I have a 1985 Camaro with a 383, HSR and ECM & wiring harness out of a 1990.

When I first installed the engine, I set the timing at 8 with the timing connector unplugged. After I set it, I shut the car off, tightened the distributor and then plugged the connector back in...and that was it. I wasn't smart enough to check it since.

Today, I checked the timing with the connector plugged in - it's at 28. I disconnected the plug and checked it, it's between 9 or 10. Plugged the connector back in, it stayed at 9 or 10 and my engine light was on. Shut the car off & restarted, light was off and timing was back to 28. I then held the idle up and checked it, I don't know exactly what RPM I was at because I was doing this by myself from under the hood but I kept creeping higher and higher until the timing stopped changing. Based on the sound, I'm guessing I was around 3,000 or 3,500 RPM. Anyway, at that point my timing was at 52 or 53. I don't think this is normal, is it?

I know how to adjust the base timing, but I'm pretty sure I don't want to go too much lower than 6 or 8. Since the timing is computer controlled, not sure how to fix this. Is this something to do with the tune? Or bad ECM?

 

9-10 base sounds a little high. I was thinking stock timing was like 4-6 degrees depending on what the motor likes. You can usually get a couple degrees more, but then you might have issues with pinging and gas quality. Once I got 6-8 degrees into mine it ran better but hated the 87/89 octane at that point.

Timing will adjust for part throttle driving and speeds. I don't believe it's static either when it goes to advance.

 

The distributor has a range of 42 advance. 52 degrees is alot but the base is fine at 9-10 depending how the sa was changed. If your getting predetonation you should contact who ever did you programing and have them correct it. Most Tuners will share the .bin the modified to your engine so you can view the sa tables yourself.

 

Some had a range of 46° and that gives 52° with the stock 6° base setting. Ideally your base timing should be set to match the ECM chip and the advance curve and amount dialed in correctly in the chip.

 

I have an aftermarket distributer (MSD-8366), but I can't find any info on what the range is.

How do I check for predetonation again? Is that based on the spark plugs? I pulled the plugs a month or so back, they all looked fine. I can probably find & post the pics again. In fact...

https://www.thirdgen.org/forums/tech...ark-plugs.html

I'm actually burning my own chip, but someone else is programming. So I datalogged, sent the file, they sent me the new file to burn, which I did. This process was repeated three times until the tuner said that was as good as they could get it. I have the files, but I have no idea how to read them - I assume I can download something to take a look in the files, but I'd have no idea what I was looking at.

If I move the base timing downt to 6, will that then "filter" to the other timings? So if I go from 10 to 6, will the 52 drop to 48 or whatever?

 

Three ways of detecting knock, reading the plugs for prolonged knock, the other bye looking at knock retard or other is those two things on the side of your head. Download tuner pro you are using a $8d mask. You can look at the spark table. Changing the base with recurve the timing.

 

Rule of thumb

A street strip SBC should not need more than 36 degrees total timing.
an otherwise stock engine with stock heads,, etc etc.. 28-32 total.
Set your base timing accordingly to be this range.

To re-establish yourself set your base timing to "0" (disconnect the distributor) at idle. shut off the car reconnect the timing plug at the distributor then run it.. rev up to 3000-3500 to see what total timing is.. if total timing is not near 28 degrees then this is how much you need to add to your base time... say you have 20 degrees total timing this means you need to reset your base timing to from "0" to "8" (8 +20 = 28) start low and work your way up; tune for best MPH, at the track or HP on a chassis dyno. You can always add more base timing until you have 32-36 total.. but you need to seed what the engine likes. always set base timing at idle... with timing wire disconnected form distributor... remember "0" is the factory starting point.. the sticker under your hood should say this...


Too much spark advance will hurt performance and is an open invitation to detonation (knock)


My 383 combo ran best with 36 degrees total timing and premium fuel (93 octane)
10.5:1 compression dart iron eagle heads etc etc.
I never had detonation issues & ran the car 12 years trouble free.


If you have a factory ECM with knock sensor you don't have to worry about detonation since the ECM will pull out timing / to eliminate it. or course you can read the plugs to make sure if you want too.


IF it pulls too much timing you are simply killing performance... at that point you want to run higher octane fuel than regular 87... try 89 or 92/93 so the engine runs at it true potential without pulling out excessive timing to prevent detonation on a low grade fuel. But rule of thumb a SBC on pump gas and even race gas should not need more than 36 degrees total timing

 

Besides verifying that your "mark" is accurate, there's not a whole lot else you can do. From that point on, it's all in how your chip is programmed; just like, with a mech dist, it's all in the springs & weights & vacuum can.

