NEED some help....idle issues after cam swap...

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MoparMagic0069

MoparMagic0069

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I know everyone has there opinions on the 284/484 Purple Shaft cams, well my grandfather and I put one in my 71 Swinger with a 340 yesterday.....the 340 is out of a 68 GTS dart so it has really good compression and the "X" heads, it's bored 30 over as well and has long tubes on it. Well we got everything in started it up, it fired up instantly and sounded great. So after a little breaking in my Pap (who's done Mopars for over 40 years) went to set the timing so we could get the idle set....and now the problem, it won't idle. It has one of the edelbrock carbs that look like the original style carbs, well the air/fuel mixture screw on the drivers side does absolutely nothing....and the idle screw is so touchy! You barley turn it and the idle runs clear up to 1200, you barley move it the other direction and it falls and than shuts off. Any suggestions?....
 
If you doing timing from the book, forget it! If trying to do it using the total timing method, forget it!

Set initial timing in the 22-26 range and see if you can get the idle under control. You'll have to fix mechanical in the distributor to hit a reasonable total timing number.

The carb will likely need the lightest step up springs for the metering rods.
 
If the idle screws do nothing, you also have to fix that before any hope of getting a stable idle!
Even more important, why is ONE screw doing nothing but the other, presumably, is altering the mixture?

Anyhow you need the transfer slot to be square (.020 or so exposed), and if you need more idle air then crack the secondaries a hair. AJ has a good guide to setting this up.
 
DrCharles said:
If the idle screws do nothing, you also have to fix that before any hope of getting a stable idle!
Even more important, why is ONE screw doing nothing but the other, presumably, is altering the mixture?

Anyhow you need the transfer slot to be square (.020 or so exposed), and if you need more idle air then crack the secondaries a hair. AJ has a good guide to setting this up.
Click to expand...

Agree. Also make sure the Idle air bleeds are clean!
 
Thanks guys, this carb has 3 screws from what I see, the two bigger ones air/fuel mixture I'm assuming on the front, and then the idle adjustment toward the drivers side. The bigger adjustment screw closer to the passenger side works fine the drivers side doesn't change anything at all, we had it turned the entire way in and it did nothing. The small idle screw is so touchy as I stated before. I should of had my grandfather make this post because he can be a lot more technical term wise than I can, he's been doing this stuff for over 40 years, I'm 21 and am used to fuel injection and not carbs, so I appreciate all the help and any further info I can get, and I apologize for not sounding very educated on this.
 
Alright sorry I was away today as for what we did for install, we lined the Dots up, the car ran fine before the cam, all you had to do was hit the gas one time for the electric choke and it fired right up and idled great, we put this cam in and it fired right up on the initial start, we got everything broke in then went to get the idle set and now have this issue. We have a carb on another 340 with the 284/484 cam that we know starts and idles great so I guess we are going to make sure the timing is set like you guys all said in other comments and put that good carb on it and see what happens...
 
i wonder maybe if your on the ported vacume hole so when you open it timing jumps up and you turn it down and timimg goes way down and with a posible lean from your idle mix not working it stalls. make sure vac tube is not hooked up if you have one try again
 
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