Running Rich?

[Bruce Wingate]

It has been cold enough here to keep me from wanting to work on the truck for a bit, but I did install a fuel pressure regulator and set it to ~5.5 psi. Doesn't seem to have helped much, but I haven't done an actual check. The truck is running cleaner and the exhaust smells better though. I think the "running rich" part is fixed and now I'm trying to get it to run "right" or "reliable."

I don't like what my mechanic said that the timing was way off and what he did seemed to make it worse. It is harder to start and will not stay idling for the first few minutes without playing with the throttle. It occasionally will start, run for a second or two and die. I also notice a slight stumble at idle - just a quick break in the idle rhythm. He said it was timed at 4 degrees. Based on what everyone else is saying, I think this should be in the 8 to 12 range. (Engine has no smog/pollution controls on it.)

My next step will be to change the plugs and fuss with the timing to get it to what I think is right. I am going to try to find TDC of the engine and see how far off the mark on the harmonic balancer actually is and then try to time it to 10 degrees.

I understand finding the compression stroke by placing a finger over the spark plug hole, but after the compression starts, how do you know then the piston is at TDC? I'm not really keen on putting the stop tool in and using that, but I'm thinking that might be my only way if the timing mark is way off.

Also, does adjusting the vacuum advance in the distributor have any effect on this?

After that will be trying to track down a possible vacuum leak.

 

[86c10twotone]

Make sure your vacuum Advance is disconnected when setting timing . Unhook the vacuum line at the distributor and plug the intake side of the hose with a screw or something.

 

[82sbshortbed]

Mine was doing that at start. Then I hooked up the choke(electric)and adjusted it and now it's much better now. The choke made it rich and would foul the plugs. I really don't know much about adjusted or tuning the quadrajet but this helped me.

 

[Bruce Wingate]

Ok - tried to quickly check timing and I think it is set at 4* BTC, and I think the mark the shop made on the harmonic balancer aligns with the stock mark (an etched line across the balancer.) My problem seems to be that the pointer on the block pretty much covers the mark and is hard to see with all stuff in the way. Tomorrow I'm going to see about retiming it and fixing the pointer.

Idle is also low at around 550
And the fuel regulator is leaking from the fittings - which might explain my continued low mileage.

 

[75gmck25]

A couple of items to mention.
Leaking well plugs were common in earlier Quadrajets, but by the time they built your 80’s vintage carb it was mostly fixed. They are sensitive to fuel pressure and float level, so it’s always good to check.

While at idle, use a large rag and your hand to cover the top of the carburetor. If idle drops and finally stalls, the mixture might be okay, but if it goes up or stays running, you have a vacuum leak.

Most of the older 350’s run better with base timing at at about 8-12. Once you get your damper and pointer issues sorted out, try more base timing, and check to see you get 18-20 degrees more from mechanical advance.

 

[Bruce Wingate]

@75gmck25: Thanks for your input.

I fully closed the choke plate by hand yesterday and the engine stalled almost immediately, so I think we're covered on the vacuum leak. But that didn't stop me from spending time on youtube figuring out how to make a smoke generator to chase down a vacuum leak.

I'm going to fix the fuel leak and run it for a while then start trying to set hot and cold idle to 800 / 1200 and see what happens. Then it will be onto fine tuning the timing.

 

[Bruce Wingate]

Fixed the gas leak with yellow Teflon tape and moderate persuasion. Double and triple checked for no leaks

Tried to time it again, and for the life of me I cannot see the timing mark at all. Gave up on that and adjusted the idle up to 750. Thought that I would go up to 850, but it just sounded right at 750.

Since I couldn't time it with the light, I figured I would try timing it to max vacuum. All warmed up and the HEI distributor vacuum connect to manifold vacuum, I checked vacuum off the large PCV port on the front. It settled in right around 20 psi. I left it alone rather than monkey with it for one or two more PSI. Took it for a shake down cruise, and mileage seemed OK (I was no longer watching the gas gauge needle in free fall). Hard numbers in a couple of days and a few more miles.

I might call this "good enough" and move along to other problems

Big thanks to @SirRobyn0 and the rest of you for your help!

 

[SirRobyn0]

Fixed the gas leak with yellow Teflon tape and moderate persuasion. Double and triple checked for no leaks

Tried to time it again, and for the life of me I cannot see the timing mark at all. Gave up on that and adjusted the idle up to 750. Thought that I would go up to 850, but it just sounded right at 750.

Since I couldn't time it with the light, I figured I would try timing it to max vacuum. All warmed up and the HEI distributor vacuum connect to manifold vacuum, I checked vacuum off the large PCV port on the front. It settled in right around 20 psi. I left it alone rather than monkey with it for one or two more PSI. Took it for a shake down cruise, and mileage seemed OK (I was no longer watching the gas gauge needle in free fall). Hard numbers in a couple of days and a few more miles.

I might call this "good enough" and move along to other problems

Big thanks to @SirRobyn0 and the rest of you for your help!

Glad we could help you out!