Timing mystery
- Thread starter mbaird
- Start date
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Could it just be the HEI messing up the timing lights at higher RPMs ?
The engine just seems to want to run better than it does... it's got a great lopy idle it pulls decent into the 5k range....its just kinda lazy and runs like loud stock 318.
Kinda like a Chevy....lol
The engine just seems to want to run better than it does... it's got a great lopy idle it pulls decent into the 5k range....its just kinda lazy and runs like loud stock 318.
Kinda like a Chevy....lol
KitCarlson
Well-Known Member
Great picture, the pickup polarity is correct.
In tuning it is necessary to give the engine what it wants. You might be too captivated by the timing numbers, and those numbers could be incorrect. There are many other non ignition variables like fueling. Timing control is multi-dimensional. The observations in your original post of base timing and advance 2500 RPM are only two points on a line, a tiny sliver of a complex control surface.
In tuning it is necessary to give the engine what it wants. You might be too captivated by the timing numbers, and those numbers could be incorrect. There are many other non ignition variables like fueling. Timing control is multi-dimensional. The observations in your original post of base timing and advance 2500 RPM are only two points on a line, a tiny sliver of a complex control surface.
TrailBeast
AKA Mopars4us on Youtube
When it doubt about the numbers I advance it while it's running until it starts to slow the engine and then turn it back just a hair till the RPM's come back up and test drive.
If it pings at WOT stop, get out and bring it back another hair and repeat till the ping is gone.
That puts it so dog gone close it ridiculous, without paying any attention to timing marks or lights.
Just a thought.
If it pings at WOT stop, get out and bring it back another hair and repeat till the ping is gone.
That puts it so dog gone close it ridiculous, without paying any attention to timing marks or lights.
Just a thought.
That is a true.... I am taking into account the total mechanical advance curve ,vacuum advance calibration ,
jetting , vacuum secondary adjustment , cam timing etc....
I just can't see THAT much mechanical advance being normal or even acceptable...
My plugs are reading a constant lean (white) regardless of how much jetting I throw at it.....I want to get this timing curve right before moving on to the final carb adjustments...
I don't expect a 12 sec car but this build should be much healthier than it is....
jetting , vacuum secondary adjustment , cam timing etc....
I just can't see THAT much mechanical advance being normal or even acceptable...
My plugs are reading a constant lean (white) regardless of how much jetting I throw at it.....I want to get this timing curve right before moving on to the final carb adjustments...
I don't expect a 12 sec car but this build should be much healthier than it is....
KitCarlson
Well-Known Member
Timing aligns the fuel burn to the crank angle where it provides the maximum beam. The spark starts the burn, but the burn rate and duration depends on engine dynamics that vary with build design and operating situations. So things like compression, fuel mixture, cylinder charge, turbulence, temperature, RPM (that can limit useful burn time) .....
My guess is the FBO limiter plates are off, by two times. I have tried to provide information how a small tape measure, scribe can be used to measure angles of rotor movement, and associated advance. A square part like a machinist ruler is use to map the rotor tip center, straight down to outer edge of distributor for scribe mark. This is a simple process and can also be applied to vacuum advance.
Back to timing. Retarded timing burns fuel on the way out. When throttle is cracked, throttle response is poor. It can burn headers, turn manifolds cherry red, make people put on aluminum radiators that are less effective, so they add electric fans that waste twice the energy. But when the engine is at WOT, all is well, too proud to run vacuum advance to get the timing they need for light throttle getting around and cruise.
Too much timing results in weird high piched noises and herky jerkey operation, especially at light loads. At WOT the engine noise over shadows, so as TrailBeast says the RPM drops. So those that are really competive, log RPM, and ignition timing, and other parameters ( manifold pressure, throttle position ..) at a high rate. Then simple math (subtraction ), is used to find the rate of change of RPM. That is acceleration... plot that out, in relation to RPM, now you have a way to track improvements. What I am saying, is the information is there to gauge performance incrementally at various RPM, to get the timing curves you need for complete response. After work with that, most discover electronic advance with 3D mapping and EFI is vastly superior to carbs and mechanical distributors.
