Wiese1

There is a video on YouTube about a kit you can add to any carbureted engine to stop dieseling. Try searching the term CarbShot, or contact me.

GNCLONE

I have the dieseling problem too and I have none of the possibilities mentioned:

I am pulling 22 in vacuum so I know I don't have any vacuum leaks.
I have the stock cam
new Carb
new spark plugs
steam vent tube connected and working perfectly
stock compression
PCV set up properly
elec fans on a discrete circuit

Dans69LS1velle

Iv'e tried it all, what seemed to help but still didn't eliminate the problem completely was using about 4-5 gallons of 100 octane with a tank of 91, 22 degrees initial timing, colder range plug and I used the step retard switch with the msd to kill 15 degrees of timing before i shut it off. Also, don't freak out, but I also tried water injection just using the engine vacuum to draw in a little water. This pretty much killed all the problems i was having and i was able to run 6 more degrees of timing with the water injection. But... Ive since took it off for now until I get further info about water injection.

TXoldskool

iTrader: (1)

I had this problem and it was too much base timing. my understanding has been that the LSx motors prefer less timing then the old sbc's. Based on that, my 0rpm timing is set at 2* and 1k rpm is like 12-15 making it around 10*-12* at 758-850rpms. Full advance is in by 3k-3500 of just 29*....and so far it seems to like it.

That said.....the MSD box adds whatever timing values are in the vacuum advance table....even if there is no MAP sensor connected. You wind up with a constant 20* of timing on top of whatever was set in the main timing table. Therefore, I have all values in the vacuum advance table zero'd out.....and just use the "mechanical" (so to speak) timing.

Pop N Wood

iTrader: (1)

I wonder if you guys with the persistent problems have a sharp point in one of your combustion chambers?

I've read car mag articles that say pulling the head and looking for a hot spot is the fix of last resort.

I had a 1979 Ford Fiesta that had a solenoid in the idle circuit. Turn off the motor and it would shut off the flow of fuel inside the carb. But that was back in the day of declining gas quality.

Seeing as how so few guys have this problem it seems hard to believe a stock compression LS motor would need something like water injection or fuel cut offs. Must be something else wrong.

3pedals

iTrader: (3)

My setup had this problem when I first pit it together, but I solved it by using alot of idle timing(15*'0-500, 36*'from 500 on) and setting idle speed to about 850. I also have 15* vacuum advance in it too.
EDIT - my engine is 9.6:1 compression, and has a modest cam -so it will tolerate more total timing(36*) than a higher compression setup.

TXoldskool

iTrader: (1)

sounds like I just need to go to the track and play with it a little then.....

tennerv8

iTrader: (7)

Post #44 contradicts post #46. Which is it? Too much base timing or too little?

3pedals

iTrader: (3)

Try both, and let us know what you find.…

Dans69LS1velle

Yes thats what i keep getting. I hear to bring down the base timing. I did that and It had trouble idling in gear. I tried 30 degrees at initial timing and it still dieseled.
I think with those new heads there could be a sharp spots or somthing in the chamber that are glowing.
I hear so many different things. ls motors love initial timing. Ls motors dont need a lot of initial timing. Ls motors love lots of total timing. Ls motors dont need much total timing. Well which is it??? I took my car out with the lap top while driving. The car responded well with 30 degrees total timing and 17-22 degrees initial at 850 idle rpm's. 10 degrees cranking.

speedtigger

iTrader: (16)

Sounds like you are in the ball park. Where do you live and what octane fuel is available?

My motor is 10.9:1 and I do not have this problem. I live at sea level and use 93 octane.

3pedals

iTrader: (3)

I agree, sounds like you are in the ballpark. you may find that your engine will want different timing as you tune the carb, and lean it out, or richen it up. generally it will want less timing as it gets leaner, and slightly more when you go richer.

TXoldskool

iTrader: (1)

as far as carbon hotspots...my motor is/was (got about 400-500mi now) brand new.

Johnmaster

iTrader: (3)

Could it be an exhaust valve not seating firmly enough (improperly adjusted) getting too hot? Just throwing an idea out there since it is a new motor.

Dans69LS1velle

No it's not getting hot. 185 all day. Maybe 200 idling in traffic for a few minutes but then quickly returns to temp.

Dans69LS1velle

Im close to sea level here in the Central Valley Ca. 91 octane is all I can get. There is a station that sells 100 octane but for 7.99 a gallon forget it....

Pop N Wood

iTrader: (1)

You could always just try adding a few gallons to see if that helps. Mixing high and low octane gas averages out to somewhere inbetween the two.

As for hotspots, it could be a burr or ding causing the hot spot. Doesn't have to be carbon.

Wiese1

Carbshot is a very simple solution to stopping dieseling in a carbureted engine. It involves the injection of an inert gas, CO2, into the carburetor. The CO2 takes away the oxygen and stops any combustion. Since the CO2 is coming from a compressed tank, it come out of the tank very cold and that also lowers the temperature of mixture entering the engine. Just a split second shot of CO2 stops the dieseling. I have been using it my boat engine for over 1 year and I never have to put up with annoying and embarrassing dieseling. There is a Carbshot video on YouTube.

Again, this solution is patent pending and I am marketing kits that you can buy that include everything you need, except for the CO2 tank. You will have to get that from any number of places including most sporting goods or paintball businesses.

I am just getting this business started and I am making introductory offers. If you are interested in a kit, please let me know. I would think the dash-mounted lever kit would be appropriate for a automobile. You can see the kits on the Lincoln, Nebraska Craigslist.

rojs234

iTrader: (5)

Since you've tried pretty much everything with no success, here's one more thing you can try...Years ago, a lot of cars used what was called an anti-dieseling solenoid. Basically it held the engine at a normal idle speed when the engine was being used but when you turned off the ignition it released the throttle and the butterflies completely closed shutting off any air or fuel. You could try it at no cost by simply setting your butterflies completely closed and then putting,or perhaps bending a piece of heavy wire fastened to a carb bolt and slipping it between the idle adjustment screw to hold the idle to normal speed. Get it up to temperature or whatever it takes to make it diesel and have someone shut it off while you pull the temporary piece out letting the throttle close completely. If it works..you can buy a solenoid and bracket made specifically for either a Holley or AFB from Summit or Jegs. I think it's advertised for increasing idle speed for A/C, but anyway it's available. I use one on the little red truck in my avatar to slightly increase idle speed when in gear and drop back in neutral. Just something to try.

Ron

Here is a link to the solenoid for a Holley:
http://www.summitracing.com/parts/HLY-46-74/ You also need the bracket:HLY-20-9 and the big nut for the solenoid:HLY-26-57

rojs234

iTrader: (5)

After I noticed how many hits there were on this thread, I thought I would revive it just to see if the OP ever found a solution to his problem.

Ron