Ok so the car idles fine and drives OK. On the top end there is still a lean issue, but I am going to toss in bigger jets to see if that fixes it.

Anyways, I can idle in the driveway all the way till at operating temp. The wideband shows 14.7, or around there, and I shut the car off.... drumm drummbb bummm... Turns itself over a few times after.

Finally dies.

If I drive it for just a couple minutes, (cold). There is no problem.

The hotter it gets, the more turnover there is.

I had the problem in the past and the dyno shop said it was running lean, but the wideband showed OK then too. I am confused. please help.

Thanks.

-Dennis

 

Timing can cause that too. It's worth trying.

 

too much or too little?

If its doing that, it would seem to me that there is too much. But I dunno.

Anyone have any input on that issue?

 

is this a fresh engine or older one?

edit- never mind, looked at your pics and its new.

 

Carbed engine right? 14.7:1 is chemically stoich yes, but in the real (racers) world, that's considered lean. Richen up your idle to 13:1 or so, and try that again.
It's almost like you have a vacuum leak now.

 

Interesting that you say that, cuz some people think thats why the motor isn't making the power it should.

I will be testing that theory soon enough. I am getting a carb hat and plumbing it so that my friend can hook up a smoke machine to it, apparently it pump smoke into the intake at about 2 PSI, and whever you see it seep out, you have your leak.


I will def try to get this test done sooner rather than later...

 

?????? What?
Tune for 13:1 at idle
Tune for 12.5:1 at WOT
tune for 14.5 or so at cruise
Then drive it around for a few days and see if anything changes. It's a simple jetting change, and a few screw turns, shouldn't take you more than a few minutes.

Smoke machine? ugh, that sounds like a lot of *work*. If you think you have a vacuum leak, then grab a 1lb bottle of propane and move it around problematic areas while idling. You'll know when you find it.
I don't think you have a vacuum leak (unless it runs funny like it does?), I just think you've set up your engine to run too lean.

 

i dont know about the propane on small small leaks, ive tried it at work a few times on vehicals that had a small leak on intake gaskets, not anythign to cause a drivability issue, but enough to make the long term fuel trim go out of wack and it never did anything. Smoke is a good alternative to carb cleaner since it doesnt make a mess, but i agree with you, doesnt sound like a vacume leak to me.

 

Common causes:
1. Compression ratio too high for fuel being used.
2. Throttle open too much at idle.
3. Timing retarded causing #2 to be necessary to maintain idle.
4. Crappy gas (can't say cheap anymore).

Or my favorite: #4 combined with #1 causing #3 to be necessary, which causes #2 to be necessary.
What is the cam, idle rpm and C/R of the engine, octane of fuel, and carb used?
A lean condition at idle would also cause it to diesel if it causes the idle rpm to be too high (vacuum leak).

 

where did u install the wideband sensor? if too close to the engine or to far it will be inaccurated

 

Taken from http://www.misterfixit.com/diesling.htm

The most common cause of that is the failure of the anti dieseling mechanism, sometimes an "anti dieseling solenoid", found on most late model carbureted cars. What is happening is that the throttle is remaining partially open when the engine is shut down, which gives the hot engine sufficient fuel to run without a spark from the spark plugs. Most hot engines have sufficient carbon build-up that remains glowing red hot and acts as an igniter for the fuel. The solution is to make sure that the throttle closes completely when you turn off the ignition switch. Check the throttle stop and make sure that the fast idle on the choke or the "bottom stop" isn't what is stopping the throttle from closing. It must be the anti-dieseling mechanism and that mechanism must be functional.

 

Gee, how come I didn't think of that one eh? That's an obvious one eh? Call up holley and ask where the adjustment screw is on their anti dieseling mechanism....
I wonder if that's an AOL hotlink?

I don't think Dennis' engine is old enough to have any carbon buildup in the chambers, and I doubt his carb is sophistimicated enough to have an anti-dieseling solenoid.

Are your spark plugs the right heat range though? I think supervisors #2 and #3 is a pretty common combo there.

 

I will double check the plug heat range. I know they are a bit hot, but can't remember.

I will also check to make sure the blades are shut all the way.

 

It sounds like your timing is too far advanced, which is causing the dieseling action. Everything being fine when the motors cold but dieseling when it's hot is a dead give away. Get a timing light and adjust the timing. Once you're within spec, drive it around and see if the problem goes away. If your idle gets rougher, do like sonix said and use the propane test to hunt down the offending vacuum leak.

 

Will do next weekend! THX