Timing issue

[PlymouthMakesIt]

Sounds like you found a pack of real automotive geniuses... no clue about how an engine works. They've likely butchered your carb trying to fix an extremely simple problem. The most likely cause of dieseling is running low octane gas in a cast iron high compression engine, either put aluminum heads on it or stop running pump gas and use avgas or race gas.

 

[1969CoronetR/T]

I am not a mechanic toolman, but I have three Coronets and the newest one is a 512

 

[toolmanmike]

Sounds like you found a pack of real automotive geniuses... no clue about how an engine works. They've likely butchered your carb trying to fix an extremely simple problem. The most likely cause of dieseling is running low octane gas in a cast iron engine, either put aluminum heads on it or stop running pump gas and use avgas or race gas.

And dieseling can be caused by too high of an idle speed. Something as simple as that.

 

[1969CoronetR/T]

I have aluminum Indy heads not iron heads.They did turn the idle speed down so that helped with the dieseling issue that was intermittent anyways

 

[1969CoronetR/T]

I know how to get the idle RPM by looking at my tach.

 

[toolmanmike]

I know how to get the idle RPM by looking at my tach.

That doesn't work properly? According to post #4?

 

[1969CoronetR/T]

The tach worked perfectly before I took it to their shop to replace a leaking heater core, fuel pump, fuel sender and to look at the dieseling issue. They are fixing the tach after they replace the distributor and my pass the vacuum advance.

 

[66 Sat]

The tach worked perfectly before I took it to their shop to replace a leaking heater core, fuel pump, fuel sender and to look at the dieseling issue. They are fixing the tach after they replace the distributor and my pass the vacuum advance.

So they ARE proceeding with the MSD distributor and blocking off the vacuum advance?
Despite all the advice you've received to the contrary?

 

[1969CoronetR/T]

I don’t see how it can get any worse. I can always have it changed back. I will call the shop on Monday to discuss it with the main mechanic and his thoughts and all the excellent help I have received in this site. My uncle, who has a 68 Charger bypassed his vac advance and have been messing with three cars since they were new.

 

[hunt2elk]

Not that thee is anything terribly wrong with MSD distributors, but I sure wouldn't let them put one on your car. Biggest reason is that I can about bet you that the distributor is not causing your dieseling issue. You need to find somebody who understands how these old rigs operate in regards to initial timing, mechanical/vacuum advance, and carb tuning.

 

[1969CoronetR/T]

I agree and will talk to them on Monday about it. The dieseling issue was improved by slowing the idle. The timing and back firing are now getting addressed.

 

[Joseph Musial]

I had my 1969 Coronet R/T at a shop to see if they can help with a run on issue (dieseling). They rebuilt my carburetor and used engine cleaner to get what they believed was a carbon build up. Lastly, they adjusted my timing. I picked the car up and it ran fine although it seemed sluggish. The next morning, it was back firing like crazy and finally stopped after warning up. The timing must be off and is stills diesels after a hard run. What should the timing be set?
499 cid engine. The cam is 545 lift with a 235/241 duration and 110 lobe separator / 106 centerline. The compression is 9.6 to 1.
Thanks
Mark

Call someone who runs a car on the dragstrip. They will know what the timing should be set at. Also check your vaccum advance.

 

[RemCharger]

I don’t see how it can get any worse. I can always have it changed back. I will call the shop on Monday to discuss it with the main mechanic and his thoughts and all the excellent help I have received in this site. My uncle, who has a 68 Charger bypassed his vac advance and have been messing with three cars since they were new.

It will be fine.

 

[1969CoronetR/T]

OST Dyno drag races cars old and new.i have used them to tune my 392 jeep in the past.

 

[Cranky]

Think if it were mine, I'd get it to where it's running good and if it's still dieseling, just shut if off in gear. Even if the car is an automatic, I've never seen one keep one diesel once the key is turned off while in gear even if was dieseling bad. When gas turned to junk years ago, that's how we shut off our cars that still had 10-1 and higher compression and lots of us were still running engines with compression ratios over 10 back in the day. Heck, I was running my 340 that was 10.5 in the 90's and it would ping on hot days once the engine temp was above 180 but a gallon of av gas on top of the 93 octane solved that problem. It never dieseled though. How much rpm to you run up to with this engine and what is the engine temp at shut down?

 

[1969CoronetR/T]

Thanks. I was using 115 race gas (non-ethanol) for a few years back in 2015 when the engine was built, but the engine builder told me to use 91 octane since the engine wasn’t built for that high 115 octane (the fuel will sit in the cylinders unburnt or something like that). I use 93 octane for all my vehicles. Plus 115 octane was $8-10 a gallon back in 2015.
I run it hard 3-4000 rpm and and it seems to diesel intermittently on hot days. I think it is mostly resolved with slowing the idle. I can’t imagine the run-on to be good for the engine.

 

[Cranky]

Thanks. I was using 115 race gas (non-ethanol) for a few years back in 2015 when the engine was built, but the engine builder told me to use 91 octane since the engine wasn’t built for that high 115 octane (the fuel will sit in the cylinders unburnt or something like that). I use 93 octane for all my vehicles. Plus 115 octane was $8-10 a gallon back in 2015.

Well, an engine with the compression ratio of what you have shouldn't need to run 115 but what is your cranking pressure?? Wouldn't think it would be all that high with the cam you're running....and the av gas I was adding (1 gallon to a full tank) was 100 but av gas is rated differently from what I understand. Also, I remember the new cars having a 'shut down' solenoid on the throttle to completely close the carb to help with the dieseling problems when the gas got shatty but it's also just easy to shut it off in gear. Should work fine unless you have a really loose converter in it. Never had to do that with cars with a loose converter so have no idea if that would make a difference.

 

[1969CoronetR/T]

Yeah, I would like to change the cam once I get the timing issue resolved and have the shop run it on their dyno. I was told it was too small of a cam and wonder if that is losing power

 

[AR67GTX]

I would be cautious about going to a bigger cam, which could also aggravate your dieseling by requiring more initial advance and higher idle speed. What are the specs on the cam you have now? Pulling the engine down a few hundred rpm with the clutch before turning the key off is the easiest patch for the issue. Or if an auto, turn the key while still in gear and then go to park.

Never mind, I see you had the cam specs in the first post. That would be a pretty warm cam in a 400 pr 440. Your extra cubic inches would tend to take some of its rowdiness off of it and make it more street able. Unless you are seeking more power or more performance I think changing cams is a waste of time. Based on some of the things your mechanic is fostering on you - sounds like he retarded your timing and then pulled the vacuum advance to cut more timing out at idle. I’m suspicious he wants to spend your money to put a bigger cam in to cut some of your low speed cylinder pressure in hopes it will ease the dieseling. That’s definitely not going to help you as a whole.

 

[1969CoronetR/T]

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