Hi, I'm experiencing a serious problem with my olds 350. This seems to be an intermittent problem as it went away for a couple of months. When I start my 71 cutlass cold the idle surges to 1300 rpm and the fast idle screw doesn't seem to disengage. I've put my timing gun on it which has a tach and sometimes the idle surges up to 1800 rpm. Repeatedly flicking the throttle linkage or getting in the car and pumping the gas pedal does not bring it down into its normal idle range 1000 rpm. It will do this for several minutes and keeps doing it even if i shut the car off and restart. Eventually it kicks down but goes into a very low RPM, usually around 600 rpm and will even sputter and eventually go lower than that and stall if I let it. When the idle is surging up high turning the idle screw on the driver side of the carb does nothing to bring it down. Of course turning that screw screws up my original idle setting. I have a 350 with edelbrock performer rpm intake and cam. an edelbrock 600 cfm 4bbl with electric choke. like i said it was intermittent until last week when i tried resetting the timing after installing hooker headers. that retune went very well, i had the car idling at 1000 rpm (recommended by the manufacturer) and timing at 16 degrees BTDC and it seemed to drive well. I let it sit for a while, wanted to see how it startd cold and boom this problem reemerged and won't seem to go away. I reversed all the changes i made as best i could and the problem persissts and now my tune is way out of whack i'm sure. To be honest I'm out of my depth here, my buddy who knows a heck of a lot more than I do and helps me with my car is out of commission for a while so I'm on my own. I've researched this and found it could be anything from a faulty electric choke (seems most likely) to a vacuum leak to a bad piston to a faulty distributor (seems possible too). the distributor is HEI and has had a new cap and rotor put on but no coil. I use a MSD multi spark device as well.

 

Just one more thing, I'm getting the battery checked tonight, seems like a simple and free and prudent thing to do. Its a fairly new battery but....

 

It's not a battery issue. Did you run a 12V source wire to the dist or use the existing resistor wire from the points? The HEI requires a 12V source to function properly.

It sure sounds like a vacuum leak to me. Get a can of carb cleaner and spray it around the base of the carb, all of the intake runners at the head, and all of the vacuum lines. If it picks up you found the leak. Also pull the vacuum line to the brake booster and cap it in the source side to rule out the booster being the cause of a leak.

 

thanks for the reply. the distributor is running 12 volts. started it up last night and it was a struggle to keep it running, only 300 rpm. it warmed up a bit and creeped up to 600 without stalling. i turned the idle screw a bit and it immediately jumped to 1600 rpm, turned it back and it dived back down to 600. there is a bit of a ticking sound coming from the passenger side of the motor near the back two cylinders. i'll try the carb trick. not running a brake booster. the HEI was already setup when i bought the car 4 years ago. only thing i've done is replace rotors and cap and add the MSD unit but that was when i first bought the car.

 

See if you can get your hands on another carb. It sounds to me like you have a vacuum leak somewhere or maybe even a clogged passage inside the carb.

With the car off turn the idle screws in all the way and then back them out 2 full turns, don't make any other adjustments. Then start the car and bottom them out one at a time to see if this makes any difference, you might have a clogged idle circuit. That would surely cause the strange idle issues you're having. It won't idle with the blades closed, but crack them and it jumps.

 

like i said this problem is intermittent, started the car up this morning and no problems. i did notice though that my fast idle cam is not coming down and contacting the fast idle screw when the engine is cold, it was in the up position and the choke was open but i managed to get it started. i let it cool about six hours and the cam still didn;t come down so i put it down manually and the choke flapped snapped shut and the car started with no problems. i got the engine back in tune to about 900 rpm with 16 degrees btdc, going to let it sit until tomorrow night and see what position that fast idle cam is in, i turned the dial on the choke clockwise quite a bit, maybe that will make a difference. i tried the carb clearner trick and it made no difference to the idle when it was running really low. i bought a vacumm gauge and the reading was 9 and holding steady.

 

That's a bit low.

With a Factory HEI you want the initial to be set to 20° BTDC @ 1100 RPM.

 

I adjusted my fast idle screw yesterday, pumped the gas one time which dropped the cam down into position and without even being in the car (just reached in through the window) I turned the key and it started up great. Fast idle was at 1600 rpm which is a bit high i think. car ran great yesterday. Thanks for your help, svnt442! I'll work on adjusting my timing this weekend. I'm told that timing should ideally be done while car is in drive, little hard to do by myself so maybe i can snag a passerby to sit in the car and put their foot on the brake while i check it out. guy at my speedshop said in drive the timing should be at 8 - 10 BTDC with rpm at 800 rpm. thoughts?

 

Ugh...Chevy guys. Olds has a different timing curve with the HEI than Chevy did. Also NEVER.....NEVER....mess with the distributor with the car IN GEAR. You set the initial with the engine at 1100 rpm and the vacuum advance disconnected and the source line capped.

You can then use a vacuum gauge to help set the idle screws. Once you have the gauge connected to a vacuum source that reads from both sides of the manifold then you can adjust each mixture screw until you reach the highest reading and you should be set.

 

haha okay okay, thanks again for your help.