It's all in the timing.

#1

Finally got around to looking at the ignition timing after changing the
timing belt a couple weeks back. ('83 245)
12 BTD at idle, as it should be.
Then the weirdness begins. Rev it up a little and timing retards to ~5
BTD. Rev a little more, say 3500, and it creeps up to 15-18. Rap it and
it appears to go up from there.
So, what's up with the retardedness? Can't be good for performance.
btw, I have the vacuum line on the knock generator plugged so the motor
doesn't ping all the time... and, so it will pass smog.

#2

clay wrote:

Quote:

Finally got around to looking at the ignition timing after changing the
timing belt a couple weeks back. ('83 245)
12 BTD at idle, as it should be.
Then the weirdness begins. Rev it up a little and timing retards to ~5
BTD. Rev a little more, say 3500, and it creeps up to 15-18. Rap it and
it appears to go up from there.
So, what's up with the retardedness? Can't be good for performance.
btw, I have the vacuum line on the knock generator plugged so the motor
doesn't ping all the time... and, so it will pass smog.

If I understand what you're saying, that sounds like it's working as
expected. Remember that BTDC is *before* top dead center, so a bigger
number means more advance and a smaller number is retarded towards TDC.
It takes time for the fuel burn to take place, so the spark fires prior
to the end of the compression stroke.

#3

On Sun, 01 Nov 2009 20:58:35 -0800, clay <cl (AT) ymation (DOT) com> wrote:

Quote:

Finally got around to looking at the ignition timing after changing the
timing belt a couple weeks back. ('83 245)
12 BTD at idle, as it should be.
Then the weirdness begins. Rev it up a little and timing retards to ~5
BTD. Rev a little more, say 3500, and it creeps up to 15-18. Rap it and
it appears to go up from there.
So, what's up with the retardedness? Can't be good for performance.
btw, I have the vacuum line on the knock generator plugged so the motor
doesn't ping all the time... and, so it will pass smog.

"Vacuum line on the knock generator plugged so the motor
doesn't ping all the time." ?????

Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place

#4

Boris Mohar wrote:

Quote:

On Sun, 01 Nov 2009 20:58:35 -0800, clay <cl (AT) ymation (DOT) com> wrote:

Finally got around to looking at the ignition timing after changing the
timing belt a couple weeks back. ('83 245)
12 BTD at idle, as it should be.
Then the weirdness begins. Rev it up a little and timing retards to ~5
BTD. Rev a little more, say 3500, and it creeps up to 15-18. Rap it and
it appears to go up from there.
So, what's up with the retardedness? Can't be good for performance.
btw, I have the vacuum line on the knock generator plugged so the motor
doesn't ping all the time... and, so it will pass smog.

"Vacuum line on the knock generator plugged so the motor
doesn't ping all the time." ?????

Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place

I was puzzled about this as well; I thought the knock sensor

(generator???) was essentially a microphone bolted into the engine
block, sending an alternating electrical waveform of varying amplitude,
dependant on whether the engine was 'knocking', so where does a vacuum
line enter this equation.
The only vacuum line I can think of on an average 240/245 engine of this
age (apart from emissions control, or possibly carburettor control) is
either going to the distributor (probably not in this case), or to the
ignition management computer. This allows the computer or distributor to
properly act upon the varying load and throttle positions, by altering
the ignition timing; surely blocking this function would severely affect
the cars performance?

Best wishes,
Ken Phillips

#5

James Sweet wrote:

Quote:

clay wrote:
Finally got around to looking at the ignition timing after changing
the timing belt a couple weeks back. ('83 245) 12 BTD at idle, as
it should be. Then the weirdness begins. Rev it up a little and
timing retards to ~5 BTD. Rev a little more, say 3500, and it
creeps up to 15-18. Rap it and it appears to go up from there. So,
what's up with the retardedness? Can't be good for performance.
btw, I have the vacuum line on the knock generator plugged so the
motor doesn't ping all the time... and, so it will pass smog.

