kevin.horton

Hey all,

I am pretty new to this form, have never owned an Olds (until recently) and have never worked with a QuadraJet...question is...I have a newly rebuilt engine, SB350, CompCam 270D/501L cam...HEI ignition, stock exhaust manifolds, and Q-Jet carb. Problem is that the car idles just fine in Park, but once you drop it into gear, it wants to die. I literally have to drive with two feet to keep the thing running. Anybody on here have any insight as to what the problem might be? I had to do this before the motor was rebuilt as well. Any help/suggestions would be appreciated. Thanks in advance.

-kph

2blu442

Hi Kevin
I don't know the answer to your problem, but want to bring this thread back to the top. Did you do anything to the carb? Any kind of vacuum leak detectable? John

MDchanic

Well, I'd say there's a wide variety of possibilities, and you need to narrow them down one by one.

Fuel is certainly one possibility.

• You could have a vacuum leak, leaving the mixture a little to rich as you come off of idle (including a throttle shaft leak).
• You could have blocked or corroded transition ports in your primary venturis.
• You could have a bad accelerator pump or power valve.
• Your idle mixture could be set way too lean, or your idle could just be set too low.
• Maybe you could have a low float level.

Spark is another possibility.

• You could have a number of bad spark plug wires, so that when the voltage requirement increases from bare minimum (at idle), the insulation can't hold the current, and they arc out to ground.
• You could have a similar problem with carbon trails in your distributor cap.
• Your timing could be off.

With more information, we may be able to offer more help.

- Eric

jpc647

I have a similar problem with mine. Mine isn't bad where it'll die, but whatever the problem is, it definitely is getting worse. The car seems to not get up an go, like it used to.

kevin.horton

Thanks John, no didn't do anything to the carb, it has done this ever since I bought the car. I don't believe that there are any vacuum leaks, but I will check. It's just when I drop it in gear that it just drops the r's so low just to back it out of the garage that I have to keep my foot on the gas.

-kph

kevin.horton

OK, I have an update on this thread....last night I started the car up, let it run for perhaps 4-5 minutes...idling fine. I put in reverse, and naturally, the idle dropped so low that I had to put my foot on the gas to keep it from dying. Next thing you know, the idle goes back up (with car still in gear) for perhaps 2-3 seconds, I take my foot completely off the pedal, it then drops back down to where I need to put my foot back on the pedal to keep it from dying. Any ideas?

Bayou Olds

I use a Comp Cams Xtreme Energy cam in my 350. The one I use is one step down from yours in lift and duration(.485/.490 and 268/280 Deg). These cams do have lope. If you are not used to it, it may seem to you like it is going to kill, but it won't. You are going to suck a bunch of vacuum with that cam. My 350 drops down to maybe 600 rpms in gear, a drop of about 500-600 rpms. But it does not die, just idles rough as those cams do.

BlackGold

Your distributor advance springs might be too weak, allowing some spark advance at idle in Park. You adjust the timing and idle speed to where you want in Park, but then when you put it in gear, the load on the engine drops the RPM slightly. The lower RPM backs off on the timing, making it idle rougher, which lowers the RPM further, which backs off on the timing more ...... etc until it wants to die.

The whole situation is possibly made worse if you're using manifold vacuum for the vacuum advance can on the distributor. At the higher idle speed (in Park) you have more vacuum, causing more spark advance. As the RPM drops, so does the vacuum, which backs off on the timing some more ..... etc. The solution here could be to use ported vacuum.

Both of these are examples of positive feedback loops -- control loops in which a change in one direction is not countered but instead is multiplied and gets worse. I'm not saying this is definitely the problem, but it's worth checking.