RE: [DMCForum] Re: Andrew's "Knocking"

["Farrar Hudkins" <fhudkins@xxxxxxx>]

Bill,

When I'm in Charlotte for the holidays I need to see if some of your
knowledge can rub off on me. Wanna work on some cars? :P

Farrar

> -----Original Message-----
> From: content22207 [mailto:brobertson@xxxxxxxxxxxx]
> Sent: Thursday, December 18, 2003 11:43 PM
> To: DMCForum@xxxxxxxxxxxxxxx
> Subject: [DMCForum] Re: Andrew's "Knocking"
>
>
> Most performance engines are timed closer to TDC, not advanced. Moving
> spark earlier in stroke lowers power. That's one reason HP killed in
> domestic blocks throughout 1970's: 1969 Ford 460 timed 10 degrees
> BTDC. By 1977 moved to 17 degrees. 1978 (last year 460 in automobiles)
> timed 20 degrees BTDC.
>
> If you're "knocking" are two different potential problems:
> pre-ignition and pre-detonation.
>
> Pre-ignition:
> Spark ignites fuel mixture too soon
> Sounds like constant drumming of diesel engine
> Worst at higher RPM's, accelerating, under load, etc
> May be unaffected by octane
>
> Pre-detonation:
> Fuel mixture spontaneously combusts before spark
> Is random, like popcorn
> Worst when cruising
> Usually improves with octane
>
> Pre-ignition can be a timing issue. Lots of higher mileage engines
> have never been re-timed.
>
> Pre-detonation usually indicates something wrong inside combustion
> chamber. Can be as simple as carbon buildup (glows red hot, and also
> reduces chamber volume -- increases compression). I suppose a weak
> coil could cause as well (little or no spark).
>
> If you're knocking on 93 octane, suspect ignition time. Even the 11:1
> engine in one of my Lincolns can be timed to run on 93 alone (no
> octane boost). Interestingly do so by ADVANCING time just a little
> from factory spec.
>
> Is your car difficult to start cold? One thing I've noticed about over
> advanced cars is engine has to spin much longer than normal before it
> will catch.
>
> Bill Robertson
> #5939
>
> >--- In DMCForum@xxxxxxxxxxxxxxx, Andrew <aos+yahoo@xxxx> wrote:
> > > Better gas. We have no knock sensor to control this. The new
ignition
> > > system may also help.  What are you going to do for a coil. His
> package
> > > didn't include one. Is it extra and how much.
> >
> > I've got no reason to believe I have bad gas.  I'm using 93 octane,
and
> > only buy major brand names, and not always at the same station.
> I've got
> > a couple of jugs of Sunoco 104 in the garage (for fun weekends with
the
> > other car).  Maybe I should toss a few gallons in the DMC and see if
it
> > manages to knock with that.  That is, if it can even ignite it at
> all.  :)
> >
> > I'm not expecting much, if anything, from the ignition upgrade stuff.
I
> > know a lot of people claim it's snake oil, but since I enjoy tinkering
> > with things, and it's fairly easy for me to get over to DMCH to pick
up
> > the parts, I figured I'd give it an unbiased opinion.  Hopefully I'll
> > finish the install tomorrow.  I ran out of light today.
> >
> > Right now I'm still on the stock coil, which I assume is 20 years
> old.  I
> > don't believe it was replaced when the performance engine was put
> in.  I
> > plan to leave it as it is for the time being, at least until I've
> had the
> > opportunity to determine what, if any, is gained by adding the
> performance
> > ignition package.  After that point, I may well upgrade it.
> >
> > Since I have the performance engine, this may well just be a case of
> > slightly too aggressive timing, so backing it off a little may also
> be of
> > some help.
> >
> > -andrew
>
>
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