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priss
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Joined: May 06, 2010
Posts: 348
Location: bradford MA
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 Posted: Thu Oct 27, 2011 5:06 pm Post subject: octane curiosity |
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1699 singleport
Dual Kads
Hemi cut stock heads
Engle 100
Stock exhaust
UNknown compression
I was just wondering about a engine symptom i noticed recently. I have had a bit of a run on problem (deiseling) with this engine from the begining. I shut off the key and it chugs a couple times before shutting off. I use the regular gas, 89
I had to buy gas while on a trip recently and my friend filled the tank with super 93. We continued on about another 30 minutes and when i shut off the car it didnt deisel at all. I have tested it with 2 tanks since altering between 91 and 89 and it is definetly the good gas that is not deiseling.
So the question is. Is there something i should be concerend about? Is there an adjustment i can make? It seems to me that if its so close to right that a couple points of octane can change the condition that there must be something easy to alter to make her shut off on 89 the same as she does on 91.
I tried timing changes to no avail. I'm not opposed to buying the expencive gas if its required. I am curious tho as to what is making it required.
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ALB
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Joined: August 05, 2008
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Location: beautiful suburban Wet Coast of Canada
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| Posted: Thu Oct 27, 2011 5:16 pm Post subject: |
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What is the timing set at?
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modok
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Joined: October 30, 2009
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Location: Colorado Springs
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| Posted: Thu Oct 27, 2011 5:29 pm Post subject: |
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It is true that the higher octane is more resistant to dieseling, but the dieseling in itself is not absolutely a problem.
I've known some odd ball engines that did it so bad you had to use the clutch to stop them, but none of them have died from it yet, because they only do it at super low rpm, so when running they are fine.
One factor that may cause it to run-on is if set too rich at idle. The extra rich mix makes for more carbon, the carbon causes dieseling. Being a singleport with kadrons, it may not be possible to adjust leaner without side effects, so don't worry about it too much, but you could try leaning the idle mix a little and see what happens. |
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DarthWeber
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Joined: November 24, 2007
Posts: 7543
Location: Whittier,CA
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| Posted: Thu Oct 27, 2011 7:56 pm Post subject: Re: octane curiosity |
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| priss wrote: |
1699 singleport
Dual Kads
Hemi cut stock heads
Engle 100
Stock exhaust
 UNknown compression |
As ALB asked, what is your timing set at? With hemi heads you'll need to increase timing 4 - 6 degrees over what you would normally run for stock. Modok may have given a clue as to the engine being too rich. With hemi cut heads you need to advance the timing. Berg ran as much as 40 degrees total. He advised that if you could run that much timing and didnt get any detonation or over heating then decrease the main jet one size and back the timing down to about 34 total. Might be something to try.
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| Mitey62 wrote: |
| Swapped the Compufire for a Bosch blue and some points I had sitting around, started 1st crank. Took her out for a drive, pulls harder, more RPM, and runs smoother. I think I'll be sticking with points from now on. |
| RockCrusher wrote: |
JB weld the case halves....that'll keep the fretting to a minimum.  |
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mark tucker
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Location: SHALIMAR ,FLORIDA
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| Posted: Fri Oct 28, 2011 9:34 am Post subject: |
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| ^^^ and run some chamber cleaner through.this is what happens when there is not enough quench+ torque is lower than it should be.low compression need more fuel,chambers with little to no turblance from quench have lower torque and need more fuel,and the extra fuel?well not all of it is burnt and becomes deposits that get hot & cause runon&detonation.if ti were mine I would snatch the heads and mill about .100 off to get a little quench back and then if the cr is to high do some chamber work that will not only help lower the cr but also make it breathe better. |
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craigman
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Joined: March 28, 2004
Posts: 2425
Location: redding
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| Posted: Fri Oct 28, 2011 10:22 am Post subject: |
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How's your tune up? Valves, plugs, wires, points, ect.?
That can make it diesel easy. |
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Luftgekült
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| Posted: Fri Oct 28, 2011 12:44 pm Post subject: |
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Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has?
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DarthWeber
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Location: Whittier,CA
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| Posted: Fri Oct 28, 2011 5:44 pm Post subject: |
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Hellooooooo Priss.............are you out there? 
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| Mitey62 wrote: |
| Swapped the Compufire for a Bosch blue and some points I had sitting around, started 1st crank. Took her out for a drive, pulls harder, more RPM, and runs smoother. I think I'll be sticking with points from now on. |
| RockCrusher wrote: |
| JB weld the case halves....that'll keep the fretting to a minimum. |
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RockCrusher
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Location: Parkesburg, PA
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| Posted: Fri Oct 28, 2011 5:57 pm Post subject: |
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| Luftgekült wrote: |
Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has? |
Not stupid at all....I'd call it astute observation.
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Bruce
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Location: Left coast, Canada
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| Posted: Sat Oct 29, 2011 12:13 am Post subject: |
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| Luftgekült wrote: |
Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has? |
Dieseling is the A/F mixture self igniting after you turn the key off. It is caused by excessive temperatures in the chambers causing hot spots hot enough to ignite the A/F mixture. The excessive temps are caused by retarded timing.
