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  #1  
Old 08-15-2002, 01:47 AM
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67SportFury 67SportFury is offline
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Unhappy Detonation

i have a points distributor in my 67 Fury, the motor is the 383 commando and it is all stock. I've tried adjusting the timing but I still get too much detonation/knock/ping. what can I do other than put in octane boost?
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Old 08-15-2002, 02:35 AM
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is it running rich? are the plugs good?? what kind of fuel do you usually put in it? (91 octane...good stuffs at pump...much $$). what is your compression ratio?

just some things to chew on...i don't know if the plugs will have anything to do with it but its worth a check...
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Old 08-15-2002, 06:14 AM
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For a start, you need to run the good gas (the most expensive at the pump). Your carb is probably running too lean, as well. If you are running a Carter or EB carb, take a look at the very top thread, for the proper way to tune this carb.

What is your timing set at? Too much advance will also cause detonation. Are you running the correct heat range of spark plug? Once you've properly tuned the carb and properly adjusted the timing, if it still has detonation, then you can take the plug down a heat range.
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Old 08-15-2002, 07:50 AM
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Not presuming that you don't already know this but for those on the board that aren't sure what exactly causes detonation here we go.

First of all the terms dieseling, ping, knock, run-on, detonation and pre-ignition are all basically the same condition.

All of these conditions are caused by the fuel igniting through heat and compression before the piston reaches the optimum firing position and allowing the plug to ignite the fuel. So, if you can imagine the combustion taking place as the piston is still on the up-stroke you have the above condition which I refer to as detonation.

Common causes:

1. Poor fuel.

When we talk about High octane we're referring to SLOW burning or explosive resistant fuel, the higher the octane the slower the burn. So to make an extreme comparison let's use 92-octane premium on one side of the scale and compare it to alcohol which if guessed at the octane rating I would say 200. You can pour alcohol on your hand and light it on fire and almost blow it out without burning yourself (don't try this, just trust me here) so using this comparison the lower the octane the more unstable and explosive the fuel, hence when you heat it in a combustion chamber and compress it it's going to ignite quicker than a high octane fuel.

Cure: Higher octane fuel

2. Combustion chamber quality

The combustion chamber in your cast head is rough and full of imperfections. Each one of those tiny bumps caused from the sand casting are potential detonators, as the engine goes through a combustion cycle those little high spots become red hot as the fuel is injected by the valve it's heated and as soon as the cylinder pressure reaches a certain point...BOOM the fuel ignites...Ping....

Cure: Again higher octane fuel, but eventually if some of these problems aren't addressed you'll be running alcohol. Allot of this problem can be corrected by carefully massaging all the imperfections out of the combustion chamber with a dye grinder and a box of rotary sanding discs. I like to polish a combustion chamber at high speed with a final grit of 100-150 then come back with a piece of wet paper at 300 grit until I can see my handsome self in the bowl. I also do the same polishing on the piston tops and have them thermal coated. You'll be amazed at the HP gain and reduction in detonation.

3. Combustion chamber temperature

If the combustion chamber is just flat too hot the same thing will happen as in #2, the fuel explodes from heat and compression.

Cure: Reduce the overall head temp by installing a lower temp thermostat, improve radiator efficiency or improve the cooling characteristics of the head. On our sprint car motors we would drill and tap the head and run a -12 line directly into the head from the radiator, of course this is not practical for your 340 but it's an example.

Your plug heat range is basically the amount of heat that the plug holds after the instant of combustion, so the hotter plugs will hold more heat and could cause detonation on the next fuel charge just like an imperfection in the casting. If this is causing your problem then a colder plug is in order. I like to keep trying colder plugs until they foul and go up one range.

4. Lean condition

A lean air fuel mixture can be catastrophic as the engine leans out tremendous heat is built up and can actually cause the piston to melt. As the mixture becomes lean it contains a higher mix of air, which is the oxygen source, the more oxygen the hotter the flame (Think of a cutting torch) and *poof*...."Houston we have a melt down." Of course this is an extreme condition usually only experienced in a racing application, I doubt your street car would even run with this extreme condition. Don't confuse this with lack of mixed fuel or too small of a carb, we're talking about air/fuel ratio not volume. I want to add here that this condition can happen in your street car if your fuel pump is junk and it runs out of fuel at the top end at WOT.....which is why I always run a fuel pressure gauge where I can see it and not buried under the hood somewhere.

Cure: Careful adjustment and balancing of the carb through the idle-primary-secondary circuits.