Take the above post with a grain of salt: "total" timing is what you have at ZERO VACUUM AND HIGH RPM (full power). It is NOT the highest it will ever go. Vac adv, or its electronically-generated but otherwise exact equivalent, adds something around 12 - 15° ON TOP OF IT. Your actual timing should therefore be expected to be around 50° at high RPMs and very low load; i.e. highway cruising.

28° sounds about typical for a EFI car at idle. Even the computer-controlled carb setup gave close to that; you'd usually see around 25° or so.

I'm not seeing anything the least bit unusual in the #s you posted. I'd suggest putting it back to where the chip was programmed to expect it to be; and if there's problems with it, take that up with the chip programmer. But, like fuel pressure, you can ALWAYS adjust it somewhere, and see if the engine runs better; that information will help chip man dial it in better. Most likely though, backing it off will only make it run a little "lazier", not quite as "crisp"; get worse gas mileage; and run hotter on the highway. Only way to know is to try it. Tuning.

 

Forgive me for being dumb, but I'm new to this...

What is meant by "total timing"? For my setup, is that the 10 base plus the 42 computer advance, which would bring me to 52? So to change that, I would need to (1) take my base down a bit and (2) use a program like tuner pro to get into the spark table and change that, is that correct?

My car does have a knock sensor, but I thought it was somewhat unreliable because it is for a 350 and I'm running a 383 (and they don't make a knock sensor for a 383). I found multiple posts on this when I was originally doing my research, but maybe that's not correct?

I've only used Premium grade (93 octane) in this car from day 1.

 

"Total" timing is the "static" (where the dist body is twiddled), plus the "centrifugal" (RPM dependent). It DOES NOT include the "vaccum" (load dependent) component.

Easiest way to understand the timing requirements of an engine are, to look at where it needs to be when running at rated load & RPM. (think of something like a lawn mower or generator engine, to zero your mind in on it) That's "total" timing, right there. It puts the engine at its most efficient AT FULL LOAD AND HIGH RPM. Now, think of what happens as you slow it down, but keep a high load on it: fuel burns in a relatively fixed amount of time (milliseconds), but all you can adjust is degrees. So, how may "degrees" is a millisecond? Well, it depends on RPM, right? So what ends up happening is, as RPM decreases below the peak HP RPM, the engine needs less and less advance in order for the fuel to be ignited and to complete its combustion at the exact instant when the piston is in the right place to start being pushed on. IOW, for your "mental picture" purpose, what you really have is, "low RPM retard", not, "high speed advance". Problem is, it's near impossible to physically execute it that way. Which is why we're stuck doing it the way we do. Then, when the engine is under LOW load, the mixture is lean and there's not as much of it in the cyl, which makes it take EVEN LONGER to burn; meaning, for it to be all done burning and the cyl ready to produce power at the instant the piston is in the right place, the burning must be started EVEN SOONER.

So, your timing curve has 3 components: "static", "RPM dependent", and "load dependent". You set the static by twiddling the dist body, and the other 2 are set independently of that (and have no knowledge of it). Expect that your motor will want something in the mid-high 20s at idle ("static" plus "vacuum", equivalent to hooking a mech dist to full manifold vacuum); when you add load (give it gas) at low RPMs it will need to drop to near the "static" value; as RPMs climb with the engine under load, so will the timing, until it reaches what we call "total" for some reason; and then when the engine is at high RPMs but low load (cruising), it will need EVEN MORE than "total", so it will get "total" plus "vacuum".

Sounds to me like the timing you're seeing is completely normal and correct, in a broad sense. Might need minor tweeeeeks here and there, aka "tuning", but the overall pattern is correct.

The knock sensor is nothing but a little microphone, tuned to listen to one specific frequency. The frequency of engine knock is determined by the bore. Since a 383 has the same bore as a 350 (give or take a sheet of paper), the 350 KS is correct for it.

 

I have done EFI & Carb setups.

The OP has EFI with the ECM controlling the timing. There is no mechanical or vacuum advance.
The ECM takes the base timing data.. and then electronicly
adjusts the timing.. per the timing table or Map created by the tuner.

My projection system had this. Very simply it was a graph; RPM to spark advance.

Your tuner would have the same with the stock ECM.

TOTAL TIMING is total timing period.


A carbureted SBC will never need more than 36 degrees total timing.. (base timing + mechanical advance + vacuum advance)

Vacuum advance is useless on a race car with a radical cam (low vacuum) so we only worry about base + mechanical but still this is total timing and is a fixed amount. My car base timing is 19 degrees & total timing of 34 degrees which is "all in" by 2500 RPM and does note change all the way up to 7200+ RPM. That is 15 degrees of mechanical advance with a fast advance curve..

