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1967 Mustang Convertible
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Discussion Starter #1
So I have been trying to get my new setup running right. Here is my new setup:

1406 600cfm Edelbrock Carb
Edelbrock Performer Heads (1.90 Intake and 1.60 Exhaust)
Edelbrock RPM air gap Intake
Howards cam 213/219 @.050 (almost exactly like a XE264HR cam)
Tri-Y headers (temporarily connected before heading to exhaust shop)

I was fighting a backfire through carb when I would try to hit the accelerator. Checked compressions (140-150 cold engine on all 8). Verified timing, 10deg BTDC. Replaced distributor cap and rotor for good measure. Looked for vacuum leaks, found an issue with PVC valve, cleaned and now the backfire is gone. Will rev good. But trying to tune just at idle with vacuum gauge it will increase in vacuum as I turn the idle screws almost completely out. But it makes my eyes burn with how rich it smells. If I turn the idle screws more in the vacuum drops a little but it still revs good. It showing about 14 HG of vacuum, was hoping for like 15. So question is do I leave it out with the higher vacuum and really rich? Or Turn them in and loose a little vacuum and not smell so rich? Also I know I have a huge leak after the Tri-y's as they are temporarily held in to my existing exhaust with some clamps, would this cause it to run different at the carb? I figured once it exiting the Tri-Ys it should not affect the carb but I could be wrong.
 

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I ran an Edelbrock 1406 for about 20 years. And one thing I can say that is good about them is that they are easy to change the Step Up Springs and the needle and seat without having to remove the top of the carb. Order the 1406 And similar carb tuning kit that has an assortment of Springs needles and seats etc and follow the chart that came with a carb and probably with that kit to determine exactly which ones to use. Once you have that dialed in you will be able to enjoy the carburetor a lot more.
 

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If its steady at 14 I would not worry about it. Also check your spark plugs, they should be a tan color if they are black it’s running to rich. I also run a 1406 at 4000’ of elevation and it was running to rich. I stepped the jets down on the primaries and secondaries and I believe changed the rods and springs. Very tunable carburetors.
 

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I would grab the Edelbrock tuning kit and start there. You may not need a jet change but just a change in the step-up springs.
 

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1967 Mustang Convertible
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Discussion Starter #5
Thanks guys. I have the Edelbrock 1487 Kit sitting in my cart right now:


Pretty sure I will need it once I start driving and testing. But this is just at idle, from what I have read the Jets and rods don't come into play until you are cruising and stepping on it not sitting at idle? I thought the idle screws is all that is needed for tuning while sitting at idle? This is the reason I was confused that my vacuum increases by like 1HG as I turn it almost all the way out, but I turned it back in till it started stumbling and then 1/4 out from there and lost 1HG in vacuum.
 

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The springs, jets, and metering rods shouldn't have anything to do with idle mixture. That's pretty much any carb. Tune your mixture screws for idle.
 

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The 1406 is jetted lean. You need to richen the fuel mixture up. Start off with the same jetting as the 600, 1405 with manual choke. That should help out a bit. My 1405 ran really great.
 

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You may have a vacuum leak and are already running lean. Which is why turning the screw out makes more vacuum. Your engine wants more fuel to account for the extra air from a leak. That's just speculation though.
 

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@Woodchuck I see a couple different circuits. The idle circuit and the main and low speed jet system. Edelbrock carbs definitely are not my specialty. So I could. Just be looking at it wrong.
 

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@Woodchuck I see a couple different circuits. The idle circuit and the main and low speed jet system. Edelbrock carbs definitely are not my specialty. So I could. Just be looking at it wrong.
Almost all modern carburetors pick up the supply for the idle and transition circuits DOWNSTREAM of the main jet. In the case of the Carter/Edelbrock, having a metering rod that is at the wrong step in the jet is going to affect all 3 circuits.

 

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Discussion Starter #12
Thanks guys. Ordering Calibration kit. Will change to match the 1405 Edelbrock as a starting point and go from there.
 
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