(this is for a '95 Tahoe TBI 350) I want to advance my base ignition timing. I can't read my timing marker (its kinda rusty) but it seems that everyone runs 8*-6* advance... can anyone let me know where this is on the timing marker. Is there a performance loss with any more advance, and should i run premium fuel.

 

You may have to run premium fuel if you go too far advanced. There really isn't a need since the inherent design of swirl port heads don't necessitate a lot of initial advance. 6° would be more than adequate. Try to get some sand paper on your timing tab. You should be able to clean off the funk and read the numbers. It also helps to paint the groove on your balancer white so that you can read the mark easier. Don't forget to unplug the EST before you set the timing.

 

About halfway down this thread is a really good picture of the timing tab and what degree is where:
https://www.thirdgen.org/techbb2/sho...timing+picture

 

ok awsome, thanx guys. I went from base 0* and up and found that about 14* advanced is the best performance. I started getting a tick past 8* advanced on regular fuel, but running on premium (93 Octane) the engine is incredibly responsive at 14* adv. (i'm a teenager with no bills to pay so i don't mind paying for premium.) This much adv. may only work in cold weather, i fear that i might start getting a ping in hot weather and will be forced to retard the timing a little... we'll see. Great free mod though

 

I run my LO3 at about 10* and premium is obviously required, but it runs awesome. No pings, no knocks, and it performs very well. Does anyone else have an LO3 with their timing advanced more than 8*?

 

Only guys with different cams. A4 cars can take more base than T5 cars. It is not uncommon for guys with the A4 to tun 6° or more of advance. I don't think it is needed though and I am sure track times would confirm that.

T5 typically hear ping and see excessive knock counts with anything more than 4° base. I know mine did.

 

i run 10* on mine but, i don't know the history of the motor (maybe an unknown cam) i don't realy know but, i doubt it. It does have 140k+ miles on the motor though, so it's seen some wear and tear.

 

i thought onset of detonation is often unaudable(sp?) to human ear. the KS will retard timing and you may not be aware unless you are a logger.

 

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You are mistakingly relying on the Knock Sensor to keep your engine safe. Back it down to NO MORE than 8* or something will eventually pop, leaving you engine-less.

It would be interesting to hook a scanner to it and see what you are getting in the way of knock counts!.

 

If you can back it down and there is no change in performance, then yes, your knock sensor was retarding the timing, if u back it down and u lose perf. then it was obviosly where it was indicated. Some people reley on their computers too much, have u guys ever worked on a Carb car? You set the timing mostly by ear and throttle response...

 

Yep

 

You are correct. However, some people set the base so high that the ECM cannot compensate. You then get audible knock. I used to get audible knock with 93 octane and 6° advance.


Why would you not want to? Why would you not rely on it when it has design features to help you in every way? Any closed loop system with real time feed back is superior to carb. Sure carb may be easier to learn and change but you don't have the fine adjustment and precision of a properly dialed in fuel injected system. Learning the system is the only way to properly mod a fuel injected car. Band aid methods are inadequate despite the quantified reasons people give.

 

The computer can be fooled, when detonation becomes audible it's already past the domain of the knock sensor's range. Preignition is never heard by the knock sensor and will definitely put a hole in your piston. 14* is a lot of advance, and even if it's not knocking, it's probably not making any more power than it would at 8*. If you need to run 14* of base timing plus what the computer is adding to make max power either your damper has shifted or you have the slowest burning heads in history.

 

Remember that my motor is an L05 (350 tbi) not a 305. And it runns better at 14* advanced than it does 8* advanced. There are no pings/knocks of any sort, i have retarded the timming from 14* to 8* in increments of 2*, and every 2* i retarded it by, the engine felt a little more sluggish. Thus the engine was not having the knock sensor pulling any timing out. And its been this way for quite a while now and havn't blown it up... can't deney the facts.

 

I am going to say that NOBODY else should try 14* on a stock L05. Either you have the lowest compression in history or some 104 octane coming from your pump. The 193 heads make their best power at 30-32* total advance. The stock 350 bins used in most trucks provide about 26* when in PE mode. That means you want 4-6* more advance than stock MAX. Maybe the balancer is shot and slipped. In that instance your engine may only be getting 4-6* advance but the balancer is saying 14+ to get it. My L05 would tolerate no more than 6* advance and it was a fresh rebuild. More timing than 6* made the engine run rough in OD pulling up long grades, at 10* you could hear it detonate on hard pulls. That is when I backed it down to 6*. I have the MSD timing control for the late model HEI so this was easy to do.

You say you are not tripping the Knock sensor, but have you had a scan tool on it while driving it. You would be suprised at the knock count you can get without hearing any audible knock.

 

i get 250 KC's when i run timing at the edge with a load on engine. not mechanical KC, the real mccoy. 93 octane and 10.1/1 compression with modern designed heads. using an aluminum vette spark curve as basis. if i back off 2 deg it goes away! A/F is 13.1 /1 today at PE. now one can run an alarm as well hooked up to knock sensor. pretty cool accessory..

 

I accidently put a 1/2 tank of regular 87 octane in my tank today so i retarded my timing back to 2* advance. The next time i get a chance to fill it up i'm gunna go up again, i'll try 4* and work my way up, when you are using the 8* advance, are you guys running 93 octane? And does anyone know how i could hook a light, or buzzer up to my knock sensor so i could really know when its picking any detonation up? just a thought... i'm waiting to get a laptop to do programing.

 

i started with 93 octane. KC's appeared in loggs at the higher load areas if i recall. i pulled 2 deg at those count areas. went away. switched to 89 oct. did not reappear. still running 89.

 

how big of a performance gain could you expect in your E/T or your MPH?