Vacuum advance was used on street cars with carbs.. my 1972 Cutlass has it.. all it does is adjust timing based on engine load (vacuum) which helps improves fuel economy, not a priority on a race car.

Again total timing is a fixed amount & does not change once it's dialed in: mechanical / vacuum or programmed in: electronic.

That's why with EFI base timing is critical. because if it's not correct it throws total timing & more important the timing table off.
Check with your tuner to confirm what he set for total timing and adjust your base timing accordingly.


The knock sensor can be installed on the cylinder head / block I forget where. If you have it, use it, its' cheap insurance. The only problem in the past was that solid lifters threw off the sensor (false reading) may not be an issue with solid roller lifters, if you have hydraulic lifters it's a non-issue.

 

I have the knock sensor and it is hooked up. My engine is also a hydraulic roller lifter motor.

 

The OP has a GASOLINE MOTOR. The "timing" requirements are largely determind by this choice of fuel. The name stamped on the valve covers makes VERY LITTLE difference. Which is of course, why pretty much ANY brand of GASOLINE motor, needs a timing curve much as described above.

Whether by way of springs weights & vacuum cans, or by way of somebody replicating those into a table for an embedded CPU to look up, HE HAS "static" (dist body setting), "centrifugal" (RPM based), and "vacuum" (load based) timing control.

The fact that they are implemented electronically vs mechanically, does NOT change the basic combustion properties of GASOLINE. Which are of course, as outlined above.

Static (twiddling the dist body) advance setting is NO MORE, and also NO LESS, critical, in an electronic setting, as compared to a mechanical one. All the engine cares, is when the spark occurs. It cannot tell what is controlling the spark time; it could be a monkey with a dartboard, for all the ENGINE cares. All it cares, is that the spark is at the right point with respect to piston motion.

One of the most humorous fallacies in all of car-dom is that somehow the twiddling of the dist body in an electronically controlled system, is any different from that in a mechanically controlled one.

Re-twiddling the dist body does not "throw the timing table off", any more, or less, than it does if that "table" is generated mechanically.

The knock sensor is installed in the BLOCK. You gotta remember, back in 1955 when those GM engineers were thinking up the small block Chevy, they already KNEW that EFI was "the comin thang"; BUT, they also KNEW, that those evil minions and henchmen over at Frod and Xler would be EAGERLY reverse-engineering ANYTHING that they did, so they didn't want to tip their hand. So they cleverly disguised the "knock sensor" hole, as a "coolant drain". So far as I know the Other Guys didn't catch on until it was too late.

A small block Chevy needs about 36° of "total" ("static" + "centrifugal") timing, PLUS about 12 - 15° of "vacuum" advance; for a total in the ballpark of 50° at high RPM highway cruising speeds. Same as about any other GASOLINE motor, give or take a ° or 2. Go check your 72 Gutless, you'll find it's not too far different from that.

You need to find out what you're talking about before you post it on the Internet, otherwise you end up looking like ... yeah. One of those. Better to keep your keyboard shut than to open it and remove all doubt.

 

For my drag car I have no additional vacuum advance because none is needed at WOT (there is little to no vacuum)

SO my total timing is simply 36 degrees.


Please read and understand before you tell someone they don't know what they are talking about... I think MSD know a bit more about this topic than you think you do...

and even with vacuum advance the MOST timing my Cutlass see is 40degrees... 50 you must be kidding me.

http://www.setyourtiming.com/Timing_Settings.html



Vacuum Advance

Vacuum advance is primarily used in an effort to improve economy, therefore you won’t hear much about vacuum advance when discussing performance and racing. There is little to no vacuum during wide open throttle which means no vacuum advance any way!

A vacuum advance canister provides a way to advance the ignition timing during moderate and part throttle conditions. This is when the load on the engine is less and vacuum is higher. There is a diaphragm inside the canister which is connected to a linkage connected to the pickup plate in the distributor. When vacuum is applied, the plate is pulled which advances when the trigger signal is created. When the engine accelerates, vacuum drops so the advance returns to the original position.

When connecting the vacuum advance, most applications connect to a port above the throttle plates. This is called ported vacuum compared to manifold vacuum which comes straight from the intake manifold. The difference here is that manifold vacuum is there constantly while the ported source provides vacuum only when the throttle blades are open. The amount of advance that occurs varies by application but generally ranges from 10°-15°. Some companies even offer an adjustable vacuum advance canister. This lets you set the exact amount of vacuum advance that your engine requires.