5. Ignition timing

If the advance curve is not set for low octane explosive fuels like they force us to run these days your advance curve may not be coming in at the right time causing the plug to fire before the piston reaches TDC and because the fuel is explosive and doesn't burn like a higher octane fuel it's all done before the piston reaches it's optimum firing point. This is pretty common on our old cars, after all 92 octane used to be regular and 102 was premium.

Cure: Switch over to electronic ignition and have the distributor curved for the type of fuel and compression ratio you have. The type of driving your going to do will affect the curve also....such as pulling a trailer or WOT drag racing.


So your ready to get to work, pull the heads and clean up the combustion chambers, install a 180 thermostat, have the radiator cleaned, a new water pump and hoses, use good fuel, get a good carb and adjust it correctly (see stickey at the top of the Performance forum) get that distributor dialed in and ...Drive it like you stole it!
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  #5  
Old 08-15-2002, 07:53 AM
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Hey Ed,
You may want to stickey this one for a few weeks, I've typed this about 20 times in the past few years.
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  #6  
Old 08-15-2002, 07:56 AM
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67sportsfury:
Surrey Eh?

My old home town.....went to NS Senior High and M.J. Shannon Jr High.....a long time ago...

We just got back from a trip to Mission see my post "What a Road Trip!"
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  #7  
Old 08-15-2002, 10:03 AM
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Ok now I have a question..
I have a 73 Charger I'm putting back together now.. it has a 400 in it and I am running with the orange ECU, and I was going to put in the lighter weight advance springs in the distributor.. I do plan on mostly driving this on the street, and will prolly use lower octane fuel. Will the light springs put my advance to far ahead for the fuel I will be using? Because I am now assuming that with the lower octane fuels I will not want the timing to be to far advanced..
Oh yeah.. I will also be running a EB performer intake and a EB 750 carb... (sorry cuda, but I had already bought all the parts and had them sitting in the garage before you started your posts on the Demons, otherwise I mighta gone that way..)

Jim
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  #8  
Old 08-15-2002, 01:27 PM
451Mopar 451Mopar is offline
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Also, if the engine burns oil, the oil in the combustion chamber acts like low actane fuel and can cause pinging/deiseling.
On an older engine with some miles you may have bad valve seals letting oil enter the chamber through the valve guides. It's also fairly easy and cheap to replace the valve seals if they are bad.
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  #9  
Old 08-15-2002, 01:34 PM
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You need to have that distributor run on a Distributor Dyno, guessing will never get it right.

Well in theroy the oil in the fuel would actually raise the octane level by slowing down the burn....I've heard stories that a witch's brew of tranny fluid, zylene, deisel fuel and 92 octane will get you up around the 104-6 area....but it's just a story so don't whip up a batch and crank 20 degrees of timing into your motor and go WOT till the valves float.
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  #10  
Old 08-19-2002, 10:47 PM
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Bump
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  #11  
Old 08-19-2002, 11:16 PM
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Quote:
Allot of this problem can be corrected by carefully massaging all the imperfections out of the combustion chamber with a dye grinder and a box of rotary sanding discs. I like to polish a combustion chamber at high speed with a final grit of 100-150 then come back with a piece of wet paper at 300 grit until I can see my handsome self in the bowl.
Can we do this ourselves or should is it best left to a pro? I've polished intakes before and done my fair share of body work (lots of sanding ha ha), but don't want to trash my heads. I'm running 915's which have that really big hot spot from the factory. I have the engine apart now and it would be convient to attempt this mod if it's not rocket science!

Thanks,

Greg
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  #12  
Old 08-20-2002, 12:29 AM
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It's definatly not Rocket Science...just don't change the shape of the combustion chamber. You can carve down the bump on the spark plug hole and unshroud the valve pocket then just polish it up.

When you get to the 300 Grit use the wet/dry type paper and use lot's of water to keep the paper clear and get the desired finish.

Here's a crude drawing of what you have and what you need to end up with on the combustion chamber side of the valve. If you not going to change the seats then stick some old valves in there so you don't damage the seats.

Figure on about 2 hours for the first hole and about 45 to an hour for each of the rest. If your going to port match and deburr allow another full day just for that, about an inch into the port is all you need to clean up for the port match. Remember, intake side gets a nice swirl pattern finish...I use 100 grit with very light pressure and swirl the die grinder evenly over the cut area. Exhaust ports get a 220 grit and hand polish with the 300.

