It's probably ok. It only takes a very small amount to distort the rubber.
Forgive me for not back reading, but is this something that just began from it running correctly or has it done this the whole time?
base timing keeps advancing by itself...
- Thread starter smokinnjokin
- Start date
-
Forgive me for not back reading, but is this something that just began from it running correctly or has it done this the whole time?
smokinnjokin
Well-Known Member
Before it ran at 14 base timing with no detonation (last fall). I just bumped it up to 10 and got a minor occasional rattle around 2500-2800 under heavy load. So looks like 8 or 9 is what it wants. Feels very strong at that setting and idles well, so maybe dampener slipped by 4-5 degrees?
smokinnjokin
Well-Known Member
Only other thing i could think of is fuel quality… maybe varying octane in the garbage 87e10 i feed it?
Joe I really do not like dial back timing lights for this reason. Can you put a timing tape on and verify the light?
Last edited:
MOPAROFFICIAL
Oogliboogli
Mark the dampener
Find tdc through plug
Mark center hub of dampener
Recheck timing
Dial back timing lights work fine, if you know how to use them.
Set the desired timing degree and then aim and adjust distributor till line shows at zzzzeeerrrrooo=0
Grab dampener by each side and turn both directions to feel for chain slop if you're curious.
Compression test.
Find tdc through plug
Mark center hub of dampener
Recheck timing
Dial back timing lights work fine, if you know how to use them.
Set the desired timing degree and then aim and adjust distributor till line shows at zzzzeeerrrrooo=0
Grab dampener by each side and turn both directions to feel for chain slop if you're curious.
Compression test.
smokinnjokin
Well-Known Member
Cast-in timing marks on cover agree with the light when dialed back, 10 BTDC. Timing light with no-dial back, lines up with 10btdc mark on cover.
MOPAROFFICIAL
Oogliboogli
Your dampener wont know where tdc is if the ring has spun.
What ignition box, 4 or 5 pin?
Pull the distributor, mark the gear inline with the slot...run it... pull distributor again and see if the line is still inline with the slot.
If you dont check that stuff, like verifying tdc on the dampener... we're done. Get a book and disregard it 'instead' of us.
What ignition box, 4 or 5 pin?
Pull the distributor, mark the gear inline with the slot...run it... pull distributor again and see if the line is still inline with the slot.
If you dont check that stuff, like verifying tdc on the dampener... we're done. Get a book and disregard it 'instead' of us.
smokinnjokin
Well-Known Member
Thank you, I understand and acknowledge that the dampener may have spun. I was addressing ray's timing light concern. I'm not 'disregarding' anybody. I am also not in the habit of taking orders from impatient strangers on the internet. We are engaging in some troubleshooting discussion on a forum page until I am able to dig deeper into diagnosis. If that angers you, move along.
Retarding initial timing is a baaaaaaaaaaad way to stop detonation. The correct fix is to modify the centri curve in the dist so that timing comes in later, &/or total is reduced. If VA is being used, it can also cause det if it does not drop off quick enough. Many variables unfortunately.
Dave999
Well-Known Member
if you have a old starter (just in case you break it) that you can use. do the kick back test.
set initial timing to 5* BTDC
start motor.
stop
advance by 2 dgrees
start
stop
advance by 2 *
repeat
do this till it labours or kicks back when starting
remove 1 degree
see if it will start, any sign of labouring
remove 1 degree. try again
no labouring
record your new initial timing
battery needs to be well charged....
regardless of if the balancer has slipped this is what it wants as its initial timing.
work from that when you recurve your dizzy and work out if the TDC mark on balancer is correct.
some risk in doing this but you do get an indicator of what it likes best.
only method that really truley works if you put on something like Webers....but works none the less for everything else.
yes it sounds like a "bodge".... but it works, provided carb is in a decent state of tune.
re set idle mixture once done for max vacuum or highest idle speed and then adjust back to 800-1000 or what is appropriate for your car on the stop screw
Dave
set initial timing to 5* BTDC
start motor.
stop
advance by 2 dgrees
start
stop
advance by 2 *
repeat
do this till it labours or kicks back when starting
remove 1 degree
see if it will start, any sign of labouring
remove 1 degree. try again
no labouring
record your new initial timing
battery needs to be well charged....
regardless of if the balancer has slipped this is what it wants as its initial timing.
work from that when you recurve your dizzy and work out if the TDC mark on balancer is correct.
some risk in doing this but you do get an indicator of what it likes best.
only method that really truley works if you put on something like Webers....but works none the less for everything else.
yes it sounds like a "bodge".... but it works, provided carb is in a decent state of tune.
re set idle mixture once done for max vacuum or highest idle speed and then adjust back to 800-1000 or what is appropriate for your car on the stop screw
Dave
Last edited:
Meant whaen the advance feature on the light is used. They are usually good when it is off or turned all the way back.
