Hey guys. I had put in a new distributor in my car and I wanted to set the timing as best as possible. I have an 88 IROC w/ a 350 Tune port and I was told that after a certain RPM its all computer controlled but under like 2000 or so its still all base timing. Is that true? And if so what would you guys suggest I advance or retard it to so I get the best throttle response and pickup? Thanks..

- Tom

 

Set it to the factory 6 deg BTDC, base timing. The ESC controls the advance whenever it is connected.

 

really ? then why does it run differently when i turn the distributor when the ESC is connected?



- Tom

 

Because the base timing is "transparent" to the ECM, It is programmed to "know" it is at 6 deg and sets its spark curve accordingly. If you move the base timing you are moving the whole spark table too.

 

Well then.... 6 degrees it is Thank you sir

- Tom

 

I'm trying to get the timing just right also. I've found that if I leave timing at 6*, the car is a pooch off the line. At 8*, it runs sooooo much stronger. At 10* base timing, the car is a wheel hopping animal! But as Morley said, it moves the whole spark curve up. I end up getting more knock counts and the ECM pulls timing out at the higher RPMs. I do get better 1/4 mile times with the timing at 8* rather than 6* though.

 

My timing is set at 12 degrees base. I have a hypertech chip with 160 stat. I have a snap on scan tool and rarely do i ever see the knock sensor register a knock with 93 octane.

 

So by moving the whole table so many degrees and getting some power low end will it sacrifice or mess things up at higher RPM?

 

A very common pitfall of newbies is advancing the timing too much. Most cars will be more responsive on the low end with some extra timing, and thus it feels faster However, the stock timing curve leaves a lot to be desired, and what ends up happeing is that extra timing then puts you into knock by the time you're in the 3k+ region and your power falls off as the ECM retards the timing. The end result is a markedly slower car with an owner who thinks he's made it faster.

If you're not monitoring knock counts on a scan tool, or at the track (or even g-tech testing), then leave your timing alone. Reason being, you have no way of knowing if you're actually losing power unless you have some way to reliably compare results. There is no greater liar than the butt dyno when it comes to fine tuning like this. Just recently i found over a mph by dropping 4' of timing and dropping my fuel pressure down 8psi from where i was. Exactly the opposite of what most people on these boards think you need to do to go fast, the difference is, i let timeslips dictate to me what the car wants, not my own hairbrain ideas.

 

lol well if i wasnt such a newbie i might be insulted Well thank you sir. Everything you said, I had never known. Any degree writing on my timing indicator things had washed away with age I think. I cant read the actual numbers. So, could you tell me what each notch is as far as degrees so I can set it back? Thanks !

- Tom

 

I'll refer to the v-shaped cuts heading in towards the block as "notches" and the tips pointing towards the radiator as "points". The one very large notch is the 0*(TDC) mark. The first point to the left of 0*(TDC) is 4*BTDC. The next notch is the 6*BTDC mark. Each point or notch is 2*.

 

Ok, I have an 88 Iroc Z with 5.7 liter motor. I just swaped in a new blcok with vortec heads. The guy told me to set my timing at base 8. I'm clueless on how to set timing, I'm new to distributors. Also will my computer mess up anything with my new motor in terms of timing..........I might not be making sense so feel free to shut me up and correct me. Besides that, my engine install is complete

 

To set the base timing, you need to temporarily keep the computer from advancing the timing. Up near the heat and air box by the blower motor, there is a brown wire that is sticking out of the wiring harness. This wire has a male to female connector on it. With the car off, disconnect this wire. Now start the car up and set the timing to 8*. Turn the car off, plug the wire back in, and reset the computer. You now have 8* initial timing. As far as how the computer is going to work with the motor, that all depends on how much different the new motor is from the stock motor.

 

each point is 2*, right, thanks


- Tom

 

Boxeat got it, the first big notch is 0, etc. Also, just for reference, the end of the timing tab is at 16' BTDC

 

if I set my base to 0* then will I get better top end, I'm not a genius so bare with me.

 

There is no set value that will give you best performance. The only way to find out is to try it, and measure it as i said above.

 

Ed 6 degree is really a dog low end. Can I put it at 8 or something so I'm not at knock at like 3000 rpm or so?