 

Those are old outdated articles that anyone who knows what they are doing don't really go by anymore. Kind of like carb tuners knowing that the holley half the powervalve thing is incorrect.
Try this article. it will shed a little more light on the situation.
http://www.maliburacing.com/forum/vi...php?f=4&t=2484

Also running a vacuum can on you race car will make it run better/smoother at idle and cursing around the pits. Now that may not matter to you, but to me it does.

As far as the op. Yes those timing numbers commanded by the comp are totally normal. Just set the base timing and don't worry about what the comp is doing. That's all in the chip which you have no control over anyway. That's what the tuner is for.

 

Thanks for all the information. My head is swimming a bit right now. All this talk about vacuum advance doesn't apply to me since my distributor is ECM controlled, but (roughly speaking), it's the same as the electronic advance that I'm getting right?

When talking to company that burned my chip, they said they did all programming assuming that both the timing & fuel pressure where stock. So this is my issue - for my situation, what the hell is "stock"? Stock for an '85 Camaro with a 305 (which is what my car had) was 0 degrees. However, I no longer have a 305, I have a 383 with a totally different fuel delivery system on it. And, I have the ECM out of a '90 so do I go with the "stock" for that?

It seems to me that I have two choices, not sure which way is best to make sure I'm maximizing performance. Do I set the timing to where it seems to be best (say, 6 or 8 degrees) and then get the chip tuned accordingly, or do I set it to "stock", get the chip tuned and then adjust the timing after?

 

You set it for the ecu. Which i believe is 6 deg.
Once the chip is tuned you should never have to change the base timing of the distributor. The base setting is just a point of reference. So when the computer commands 36 deg it gets it. If you set it to 10 then every time the comp commands 36 it will get 40 which will most likely cause knock.

 

All I was trying to explain to OP was not to worry about what someone else says about vacuum or mechanical advance because these do not apply to an engine with computer controlled timing...

Base timing needs to be correct that and that is all.. the timing tables burned into the PROM does the rest.

I think sofa*** took offence to someone pointing out the irrelevance of their additional info.

Sorry for hi-jacking the OPs thread..

Yes you can do that on your race car... if it helps you.

I don't run power valves.. and have idle bleed ( return line) My car idles great and driving in the pits is no problem since my base timing is only 19 degrees.

 

THIS /\ !!!

 

Excellent! Thank you...will adjust down to 6 & run the car a bit, see how it operates...just as soon as I fix my new trans line leak

 

Exactly: in the IDENTICAL SAME WAY that the "timing tables burned into" the springs & weights and the vacuum can, "take care of the rest" in a mechanical distributor.

And similarly, if your car happens to have a mech dist with springs & weights and all that in it that are mismatched to YOUR ENGINE, you can often improve the overall results by altering the static setting. Computer-controlled cars are NO DIFFERENT.

It makes NOT THE SLIGHTEST DIFFERENCE to the overall effect, where the "timing tables" come from. All the engine cares about, is when the spark occurs, relative to piston motion; it doesn't know, can't find out, and wouldn't care if it could, whether the "timing tables" are in the form of moving pieces, or digital values stored in a chip.

Base timing needs to be correct, to the point that whenever the "timing table" says that at such-and-such RPM, so-and-so vacuum (MAP< engine load, whatever you want to call it), and so on, the spark occurs where the engine wants it. If the values burned into the PROM, or burned into the mech parts, don't agree with what the engine wants, then by twiddling the dist body to alter the static setting, one can often determine what the "burned in" values need to be changed to. Static timing is NOT a matter of putting where "The Book" says, and somehow that's automatically perfect. IT ISN'T. That's where the human factor takes over, doing that fun thing called TUNING.

This is only correct to the extent that "the chip is tuned". If 99% of the time that you're driving around the timing doesn't match WHAT THE ENGINE WANTS, but 1% of the time that 36° is spot on, then is "the chip tuned"? NO. Might the engine run better some significant part of the time if the static timing is set somewhere else? YES. Will you ever even FIND THIS OUT if you just stick it somewhere and leave it there and never touch it? NO.

Tuning is a living, breathing, adapting, growing, experimenting, learning, finding out, feeling your way around, PROCESS. Not a "The Book says x so there's nothing else I can do" dogma.

 

Sofa I think your under the impression that most people are capable of properly tuning their cars, or even want to take the time when in reality this is far from the truth. The reason I make a living setting up cars is because most people cant do the fine adjustments of timing and carb tuning or efi tuning. It's just the way it is.
For Fronzizzle and most other people the best thing they can do is find a tuner they trust and set the distributor to what the tuner says and just forget about it. As long as the tuner knows what they are doing the car should be 99%. Which is better than most.

 

I think I'm under the impression that "I bolted it up and it's no good" is no way to go through life.

