Another dieseling thread

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1985c20

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My 85 will diesel with a crappy tank of gas in it too. I adjusted the timing up so I could lower the idle and that took care of it but it pinged too easily on hills so I had to back it off. And usually if I let the clutch out when its dieseling it'll cause a backfire which is more embarrassing then the dieseling haha. Only fix I have for it right now is to run premium gas. Cost around $6 more a tank but i only drive the truck once a week so its worth it to me. I'm switching to TBI soon anyway.
 

Ronno6

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My 85 will diesel with a crappy tank of gas in it too. I adjusted the timing up so I could lower the idle and that took care of it but it pinged too easily on hills so I had to back it off. And usually if I let the clutch out when its dieseling it'll cause a backfire which is more embarrassing then the dieseling haha. Only fix I have for it right now is to run premium gas. Cost around $6 more a tank but i only drive the truck once a week so its worth it to me. I'm switching to TBI soon anyway.

I bought 5gl of 93 octane non-ethanol this morn. $3.18/gl.
I am gonna siphon the current gas out (I hope...) and try the good stuff............
 

1985c20

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Sounds good. Also, rock auto sells the idle solenoid’s new with the bracket if you’re like me and don’t have a junkyard to source parts from. AC Delco part 2142138. They call it an “idle stop solenoid”
 

Ronno6

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Sounds good. Also, rock auto sells the idle solenoid’s new with the bracket if you’re like me and don’t have a junkyard to source parts from. AC Delco part 2142138. They call it an “idle stop solenoid”

Excellent! That beats the Holley part by $30.00 !!

So far, so good on the good 93octane non-ethanol gas and 12°BTDC....................
 

QBuff02

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Maybe this has been flogged to death...........
Just built my 355.
Compression 10.1:1
initial timing 10° BTDC, but not sure what idle speed.........
87 octane fuel non-ethanol.
I can idle the critter for 5 minutes and get some dieseling when I shut 'er down.
No pinging when I rev it up, but have not driven on the street.

Spark plugs are Accel shorty's, heat range 4 which is as cold as the shorty's go in my configuration.

Might this be new engine-itis?
If not, where should I begin??


Where did you degree the cam when you installed it? What did the cam card call for? Depending on how the cam was ground and where you installed it can have quite an effect on cylinder pressures. I wouldn't run any less than 93 octane on a 10:1 compression ratio engine. Especially if it has iron heads. so say, If the cam was ground 4 degrees advanced and you used a timing set with an additional 4 degrees or so in it, your valve events are going to happen that much sooner, which also means that your intake valve is going to be closing that much sooner and building cylinder pressure sooner and more of it. Remember, valve timing has nothing to do with ignition timing. Short octane gas only makes the problem worse. I'd add a few degrees of extra timing and bump up to 93 octane or so and see where that gets you.
 

Ronno6

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It has been a while since degreeing the cam.........
I think I have a thread on that somewhere...
As I recall, Willhoite said they put 4° advance into the cam, and I instaalled it with no additional advance.
It degreed out perfectly to the specs when I checked..........

Heads are aluminum BTW....
 

QBuff02

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It has been a while since degreeing the cam.........
I think I have a thread on that somewhere...
As I recall, Willhoite said they put 4° advance into the cam, and I instaalled it with no additional advance.
It degreed out perfectly to the specs when I checked..........

Heads are aluminum BTW....