Uncle Bob
Shiny paint causes stress.
Are you readjusting the max advance when you reduce the initial? If not your detonation may come back when you do, and if you don't you might not be getting the optimum performance out of it.
If it was me I'd run that out or drain it, and quit using it. My wife sent me out yesterday "Sheetz has gas for 3.99!". Yeah, it was flex fuel.
If it was me I'd run that out or drain it, and quit using it. My wife sent me out yesterday "Sheetz has gas for 3.99!". Yeah, it was flex fuel.
512Stroker
We are all here because we are not all there.
You are going to have a difficult time trying to develope a tune using 87 octane fuel with 10 % ethanol, been there tried that. You may solve some of your issues by upgrading to non ethanol 91 or 93 octane fuel.
Whats the compression ratio?
Show us some pic's of the plugs.
The cheap *** fuel may be causing the detention.
KitCarlson
Well-Known Member
I drive daily with 13:1 on 87. Runs great! EFI, direct injection. 
MOPAROFFICIAL
Oogliboogli
Impatient ...or are you incapable.
It's been over a week!
Stranger? Lol
Hey guess what? You're the stranger around here!
We are generous enough to be giving advice to youuuuu!
smokinnjokin
Well-Known Member
To address the latest posts in order, sorry I generally only get on here once a day. Working long hours.
smokinnjokin
Well-Known Member
Again, you are free to move along. Others have been very helpful, you have been rude. You can't ignore all previous information shared in the thread, give a shotgun blast of condescending generic troubleshooting instructions, and then get angry when I don't immediately ignore everyone else and drop what I am doing to follow your instructions, as you are A STRANGER who I do not know and do not particularly like. So kindly unfollow this thread and mind your own business.
To address the other poster's suggestions, some background info that may have been missed further up the thread.
1) This is a smog motor, recently rebuilt. Dished pistons, factory smog heads low compression build. It has been successfully running 87E10 since day 1, carb tuned to perfection according to instructions on this forum, the intent was always to run 87 octane. It has been suggested multiple times to just buy better gas, but that seems like a band-aid for a problem that can be fixed.
2) timing curve is custom, done by Ray, motor ran well for over 5k miles over a summer with no major changes to timing. 14 degrees initial, 22 mechanical with a fast curve. The problem began after storing over the winter and spring. Detonation from 2k-2500 under load, did not pop up right away but after a few tanks of gas.
3) ignition is pertronix gen 1 (simple magnetic trigger)on a points distributor with pertronix coil, bypassed ballast resistor. 0.040" gap. fires right up with ease hot, cold whatever and plugs stay spotless.
4) Dial back timing light is working properly, verified against timing cover marks at least up to 10 degrees.
I just put a fresh tank of gas in it from a different station then previously, will attempt to bump up timing a bit to see if that made a difference. It seems very possible that I got a really bad or contaminated batch of gas, with degraded octane content. I have pulled plugs several times, they are very clean porcelain no signs of detonation, about 2-3 turns of color and full ring of soot around fuel ring. I also am not allowing the motor to stay under detonation condition (it is only rattle under heavy load condition from 2-3k) so it is unlikely that it would show on the plugs.
Current leading theory is that the weakened distributor spring just exacerbated a problem that was already there (bad fuel or something else). Working on fabricating a piston stop to rule the dampener out (seems unlikely, no distortion on the rubber or movement). Already ruled out timing chain slop. Another possibility is heat. My temp gauge is not accurate (just had recalibrated by instrument specialties, still showing bottom range of cold when engine is fully warmed up) so i'm going to get a infrared thermometer tomorrow and ensure that the water temp is acceptable when the detonation rattle is occurring. Just in case thermostat has failed or some other heat related issue.
Phreakish
Well-Known Member
Define that 22 degrees better. Is that measured at the balancer, or added by the distributor? 14+22 = 36, which is reasonable. But 22 total is not. It's not clear from your statements which one it actually is, or I've skim read too quickly.
No carb is ever "perfectly tuned", especially for e10. Between the water solubility and the fact that e10 is not stable (it's UP TO 10%, not just a straight 10%) there's no such thing as tuning perfection. Modern efi engines can deal with it fine, but a carb has more issues with it. The only way to know if your car is working consistent is to eliminate other inconsistencies and see if it has an effect or not.
