65 289 new intake and Carb. Help required!

Ricktheninja

New Member
Jan 24, 2020
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Hey all, new to the forum and wondering if I may ask for a little advice.

I recently took ownership of my 65 mustang, with a stock 289 and c4 auto box. Wanting to make a few upgrades, I've bought and fitted an edelbrock air gap rpm intake manifold, edelbrock performer 600cfm Carb, and a few other small bits and pieces to get me started.

Issue I'm having is, all the new parts are fitted, but I'm struggling to get the car running at its usual idle speed. I've checked all vacuum ports and mating faces for leaks, checked timing and checked fueling. I've also adjusted the fast idle and regular idle screws and, when the idle rpm drops below a certain speed (still way higher than before the new parts were fitted) she cuts out.

So basically I have a high idle and I can't figure out why. Any help would be much appreciated. Thanks all, and thanks for having me
 
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LILCBRA

I wish I didn't have all of these balls in the air
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Dec 6, 2005
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Double check your vacuum ports. That's usually what it is in my case, I'll forget to hook up a line somewhere. Once I do it'll settle right in. Basically what it sounds like it's doing is sucking more air than it should and needs the extra fuel to compensate.

It could also be that the carb is too large, but a 600 should be ok with a 289. :shrug:
 

Ricktheninja

New Member
Jan 24, 2020
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Uk
Double check your vacuum ports. That's usually what it is in my case, I'll forget to hook up a line somewhere. Once I do it'll settle right in. Basically what it sounds like it's doing is sucking more air than it should and needs the extra fuel to compensate.

It could also be that the carb is too large, but a 600 should be ok with a 289. :shrug:
Thanks for the reply.

Yeah, anyone I've asked seems to agree that it's some kind of vacuum leak. I'm going to go through all the hoses etc and see what I can turn up.

Any more suggestions are welcome
 

LILCBRA

I wish I didn't have all of these balls in the air
10 Year Member
Dec 6, 2005
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You're welcome - hopefully you can get it ironed out!
 

southcross2631

Active Member
Dec 13, 2019
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Do you have a propane torch ? Put a rubber line on the end and turn the gas on. Disclaimer . do not light the torch. Use the rubber hose to go around the base of the carb and the intake when the motor speeds up you have found the vacuum leak. It's called a propane enrichment test. Has been in the Ford manuals for years before computers.
 
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