Same on the intake so everything has a nice smooth transition. Most people get way too aggressive with the die grinder and forget about velocity and slick air going through the runner and just try and make it big...sometimes bigger is not always better.

This is the link to Standard Abrasives it explains basic head porting and the tools to do the job right, they're a very good company and always willing to help you out...I highly recommend them to beginners and pro's.

http://www.sa-motorsports.com/diyport.htm
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  #13  
Old 08-20-2002, 12:34 AM
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hehe, nice drawing cuda!!

i get the picture though!

hehehehe
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  #14  
Old 08-20-2002, 12:46 AM
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Hey don't laugh....I make my living as a Graphic Artist....If I could only figure out how to post Corel 8 art to this board I could really do you a Picasso....LOL

....as long as you get the idea this isn't a coloring book contest......you should see my workbench top....hahahaha... I have wipe it off with carb cleaner once month to get all the sharpee drawings off it....I carry a white china marker in my car and use that huge back window for a chalk board in the staging lanes to make tech drawings or sketch logos for race teams....I will occasionally draw cartoons if we have an oil down...passes the time and everyone gets a chuckle out of it.
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  #15  
Old 08-20-2002, 02:42 AM
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The heads have already been ported, but the combustion chambers were not smoothed out like you described. It sounds simple enough that I'm going to give it a shot. Hell, if I screw it up too bad I wanted the EB heads anyway (even more truth to your sig about the visa card!)
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  #16  
Old 08-20-2002, 03:08 AM
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hehehehe cuda, your funny!
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  #17  
Old 08-20-2002, 03:07 PM
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I cant ever see putting anything less the premium gas in my car, gas today sucks .... even the(so called) good stuff is only 91 or 92 if your lucky.. 87 oct or even 89 is a slap in the face to a mopar muscle car, for any car built before (gunna strech it time period) say 1973. the price difference a average of 20 to 30 cent per gallon, from 87 to 91 octane 20 gallons is like 4 to 6 dollars per tank fill well worth giving up 4 big gulps if your tight on cash, I use a octane booster also, sure makes big difference... gas less than 91 is for other things like ( well any thing other than a mopar muscle car).
anyone ever try the scented fuel additive?

coolcarz
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  #18  
Old 08-20-2002, 08:44 PM
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Carbon deposits are the main culprit of preignition and simple to remove,1st run a can of carb cleaner down the carb at considerable rpm of course,then very carefully take a spray bottle full of COLD water and run it down the carb 1 squirt at a time,dont use a garden hose thats trickling because a surge in water pressure can result in a bent rod!!,carbon remains hot after the combustion cycle,hot enough to ignite the next compression stroke long before the spark gets there,their caused by un burned fuel,you could be too rich or even maybe just a little rich but over the long haul it will build up.Its a worth a try and cost next to nothing.A 67 fury prob has a 383-2bbl,which is an 9:1 motor and should run on 85-87 octane.......PRO.....
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  #19  
Old 08-21-2002, 12:51 PM
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Default Detonation Detection

How would you know if your detonating when cannot hear it (open header)?
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  #20  
Old 08-21-2002, 02:45 PM
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By reading the spark plugs.....

This is a long detailed post that I'm already working on, but for detonation watch for small specs of shiney material on the porcelin...they'll appear shiney as they are aluminum...your piston tops...

In extreme cases you may even find chucks of the porcelin knocked off.
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  #21  
Old 08-25-2002, 05:12 PM
69Dodgedart360 69Dodgedart360 is offline
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my 360 has 10.5:1 compression, and it pings at anything over 2/3 throttle with anything less than 92 octane in it.
BUT
i drive it everyday and in order to a) same myself money on gas and b) same myself money on speeding tickets i run 87 octane and just keep the revs below 3000 rpm when not planning on racing around or going to the track. it does not ping on 87 octane unless i open it up fairly well, so i assume this is safe practice.
BUT
my advance is fully advanced at 2500. is this too much for 87 octane? it does not ping so it should not hurt it right.
please tell me if i'm gonna hurt this engine by using cheap gas 75% of the time. it still runs pretty good on the cheap gas and i haven't had a problem with it yet and the motor is only a few months old.

thanx
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  #22  
Old 08-26-2002, 07:38 AM
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Oh it's detonating alright ...you just can't hear it......What kind of pistons are in it? If there the stock cast variaty you'll probably survive for awhile, but eventually you'll kill it.