I consider it worthwhile to help people take their fates into their own hands and make their lives better.

In the America I grew up in, people were required by the circustances of their daily lives, to accept responsibility for the outcome of things they did. For better or worse. That means, when you WANT something, you FIGURE OUT how to get it. Which is a lot different from DEMANDING that someone else do it for you.

For the OP and about everybody else in the same plight, the only way for them to even get somebody else to do their tuning for them and get it right, is to (a) pay gobs of money for dyno/track time so that the changes can be measured and validated; or (b) accept some personal responsibility for obtaining enough data to at least tell the vendor what the car needs. "My chip sucks" isn't very likely to end up with something better. "It's lazy around town and overheats on the highway, but if I crank the dist body about 10° both of those get better but the pinging is intolerable and if I crank it about 15° it's great except I can't accelerate at all without pinging" is AHELLUVALOT more likely to get results.

 

[QUOTE=sofakingdom;5600679]I think I'm under the impression that "I bolted it up and it's no good" is no way to go through life.


In the America I grew up in, people were required by the circumstances of their daily lives, to accept responsibility for the outcome of things they did. For better or worse. That means, when you WANT something, you FIGURE OUT how to get it. Which is a lot different from DEMANDING that someone else do it for you.

QUOTE]

Agreed,,, but unfortunately people like us are not the common denominator.

You can only lead so many horses to water, before you realize that unless they have the desire and right attitude you can't teach them anything.. it can't be forced upon them. This makes you seek out and concentrate on the "right kind of horses".

No dis-respect to the OP, but how did all these "car guys" before get anything done without an internet forum?!

There was no internet for me when I started... there was the neighborhood mechanic who worked at the Amoco Station and my dad.
The library & shop manuals. You learned by doing there was no choice, unless you were a rich kid... (which I was not)

 

Well, since we are already off topic and I’m the OP, I’llchime in…

Internet forums today are the newer version of going to thelibrary or asking a mechanic, right? Notsure I understand the difference, other than using new technology to reach moreknowledgeable people. We use someversion of this for just about everything we do, don’t we? How many people pick a new TV by “trial anderror”, just walk into a Best Buy or whatever and pick one off the wall? Whether we decide where to go to dinner orwhat movie to see based on recommendations from friends, buy a car based on JDPower, use Consumer Reports to pick a new washing machine…I mean, everyone gatherssome amount of information from other sources, in most instances.

For me, I’m not looking for someone to “tell me how to do it”or DEMANDING someone do it for me; I’m looking for some information on where tostart and in some cases, how to proceed. If you don’t know much about cars – or about something specific liketiming – then it’s hard to know what you don’t know, if that makes sense. So many things on a car are pretty straightforward– “Torque the wheels down to 100 ft./lbs.” – that maybe the inclination is tothink everything is like that. Basetiming should be 6 degrees, so set it at 6 degrees. Done.

One thing I will say for the internet age is that the lackof information isn’t the problem; too much information is. No matter what you want to find or look up,you will find opposing view points. Justlook at my original post; one person says my timing curve appears to be fine,another says that 50 is way too much.

I certainly understand the “do it yourself” and “trial anderror” thing with cars. But, again, ifyou don’t know…well, for me, my fear is hurting something. Set the fuel pressure too high and blow outan injector or the timing is too high and I burn a piston or something. Maybe these things are ridiculous once youunderstand more, but when you are first starting out they don’t seem that way.

And the final thing is, trial and error and experimentationis fine but if you can gather information on a good starting point as well aswhat has worked for other people…isn’t that just good use of your time? I can take my fuel pressure from, say 35 psito 55 psi. Of course, I can set it atevery point in between there, drive it & see how it acts. Or I can use information gathered from otherpeople to know that the “most likely” setting is someplace in the 42-46 rangeand go from there. Doesn’t mean I wantsomeone to tell me to “put it at 43 and leave it” or that I can’t/won’t test itat other pressures.

I guess the bottom line for me is that I find the forumslike this incredibly useful; it’s my equivalent of sitting around with friendsor mechanic & discussing these issues. My real friends aren’t into cars at all, so I don’t have that option.

 

THE DIFFERENCE is this keyboard and screen are merely a proxy
for human interaction.. it's good, but not great.

ALOT more can be communicated verbally or face to face.

A lot of people mistake this technology as a replacement for actual interaction: you see it with texting, emails.. etc..

if your "real friends" are not into cars, you should get to know some who are... you will get more accomplished with people who have similar interests that are a phone call way.

Yes these forums are useful you just have to sift thru a lot of BS. but what's even better is the shop manual for your car.. that have pretty much all the info you will ever need..