Author Topic: Help with Carb? FIXED  (Read 7346 times)

rotorshawn

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Help with Carb? FIXED
« on: January 31, 2013, 05:01:00 PM »
Hello.  On my 67 Mustang.  I just rebuilt my Edelbrock 1406 carb (on a 289 with Edelbrock Performer 289 intake) and am wonder if I could get some advice on how to fine tune it...  Here's what it's doing:

Car starts just fine.  All 8 cylinders fire until it warms up and the choke opens..  Then I loose #3 cylinder.  As soon as I bring the engine up to about 2500rpm OR close the choke at idle, #3 kicks back in...  I just loose #3 at idle with an open choke.  Any advice?

Thank You

Topless_Horse

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Re: Help with Carb?
« Reply #1 on: February 01, 2013, 07:25:55 AM »
Edelbrock has an excellent manual (http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf) that provides detailed tuning instructions for that carb (I have one and was able to dial mine in fairly easily just by reading and following their instructions).  But usually a carb issue will not affect only one cylinder. 

I would look for things like a damaged #3 plug wire, a loose #3 plug wire in the distributor cap or on the plug, or maybe something got into the intake manifold while you had the carb off.

rotorshawn

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Re: Help with Carb?
« Reply #2 on: February 01, 2013, 11:12:01 AM »
It's so strange.  Plug 3 is fine and so are the wires..  They are all new..  It was #1 and #4 first, then I played with the carb and now it's just #3...  I'm thinking it's a fuel issue...  It may not be getting enough fuel (or too much air) at idle and it's moving through the intake wrong... I don't know...  I'll keep playing with it...

Topless_Horse

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Re: Help with Carb?
« Reply #3 on: February 03, 2013, 09:48:07 AM »
If other cylinders in the right bank are affected it could be that the primary jet and/or rod on that side are too small or not working together correctly, or that the spring that goes on the rod is the wrong one (it should the same as the spring on the left-side rod).

I know it's easy to get the rod in wrong so it is not seated correctly and I have on occasion missed the jet entirely when putting in the rod.  So that would be something to look at.  If you loosen the screw on the little cap on top of the carb that lets you access the rod you could try that to see if the rod moves up and down freely.  If it does not, pull it out, make sure that the rod is properly attached to the little piston and that the spring under the piston is in correctly, then reinstall the rod, making sure it moves up and down freely after it is installed.

rotorshawn

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Re: Help with Carb?
« Reply #4 on: February 04, 2013, 08:08:01 PM »
I will try that now... Are you referring to the step up pistons springs?  I did have them out but I will check to see if the spring is where it should be.. 

I did rebuilt the carb and here is the issue now.  I'm sure it's fuel flow, but..  Car starts and runs perfectly while chocked on the primary inlets...  After it warms up and the choke opens, it looses #3.  If I just very slightly crack the secondary lower paddles (letting just a little air/fuel in), it runs fine again..

rotorshawn

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Re: Help with Carb?
« Reply #5 on: February 04, 2013, 09:25:39 PM »
do the step up jets manage fuel from the carb into the intake or fuel in the carb from the reservoirs? 

Topless_Horse

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Re: Help with Carb?
« Reply #6 on: February 06, 2013, 10:14:30 AM »
The rod and jets manage fuel to the intake but, unfortunately, not at idle (sorry, I forgot that these carbs have a dedicated idle circuit that's controlled by the little screws on each side of the carb).

So, are both of those screws adjusted per the Edelbrock manual?  It sounds as though the right (pass) side screw might be all the way in.  If it's adjusted correctly or if you can't get it to work like the manual says, then you could try removing it completely and blowing out the passage with air to see whether that helps.  There could be some debris in there.

Also, just out of curiosity, did it work correctly before you rebuilt it?  I assume you did set the float levels properly when you rebuilt it, right?

rotorshawn

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Re: Help with Carb?
« Reply #7 on: March 01, 2013, 06:03:45 PM »
Found the issue and it was so simple...  Turns out the hose that goes to the transmission Vacuum Diaphragm was not connected (at the back of the transmission) and it was causing a vacuum leak that was affecting the carb...  Hooked it up and it purrs like it was new...

 

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