Thanks


- Tom

 

If you have no way of monitoring knock or performance, you're just playing with yourself to move the timing around. With a stock chip my car wouldnt' take any extra timing, of course i believe i also had a sluight injector imbalance, but still to be so close to detonation was a real condition.

And thats why people who've ben in their chip tell you that it's a good idea. It lets you give the car what it wants across the board. I was (am) running a lot more timing on the low end than a stock chip and my car loves it. And since i'm in the chip, it doesn't come at the expense of all my real power and torque.

 

Your chip? You mean you've reprogrammed ur ECM or something? or you bought an aftermarket Jet chip? Also can you feel loss of power after 3000? An could I hear the knocks ? THanks!

 

All this talk about base timing has really got me wondering, why doesn't anyone use total time figures? When I time my car I have always thrown the ECM into diagnostic mode (jump pins A and B on the ALDL connector) and timed my car at about 3000 RPM. I have always found that method to be very reliable as far as getting the timing where the motor wants it to be. By timing it that way I have never run into a detonation problem ( once the timing gets set in an apropriate place). Nothing on my car is even remotley stock anymore, so why should I try to set my non stock motor to stock timing. BTW my motor seems to like an aweful lot of timing compared to a lot of the carburated small blocks I've built in the past, it is currently happy at 36 degrees. so maybe 7 degrees base isn't so bad. I don't know, that's just how I've always done it and it seems to work fine.
-mike

 

For a stock application, You prolly don't want too much timing. I run a total of about 36 degrees timing, and I set my base to around 8 degrees.

I'm running a stock prom for now, because I'm not sure if I want to mess with the GM ECM, or get a better system.

You will get knock counts at higher RPM if the base timing is set to wild, but that is easily corrected. Running 1-2 points lower heat range plug will of course help, and running a higher octane
fuel at the track.

I was running 12 degrees advance a month ago, with a 45 heat range plug, I was ripping it up off the line. I've since lost a little low end by reducing timing, and a colder plug, but I _WAS_ detonating the front two cyls.

I prolly actually want to reduce my timing tables. I'd like to have about 12 degrees of initial timing, but keep my advance from going much higher than 36. I was under the impression that the 165 ECM only advances about 24 degrees, but dialing in timing at
high RPM proved otherwise. I saw it go as high as 40 degrees.



-- Joe

 

Max, you set your timing while thie motor is runnin at 3000 ? How do you go about doing that? Do you stick the throttle at some point ot stay at 3000 while you time? Hmm.. Thanks!

- Tom

 

This is flat out wrong, a complete myth.....

You CANNOT read your WOT timing curve unless you are under load. In the MAF ECM, timing is doled out based upon measured airflow through the MAF. Free revving an engine without load is NOWHERE near the same amount of airflow as at WOT under load. What you were seeing is a low load, high RPM timing value, which could easily be 40' or so.

And rather than just be an *** about it, i'll show you exactly what i mean. The attached image is the main spark table from the famous ARAP bin. It is much more aggressive than stock GM bins delivered in f-bodies. Notice how the low load timing is way higher than high load. I rest my case.

 

Yes i burn my own chips. And off the shelf 'performance' chips are complete JUNK. There is perhaps no bigger waste of money for these cars than one of those chips. I explained why a few months ago in this post:
https://www.thirdgen.org/techbb2/sho...hreadid=104792

 

couple ways.....if your not running a CD ignition than a good old tach/dwell meter works just fine, or if you have someone standing around while you work on your car (which usually happens I'm sure I'm not alone in this) you can have someone watch the tach, or you can do it by ear. Up to you...
-BTW on most stocker f-bodys I've worked on for people when I set the timing I unplug the spout connector and set the timing to zero...with the spout plugged back in after it usually reads eight...which is right where I leave it.

 

Since you have an RS, i'll clue you in that the factory spec for initial timing (EST bypass spout disconnected) is 6' BTDC for all TPI cars, LB9 and L98, all years.
The TBI cars were 0 (which i'm sure is where you got the idea from)

 

checked my timing the other day, it was a 5 degrees base time

I advanced it 5 degrees so now its at 10 degrees base time w/ no pre detontaion.

feels like I woke up a sleeping giant bwahaha.