My guess is the FBO limiter plates are off, by two times. I have tried to provide information how a small tape measure, scribe can be used to measure angles of rotor movement, and associated advance. A square part like a machinist ruler is use to map the rotor tip center, straight down to outer edge of distributor for scribe mark. This is a simple process and can also be applied to vacuum advance.
Back to timing. Retarded timing burns fuel on the way out. When throttle is cracked, throttle response is poor. It can burn headers, turn manifolds cherry red, make people put on aluminum radiators that are less effective, so they add electric fans that waste twice the energy. But when the engine is at WOT, all is well, too proud to run vacuum advance to get the timing they need for light throttle getting around and cruise.
Too much timing results in weird high piched noises and herky jerkey operation, especially at light loads. At WOT the engine noise over shadows, so as TrailBeast says the RPM drops. So those that are really competive, log RPM, and ignition timing, and other parameters ( manifold pressure, throttle position ..) at a high rate. Then simple math (subtraction ), is used to find the rate of change of RPM. That is acceleration... plot that out, in relation to RPM, now you have a way to track improvements. What I am saying, is the information is there to gauge performance incrementally at various RPM, to get the timing curves you need for complete response. After work with that, most discover electronic advance with 3D mapping and EFI is vastly superior to carbs and mechanical distributors.
Marcohotrod
Well-Known Member
45* total mechanical is too much, we all know that, U have the limiter plate, use it yesterday with a smaller slot and go for a drive
Update....
I verified phasing using timing light.
Then I moved the Advance plate to the locked position (zero mechanical) and set initial timing to 21*..... Revved her to 2500 rpm and got 35* !! WTHeck ! No shaft movement latterely .....minimal up and down.
It almost acts like the wiring from pickup is backwards but when I reversed it the car would barely start and ran like crap......
I verified phasing using timing light.
Then I moved the Advance plate to the locked position (zero mechanical) and set initial timing to 21*..... Revved her to 2500 rpm and got 35* !! WTHeck ! No shaft movement latterely .....minimal up and down.
It almost acts like the wiring from pickup is backwards but when I reversed it the car would barely start and ran like crap......
New bushing ... I have not checked shaft for play other than checking play by twisting rotor back and forth which results in maybe 1/8th inch movement... Even if shaft was worn a bit would there be 14* of slop in it ?
I am referring to the intermediate shaft.....
I am referring to the intermediate shaft.....
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TrailBeast
AKA Mopars4us on Youtube
You may just have to bring your initial back a hair more and go with it.
If it pings at 35 total with WOT bring your intial back to 12-13 and retest.
If it pings at 35 total with WOT bring your intial back to 12-13 and retest.
I've read a few other threads that indicate reversed wiring on the reluctor pickup showed similar symptoms ....but unless I need to retime when I reverse the wires
it doesn't appear to that because the car barely runs when I switch them..
Maybe I should get a new pickup and try that ??
it doesn't appear to that because the car barely runs when I switch them..
Maybe I should get a new pickup and try that ??
if your saying leave the dizzy locked I dont think I want to do that because it ran worse even though it was "showing" the correct amount of total mechanical....
I really want to get this right and not just settle for a halfassed tune.
It's got to be something simple that I am missing or a freekie component issue.
I really want to get this right and not just settle for a halfassed tune.
It's got to be something simple that I am missing or a freekie component issue.
Darthomas
Ashamed to be seen in foreign cars
Pull the dist and see if there is in/out movement on the lower shaft.
If there is, add spacers until there is minimal movement. That will eliminate one potential place where timing can become "fuzzy".
KitCarlson
Well-Known Member
An 1/8" slop measured from the outer perimeter of distributor body, is about 8.5 degrees at crank.
Have you correctly set reluctor to pickup gap? Timing advances some with RPM, with signal amplitude increasing, reducing time to reach trigger point. Trigger point can vary, if it is high there will be more advance change. It can be easily measured with scope.
Most timing lights are polarity sensitive with clamp polarity. One side correctly faces plug.... if reversed, it might trigger on start of dwell, just guessing. That would really mess with measurements.
Have you correctly set reluctor to pickup gap? Timing advances some with RPM, with signal amplitude increasing, reducing time to reach trigger point. Trigger point can vary, if it is high there will be more advance change. It can be easily measured with scope.