a lot of people don't go through the trouble of degreeing a cam when they install it which is why I curiously asked.
Have you done a compression test to see what the actual cranking pressure is?
Excess fuel and too much residual heat (from higher compression) in the cylinder is a major contributor of run-on.
Something I've taken with me through life, my old engine builder mentor taught me. is that In a perfect world, everything works as it should. And you can get away with a lot of little things here and there, a touch more or less timing, a little less octane, maybe a little more or a little less jet. Some tweaking here and there. Lol However, none of us really live in a perfect world but the real world and that's why this rule applies. "Whatever the compression ratio is, move the decimal point one place to the right, and there's what octane fuel you should be running kid. That way, you don't screw it up." I've thrashed on a lot of engines over the years taking that little tidbit of advice and I've never burned one down yet. Lol Now do we really need to be running 100 octane in a 10.1:1 engine? No! But a good quality gas does matter and will make a difference. Anyway, all things considered the carb would be the next place I'd be digging into as discussed. but throttle stops and the like are merely a bandaid. What carb are you running? If it's a brand new carb topping the engine, take it apart and go through it. At the least flush through the idle circuit and air bleeds with some carb and choke cleaner. If it was sitting on the bench a while, clean it. I've seen carbs waaaay misadjusted because of plugged circuits and junk in them. (My 850 Demon on my big block was a prime example!) You have to open or close one thing to compensate for something wrong elsewhere in the carb. idle circuits that aren't working correctly so you open the butterflies too much to compensate for lack of idle quality and now you're uncovering the transfer slots too much and you're adding fuel from another circuit to make/keep it running. The best way to tune an engine is with a vacuum gauge, it's a sometimes time consuming process (especially with 4 corner idle circuits) but the results are worth it! And remember that initial timing needs set with the vacuum advance disconnected and plugged off. I saw it mentioned when I was reading through some of the replies that you're not sure on idle rpm and if you don't have a tach a timing light that reads rpm is a good, cheap addition to any mans toolbox. Start back at the basics and work your way around the engine, nothing worse than having a nice fresh engine that has problems. it's frustrating!
 

Ronno6

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I currently lack a vacuum gauge.
I have a cylinder pressure gauge somewhere....
I do need tach anyway...

The carb is a relatively new Holley 4160 Street Warrior 600 cfm.
I purchased it for my 305 last year, but did not drive it much,
I have been sing non-ethanol gas, so I do not consider the perils of ethanol to me an issue.
It may could use some adjustment......

The compression ratio is a result of my concern with the quench distance.
I had the deck machined to .028" height from piston top and am using 0.15" gaskets
to arrive at a quench distance of .043"
With the 64cc chamber heads and 4 falve dents, that's just where the C/C wound up.
My hopes were that the use of alum. heads would mitigate the detonating.
As I have not driven the new engine yet, I cannot vouch for on street performance.
But, if I gotta run premium gas, I'll just do that..........

It is a possibility that fuel injection may be in my future, but that would optimally
involve a tank swap as I have dual saddle tanks now.That would involve spare tire location issues,tho.............
The dominoes are in control.
 

QBuff02

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I currently lack a vacuum gauge.
I have a cylinder pressure gauge somewhere....
I do need tach anyway...

The carb is a relatively new Holley 4160 Street Warrior 600 cfm.
I purchased it for my 305 last year, but did not drive it much,
I have been sing non-ethanol gas, so I do not consider the perils of ethanol to me an issue.
It may could use some adjustment......

The compression ratio is a result of my concern with the quench distance.
I had the deck machined to .028" height from piston top and am using 0.15" gaskets
to arrive at a quench distance of .043"
With the 64cc chamber heads and 4 falve dents, that's just where the C/C wound up.
My hopes were that the use of alum. heads would mitigate the detonating.
As I have not driven the new engine yet, I cannot vouch for on street performance.
But, if I gotta run premium gas, I'll just do that..........

It is a possibility that fuel injection may be in my future, but that would optimally
involve a tank swap as I have dual saddle tanks now.That would involve spare tire location issues,tho.............
The dominoes are in control.


So my first order of business without a few of the tools to help you out would be get it running at idle and check the float levels on carb. They could simply be set too high, or if you installed a new fuel pump the pressure could be enough that it's now pushing past the float and putting too much fuel into the carb. You'd see fuel possibly dripping past the boosters if this was the case. So get the float level correct, or verify its correct and then for a simple check, with the engine idling, slowly turn in the air/fuel mixture screws on the metering block and see what happens. Should kill the engine when you get them turned in enough. If it doesn't, then you'll know you're drawing fuel past the butterflies from the transition. Of which it would be a simple reset and readjust of the butterflies and then make your adjustments for idle on the air/fuel adjustment and go from there.


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