hi have an 88 iroc 5.7 converted to 5 spd looks just like would of from factory,im running 6 degrees has anyone been running 9/10 and acheived better performance?im always running 91 octane,also with 6 right now my idle is like 600 id like to see my idle a tad higher

 

Everybody does. At least, everybody that's not one of the sheeple, and is willing to actually TRY stuff and then believes what they see, instead of genuflecting at the high altar of the "book" and thinks that the "spec" is the be-all end-all, and worst of all, thinks that their "mark" is actually accurate when they shine their "light" on it (which it VIRTUALLY NEVER is).

Advance it and see what happens. One of 3 things will happen: it will run better, it will run worse, or it will run the same.

If it runs better, so it some more; and keep doing it until it starts running worse.

If it runs worse, go back to where it was, and then some more. See above.

If nothing happens, make a bigger adjustment, until something DOES happen.

It's just not that hard.

Can't do much about the idle without reprogramming the ECM. It has complete control of the idle speed.

 

what degree are you running on yours?thanks for the reply

 

The best "base timing" depends on the cam duration. As soon as you touch the throttle, that timing position means nothing.

With the old distributors, you could modify the mechanical timing to adjust what the total timing will be. You could also modify the vacuum advance for part throttle operation.

Now, the distributor is computer controlled so what you can change is only base timing but like I already dais, the best base timing depends on the cam grind.

As already mentioned, what you see on the timing marks is probably nowhere near accurate. With timing gear wear and chain stretch, the timing could be anywhere. Only using a degree wheel with some sort of piston stop can tell you if the timing mark is close enough to accurate.

Typically, it's recommend 10- to 12-degrees of initial timing when the duration of the camshaft is less than 220-degrees @ 0.050” of valve lift; 14- to 16-degrees of initial timing with a camshaft duration of less than 240-degrees @ 0.050”; and 18- to 20-degrees of initial timing when the camshaft duration is less than 260-degrees @ 0.050” of valve lift.

I'm not sure how the computer adjusts the total timing but generally if you advance the base timing, you're also advancing the total. With the older distributors, you adjusted the base timing to the above guideline then adjusted the weights to control the mechanical advance to get total timing. The springs were used to adjust how quickly the timing advanced. You want to be at full advance by 3000 rpm. No weights and springs to play with in the small cap HEI system.

So before you start playing with the timing, leave it set at the factory setting then see how much total advance the computer allows. You'll need either an advance timing light or a balancer marked with all the timing marks. Once you know how much total the computer allows, bump up your base timing to the suggestions then see if the computer allows more total. If the total timing is too great, the engine will knock under load and the knock sensor will detect it. The ECM will then retard the timing until the knock goes away. If the engine doesn't knock under load then higher octane fuel is not required. You'll never hear the knock unless it's severe. You'll need a scan tool that can show knock counts.

Where an engine likes it's total timing is a guess or tune on a dyno. Where one engine likes it's total timing, another engine may hate it. Generally total timing can be anywhere from 32-45*. Each engine is a little bit different so it's trial and error to see what it likes the best.

 

No particular idea... never really bothered to check. All I know is, where it runs the best.

I'd suspect it's around 15° static, 35° or 36° "total" with the curve starting just off idle and "all in" by around 3000, with about 14° of vac adv on top of that.

 

If you're stock, you most likely are not going to tell a difference bumping it a few degrees. Mine ran best at 9 degrees. I couldn't tell a difference, but track times verified it liked 9 the best. Just don't expect big results.

 

thanks everyone for all your replys much appreciated