IOW, advance your timing to prevent the hot spots that cause dieseling.
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priss
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Joined: May 06, 2010
Posts: 348
Location: bradford MA
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| Posted: Sat Oct 29, 2011 11:20 am Post subject: |
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| DarthWeber wrote: |
| Hellooooooo Priss.............are you out there? |
yes Darth.......waaaaayyy out there!
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GusC2it
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millerje78
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Joined: October 16, 2005
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Location: Holmes County, Ohio
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| Posted: Sat Oct 29, 2011 3:44 pm Post subject: |
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| Bruce wrote: |
| Luftgekült wrote: |
Maybe it is an stupid question but,
if ignition is off, why does it matter how much advance it has? |
Dieseling is the A/F mixture self igniting after you turn the key off. It is caused by excessive temperatures in the chambers causing hot spots hot enough to ignite the A/F mixture. The excessive temps are caused by retarded timing.
IOW, advance your timing to prevent the hot spots that cause dieseling. |
are hot spots necessarily the problem though? I understand that dieseling can also be caused by the idle being set too fast, or from the idle circuit being too rich.
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Bruce
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Location: Left coast, Canada
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| Posted: Sat Oct 29, 2011 6:43 pm Post subject: |
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When you turn the key off, it stops power to the ignition. Therefore, there must be some other way to cause the A/F mixture to ignite. A high idle speed or a rich mixture doesn't provide that source of ignition.
I've worked on plenty of engines that were set really rich that never ran-on after you turned the key off.
When you have retarded timing, the burn is still happening when the exh valve opens. That sends the head temps way up because all that fire is now in the exh port. If you advance the timing, more of that heat stays in the chamber and gets converted into work, pushing the piston down. Thus, the exh gasses that leave the chamber are much cooler, and head temps reflect that.
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| overheard at the portland Swap Meet... wrote: |
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millerje78
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Joined: October 16, 2005
Posts: 2445
Location: Holmes County, Ohio
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| Posted: Sat Oct 29, 2011 6:58 pm Post subject: |
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| Bruce wrote: |
When you turn the key off, it stops power to the ignition. Therefore, there must be some other way to cause the A/F mixture to ignite. A high idle speed or a rich mixture doesn't provide that source of ignition.
I've worked on plenty of engines that were set really rich that never ran-on after you turned the key off.
When you have retarded timing, the burn is still happening when the exh valve opens. That sends the head temps way up because all that fire is now in the exh port. If you advance the timing, more of that heat stays in the chamber and gets converted into work, pushing the piston down. Thus, the exh gasses that leave the chamber are much cooler, and head temps reflect that. |
this explanation makes good sense to me, Bruce. The reason that I mentioned idle speed is because I am currently dealing with a wandering idle speed condition in my sedan. I do not know why my engine is doing this, but sometimes it idles nice and low and sometimes it idles quite fast, above 2000 RPMs in fact. When I shut down the ignition when the idle is high, it diesels a bit; when I shut down the ignition when the idle is low, it stops cold. hmmm....perhaps I should get to the bottom of this idle situation.
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modok
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Joined: October 30, 2009
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Location: Colorado Springs
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| Posted: Sat Oct 29, 2011 7:41 pm Post subject: |
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yeah, ok
mixture and timing will have an effect on it
Is it a problem? maybe maybe not.
But you can notice if it is worse or better depending on changes in mixture and timing, and that might tell you something useful |
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Bruce
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Location: Left coast, Canada
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| Posted: Sat Oct 29, 2011 8:01 pm Post subject: |
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| millerje78 wrote: |
| I am currently dealing with a wandering idle speed condition in my sedan. I do not know why my engine is doing this, but sometimes it idles nice and low and sometimes it idles quite fast, above 2000 RPMs in fact. When I shut down the ignition when the idle is high, it diesels a bit; when I shut down the ignition when the idle is low, it stops cold. |
I bet you have a 009 distributor.
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| overheard at the portland Swap Meet... wrote: |
| ..... a steering wheel made from a mastadon tusk..... |
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Glenn 
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Joined: December 25, 2001
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Location: Sneaking up behind you
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| Posted: Sat Oct 29, 2011 8:08 pm Post subject: |
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| Bruce wrote: |
| millerje78 wrote: |
| I am currently dealing with a wandering idle speed condition in my sedan. I do not know why my engine is doing this, but sometimes it idles nice and low and sometimes it idles quite fast, above 2000 RPMs in fact. When I shut down the ignition when the idle is high, it diesels a bit; when I shut down the ignition when the idle is low, it stops cold. |
I bet you have a 009 distributor. |
D'oh.
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lostinbaja
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| Posted: Sat Oct 29, 2011 9:16 pm Post subject: |
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There is a reason VW designed a fuel shutoff solenoid for the idle circuit of the carb. Is it working? Shut off the air and the fuel and it WILL NOT keep running, no matter how many hot spots there are. 
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modok
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Location: Colorado Springs
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| Posted: Sun Oct 30, 2011 12:19 am Post subject: |
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kadrons don't have cutoff solenoids.......right?
But yeah, they surely put those on for a reason |
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