The Stovebolt Site Forums The Shop Area Engine Shop 1969 292 valve settings? Rough idle

Hi. Been driving about in the 59 1 ton, but its been running hot. Ran ok, old points, new plugs, new wires, new rotor, new cap. Timing was way advanced - so figure that's contributing to the engine running hot.

Replaced the points, set everything back to spec. Ran good, a little balky off idle, then later on it backfired, and ran like poop, would not idle - had to hold speed up with accelerator.

Rechecked everything, reset points gap to .019 (new points), set timing to 4 btdc (vaccum hose off distributor - idle speed around 7-800) but it really doesn't want to idle at the 550 rpm it should be at. Funny thing was that it ran ok for about 30-40 minutes right after I did this the first time.

I noticed that the timing is very sensitve to engine speed - perhaps the distributor mechanical advance springs are too weak? A little more RPM gives a timing change.

I have just gone through it all again, adjusting everything, but it still doesn't want to run right. Rough idle. Ok if engine is spun up a bit.

So I was thinking maybe the guy had the timing set way advance (like 16) because valves were off. So anyone got those specs, or is that a blind alley as the engine might have hydraulic lifters. (But I doubt it - does leak a bit on rear pushrod cover)

Spark plugs are relatively new champion 4405s the majick black and gold truck plug. Plugs look like mixture is right - light brown. Gap is .035 and right at spec.

Don't really see any vaccum leaks. Vaccum line to distributor makes a significant difference to timing when its removed and replaced. So I assume its ok.

I am a little puzzled as to what happened...

If there's a brass float in the carburetor, that backfire might have collapsed it. You might be experiencing a little flooding, resulting in the rough idle. Just a thought, as you've pretty well covered all the ignition-related problems. I believe all the 292's had hydraulic valve lifters, which require a pretty simple adjustment procedure. Each cylinder is brought to top dead center on the compression stroke, (engine stopped) the valve adjustment is loosened until the pushrod is sloppy, and then tightened to just remove the slack. Then tighten an additional 3/4 to 1 turn. (both valves). Turn the engine to TDC on the next cylinder in the firing order, and repeat until all cylinders have been adjusted. Don't try a running adjustment, it's sloppy and inaccurate!
Jerry

if I had never put the timing light on it, I probably would have been happier. Went through the whole mess again, runs worse than it did. Wonder if the new points or condesor is a turd.

I am going to buy a pertronix and be done with it. Points with no window distrubtor and cam tool are a pain in the butt. :mad:

Do you have a 59 with a 69 engine in it?
If you have the monojet carb they are bad about
the gasket between the float bowl & thottle
body getting wallowd out. If your points are still
gapped correctly your problem is a vacuum leak
or carburetor.
George

Did you check to make sure the harmonic balancer is still good? They tend to slip after a while on 292's and the timing marks end up being incorrect.

You may be seeing the vacuum advance coming in with your throttle blipping. Disconnect the line at the carb and plug the hole.

Too tight valves will cause the engine to lose compression when hot and can cause poor idle and hot running, due to the exhaust valves not spending enough time on the valve seats. It is best to run slightly to the loose side of spec on a stock engine, especially in the summer; it does not hurt anything and helps the valves run cooler.

I had let the lifter adjustments on my 6 cylinder BMW go for too long once and was getting an intermittant check engine light and a code for a bad lambda sensor, along with poor gas milage and rough idle. I knew the sensor was good, so I did a tuneup and valve adjustment and it fixed it. The valves were too tight.

how do you check to see if the harmonic balancer has slipped? Isn't it keyed?

The balancer is a 2-piece unit, with a layer of rubber bonded between the hub and the outer ring. The bond can fail, and allow the ring to slip, making the timing mark inaccurate.

Here's a quick check: Take an old spark plug, and knock the porcelain center section out of it. It's usually necessary to grind away the rolled edge where the shell meets the porcelain first. Thread the shell for a 3/8-16 carriage bolt, with a locknut above the plug shell. Install the modified plug into the #1 cylinder, and screw the bolt in far enough to touch the top of the piston before it reaches the top of the stroke, and lock the nut down. Carefully turn the engine by hand until the piston touches the bolt, and stops its travel. Scratch a mark on the balancer outer ring under the timing pointer. Turn the engine backwards until it stops again. Mark the balancer under the timing pointer at this position. The TDC mark should be exactly halfway between the marks, if the balancer is in its original position. If not, replace it. There's no way I know of to reposition one, and once it slips, it will do it again.

It's a little fuzzy, but here's a tool I made for checking TDC:

[img]http://www.hunt101.com/img/192632.jpg[/img]

Jerry

and if you like Tom and Ray, we stumped most of the chumps (including me), but the right answer came from:

WrenchBender retired.

(ta dah! yay! applause!)

The key was the backfire I heard. Today I started in on it again on the assumption that the condenser was bad and that I have seen that problem before with similar results - only once - but sometimes I have a memory like an elephant.

Put in old points and old condensor. No real change. So I opened up the carb to see if the floats were ok - and they were. So that wasn't it. Carb was recently rebuilt.

So, then I sez, hmmm...dat ain't rite. So I put a vaccum gauge on the distributor vaccum feed line - 8 psi. Dat ain't rite. So I start looking at the various lines. Power brake line was fine, but when I checked the PVC valve line, it was ok at the valve cover, but, the press fit nozzle on the manifold was loose! Dang it!

Stuff a bolt wrapped in plastic on it, bingo, adjusted timing back to 4 btdc, 550 rpm, rock solid. I knew it had run correctly for a while, and so that was what was stumping me. How could valves or carb go to manure mode so quick? Couldn't. Only bad thing could be bad points or condensor, or, as Wrenchbender sez, vaccum leak.

Now I just have to figure out a new press fit nozzle for the PVC valve, or tap in a new barb. I am relucant to tap because of swarf getting into the engine, so I might JB weld or see what else I could make.