If I understand what you're saying, that sounds like it's working as
expected. Remember that BTDC is *before* top dead center, so a
bigger number means more advance and a smaller number is retarded
towards TDC. It takes time for the fuel burn to take place, so the
spark fires prior to the end of the compression stroke.

Right.
I understand about ignition advance curves, etc.
That's why I said that the timing retarding initially can't be good for
performance (or emissions...)
Googling around for the correct name for the 'knock generator'... the
Chrysler ignition control module, I found an explanation posted in this
group back in 2002.
Now to find the specifics of the recall to get rid of the retard, and
figure out why I'm not getting more advance with higher rpms.
Possibly because the motor has the Chrysler module but a Bosch
distributer. As I understand it, the distributer cap should be white but
it's a Bosch red one...

Quote:

From: "volvowrench" <radietz (AT) ioip (DOT) com

Mike, Any 240 that has the Chrysler ignition box will pass NOx with
flying colors, provided the cat is at all sound and the ignition
secondary is in reasonable condition, when the vacuum hose to the
control unit transducer is plugged. On the dyno and on the street,
unless you're really flooging it, you can tell no difference in
performance. What happens is that the "limp home mode" for the
Chrysler box closely matches a conventional distributor curve; i.e.
advance retards 5 degrees when the throttle is opened and climbs with
engine rpm to approximately 33 degrees instead of swinging
immediately to 52 degrees and backing down to below ping levels. It's
this high sustained advance on the verge of ping that drives NOx
high. Typically in this area the NOx reading is just a few points
over the allowed limit, and after replacing the converter in drops to
just a few points under the limit. But with the transducer hose
plugged, you can expect to see a drop of over 400 points on an old
converter and as much as 700 points on a new converter. There was a
recall on the 83-84 models to install a vacuum delay valve in the
distributor hose (to cancel the retard off idle) and a delay valve in
the transducer line from before the throttle (instead of manifold
vacuum) to delay the advance curve to quell high NOx readings and
satisfy the EPA. I rarely see one of those cars that still has that
particular modification intact. There were serious performance issues
even on cars in a good state of tune. By disabling the transducer you
gain all the dwell extension features of the lean burn system without
sacrificing the marginal at best mpg gains that were so highly touted
at the system's inception. If there were some valid reason to not do
this I wouldn't recommend it, however NOx is the most potent
pollutant, after ozone, in producing smog in cities and valleys. NOx
at high altitudes, according to NASA studies in Hawaii, is more of a
destructive catalyst in O3 reduction to O2 than even Cl2F2H (Freon
R-12).

#6

Ken Phillips wrote:

Quote:

Boris Mohar wrote:
On Sun, 01 Nov 2009 20:58:35 -0800, clay <cl (AT) ymation (DOT) com> wrote:

Finally got around to looking at the ignition timing after changing
the timing belt a couple weeks back. ('83 245)
12 BTD at idle, as it should be.
Then the weirdness begins. Rev it up a little and timing retards to
~5 BTD. Rev a little more, say 3500, and it creeps up to 15-18. Rap
it and it appears to go up from there.
So, what's up with the retardedness? Can't be good for performance.
btw, I have the vacuum line on the knock generator plugged so the
motor doesn't ping all the time... and, so it will pass smog.

"Vacuum line on the knock generator plugged so the motor doesn't ping
all the time." ?????

Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things)
http://www.viatrack.ca

void _-void-_ in the obvious place

I was puzzled about this as well; I thought the knock sensor
(generator???) was essentially a microphone bolted into the engine
block, sending an alternating electrical waveform of varying amplitude,
dependant on whether the engine was 'knocking', so where does a vacuum
line enter this equation.
The only vacuum line I can think of on an average 240/245 engine of this
age (apart from emissions control, or possibly carburettor control) is
either going to the distributor (probably not in this case), or to the
ignition management computer. This allows the computer or distributor to
properly act upon the varying load and throttle positions, by altering
the ignition timing; surely blocking this function would severely affect
the cars performance?

