390 issues

Agreed - I run a 270H cam in my 427W stroker and the idle is almost smooth, with tons of torque. I chose that cam for street and cruising use and it fits the bill. Maybe a leak-down test would show any other issues hiding in there.

David

well i did a tune up, just the basics, plugs wires, oil filters. when i go shut it off chugga chugga chugga. seems that the only decent way to get it to shut off is eaither leave it in gear or give it a mondo rev right before i shut it off.
ill research a leak down test to see if i can do that, thanks for the suggestion. ill see if i can get a video of it also.
i dont know what to adjust it doesnt have much to adjust edelbrock carb, no points its got the pertronix kit, aftermarket intake, and thats about it.
i gapped the plugs to 35 per the monkey at the local parts depot. i know that can change timing as well. carb is about 2.75 turns out on the needles on the idle circuits so its not too far from factory settings.
i dont know man, its frustrating.

*edit*
leak down test like a compression ck to see if your leaking air, got it.

Does it run-on cold, hot or both? If hot it's likely a carbon issue perhaps combined with a timing issue. If cold it may be a bad voltage regulator backfeeding the coil allowing run-on. You can test the coil terminals with a meter to verify it's totally dead after key-off.

David

An awful lot of dieseling "after-run" issues are caused by too much closed throttle airflow. You have the primary barrels open too far - probably trying to compensate for the retarded timing. Try more timing and closing down the idle speed setting on the carb. The clue here is that 2.75 turns out on the mixture screws is usually too much - should be close to half that...

it does do it at hot and cold, ill have to ck the coil. if i turn the idle screws lower than that the motor will do more headbanging than an 80's rock concert. when i add a little more advance by turning the dizzy i go to mash on the pedal and it sounds like a gangsta movie under the hood, pinging all over the place. as for the carbon, it could be, its a fairly new engine. i did a test once i had 1/2 a tank and poured octane booster in it. i was told a 390 is a high compression engine and it required high octane. so i poured a bottle in it (it treated 20 gal) so i had 2 times the amount required and for the most part it liked it, not really any dieseling when turned off. am i doomed to pay for the good stuff at the pump?
ill try readjusting those things and report back.
Raf

What is your initial timing and total timing set at?? I know from my experience that if the timing it set too advanced the engine will run on after shut off. What is your idle rpms? How old is your dizzy? You might not have the right curve weights in there.(possibly mismatched for your engine combo). I use nothing but 92 Octane in mine to feed my 11:1 compression motor. ((You have to pay.....for the better gasoline.... to play))

being that its somwhat of a mutt motor and i dont know what the timing is at i know it doesnt ping, when i goose it.
but i think that the gas is going to be a big deal when it comes to not dieseling.
ill have to try some of the good stuff. as fat as weights it appears that he PO just placed a pertronix kit in the stock dizz.
if i rev it right before shut down, it does ok. not great but ok. most of the time it goes off. ill be away for a week and then ill get crackin into it. thx

the PO installed the dizzy, im curious, would one tooth off on the dizzy give me dieseling when i shut it down but a good run when i goose it? im just at my witts end with this thing!
Raf

Originally Posted by $arge

the PO installed the dizzy, im curious, would one tooth off on the dizzy give me dieseling when i shut it down but a good run when i goose it? im just at my witts end with this thing!
Raf

One tooth can make a large difference but still run. Depending on which way the timing jumped, you either have about 9° additional ignition advance or the same in retard (which can cause dieseling), but you'll also have the same amount of camshaft advance/retard. I had a small block do this and the engine ran like crap at low rev's but actually ran pretty good at higher speeds. In my case, the timing advanced and it would ping just trying to drive normally. Since you don't apparently have detonation (ping), that would tend to indicate you have retarded timing and cam - a combo that would do what's happening here.

I would certainly verify your ignition timing first, since it's easy to do, before tearing into the timing cover. In-fact, that should be the first step in all of this, otherwise you're working blind. You can use a borrowed timing light (I bought 2 of mine at yard sales for $5), or use a continuity tester or multimeter, to establish where it's timed now. Get that done first.

I just installed and set timing on a PerTronix the other day with a continuity meter (engine off). When cranked and checked with a timing light I was 1° off of the 10°BTDC I was after. Easy stuff. Disconnect the PerTronix wires and run a jumper wire from the battery (+) to the red wire. Then hook your meter or tester between the black wire and a good ground. Turn your crank with a socket and breaker bar to your proper idle timing (let's say 10°BTDC) and turn your distributor 1/2" either way. At some point the meter will swing from grounding to open (not grounding). That is your firing point. Carefully find that exact spot and lock your distributor down. It shouldn't be far from where it was. Note that it must be the point that it goes from grounding -> not grounding (or conducting/not conducting), as the opposite is not a firing point. That will set your correct static timing.

To first find where your timing is now with a meter (to see if you might have jumped a tooth) do as above, but rotate the crank with the wrench instead of the distributor. The PerTronix will change from conducting to non-conducting through the black wire when it would normally fire the coil. Be sure you're doing all this with the engine on the #1 cylinder compression stroke (the rotor should be roughly pointing at the #1 plug wire cap terminal) and with the black wire disconnected from the coil for measuring and so it won't fire. Hope that helps.

David

EDIT: BTW - I'm talking the timing chain jumping a tooth. Not the distributor off 1 tooth as that can be simply adjusted out but the jumped chain can't.

seems easy enough. with what you explained, i bet thats exactly what has happened to this block. or so i hope. i developed a small exhaust leak so as soon as i get it put back together ill get on this...
thanks david!
Raf