240 C.I. CARTER YF ON 200C.I.=HIGH IDLE! WHY?!!!

[Anonymous]

I put a Carter YF from a 240 ford on my 66 mustang 200 six. It won't idle below 1200RPM's. I cannot seem to get the timing set because the distributer has that duel vacum advance thing. Do you set the timing with both the vacum lines on, off, or one and on one off?
Is the Carter to big for this engine? I put a 1980 head on it, wich I ported and polished, then sent to the shop for a reground on the valves, with other basics (hot tanked, magna flexed, and made sure the head was flat.) I plan on putting a petronix stage 2 ingition w/45k volt coil on it soon.
As I said above I can't get the idle below 1200, I have about 15psi on the vacum gauge, It seems to run smoother as I richen the mixture, but still won't come down. I noticed an idle fuel mixture jet in a book, and wondered if that had anything to do with it.
well anything you guys can tell me to help me out would be great. Thanks

 

[CZLN6]

Howdy Dustin:

And welcome to The Forum.

I think it is more likely that you either have a vacuum leak somewhere in the intake system, or a throttle plate stop/adjustment that you're missing, possibly on the automatic choke fast idle cam.

The other possibility is that if you removed the butterfly on a rebuild and cleaning you misaligned the butterfly on reassemble and it is not sealing tightly. Try loosening the screws that hold the butterfly throttle valve, open and allow it to snap shut. This will align it and give a tight seal. Be sure to retighten the set screws.

Please report back with any success or lack of it. Good luck.

Adios, David

 

[Anonymous]

I reset the butterfly, nothing, It's a new-remanufactured carb so it shouldn't be missing anything. I checked all the hoses, and fittings for leaks and found nothing. I then took off the carb and checked to make sure all it's gaskets were properly installed and sealed, they were. After reinstalling the carb I blocked off all the vacum lines except for the one going to the dist, (which I checked to make sure was working) still nothing. I sprayed WD-40 around everything to see if there were any unseen leaks left, nothing. Do you think it could be a head gasket leak? I just put on that 1980 head with a new fel-pro gasket. I don't think that's it but I will check to make sure. I'm getting about 15 psi at idle, what should it be? What kind of gas mileage should I expect with the 240 carb? Would it be better to switch to the 300? I have a stock cam so I think the 300 would be too much.

 

[MustangSix]

Did you somehow disconnect a PCV or transmission modulator line?

 

[Anonymous]

The PVC is the line to the valve cover right, I hate to sound ignorant, just wanted to check. If so then it's connected. is there something more to it? I disconnected the lines to the tranny and then plugged them trying to isolate any leaks but that didn't effect it either.