"Knock generator" = Chrysler ignition control module. A lame attempt to
squeeze a little more performance out of an anemic four banger.
See my reply to James.

#7

clay wrote:

Quote:

James Sweet wrote:
clay wrote:
Finally got around to looking at the ignition timing after changing
the timing belt a couple weeks back. ('83 245) 12 BTD at idle, as
it should be. Then the weirdness begins. Rev it up a little and
timing retards to ~5 BTD. Rev a little more, say 3500, and it
creeps up to 15-18. Rap it and it appears to go up from there. So,
what's up with the retardedness? Can't be good for performance. btw,
I have the vacuum line on the knock generator plugged so the motor
doesn't ping all the time... and, so it will pass smog.

If I understand what you're saying, that sounds like it's working as
expected. Remember that BTDC is *before* top dead center, so a
bigger number means more advance and a smaller number is retarded
towards TDC. It takes time for the fuel burn to take place, so the
spark fires prior to the end of the compression stroke.

Right.
I understand about ignition advance curves, etc.
That's why I said that the timing retarding initially can't be good for
performance (or emissions...)
Googling around for the correct name for the 'knock generator'... the
Chrysler ignition control module, I found an explanation posted in this
group back in 2002.
Now to find the specifics of the recall to get rid of the retard, and
figure out why I'm not getting more advance with higher rpms.
Possibly because the motor has the Chrysler module but a Bosch
distributer. As I understand it, the distributer cap should be white but
it's a Bosch red one...

There was more than one Chrysler ignition system. Early K-jet cars used
the one with the white distributor cap, later LH Jet 240s used a
different system with a normal Bosch distributor. You should be able to
retrofit in a later Bosch EZK ignition system if you want, although I
haven't heard of too many problems with the stock ignition. You can
install a hotter cam and higher flowing exhaust system to gain some
power as well, although the biggest improvement is converting to a
manual transmission if the car does not already have one. The old
slushbox saps a lot of power.

#8

James Sweet wrote:

Quote:

clay wrote:
James Sweet wrote:
clay wrote:
Finally got around to looking at the ignition timing after changing
the timing belt a couple weeks back. ('83 245) 12 BTD at idle, as
it should be. Then the weirdness begins. Rev it up a little and
timing retards to ~5 BTD. Rev a little more, say 3500, and it
creeps up to 15-18. Rap it and it appears to go up from there. So,
what's up with the retardedness? Can't be good for performance. btw,
I have the vacuum line on the knock generator plugged so the motor
doesn't ping all the time... and, so it will pass smog.

If I understand what you're saying, that sounds like it's working as
expected. Remember that BTDC is *before* top dead center, so a
bigger number means more advance and a smaller number is retarded
towards TDC. It takes time for the fuel burn to take place, so the
spark fires prior to the end of the compression stroke.

Right.
I understand about ignition advance curves, etc.
That's why I said that the timing retarding initially can't be good for
performance (or emissions...)
Googling around for the correct name for the 'knock generator'... the
Chrysler ignition control module, I found an explanation posted in this
group back in 2002.
Now to find the specifics of the recall to get rid of the retard, and
figure out why I'm not getting more advance with higher rpms.
Possibly because the motor has the Chrysler module but a Bosch
distributer. As I understand it, the distributer cap should be white
but it's a Bosch red one...

There was more than one Chrysler ignition system. Early K-jet cars used
the one with the white distributor cap, later LH Jet 240s used a
different system with a normal Bosch distributor. You should be able to
retrofit in a later Bosch EZK ignition system if you want, although I
haven't heard of too many problems with the stock ignition. You can
install a hotter cam and higher flowing exhaust system to gain some
power as well, although the biggest improvement is converting to a
manual transmission if the car does not already have one. The old
slushbox saps a lot of power.

