gettin ready to leave on a road trip in an hour and having a problem. when idling my car keeps surging from 600-1300 or so. it'll stay at each for maybe 4-5 seconds and then will either go up or down and will sometimes want to stall unless i give it a little gas. i have a holley 4160 750cfm on it. doesn't appear to be any vacuum leaks. anyone know what's up? thanks

 

Sounds like a vacuum leak.

This car just got worked on, didn't it? Head gaskets IIRC? Did it do it before it got worked on? If not, then check your work, something probably got missed.

 

it didn't do it before i changed the head gaskets, besides the oil smoke it ran fine for nearly a week until yesterday when it started the surging. so i changed the intake gaskets again this morning and it's still doing it. i plugged the vacuum lines and no change. maybe the carb base gasket went out somehow, i never took the carb off of the intake though.

 

You've got a Holley, and you're concerned with idle stability? In my opinion, the two are almost mutually exclusive. You can set the idle mixture, (old ones with four screws), mixture rate, and throttle stop at one temperature, and as soon as the weather changes, you're totally fornicated, and are starting all over again.

 

I've never had trouble getting Holley to have a stable idle, as long as its throtte shafts weren't worn out; but that's not your problem.

Have you tried re-tightening the intake bolts? Looked for vacuum leaks with some spray carb cleaner or something?

 

All four seasons? (From 105° to -30°?)

Got a vacuum reading at idle? (Along with cam information?)

 

Yup, all 4 seasons. Especially in Southern California!

Seriously, yes, even in a place that has seasons. A properly calibrated Holley with a functional choke works just as well as almost any other carb, in the winter, summer, whatever.

I could give a list as long as my right arm of my own cars, my brothers' cars, friends cars I've helped set up, etc. Of my own stuff, the most recent was a Holley 6211 (800 CFM man sec dbl-pump) on a 400 with a Comp XR282HR. Pretty mild cam, but still, a good bit more than stock. That combo also did 18 mpg on the highway fairly dependably, with 3.73 gears.

I try real hard not to fool around with the cheapie too-universal Holleys like the 1850 POS. But again, with enough patience and care, even those weenie things can be made reasonably stable.

Holleys came stock on an awful lot of cars all through the 60s; including lots of luxury cars in addition to the muscle cars. My stepfather used to bring home things like New Yorkers with 440s that had Holleys on them all the time, as well as 6-pack Cudas with Holleys, 426 Hemi Chargers with Holleys, and all the rest of the products of that brand. Even Brand F used them on their big sled motors like 390s in the Galaxie 500 and Mercury Marquis and Lincolns and so on. The type of people who drove cars like that back then, wouldn't accept a car that that was incapable of cranking up and driving right on a cold morning, any more than your own grandma would today.

 

You're a better (more patient) man than I am. I prefer the smaller primaries and only had good luck with the older 4150s that came with Chevys and had air bleeder AND rate adjustments for the idle (like on the cam-eating 366Ts I used to play with). WOT is failry easy with jetting and power valve selection, but that low- and intermediate-range always frustrated me.

Thank goodness for feedback systems.