I think you have much too much faith in a lot of the tuning parameters of this engine. Doesn't matter how low compression, low power it is. It shouldn't rattle under load. It could be lean, it could be a cylinder to cylinder imbalance. It could be too little or too much timing... The problem is that none of this can be ruled out until the accuracy of the measured information can be confirmed. An engine can "run great" while slowly, or quickly, destroying itself. Simply jumping at the timing may not be the solution to the issue. Ignoring other possibilities is a great way to wind up looking at a rebuild instead of a rejet or new distributor springs.
A piston stop is nice, but not needed to rule out a 10 degree slip of the balancer. A long screwdriver will do. A dial indicator could work too. More than one way to skin a cat.
A piston stop isn't needed to check the spark plugs and look for signs of detonation or cylinder imbalance. Plugs can also help shed some light on what's going on with the timing too, which could corroborate whether the balancer is actually suspect or not. They can also shed some light on actual mixture and mechanical condition. A compression test is a good way to ballpark timing and engine health as well. Your engine is doing something it shouldn't, and which is uncommon. It's best to get to the root cause instead of bandaid or assume one unproven approach will fix it.
There's a lot of gruff personalities on this site, but they're still here to help. The fact that the timing wasn't actually moving itself, despite your conviction to the contrary, tells us how experienced you are with this stuff - you're not. Which is fine, theres all kinds of things all sorts of people don't know, but it means that no one can take any info as gospel until it's confirmed or proven. The requests and suggestions being made all have a purpose, and you're just not going to know exactly why until you get a better grasp on the systems in these cars. If you do follow some of them, you're likely to learn a whole bunch in a hurry.
MOPAROFFICIAL
Oogliboogli
smokinnjokin
Well-Known Member
Thanks for the tips. After confirming TDC, I went back in to take a look at the carb. Did a full throttle pull, killed engine and pulled plug, it showed almost completely clean. Ordered needles (Edelbrock avs) to go richer. Will see how that effects things.
So no change with the new spring?
smokinnjokin
Well-Known Member
Ray, new spring helped, slowed the timing curve but did not completely get rid of the rattle. Phreakish's comment "An engine can "run great" while slowly, or quickly, destroying itself. Simply jumping at the timing may not be the solution to the issue. Ignoring other possibilities is a great way to wind up looking at a rebuild instead of a rejet or new distributor springs" got me thinking that my previous state of tune was possibly right on the edge of detonation, and that a weak distributor spring or bad tank of gas just pushed it over the edge. So I am going back through all systems and double-checking.
512Stroker
We are all here because we are not all there.
You are gpoing to need more than "needles" if it is that lean.
Suggest you buy the Edelbrock carb tuning kit for your carb.
You're going to need it
MOPAROFFICIAL
Oogliboogli
@smokinnjokin Change the step up spring for a lighter color one!! Blue, 'yellow,silver, orange,pink'
Yeah...confusing, got it.
You want full jet or more jet sooner.
Heres the thing..
Lean enough to detonate...would mean youre past exhibiting any mild surge. So.. how would your motor go from bitchin...to detonation in one season. Change of fuel blend perhaps. How rough was the bore finish? Got any oil deposits?
I'd expect ,if any change.. it would be mostly noticeable by the performance and plug reading..not detonation. Like one jet change maybe.
What's the cranking compression with one plug out and carb held at wot?
What's the distributor cap look like inside?
Show us the plug, up close, focused right after it's been detonating.
Man...4 pages later and he finally checked his tdc.
party time!
Yeah...confusing, got it.
You want full jet or more jet sooner.
Heres the thing..
Lean enough to detonate...would mean youre past exhibiting any mild surge. So.. how would your motor go from bitchin...to detonation in one season. Change of fuel blend perhaps. How rough was the bore finish? Got any oil deposits?
I'd expect ,if any change.. it would be mostly noticeable by the performance and plug reading..not detonation. Like one jet change maybe.
What's the cranking compression with one plug out and carb held at wot?
What's the distributor cap look like inside?
Show us the plug, up close, focused right after it's been detonating.
Man...4 pages later and he finally checked his tdc.
party time!
Last edited:
smokinnjokin
Well-Known Member
Yeah I have been eyeballing the 650 avs2 for a long time, comes quite a bit richer out of the box. If my needle change (2 stages richer in power mode) is a step in the right direction I might just go ahead and pull the trigger on the new carb and start tuning that.
Reading the Edelbrock manual.. it says to go to a stronger step-up spring to cure a lean spot. Am I misreading it? Currently has the yellow (4") spring which is one step weaker than factory, put in after the new cam which produces a bit less vac at idle than stock. Also suggests this spring is just for transitions, my detonation rattle is only at 3/4 to WOT throttle and is is sustained if I hold the pedal down.
And I told you I was going to check TDC, just had to wait till the weekend when I was off work.
-