Most timing lights are polarity sensitive with clamp polarity. One side correctly faces plug.... if reversed, it might trigger on start of dwell, just guessing. That would really mess with measurements.
Very little up/down movement of Dizzy input shaft.
Reset reluctor @.008 using brass feeler.
The 1/8" slop is rotationally and seems as good or better than every other mMopar Dizzy I have owned....some being brand new.
Reset reluctor @.008 using brass feeler.
The 1/8" slop is rotationally and seems as good or better than every other mMopar Dizzy I have owned....some being brand new.
TrailBeast
AKA Mopars4us on Youtube
If you think there is any way this could be related to the HEI module too Bad. 
Just kidding.
You might want another module for a backup anyway, but if you pick up another one and it straightens things out I will reimburse you for it within reason. (your word will be good enough for me)
To get another one order for 1996 GMC Sierra 1500 with a 5.7
If you do this you will need to knock the two plastic tabs off the bottom of the module so it sits flat on the aluminum heat sink.
I use plenty of compound between them so you should be able to recover what you can off the old module and transfer it to the new one.
I do run these on my own car before I ship them, but it is possible that something changed.
I'm sure I would have noticed that much timing here.
That would just suck if my product caused you all this trouble.
Just kidding.
You might want another module for a backup anyway, but if you pick up another one and it straightens things out I will reimburse you for it within reason. (your word will be good enough for me)
To get another one order for 1996 GMC Sierra 1500 with a 5.7
If you do this you will need to knock the two plastic tabs off the bottom of the module so it sits flat on the aluminum heat sink.
I use plenty of compound between them so you should be able to recover what you can off the old module and transfer it to the new one.
I do run these on my own car before I ship them, but it is possible that something changed.
I'm sure I would have noticed that much timing here.
That would just suck if my product caused you all this trouble.
TrailBeast
AKA Mopars4us on Youtube
It seems after everything you have done it could only be the distributor pickup or the HEI module, but one thing I would like you to check.
When I build these I remove the wires out of the other plug that isn't used but has the rubber in the end of it.
Pop that rubber out and make sure there isn't a tiny piece of wire that I might have missed crossing to one of the other pins.
Never had it happen but these are the only other things I can think of to suggest.
When I build these I remove the wires out of the other plug that isn't used but has the rubber in the end of it.
Pop that rubber out and make sure there isn't a tiny piece of wire that I might have missed crossing to one of the other pins.
Never had it happen but these are the only other things I can think of to suggest.
mguner
How many is too many?
I think his timing light is on drugs.... 
Darthomas
Ashamed to be seen in foreign cars
After 10 years with a car still basically at factory spec, you shouldn't even need a timing light anymore, if you can hear and see decently.
Seat-of- pants results is the confirmation.
Seat-of- pants results is the confirmation.
Trailbeast... I might need a visual of this plug.. I am going to stop and get a new pickup from NAPA after work.
mguner..... all 3 of my timing lights are on drugs then... The same drug...lol
Darthomas...... Its not just that the timing marks are off.... Im trying to get the car to kick me in the seat of the pants (aka...its a pooch)... something is off with my ignition
mguner..... all 3 of my timing lights are on drugs then... The same drug...lol
Darthomas...... Its not just that the timing marks are off.... Im trying to get the car to kick me in the seat of the pants (aka...its a pooch)... something is off with my ignition
Darthomas
Ashamed to be seen in foreign cars
I have fought ignition do-funnies in the past
that simply dissolved and I couldn't say just what I did to cure them.
It's a Zen thing.
Fight the bug as your body would an illness.
Trailbeast.... I'm not ready to place blame on your product quite yet... besides you dont make the modules so I cant really blame you if it turns out to be the module.
I have another new module but it is the flat kind with 2 prongs on each end. I would have to do some thinking about how to wire it up to your system or just start from scratch.... I will be the first to admit that electronics are not my forte...
I have another new module but it is the flat kind with 2 prongs on each end. I would have to do some thinking about how to wire it up to your system or just start from scratch.... I will be the first to admit that electronics are not my forte...
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