I didn't know they used a Bosch distributer with the Chrysler module.
Thanks for that.
It's a slushbox. Not looking to hotrod it. It's too tired for that. Just
want to get the motor running like it's supposed to.
Off to track down that vacuum delay valve.

#9

On 11/2/2009 11:48 PM, clay wrote:

Quote:

James Sweet wrote:
clay wrote:
James Sweet wrote:
clay wrote:
Finally got around to looking at the ignition timing after changing
the timing belt a couple weeks back. ('83 245) 12 BTD at idle, as
it should be. Then the weirdness begins. Rev it up a little and
timing retards to ~5 BTD. Rev a little more, say 3500, and it
creeps up to 15-18. Rap it and it appears to go up from there. So,
what's up with the retardedness? Can't be good for performance.
btw, I have the vacuum line on the knock generator plugged so the
motor doesn't ping all the time... and, so it will pass smog.

If I understand what you're saying, that sounds like it's working as
expected. Remember that BTDC is *before* top dead center, so a
bigger number means more advance and a smaller number is retarded
towards TDC. It takes time for the fuel burn to take place, so the
spark fires prior to the end of the compression stroke.

Right.
I understand about ignition advance curves, etc.
That's why I said that the timing retarding initially can't be good for
performance (or emissions...)
Googling around for the correct name for the 'knock generator'... the
Chrysler ignition control module, I found an explanation posted in this
group back in 2002.
Now to find the specifics of the recall to get rid of the retard, and
figure out why I'm not getting more advance with higher rpms.
Possibly because the motor has the Chrysler module but a Bosch
distributer. As I understand it, the distributer cap should be white
but it's a Bosch red one...

There was more than one Chrysler ignition system. Early K-jet cars
used the one with the white distributor cap, later LH Jet 240s used a
different system with a normal Bosch distributor. You should be able
to retrofit in a later Bosch EZK ignition system if you want, although
I haven't heard of too many problems with the stock ignition. You can
install a hotter cam and higher flowing exhaust system to gain some
power as well, although the biggest improvement is converting to a
manual transmission if the car does not already have one. The old
slushbox saps a lot of power.

I didn't know they used a Bosch distributer with the Chrysler module.
Thanks for that.
It's a slushbox. Not looking to hotrod it. It's too tired for that. Just
want to get the motor running like it's supposed to.
Off to track down that vacuum delay valve.
I can send you the service information for the delay valves if you like

just let me know where it is 15 pages
Glenn K
Volvo Certified Technician 2008
ASE Certified Technician 2008

#10

GlennK wrote:

Quote:

On 11/2/2009 11:48 PM, clay wrote:
James Sweet wrote:
...

There was more than one Chrysler ignition system. Early K-jet cars
used the one with the white distributor cap, later LH Jet 240s used a
different system with a normal Bosch distributor. You should be able
to retrofit in a later Bosch EZK ignition system if you want,
although I haven't heard of too many problems with the stock
ignition. You can install a hotter cam and higher flowing exhaust
system to gain some power as well, although the biggest improvement
is converting to a manual transmission if the car does not already
have one. The old slushbox saps a lot of power.

I didn't know they used a Bosch distributer with the Chrysler module.
Thanks for that.
It's a slushbox. Not looking to hotrod it. It's too tired for that.
Just want to get the motor running like it's supposed to.
Off to track down that vacuum delay valve.
I can send you the service information for the delay valves if you like
just let me know where it is 15 pages
Glenn K
Volvo Certified Technician 2008
ASE Certified Technician 2008

That would be great. Is it PDF or something could be sent email or paper
copy?
email is clayt
and the domain is @pacbell
not .com though, .net
If it's paper, would FAX be easy? Snail mail is a pita. Stamps,
envelopes, and all...

Not much about it on Google or in my anemic Haynes manual.

Thanks!