump and carb. Engine now runs better than it has in years. I also think I have the carb too lean at cruise settings. I discovered that I was changing the metering rods reversed- that is at high vaccuum the rod is down not up- the bigger part of the rod is the cruise portion. Details details. I think I will come up with an easy check for spark plug wires to make sure they are firing.



From: Liv42dayOK
Sent: 2/15/2005 8:19 AM

"I finally resolved the Carb/fuel pump problem- my spark plug wires were burnt at the headers!"

This is another, current example which reinforces the advice given in previous "pros/cons of having headers" discussions that, if you choose to install headers, you really need to use high-temp wire boots/wires and any other means to protect them from the heat.  You can change the wires but, if they're not properly protected, they'll be 'fried again' by your 'short-order cooks'.   - Sob



From: Slantsixness
Sent: 2/15/2005 8:39 AM

" I think I will come up with an easy check for spark plug wires to make sure they are firing."

Simple check:

If they are visually ok, start the motor. now grab the insulation on one or more (only if necessary). If it shocks you, they're bad. if it doesn't, they're good and firing.

There are several other ways, like a resistance reading, taking a spare plug and looking at the spark, turn off the lights at night and look for blue or orange arcing... etc. mostly they don't work as well as getting the [whoopie!] shocked out of you!

An old mechanic once told me:
"If you've got a bad plug wire... it'll get you...before you get... it"

But really, as long as you don't have a pacemaker or a heart condition, just grab the insulated cable, it really works. (please don't stand with your bare feet in a bucket of water and do this... it may zap you, but not normally injure the average person. It will most certainly wake you up!)

Try this on your own. I'm not recommending that you go shock or injure yourself, or hold your buddies hat for ransom with a leaky plug wire, but It does work!

An alternative method is to take an NE-4 neon bulb and run it along the suspected ignition wires. If it lights up, the insulation is either breaking down, or was insuffiecient to start with.