'69 Olds 442 Idle Problem

If I had to guess, I'd start with the ignition, if you find the idle mixture is about right - with the higher compression the ignition is more critical - put the stock Dist back, new plugs and new wires (and dist cap, etc) and see if it's better.

I'll second the motion. My old man had a saying for old cars, "Its always the ignition, when you're sure its something else, its in the ignition". Plus you can see the other shop has beat carburation and valve timing to death with no effect.

I'd tell this guy, strickly time and materials, no promises. Or, he'll just be mad at you, also.

Karl

As crazy as it sounds, I would swap out the coil, even with a used one, just to check. I have seen ignition coils do some really weird things.

Please let us know what you find out. I love to hear stories of mechanical puzzles. Seem far to many of them.

Any

All carbs tested could not get a good idle. Any 4 BBL carb should get a smooth idle on a V-8, as jets do not affect the idle circuit, unless the power valve is opening.

Check Harmonic balancer for slippage. (i.e. is TDC really TDC?)

What kind of gas is he using? My 442 I used to have had 10.5:1 compression, and would knock like hell unless using at least 96 octane. Wrong fix is retard initial timing, and delay mechanical advance. Causes low vacuum, poor idle.

How is the vacuum advance hooked up, ported or direct?

What idle speed are the readings obtained from? Should be about 625-650 rpm in park, and about 600 in drive.

Dump the Quadrajet.

One other thing, kind of a long shot, but I've seen it happen before: when the other shop finished with the rebuild, did they get the plug wires back on properly? Incorrect firing order would easily account for the idle being worse, and power way down.

Two thoughts:

Cracked manifold can lean the mixture, as it is part of the PCV circuit. It would have the same effect as a PCV valve stuck open, or a cracked hose to PCV. It does have a PCV valve, right? And an air inlet in the other valve cover?

Camshaft - if it has any more overlap than stock, the idle mixture can go rich. We used to have to crack the secondaries a bit on Holleys to compensate for a hotter cam. Yours may not be hot enough to matter, and the secondary butterflies may not have an adjustment. Look at the overlap specs on the cam, and consider going back to stock cam.

Vac 12 inches - at what vacuum does the power enrichment kick in on the Qjet? It's possible it is set to something close to the average vacuum, and just dribbling additional fuel, but not enough to raise the avg mixture on your A/F meter.

Hmmm... just for snorts & giggles, take a look at the harmonic balancer. Has deteriorating rubber allowed the outer ring (along with the timing mark) to slip around?

Your low manifold vacuum that improves with advanced ignition timing is what makes me suspicious. Slipped balancers are not unheard of, especially on older engines.

If this should be the case, there are places around that rebuild them for a lot less than new, ask the folks at your machine shop.

Good luck, let us know how it comes out.

Erik

Stock carb, and the carbs they tried, could all have worn throttle shaft bushings.

It's easy to overlook this vacuum leak, and it also allows the throttle plates to randomly open-and-close a bit as it idles.

A Qjet in good shape is a *great* carb.

Dave

">

on most cars, the damper is pinned, though it can shift a little - the place I use for rebuilding (they do good work) is "DameprDoc"

No EGR on that one, though the aluminum manifold may have provision for one.

if the idle is irregular the vacuum will be low, whether the irregularity is due to ignition problems, valves, a leak, or something else. To me, at least, on that vintage engine, the sound of the engine is very distinct if it is fuel starved, or fuel rich, and it changes if the timing (ignition timing) is off also. Of couse the descriptions here are text only and don't include sound files, but here's my impression

lean - harsh sound rich - soft labored sound advanced - sharp stacatto sound retarded - labored and weak sound

take a thin hose, hold one end near your ear and move the other end around the manifold, carb, plugs, etc - listen and see if you hear leakage

Find a "high energy"distributor from a later model olds and put it in. Guaranteed adequate spark. Then go from there. If 60,000+ volts won't fire the plugs, nothing will

balancer and TDC needs to be verified. Don't overlook

Don't overlook the vacuum break for the automatic choke either. VERY common failure point on '60s QJ carbs. If the diaphragm is leaking you will NOT get it to idle smoothly. PERIOD.

First thing I would do is verify compression. A good leakdown (aircraft type) tester would be handy as well. Then VERIFY ignition timing mark (damper) - and if compression is even but low verify valve timing. A good ignition scope and someone who knows how to read it can verify both primary and secondary ignition - I'd put a NEW set of the proper AC plugs in. With a hot cam, the proper plug will be COLDER than original. Then check or replace the wires and coil. My preference would be to put in a later model high energy (electronic) distributor with the coil built in. and 8mm mag-core wires Then check ALL vacuum devices for leaks. Block the lines to the heater controls for testing purposes, and use a "mighty-vac" to check all diapragms etc. Feed a bit of propane through a hose to all suspected vac leak areas (throttle shafts, base gaskets, etc that cannot be verified mechanically..

Unless the replacement cam is "wild" getting it to idle should not be hard. Getting it to PERFORM can be more difficult.

by the way, a friend used to drive a olds 442 - a bit older than 69 - there is nothing like shifting into 4th and burning rubber at 120mph to prove that you have way too much horsepower.

The key is low idle vacuum. You have a leak or you have lost index on the balancer and TDC needs to be verified. Don't overlook the brake vacuum booster, throttle shafts on the carb,PVC valve or EGR valve leakage. Steve

Kudus for all the good replies. I vote for 2 problems:

1. Problem started after 1st ditributor replacement: Timing is off. Going through several mechanics-must be basic, thus unfound. Verify TDC #1-ck balancer
2. Vacuum leak-def>Some metal content, (barely)...This started last spring actually when

-------------------------------------------------------------- Home Page:

-------------------------------------------------------------- Dependence is Vulnerability:

-------------------------------------------------------------- "Open the Pod Bay Doors please, Hal" "I'm sorry, Dave, I'm afraid I can't do that.."

On Thu, 27 Aug 2009 20:59:09 -0700, the infamous JR North scrawled the following:

Huh? Y'mean "kudos", Jace?

This is one I'd never seen while wrenching, but I have heard of it happening.

Yeah, vacuum leaks are #2 for rough or no idle after clogged idle jet circuits (in unrebuildable Holleys. ;) I didn't see many open brake boosters but saw lots of loose or split vacuum hoses, missing caps, misrouted vacuum lines, and open EGR valves in later models. I'd vote for the leak at the new Edelbrock intake. I saw that a whole lot.

Yeah, I much preferred Rottenchesters to Holleys for GM products.

-- A striking fact of the last two years of financial trouble is how accountability has differed in the public and private spheres. On Wall Street and across the country, decades-old firms have failed, fortunes have vanished, and some former captains of finance face jail or fines. In Washington, meanwhile, most regulators and Members of Congress remain on the job, often with enhanced power. -WSJ "Bernanke's Second Chance" 26aug09

....or not enough tire!