Hello,

I think I need to do something about the ignition timing in my Jeep.
One of the things it does is; it 'diesels' a bit after I shut the
engine off.

Here is what I found in the manuals:

79 258 with bbd carb and manual transmission:
timing: 6 - 8 degrees BTDC
fast idle: 1600 rpm
idle: 700 rpm

However, I did the 4.0 HO head conversion, have a Holley 390cfm (4bbl)
carb and I also converted to the HEI ignition.

From write ups of people that did the HEI ignition on a 258 I saw they
set their ignition timing to as much as 9 degrees BTDC at 1600 rpm.

any thoughts on this ?

thanks,

Ron

On a '79 cj5 with a 258 do I have to double check that when #1 is tdc
the timing markers are on zero degrees or is there no chance that it
can be 'off' ?

If so, what is the best way to set #1 TDC and check it is (without
taking the head of)

It's very common for the harmonic balancer to slide in it rubber
dampener. Use a screwdriver and let it slide in your hand to eyeball in the
crank. Your engine will probably run best with a total of about thirty
eight degrees, mark the crank and time at about three thousand RPMs.
God Bless America, Bill O|||||||O
mailto:BillHughes (AT) billhughes (DOT) com
http://www.billhughes.com/jeep_bookmark.htm

"csdude" <ron.croonenberg (AT) gmail (DOT) com> wrote

FYI...the problem of an engine "dieseling" after the ignition switch is turned off has nothing to do with ignition timing, since the plugs are no longer firing. If the engine was "pinging" on acceleration or part throttle cruise, then I would look at the timing or EGR if so equipped.
You might try the old de-carbon the cylinders trick by running a little water down the carb when the engine is at about 3000 rpm and see if that helps. lets us know what you figure out. Good luck
Glen

"csdude" <ron.croonenberg (AT) gmail (DOT) com> wrote

These are probably better news groups for you:

aol.rant.and.rave
news.whine.whine.kick.kick
alt.whine
alt.dumb

and of course there are the test newsgoups that you posted in


(oops... damnit... I top posted again....)

38 degrees BTDC ? really ? That seems an aweful lot. Why would it
need to be that big an angle btdc ?

On Mar 26, 12:19*am, "L.W.\(ßill\)Hughes III"
<BillHug... (AT) billhughes (DOT) com> wrote:

Well, when I shut the engine off sometimes it will just rotate
another few revolutions with what it seems fuel igniting. Also there
is a chance that fuel mixture is blown into the exhaust and ignites
there (causing a loud bang)
The engine is not pinging I think. Uhm, No EGR anymore.

The "old de-carbon the cylinders trick".. wel.. when we took that
258 aparrt to put a 4.0 head on, we didn't see any carbon. So no
sense in doing the "old de-carbon the cylinders trick", right?

I want to see and check if my engine is running right.

First thing I wanted to check is to see if the ignition timing is
correct. (I do realize though, that with the 4.0 head, headers,
different intake and carb, the timing setting might need to be
different than stock.

After I figured out timing I want to check and see if it is idling ok
and not running too lean or rich.

Ron


On Mar 26, 12:45*am, "Glenn news" <bigglen5... (AT) verizon (DOT) net> wrote:

here is a link to a picture of the 'timing mark scale'

http://farm4.static.flickr.com/3540/3387636783_307e9aeb39.jpg?v=0

I think the scale is a bit 'odd' as you can see, from 0 to 4 is 2
notches, from 4 to 9 is 2 notches etc.

But it looks like 0 degrees is at the second notch from the bottom ?
(That means that the first notch is 2 degrees ATDC?)


My timing light just came in, I hooked it up.

Fast idle (cold) is around 1650 rpm.

The timing is at 24.1 degrees (with the vacuum advance disconnected,
and hose plugged.





On Mar 25, 12:23*pm, csdude <ron.croonenb... (AT) gmail (DOT) com> wrote:

here is a link to a picture of the 'timing mark scale'

http://farm4.static.flickr.com/3540/3387636783_307e9aeb39.jpg?v=0

I think the scale is a bit 'odd' as you can see, from 0 to 4 is 2
notches, from 4 to 8 is 2 notches etc.

But it looks like 0 degrees is at the second notch from the bottom ?
(That means that the first notch is 2 degrees ATDC?)

My timing light just came in, I hooked it up.

Fast idle (cold) is around 1650 rpm.

The timing is at 24.1 degrees (with the vacuum advance disconnected,
and vacuum hose plugged.

On Mar 25, 12:23*pm, csdude <ron.croonenb... (AT) gmail (DOT) com> wrote:

You are right that the fuel is igniting when the engine "diesels", but it is not caused by the spark plugs firing. For some reason, you have hot spots that are igniting the fuel mixture after the key is turned off. Electronic fuel injected engines don't due this because the injectors stop spurting fuel once the key is turned off, but a carbureted engine is still getting fuel sucked into the cylinders. Make sure the idle is not set to high, as this lets in more fuel/air mixture than you want, and can contribute to "dieseling" when the key is off.
To find out if the crank dampener outer ring has "turned" and no longer reading correct TDC, I would use a dial indicator in the spark plug hole of # 1 cylinder to find the exact TDC of the piston and then see if the crank pulley is indicating TDC or zero. BTW, when someone says 38 degrees timing, they are talking about total timing advance, not timing (reading) at idle or 1500 RPMs.
As far as trying to see if an engine is running rich or lean, the best way is to put the jeep on a dyno-smog machine and read the 5 gases coming out of the tail pipe under load as well as idle. Short of that, drive the jeep for a couple of days, then pull out a couple of spark plugs and see if they are carbon fouled (too rich), nice brown/tan (normal-OK), or white cooked (lean). Just like checking an old dirt bike after a carb or jet change, same principle. Try to keep things simple...the same thing that makes a model "A" run, makes a brand new Corvette run. Just different (better) delivery and control methods.
Glen

"csdude" <ron.croonenberg (AT) gmail (DOT) com> wrote

Well, when I shut the engine off sometimes it will just rotate
another few revolutions with what it seems fuel igniting. Also there
is a chance that fuel mixture is blown into the exhaust and ignites
there (causing a loud bang)
The engine is not pinging I think. Uhm, No EGR anymore.

The "old de-carbon the cylinders trick".. wel.. when we took that
258 aparrt to put a 4.0 head on, we didn't see any carbon. So no
sense in doing the "old de-carbon the cylinders trick", right?

I want to see and check if my engine is running right.

First thing I wanted to check is to see if the ignition timing is
correct. (I do realize though, that with the 4.0 head, headers,
different intake and carb, the timing setting might need to be
different than stock.

After I figured out timing I want to check and see if it is idling ok
and not running too lean or rich.

Ron


On Mar 26, 12:45 am, "Glenn news" <bigglen5... (AT) verizon (DOT) net> wrote: