Timing/Dieseling problems on my sbc
Timing/Dieseling problems on my sbc To start i have a small block chevy 355 with vortec heads-around 440HP and torque. The motor was dynoed and given a set of recommendations. I'm having tons of problems as far as throttle response, idling, and just the feeling of not having the power.
Everything is brand new- Holley 770 Street avenger with stock jets, HEI dizzy with the 65000 volt coil ontop. Brand new spark plugs(champion RS12YC), new mallory 8mm plugs.
The motor calls for 32 degrees of total timing. The idle is set at an average of 12-14 degrees. The timing is completely set, but when i turn off the ignition the motor will diesel and keep turning over after i turn the key off. Which in turn is a sign of in proper timing. The idle mixture screws were adjusted with vacuum gauge. There are lighter springs in the dizzy to make the advance kick in quicker.
So my question is, why is it still dieseling and lacking all this power. I should be able to roast my tires and feel like i have 440hp. I have no low end torque and when i snap the throttle while driving there will be a slight delay. I run 93 octane gas and it passes through 2 fuel filters. Are my jets too large and need to be smaller? And this motor has less than a 1000 miles on it. Its brand new
Here are pictures of my #1 spark plug that i just replaced 2 days ago.
Here is the number 2 plug that has been in the motor for about a month
Everything is brand new- Holley 770 Street avenger with stock jets, HEI dizzy with the 65000 volt coil ontop. Brand new spark plugs(champion RS12YC), new mallory 8mm plugs.
The motor calls for 32 degrees of total timing. The idle is set at an average of 12-14 degrees. The timing is completely set, but when i turn off the ignition the motor will diesel and keep turning over after i turn the key off. Which in turn is a sign of in proper timing. The idle mixture screws were adjusted with vacuum gauge. There are lighter springs in the dizzy to make the advance kick in quicker.
So my question is, why is it still dieseling and lacking all this power. I should be able to roast my tires and feel like i have 440hp. I have no low end torque and when i snap the throttle while driving there will be a slight delay. I run 93 octane gas and it passes through 2 fuel filters. Are my jets too large and need to be smaller? And this motor has less than a 1000 miles on it. Its brand new
Here are pictures of my #1 spark plug that i just replaced 2 days ago.
Here is the number 2 plug that has been in the motor for about a month
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"The timing is completely set, but when i turn off the ignition the motor will diesel and keep turning over after i turn the key off. Which in turn is a sign of in proper timing."
Don't know where you got that idea. Dieseling is normally a symptom of too much initial advance. Also, by looking at the plugs you're running rich as hell.
Don't know where you got that idea. Dieseling is normally a symptom of too much initial advance. Also, by looking at the plugs you're running rich as hell.
Launching!
Joined: Oct 2006
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You mentioned the motor was dynoed...did it run okay on the dyno? If it did, we can narrow your problem down to what changed between now and then. As for the plugs, the #1 porcelain looks white and the strap isn't discolored. The mixture is probably close in that cylinder. The soot on the #2 threads could just be from the plugs not being tight enough or it could be rich. Its hard to tell from the photos. The better indicator of lean/rich is the part of the porcelain buried down deep in the plug. It is hard to see without a good light...or cutting the threaded portion of the plug away. You want a tan-colored ring down near the base of the porcelain.
yeah it looks like your running of the main metering circuit at an idle=your throttle blades are open too far and your bypassing the idle circuit.Now this does have a direct relation to timing and your current dizzy setup,I would put one medium spring and one light to get your total advance to come in at 3400-3500,go back and set you initial at 18*,now here is how they are all tied in the more you advance you initial timing the higher the idle speed therefore letting you turn back your idle speed screw(not the mixture screws)and closing throttle blades enough to start using the idle circuit.try this and tell us what happens
I would start with retarding the timing.
But also making sure that you are not off a tooth, I'm going to assume your aware of the old school bring to TDC on #1 and making sure the rotor and #1 plug wire on cap are aligned procedure.
The hesitation could aslo be a carb issue, mainly the accelerator pump being adjusted wrong.
What size is your cam? Compression ratio? Do you have any clue as to the size of your jets you have now?
I'm running a 67(I believe) jet in my 625 Demon, on my 383, with aluminum heads and a .500 lift cam...
Those plugs do say your running pretty rich, that 770 may be too much.
But also making sure that you are not off a tooth, I'm going to assume your aware of the old school bring to TDC on #1 and making sure the rotor and #1 plug wire on cap are aligned procedure.
The hesitation could aslo be a carb issue, mainly the accelerator pump being adjusted wrong.
What size is your cam? Compression ratio? Do you have any clue as to the size of your jets you have now?
I'm running a 67(I believe) jet in my 625 Demon, on my 383, with aluminum heads and a .500 lift cam...
Those plugs do say your running pretty rich, that 770 may be too much.
Its a crate motor built by yearone, they send a spec sheet and dyno results. So im hoping it ran good on the dyno lol. The #1 plug was changed 2 days ago and #2 has been in there for a month. At certain times when idling it smells like fuel pretty bad. So i might need to de jet the carb., buy all new plugs and go from there. But still want to see if i can solve the problem before going to that next step. Thanks for all the help guys-If need be, i will try and get a better picture of that #1 plug
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Launching!
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Did a quick search. Here was another guy having your same problem with an Avenger carb...
http://www.camaros.net/forums/showthread.php?t=93870
http://www.camaros.net/forums/showthread.php?t=93870
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Verdad Gallardo I would start with retarding the timing.
But also making sure that you are not off a tooth, I'm going to assume your aware of the old school bring to TDC on #1 and making sure the rotor and #1 plug wire on cap are aligned procedure.
The hesitation could aslo be a carb issue, mainly the accelerator pump being adjusted wrong.
What size is your cam? Compression ratio? Do you have any clue as to the size of your jets you have now?
I'm running a 67(I believe) jet in my 625 Demon, on my 383, with aluminum heads and a .500 lift cam...
Those plugs do say your running pretty rich, that 770 may be too much.
But also making sure that you are not off a tooth, I'm going to assume your aware of the old school bring to TDC on #1 and making sure the rotor and #1 plug wire on cap are aligned procedure.
The hesitation could aslo be a carb issue, mainly the accelerator pump being adjusted wrong.
What size is your cam? Compression ratio? Do you have any clue as to the size of your jets you have now?
I'm running a 67(I believe) jet in my 625 Demon, on my 383, with aluminum heads and a .500 lift cam...
Those plugs do say your running pretty rich, that 770 may be too much.
Yeah i did it the old fashioned way. Set to TDC and drop dizzy in untill its aligned with #1.
The cam is a 520 lift, 218/228 duration
9:5:1 compression
Jet size i have no idea yet. I will need to pull the bowls and look
Did a quick search. Here was another guy having your same problem with an Avenger carb...
http://www.camaros.net/forums/showthread.php?t=93870
http://www.camaros.net/forums/showthread.php?t=93870
Launching!
Joined: Oct 2006
Posts: 289
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It seems that too much vacuum advance (springs too light) and the throttle blade issue were the keys (primaries open too far to maintain a decent idle) for that guy.
You could always contact year one for some help...
You could always contact year one for some help...
If you had a REAL cam, that carb would work better, you have too much carb for one, meaning as much as you need to lean it out might not completely solve your problem, you need about a 650. That cam is tiny, not much bigger than some stockers.
See what jets you have and if you have a jet kit, go down 2 jettings at a time and see if it helps. From there you should also start out by screwing the idle mixture screws in all the way and then pull out by 1 and a half to start. As mentioned, you need to make sure timing is in effect with the throttle blades being as close to shut as possible, that tame cam should be able to idle about 5-600 RPM no problem. You might need to lower the squirter size as well.
Like i said, it is allot of carb for a 350 with such a mild cam, you need to really detune that thing to get it right.
See what jets you have and if you have a jet kit, go down 2 jettings at a time and see if it helps. From there you should also start out by screwing the idle mixture screws in all the way and then pull out by 1 and a half to start. As mentioned, you need to make sure timing is in effect with the throttle blades being as close to shut as possible, that tame cam should be able to idle about 5-600 RPM no problem. You might need to lower the squirter size as well.
