Vintage Mustang Forums banner
1 - 5 of 5 Posts

Discussion Starter · #1 ·
Finally got the idle smoothed out by backing the idle mixture screws out by 3 1/2 to 4 turns. Books says 1 to 1 1/2. Purrs like a happy cat, but seems odd that I should have to do that. Is that indicative of a vacumn leak, and I'm just treating the symptom and not the cause?

· Registered
270 Posts
Yeah, something's wrong there. I currently have, don't laugh now, a 2100 from a Mercury Monarch adapted to an Edelbrock Performer intake, and it runs and idles nicer than the Holley 600 I used to have ever did. You're on the right track, thinking it may be a vacuum leak. I didn't see any earlier post of yours, but I assume you've rebuilt the carb and there isn't a big lump of crud in there somewhere gumming up the idle circuit.

Discussion Starter · #3 ·
Carb should be good. Was rebuilt shortly before we got her, say 6 months ago or less. Can't seem to find a vacumn leak even though I've been hunting for two weeks. Checked the two lines from the manifold and both the carb gasket and intake gasket.

Other diagnostics done include:

fuel pump volume and pressure - OK
new condenser and points (017) - OK
Actual TDC matches up with mark on balancer
Timing at 6 BTDC (steady, no float)
Compression 130 lbs +/- 5 on all cylinders
New Coil
No shorts on spark wires
PCV valve - OK
Needle valves look fine

I'm just probably missing a vacumn leak somewhere.

· Premium Member
18,950 Posts
Depends upon the definition of 'turn": Don't laugh! A true turn is 360 degrees, yet most people think it is 180 degrees. If you adjusted 4 turns of the latter, you're in the ballpark.

A quick check of a vacuum leak is while the car is idling, put your hand over the housing inlet and see if you can stall the engine. If you can't, air is getting in elsewhere.

Discussion Starter · #5 ·
Do you have the distributor plumbed to the correct fitting?

Have you actually verified the carbs state of rebuild? Take it off and check the tuning measurements in the repair manual. Look for things like throttle plate clearance when closed, choke adjustments. There are a bunch of things that get adjusted at a rebuild.

With the engine running, spray something like carb cleaner at the base of the carb and at other gaskets and places that may leak. If the engine speed changes, you found your leak. (Carb cleaner won't leave a residue you have to clean up). Obviously, don't use starting fluid. (boom!)

Make sure there are not any uncapped spare vacuum ports on the carb.
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.