Recurve the distributor and reduce the max advance. If your using an MSD look at a timing retard switch that you can adjust, like the ones they use for blowers or nitrous.

Use an octane booster.

Colder thermostate

Make sure your not lean on the primary circuit.

Try a colder spark plug.

....ultimately...reduce the C/R and polish out the combustion chambers.

Don
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  #23  
Old 08-27-2002, 10:21 AM
John at J&S John at J&S is offline
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Default knock controller

Excuse the plug here, but have you heard about our J&S SafeGuard?

It's a knock sensor based ignition unit, able to retard only the cylinders that are knocking . It will trigger from points, and has a built in high energy inductive discharge ignition, similar to a GM HEI.

Using a single knock sensor, the unit can retard the knocking cylinders as much as six degrees before they can fire again.

The unit works on this principle:

The unit makes a spark, then listens to the knock sensor. If it hears a knock, it knows that it had to come from the cylinder that just fired.

The unit knows that the knocking cylinder won't fire again for two more revolutions.

When the knocking cylinder is ready to fire again, the unit cranks in the calculated retard amount.

It does this as each cylinder goes by, building up a different retard curve for each cylinder.



more information at http://www.jandssafeguard.com
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  #24  
Old 08-27-2002, 11:54 AM
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Very Interesting.....

Whats the retail on a unit?
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  #25  
Old 08-27-2002, 05:11 PM
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hmm...that DOES sound interesting...

how much work is involved? what needs to be drilled?

i'm also kinda interested...how much?

*edit* had some more questions AFTER i pushed submit post...

does it hardwire into exsisting electronic ignition?

is that already a type of electronic ignition?

do you have to change distributors?

BTW: for some unknown reason, that link won't work for me, otherwise i'd go there...
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  #26  
Old 08-28-2002, 04:33 PM
John at J&S John at J&S is offline
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Roadrunner:

The system connects between the stock ignition module and the coil negative. It has it's own high current ignition transistor and dwell control circuits, so you can even bypass the ballast resistor, for higher spark energy.

When ordering, you can specify four rev limits, selectable with two of the mode switches on the front panel.

Stock distributors are fine. The distributor still needs to have mechanical advance, though, since the unit can only retard. Newer cars with engine management systems can use it as well.

The latest V.1 units have a built in two bar MAP sensor, able to read vacuum and up to 15 pounds of boost.

A mode switch on the front panel lets you select between forced induction or naturally aspirated operation.

In the forced induction mode, the MAP sensor is used for boost retard. Two knobs control this.

The "Start" knob lets you dial in at what psi you want the boost retard to begin, and is adjustable from 0 to 10 psi.

The "Rate" knob lets you dial in the amount of retard per pound of boost, and is adjustable from 0 to 2° per psi.

In the naturally aspirated mode, the Start knob can be used to make the unit retard as the vacuum drops below ten inches. Instead of boost retard, it's like having an adjustable electronic vacuum advance. During cruise, no retard. As you step down on the gas, and the vacuum drops below ten inches, the unit will start to retard.

The knock sensor is enabled in the forced induction mode when the vacuum drops below five inches, and the engine is above 1250 RPM.

In the naturally aspirated mode, the knock sensor is enabled as the vacuum drops below 15 inches.

Prices here:
[url]http://www.jandssafeguard.com/orders.html[/url
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  #27  
Old 08-28-2002, 04:44 PM
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john:

thanx for the info... a bit pricey though ...course, i didn't really expect sumthin that technologically advanced to be cheap either...

i'm still savin up for my new system, doubt i could get that too, i've got enuff electronix in my car though... after i get my system upgraded to 2 12" MTX Thunder8000's, and a Lanzar 900watt amp, then i'll save up for an MSD ignition and Pro-Billit dist... so far it runs fine, thats why i'm not doing the ignition first...
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  #28  
Old 08-29-2002, 11:27 PM
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Cuda,
That was a nice response. Very informative.
66 Plymouth
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  #29  
Old 08-30-2002, 12:58 AM
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I try to give well researched and informative responses to most questions...and some I just guess at and use alot of big words and hope nobody understands what the hell I'm talking about anyhow...LOL
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  #30  
Old 08-30-2002, 09:46 AM
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wow Hey cuda....

If I have to scrub w/ Windex to get shoe polish off my rear glass, how in the world do you get China Marker off ?

Hahahahahahhahaa

PS- I'm a landscape architect. We talk with our pencils, too..... Sketching on the car just hadn't occurred to me...... Hahhaa
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