Like i said, it is allot of carb for a 350 with such a mild cam, you need to really detune that thing to get it right.
One day ill beef this motor up 
So i need to possibly make sure the timing is correct. Turn idle screws 1 1/2 turn, de jet the carb and throw some heavier springs on the initial side? What do you guys mean the throttle blades as close as they can be to being shut? So your saying look down the carb while its at full advance and see how far open the butterflies are?
So i need to possibly make sure the timing is correct. Turn idle screws 1 1/2 turn, de jet the carb and throw some heavier springs on the initial side? What do you guys mean the throttle blades as close as they can be to being shut? So your saying look down the carb while its at full advance and see how far open the butterflies are?
ok here ya go the throttle blades at an idle are what we are talking about so here are some pics to help you out
pic#1 throttle blades completely shut idle speed screw backed all the way out the car will not run like this.
pic#2 blades open part throttle notice the long skinny slot on the venturi wall? that is you idle transfer slot the next pics will deal with this
pic#3 are the throttle blades at the preferred setting at an idle notice the the slot is showing about the same length as it is in width(it looks square)now do you have to pull the carb off the set this? no this is just showing you where the carb should have been baselined before it was installed and adjusted from there.Now you can have too much of this slot showing and it will bypass the idle circuit on the carb and run off the primary metering circuit this is not a good thing it will run way rich and have slugish response from the carb even stumbling and falling on it's face when you wack the throttle under load. there is a direct relationship between initial timing and how your idle circuit works on your carb.now the one thing you haven't told us is do you have a vacuum advance on your dizzy if so explain how you go about setting your initial timing.edit i just realized you carb choice and as stated above it is way too big a 650 would of been a much better choice,so year one sold this crate to you carb to pan or was it just a long block?
pic#1 throttle blades completely shut idle speed screw backed all the way out the car will not run like this.
pic#2 blades open part throttle notice the long skinny slot on the venturi wall? that is you idle transfer slot the next pics will deal with this
pic#3 are the throttle blades at the preferred setting at an idle notice the the slot is showing about the same length as it is in width(it looks square)now do you have to pull the carb off the set this? no this is just showing you where the carb should have been baselined before it was installed and adjusted from there.Now you can have too much of this slot showing and it will bypass the idle circuit on the carb and run off the primary metering circuit this is not a good thing it will run way rich and have slugish response from the carb even stumbling and falling on it's face when you wack the throttle under load. there is a direct relationship between initial timing and how your idle circuit works on your carb.now the one thing you haven't told us is do you have a vacuum advance on your dizzy if so explain how you go about setting your initial timing.edit i just realized you carb choice and as stated above it is way too big a 650 would of been a much better choice,so year one sold this crate to you carb to pan or was it just a long block?
Last edited by Hippi; Aug 27, 2009 at 01:10 AM.
nice pics, that explains a lot. I can easily take my carb off if i need too.
Long block. The only thing i needed to add was carb, fuel pump, front accessories.
HEI dizzy was vacuum adv., i have the old fashioned timing light, so this is being done with a timing tape.
Long block. The only thing i needed to add was carb, fuel pump, front accessories.
HEI dizzy was vacuum adv., i have the old fashioned timing light, so this is being done with a timing tape.
But they recommend a holley 750 double pumper? I have the same motor with a basic holley 750, not a street avenger, and it runs like a damn beast!! Different carb which means different settings, but i still would know when this motor is running good because it moves a 4000 pound camaro verrrrry easily with 18inch wide wheels.
so your just running the mechanical advance or both?if your running the vac. you are unplugging the vac advance to set your initial?if so what does your timing jump to when you plug it back in?
nono, when setting the initial its with it hooked up, then when setting total its plugged.
But i havent set the initial yet completely because to be honest i didn't know where to start and set it at. So the total timing is set
But i havent set the initial yet completely because to be honest i didn't know where to start and set it at. So the total timing is set
just making sure I know alot of guys that set it backwards.ah so there is part of you issue set your initial first then the advance as far as sbc's go i like 18* at an idle and nothing over 36 total,now is your vac advance adjustable I.E small set screw in the module itself to control the amount it advances?