It's all in the timing.

[clay]

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.

[James Sweet]

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.

[Boris Mohar]

"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

[Ken Phillips]

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

[clay]

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...

>
> From: "volvowrench" <rad...@ioip.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).

[clay]

"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.

[James Sweet]

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.

[clay]

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.

[GlennK]

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

[clay]

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!

[clay]

Got it, thanks!

[Jon Robertson]

Is your main pulley floating on its rubber the harmonic balancer gives up
ant the timing goes accordingly ?.

"clay" <c...@ymation.com> wrote in message
news:hclotu$hqi$1...@news.eternal-september.org...

[clay]

Jon Robertson wrote:
> Is your main pulley floating on its rubber the harmonic balancer gives up
> ant the timing goes accordingly ?.
>
>

No rubber on the front pulley. Straight steel.