Ok. I decided to fork for new spark plugs. Installed a set of NGK's. Started it up, retuned the idle mixture screws to run lean again so I could further attempt diagnose the problem. The surge came back so bad when I tuned the idle mixture down back to normal, instead of purposely running rich to calm it down (and get extremely bad gas mileage).
I don't know why this didn't occur to me at first. if making the idle mix rich masked the problem, then the car must be running lean at idle and part throttle/cruise. When I give it alot of gas, the main throttles start dumping gas through my jets, and the problem clears up.
Now-- for the experts. Vacuum leaks aside-- because I've gone that route and found nil-- what could cause this lean idle condition, if the idle mixture is adjusted properly? Someone suggested the transfer circuit is lean, but how would that effect idle surge? PS: I don't even know where the transfer circuit is.. A vacuum guage, patience and a screwdriver I can do the idle mixture.. but.. aside from that?
Its a 460 CID BB
holley 4779 750 DP upper w/ 850 baseplate.
Cam is Hyd. roller 286 @ .006, 230 @ .050 .639 lift.

This problem recently occured 'on its own.'

Thanks everyone!
Matt

hey Mat
I asked you to give me a call and I will explain it to you.Whats the problem?

Marv, located at the top of the carb, just inside the choke tower...on either side of the vent tube will be 4 air bleeds. The 2 outside bleeds are the high speed bleeds and the 2 inside ones are for idle. Either that or it's vice versa. :rolleyes:

With the engine off, give these bleeds a quick squirt with some carb cleaner. They can get gummed up which would give you less air at idle and at high speed.

Oh yeah, those 4 bleeds should be located on the secondary side as well.

You might have tried that already, as I just read this thread and don't know what happened in Part 1. Something to try, tho. Good luck!

68,

I never got a reply to the email I sent you? I didn't mean to offend if you thought that was it. I've been looking the last few days for it too.

Did you get the mail i sent you?

matt

Either way, I think this problem is sort of out of my league. My engine builder gave me the # of a local tuning shop that should be able to iron out the kinks. Appointment tuesday.. I've been at this for 3 weeks, to no avail. graemlins/sad.gif

matt

Mat
I will send another email,this is an easy fix

Hey 1968, why not share the easy fix with the rest of us? You got some top secret military info on Chevelles you ain't allowed to divulge? :D

K

Chevello
no not top secret,just alot easier to explain over the phone than typin my azz off.but the first I'd look for is to check his base to carb body gasket for a leak,also to make sure the passages line up correctly and are not clogged.A cam that mild in a motor that big should not have a lean idle or transition problem.I would post a couple of pics but I don't have a scanner.